GARY PADGETT'S MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY SEPTEMBER, 2000 (For general comments about the nature of these summaries, as well as information on how to download the tabular cyclone track files, see the Author's Note at the end of this summary.) *********************************************************************** SOUTHERN HEMISPHERE TROPICAL CYCLONE NAMES 2000 - 2001 SEASON TROPICAL CYCLONE NAMES for the AUSTRALIAN REGION The Australian Bureau of Meteorology maintains three Tropical Cyclone Warning Centres (TCWC): Perth, Western Australia; Darwin, Northern Territory; and Brisbane, Queensland. Each centre is allotted a separate list of tropical cyclone names for tropical cyclones forming within its area of responsibility (AOR). In addition a TCWC located at Port Moresby, Papua New Guinea (PNG)--a former Australian territory-- maintains a list of native names to assign to the very rare tropical cyclones which form within its AOR. The AORs of the respective centres are: (1) Perth - 125E westward to 90E. Technically, Perth's AOR is south of 10S with Indonesia being responsible for waters north of 10S, but I believe the plan is that any rare tropical cyclone which might form north of 10S would be named by Perth. (2) Darwin - 125E eastward to 138E and extending northward to the equator. There is a little irregularity with the eastern border in the Gulf of Carpentaria. The Darwin TCWC issues High Seas Warnings for the entire Gulf of Carpentaria, but Brisbane issues Tropical Cyclone Advices and names cyclones in the eastern portion of the Gulf. (3) Brisbane - 138E eastward to 160E and generally south of 10S. The northern border with the Port Moresby AOR is somewhat irregular. (4) Port Moresby, PNG - immediate vicinity of the island of New Guinea and eastward to 160E generally north of 10S although the southern border is somewhat irregular. Names for the 2000-2001 season (** indicates name has already been assigned): Perth Darwin Brisbane Port Moresby ----------------------------------------------------------------------- Sam ** Winsome Wylva Epi Terri ** Alistair Abigail Guba Vincent Bonnie Bernie Ila Walter Craig Claudia Kama Alex Debbie Des Matere Bessi Evan Erica Rowe Chris Fay Fritz Tako Dianne George Grace Upia Errol Harvey Fiona Ingrid Graham Jim Harriet Kate Inigo Larry Jana Monica Ken Nelson TROPICAL CYCLONE NAMES for the SOUTHWEST INDIAN OCEAN and the SOUTH PACIFIC OCEAN The Tropical Cyclone Warning Centre (TCWC) at Nadi, Fiji, has tropical cyclone warning responsibility for the South Pacific east of 160E and from the equator to 25S. The Meteorological Service of New Zealand at Wellington has warning responsibility for waters south of 25S, but almost all tropical cyclones in this basin form north of 25S. When a rare cyclone forms in the Wellington area of responsibility (AOR), it usually will be assigned a name from the Fiji list (such as was done for Tropical Cyclone Gita in February, 1999.) Tropical cyclone warning responsibility for South Indian waters west of 90E are shared by several TCWCs. The Regional Specialty Meteorological Centre (RSMC) for the region is the office of Meteo France on the island of La Reunion. However, following a long-standing practice, the sub-regional centres at Mauritius and Madagascar share the responsibility for actually naming tropical storms with Mauritius naming systems east of 55E and Madagascar covering the area west of 55E. RSMC La Reunion issues warnings for the basin independently of these sub-regional centres, but only advises regarding when or when not to assign a name to a developing cyclone. (I included the Southwest Indian names in the August summary but am repeating them here for completeness.) Names for the 2000-2001 season (** indicates name has already been assigned): Southwest Indian South Pacific ----------------------------------------------------------------------- Ando ** Nancy Oma Beni Bindu ** Oda Paula Cilla Charly ** Premnath Rita Dovi Dera Quirin Sose Eseta Evariste Rakoto Trina Fili Francois Suzy Vicky Gina Gaby Tovo Waka Heta Hans Ursula Yolande Ivy Idriss Vimla Zoe Judy Jakoba Wenda Ami Kerry Kiran Xino Lanto Yul Mathieu Zoe ************************************************************************* SEPTEMBER HIGHLIGHTS --> Atlantic basin very active with seven named storms --> Active Northwest Pacific basin features two super typhoons *********************************************************************** ***** Topic of the Month for September ***** SEASONAL STATISTICS FOR THE CENTRAL NORTH PACIFIC For the Topic of the Month feature in the July summary I presented some seasonal statistics for the Eastern North Pacific compiled by John Wallace of San Antonio, Texas. This month I am including a similar table for the Central North Pacific--that region of the North Pacific lying between longitudes 180 and 140W. I prefer to consider the entire North Pacific east of the Dateline as one basin (Northeast Pacific), but due to the fact that warnings are handled by two different agencies (TPC/NHC in Miami and CPHC in Honolulu), the areas east and west of 140W are often considered separately. A full description of the seven parameters in the table below would needlessly lengthen this article. Definitions can be found on the Colorado State University Tropical Meteorology site: I will, however, simply explain the abbreviations: NS: Named Storms (includes unnamed storms added in post-analysis) H: Hurricanes IH: Intense Hurricanes NSD: Named Storm Days HD: Hurricane Days IHD: Intense Hurricane Days NTC: Net Tropical Cyclone Activity (%) The statistics given in the following table are based upon all tropical cyclones of tropical storm intensity or higher which either formed in or moved through the Central North Pacific. The various "days" parameters include only the period in which the cyclone was located between longitudes 180 and 140W. Three storms which formed west of the Dateline and moved eastward into the Central North Pacific are not included due to their omission from the Northeast Pacific Best Track file. These storms are: Virginia (1968), Carmen (1980), and Skip (1985). The latter two actually formed as tropical depressions in the Central Pacific, moved westward across the Dateline and were named by JTWC, then recurved eastward and existed briefly as tropical cyclones east of longitude 180. However, for Hurricane John of 1994, the time spent east of the Dateline after it had recurved and moved northeastward is included in the NSD and HD parameters. Central North Pacific Seasonal Parameters 1966 - 1999 YEAR NS H IH NSD HD IHD NTC 1966 3 1 0 8.75 2.25 .00 54 1967 3 1 0 11.00 .50 .00 51 1968 0 0 0 .00 .00 .00 0 1969 0 0 0 .00 .00 .00 0 1970 2 1 0 5.50 .50 .00 36 1971 2 1 0 3.25 1.75 .00 37 1972 5 1 1 20.75 9.00 1.75 170 1973 2 1 1 10.50 4.50 .25 92 1974 2 1 1 4.50 3.50 .25 77 1975 1 1 0 3.00 .75 .00 26 1976 1 1 0 8.75 4.75 .00 53 1977 0 0 0 .00 .00 .00 0 1978 6 4 2 30.00 16.25 2.75 301 1979 0 0 0 .00 .00 .00 0 1980 1 1 0 4.50 2.75 .00 37 1981 2 0 0 3.00 .00 .00 17 1982 10 5 1 30.25 6.50 1.50 252 1983 4 1 1 12.00 1.50 1.25 110 1984 4 1 1 10.25 2.75 .25 96 1985 5 4 2 18.25 12.75 2.75 260 1986 2 2 1 6.50 4.25 1.50 116 1987 4 1 0 12.50 4.25 .00 75 1988 4 2 2 14.25 10.75 4.25 238 1989 1 1 0 4.50 2.50 .00 36 1990 3 1 1 10.75 2.75 2.25 123 1991 2 2 0 4.50 1.50 .00 50 1992 7 2 2 16.25 8.50 2.50 223 1993 3 2 1 13.25 8.50 1.50 151 1994 8 5 3 34.00 18.50 12.75 527 1995 0 0 0 .00 .00 .00 0 1996 0 0 0 .00 .00 .00 0 1997 4 0 0 11.50 .00 .00 44 1998 1 1 0 2.00 .25 .00 22 1999 2 2 1 9.00 7.25 .25 112 Avg. 2.8 1.4 0.6 9.5 4.1 1.1 100 In terms of NTC the year 1994 stands head-and-shoulders above all other years. It is not the year with the highest number of named storms and ties 1982 for the highest number of hurricanes, but in terms of HD and IHD it ranks far above all other years. All three of the intense hurricanes that prowled the waters of the Central Pacific that summer were Category 5 hurricanes on the Saffir/Simpson scale--Emilia, Gilma, and John. Hurricane John lasted 31 days and holds the record as the world's longest-lived tropical cyclone. John is also the only tropical cyclone on record to travel from the Eastern North Pacific across the Central North Pacific and enter the Western North Pacific, and then move back eastward and re-enter the Central North Pacific. A majority of the tropical cyclones in the Central North Pacific are visitors from east of 140W. Of the 98 tropical storms or hurricanes in the region from 1966-2000 (there were four Central Pacific storms in 2000), 32 actually formed between 140W and the Dateline. Those storms are listed below (an asterisk following the name indicates that the cyclone moved across longitude 180 into the Northwest Pacific basin): 1967 - Sarah * 1985 - Nele 1970 - Dot 1987 - Oka, Peke * 1972 - June, Ruby * 1988 - Uleki *, Wila 1974 - Olive 1990 - Aka * 1975 - unnamed 1992 - Ekeka *, Hali, Iniki 1976 - Kate 1993 - Keoni * 1978 - Susan 1994 - Li *, Mele, Nona 1982 - Akoni, Ema, Hana, Iwa 1997 - Oliwa *, Paka * 1984 - Keli, Lala, Moke 2000 - Upana ++, Wene && ++ - Upana weakened and warnings were dropped by CPHC, but the remnant LOW moved into the NWP basin, redeveloped, and was named Chanchu by JMA && - Wene actually formed as a tropical depression just west of the Dateline, moved northeastward, and reached tropical storm intensity near 179W *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for September: 1 tropical depression 2 tropical storms 5 hurricanes NOTE: Much of the information presented below was obtained from the TPC/NHC discussion bulletins issued with every regular advisory. All references to sustained winds imply a 1-min averaging period unless otherwise noted. Atlantic Tropical Activity for September ---------------------------------------- After getting off to a slow start, the month of September became very active in the latter half. Seven named tropical cyclones formed, plus one short-lived tropical depression. The only other two years on record in which seven storms formed in September are 1949 and 1988. Also, five of the cyclones reached hurricane intensity--above normal, but not all that uncommon--five hurricanes formed in September, 1998. Two storms, Gordon and Helene, made landfall along the Gulf Coast of the U. S. as tropical storms. Hurricane Keith formed at the end of the month in the northwestern Caribbean and quickly intensified into a Category 4 hurricane on the Saffir/Simpson scale just off the coast of the southern Yucatan Peninsula. After stalling just offshore, the hurricane weakened and made landfall near the Belize/Mexico border as a strong tropical storm. Keith later re-intensified in the Bay of Campeche and made a final landfall in eastern Mexico north of Tampico as a strong Category 1 hurricane. Hurricanes Florence, Isaac, and Joyce as well as weak Tropical Storm Ernesto all remained at sea. A short-lived and generally weak tropical depression formed in the northwestern Gulf of Mexico on 8 September and moved inland the next day near the mouth of the Sabine River which forms the boundary between Louisiana and Texas. The depression was spawned by the interaction between a low-level trough which had persisted over the Gulf and a convective cluster associated with a tropical wave. Squalls with gusts to tropical storm force occurred well to the east of the center at some buoys and a C-MAN station near Southwest Pass. More information on this system can be found in the official report authored by Jack Beven on TPC/NHC's website: . The official TPC/NHC tropical cyclone reports prepared by the Hurricane Specialists are now available for most of the 2000 Atlantic basin tropical cyclones. The reports are very interesting and informative, and links to them can be found at the following URL: . Since I am running so far behind schedule, and since I think it highly likely that just about every person who reads these summaries has access to the internet, I am going to trim down the amount of material I write about the remaining Atlantic cyclones--primarily including a few items of interest which are not mentioned in the official NHC reports. Tropical Storm Ernesto (TC-08) 2 - 3 September ------------------------------- The first mention of the tropical wave which ultimately developed into Tropical Storm Ernesto was in a Tropical Weather Outlook issued by TPC/NHC early on 29 August. A tropical wave was passing south of the Cape Verde Islands. Whether or not this was the same wave which moved off the coast of Africa on 27 August or a second wave on its heels isn't completely clear. A 1010-mb LOW was noted on the wave axis at 1800 UTC, and the Tropical Weather Outlook at 2230 UTC on the 30th indicated that convection had become better organized. At the time upper-level winds in the region a few hundred miles west of the Cape Verdes were favorable for continued development, but became less favorable later as the system moved farther to the west. The wave was given a poor chance for development on 31 August due to hostile winds aloft, but at 0900 UTC on 1 September a Special Tropical Disturbance Statement was issued which indicated that strong thunder- storms had developed overnight near the center of circulation and that a depression could possibly form during the day if the convection persisted near the LLCC. However, the system was moving west- northwestward at 17-22 kts and this rapid translational speed was judged to be an inhibiting factor for significant strengthening. The system remained well-organized and by the afternoon of the 1st it appeared that a depression might be forming. Advisories were initiated on TD-08 at 0300 UTC on 2 September with the poorly-defined center estimated to be about 750 nm east of the island of Martinique. The depression was moving slightly north of due west at about 12 kts. Deep convection increased significantly overnight near the LLCC and TAFB assigned a Dvorak rating of T2.5 at 0600 UTC. This, in conjunction with some 30-kt wind reports from a buoy well north of the center, was the basis for upgrading the depression to Tropical Storm Ernesto at 0900 UTC. Outflow had improved somewhat to the north, but the cyclone was still experiencing the effects of southerly shear. Ernesto never intensified beyond minimal tropical storm intensity. The hostile upper-level environment over the eastern Caribbean which had sheared Chris and Debby persisted for two or three weeks and Ernesto became its next victim. Such a highly unfavorable pattern during the peak of the hurricane season is rather unusual, especially in a year which was overall quite active. Had this feature not been present, and Chris, Debby and Ernesto been allowed to have developed into well-organized hurricanes, things could have been very different for the U. S. East Coast. Satellite images around 0000 UTC on the 3rd revealed that the LLCC was located on the edge of the deep convection but close enough to justify keeping Ernesto as a tropical storm. In addition a QuikScat pass at 02/2200 UTC showed several places with tropical storm-force winds to the north of the center. The weak tropical storm continued to move to the west-northwest at about 15 kts on 3 September, and the large upper-tropospheric trough situated about 15 degrees to the west continued to create strong south- southwesterly shear over the cyclone. During the afternoon the cloud pattern began to deteriorate rapidly and low-level cloud motions indicated that a closed circulation no longer existed, so Ernesto was downgraded to a tropical wave at 2100 UTC. The final advisory position was roughly 300 nm northeast of Guadeloupe. Interestingly, as was the case with Debby, some of the numerical models had forecast that Ernesto would strengthen in spite of the shearing environment. And again, as with Debby, this failed to materialize. NOTE: The official report on Tropical Storm Ernesto, authored by Miles Lawrence, is now available on TPC/NHC's website at the following URL: . Hurricane Florence (TC-10) 11 - 18 September --------------------------- Hurricane Florence was a Category 1 hurricane on the Saffir/Simpson scale which formed in the subtropics and later brushed the island of Bermuda as it accelerated to the northeast. The official storm report on Florence, prepared by James Franklin, can be found at the following URL: . I recommend that interested readers first connect to TPC/NHC's website and read James' report, which contains a tabular listing and plot of the analyzed "best track" as well as plots of meteorological information. Florence serves as a good illustration of the revisions to the operational track and (especially) intensities that are often made during the post-storm analysis process. The "best track" indicates that Florence had reached tropical storm intensity by 1200 UTC on 11 September--this based on a QuikScat pass. The 1030 UTC Tropical Weather Outlook still referred to the system as a non-tropical LOW but indicated that convection was becoming better organized and that there was a potential for tropical cyclone development over the next few days. The first advisory on the LOW was issued at 11/1500 UTC, classifying the system as Tropical Depression Ten. The discussion bulletin mentioned the earlier QuikScat pass and indicated that a reconnaissance aircraft was on the way to investigate the system. A special advisory was issued at 1800 UTC, upgrading Florence to a 50-kt tropical storm. This was based on a reconnaissance report of winds to 64 kts at 300 m in convection southeast of the center. While the "best track" indicates that Florence reached hurricane intensity for a brief period at 1800 UTC, it should be pointed out that in real- time the storm was not upgraded to a hurricane until 2100 UTC on the 12th. The discussion bulletin issued along with the 11/2100 UTC advisory contains a good example of the sort of decisions the forecaster often has to make on the spot, some of which (as in this case) are later revised after a thorough analysis of all the data. I quote from Discussion Number 3 (5 PM EDT Mon, Sep 11 2000), written in fact by James Franklin: "We are reminded once again that there is no substitute for aircraft reconnaissance observations. While the Dvorak satellite technique estimated an intensity of 35 kts, the recon found a large area of winds at the 1000 ft level in excess of 60 kts, and even a small area of winds in excess of 75 kts on the edge of the convection. This supports surface winds of 60 to 65 kts. I would like to see these winds persist a bit before making Florence a hurricane." Since the convection soon began to wane, the decision was made not to upgrade Florence to a hurricane at the time, but in post-analysis it was apparently felt that the observations from the reconnaissance plane justified upgrading the storm to minimal hurricane status for a 12-hour period. Eric Blake, who wrote a summary for me of Hurricane Alberto, researched the "best track" database and concluded that Alberto was the first known Atlantic hurricane to have reached hurricane intensity three separate times during its history. Remarkably, the same thing happened again just a month later with Hurricane Florence. Florence later passed only 65 nm to the northwest of Bermuda but had no significant effects on the island. There were three drownings along the coast of North Carolina due to rip currents likely related to the storm. In its later stages Florence was headed for the Cape Race, Newfoundland, area but was absorbed by a large extratropical LOW while still to the south of the island. The peak intensity of 70 kts was reached on 16 September when Florence was located about 275 nm north- east of Bermuda. Hurricane Gordon (TC-11) 14 - 19 September ------------------------- Hurricane Gordon was a Category 1 hurricane on the Saffir/Simpson scale which formed in the northwestern Caribbean Sea near the Yucatan Peninsula, reached hurricane intensity in the southeastern Gulf of Mexico, and later weakened to a tropical storm before making landfall in the Big Bend area of northwestern Florida. The official storm report on Gordon, prepared by Stacy Stewart, can be found at the following URL: . I recommend that interested readers first connect to TPC/NHC's website and read Stacy's report, which contains a tabular listing and plot of the analyzed "best track" as well as plots of meteorological information. As the official report points out, Gordon developed from a tropical wave which left the coast of western Africa on 4 September and traveled across the Atlantic and Caribbean. This wave was somewhat interesting in its pre-depression stage in the northwestern Caribbean in that for a couple of days its appearance in satellite imagery was suggestive of a tropical depression, but reconnaissance flights on both 12 and 13 September could find no evidence of a low-level circulation, although a well-defined mid-level circulation was quite apparent. Finally on the 14th a reconnaissance plane was able to find a small circulation just off the Yucatan coast, so advisories were initiated on Tropical Depression Eleven at 1500 UTC. Immediately after being upgraded to a depression, the system moved inland over the Yucatan Peninsula. During the morning of 15 September the low-level center reached the north-central coast of Yucatan while the mid-level center and deeper convection were farther to the east. Richard Henning, a meteorologist at Eglin AFB and a member of the 53rd Weather Reconnaissance Squadron, The Hurricane Hunters, was present on a flight into the depression on the evening of the 15th. Rich related to me that the low-level center, which had for much of the day been "wandering along the beach" to the west of the mid-level center, suddenly seemed to be "sucked into" the deeper convection to the east or northeast. That flight found 59-kt winds at 450 m just east of the center, leading to Tropical Storm Gordon's being named at 2100 UTC. Based on a ship report Gordon was upgraded to a hurricane in a special update issued at 2145 UTC on the 16th. The storm reached its estimated peak intensity of 70 kts around 0600 UTC on 17 September. Operationally, the highest MSW assigned to Gordon was 65 kts, the slight increase of 5 kts being decided upon during post-storm analysis. There was another interesting aspect of Gordon which should be pointed out. The peak flight-level wind found by a reconnaissance aircraft was 89 kts at 0544 UTC on 17 September. The accompanying minimum CP found at that time was 992 mb. A little over two hours later, at 0805 UTC, the pressure had fallen 11 mb to 981 mb--the minimum for the storm--but the maximum flight-level wind found during that pass was only 80 kts. Gordon weakened to a 55-kt tropical storm before making landfall due to the combined effects of southwesterly shearing and entrainment of drier air into the circulation. The center of the cyclone made landfall just northwest of Cedar Key, Florida, near the mouth of the somewhat-famous Suwanee River. Damage from the storm was relatively light--mainly downed trees and power lines. Some homes along the Florida west coast between Tampa Bay and Cedar Key had minor roof damage and some coastal roads were flooded. The damage estimate for the U. S. is $10.8 million. One death occurred when a surfer drowned in heavy seas near Pensacola, Florida, as Gordon was making landfall farther to the east. There were 23 deaths reported in Guatemala due to flooding from heavy rains in mountainous areas which may have been due in part to the depression and pre-depression stages of Gordon in the northwestern Caribbean and over Mexico's Yucatan Peninsula. Tropical Storm Helene (TC-12) 15 - 25 September ------------------------------ Tropical Storm Helene was a fairly long-lived and much-traveled tropical cyclone which reached tropical storm intensity twice and made landfall along the Florida Panhandle coast near Fort Walton Beach. The official storm report on Helene, co-authored by Eric Blake and Lixion Avila, can be found at the following URL: . The author recommends that interested readers first connect to TPC/NHC's website and read Eric's and Lixion's report, which contains a tabular listing and plot of the analyzed "best track" as well as plots of meteorological information. Like Florence, Helene serves as a good illustration of the revisions that may be made in the "best track" as compared with the real-time operational warnings. The most notable change was the reclassification of the system as a tropical storm after it emerged back into the North Atlantic off the Virginia coast on 24 September. No operational advisories were issued for this portion of Helene's life--the storm being carried operationally as a non-tropical system. The global tropical cyclone tracks file for September, which I disseminated in late October, indicated that Helene had subtropical characteristics during this phase of its history. This was based on the opinion of David Roth, a meteorologist at HPC who has extensively studied hybrid and subtropical systems. During post-storm analysis it was decided to treat the system as a tropical storm even though its appearance was not exactly that of a classic tropical cyclone. Reports from a ship, the Neptune Olivine, were extremely helpful in determining the intensity of Helene during its North Atlantic phase. The analyzed "best track" reports a peak MSW of 60 kts at 25/0600 UTC--the same as the peak intensity attained by Helene while in the Gulf of Mexico. Helene developed from a tropical wave which left the African coast around 10 September. The system was upgraded to Tropical Depression Twelve on 15 September about 500 nm east of the island of Guadeloupe. However, the next day the system appeared to be weakening and a reconnaissance flight discovered that there was no longer a closed low-level circulation, even though winds to 55 kts at 450 m were found north and east of the wave. The residual wave continued to move west- ward through the Caribbean Sea, and on the afternoon of the 19th a NOAA plane found that the depression had regenerated in the north- western Caribbean near Grand Cayman and was moving west-northwestward. All conditions seemed to be on "go" for continued intensification of the regenerated TD-12, but the system remained very weak with minimal convection through the 20th. It is possible that an area of convection in the southwestern Gulf of Mexico, which on 19 September seemed to be rapidly organizing, may have helped to inhibit the depression from strengthening further at the time. By the 20th the outflow from Tropical Storm Norman in the Pacific was streaming across the Bay of Campeche and the disturbance in that area weakened. TD-12 moved into the southeastern Gulf of Mexico late on the 20th, and by the early morning of 21 September the satellite signature had improved with deep convection forming near the center and enhanced outflow evident. Buoy reports indicated that the cyclone was strengthening, and during the morning a reconnaissance flight found winds of 58 kts at 450 m. An update was issued at 1300 UTC upgrading the depression to Tropical Storm Helene, and the first regular advisory was issued at 1500 UTC. The highest MSW reported operationally for Helene was 55 kts, but in post-analysis this was increased to 60 kts at 1800 and 22/0000 UTC. Increased shear caused the storm to later weaken and also caused most of the associated active weather to be displaced well to the east of the center. The center of Helene made landfall about 7:00 AM locally (1200 UTC) near Fort Walton Beach, Florida, with winds of only 35 kts and quickly weakened into a depression. The author spent the night of the 21st in Fort Walton Beach at the home of a friend and co-worker. We had dinner in a restaurant over- looking the beach and then walked out to the end of a fishing pier which extends about 300 ft (~100 m) into the Gulf. We estimated that the waves breaking on the beach were about 3 ft (1 m) in height. At one point during the wee hours of the morning I woke up and looked out the door to see the rain coming down nearly horizontally, but the next morning there were only a few small twigs and pine needles on my car. At around 7:00 AM--the time of landfall--I walked outside and the wind was completely calm. The only fatality reported in association with Tropical Storm Helene was a man killed in an F2 tornado in South Carolina as the tropical depression moved through the region on 23 September. Near Tallahassee, Florida, the storm dumped almost 230 mm of rain, causing extensive flooding, but no damage figures are available. Hurricane Isaac (TC-13) 21 September - 2 October ------------------------ Hurricane Isaac was a classically-forming Cape Verde hurricane which followed a rather smooth parabolic track over the eastern and central Atlantic. The storm attained Category 4 status on the Saffir/Simpson scale as its winds climbed to an estimated peak of 120 kts--tying Isaac with Hurricane Keith as the most intense hurricanes of the season. The official storm report on Isaac, prepared by Richard Pasch, can be found at the following URL: . I recommend that interested readers first connect to TPC/NHC's website and read Richard's report, which contains a tabular listing and plot of the analyzed "best track" as well as plots of meteorological information. Since my purpose here is to complement the storm report already available on NHC's website, and since Isaac remained far from any populated shores, there is not a whole lot to write. A few slight modifications to the operational MSW values were made in the "best track". Operationally, Isaac was not upgraded to a hurricane until 23/1800 UTC, but the "best track" shows it reaching hurricane intensity six hours earlier. Between its two periods of Category 3 intensity, when the hurricane underwent some shearing, the operational MSW did not drop any lower than 80 kts, but in the post-storm review the MSW was decreased to 75 kts for a twelve-hour period on 26 September. Isaac's initial intensification to Category 3 status in the far eastern Atlantic on 24 September was quite unusual, especially considering that its winds climbed to 105 kts over SSTs less than 27 C. Another very interesting aspect of the storm becomes evident when perusing a tracking map of all the Atlantic tropical cyclones for the season. Hurricane Isaac's track was amazingly close to the track of earlier Hurricane Alberto. Both cyclones began in almost the same location, and the two tracks veritably lie on top of each other in several spots. Isaac passed about 200 nm farther east of Bermuda than did Alberto, but the storm's tracks cross again near 50W. At this point Alberto's track begins the huge week-long clockwise loop whereas Isaac's continues on a straight shot toward the British Isles. Although Isaac remained far from U. S. shores, passing about 450 nm east of Bermuda, swells generated by the large, powerful hurricane were responsible for the capsizing of a boat off Long Island. One man on board the boat reportedly drowned before he could be rescued. Hurricane Joyce (TC-14) 25 September - 2 October ------------------------ Joyce was another Cape Verde hurricane which formed on the heels of Isaac. However, in stark contrast to the earlier hurricane, which recurved and intensified into a Category 4 storm on the Saffir/Simpson scale, Joyce followed a slightly oscillating westward track at low latitudes--always remaining south of 13N--and peaked at only 80 kts. The official storm report on Joyce, prepared by Miles Lawrence, can be found at the following URL: . I recommend that interested readers first connect to TPC/NHC's website and read Miles' report, which contains a tabular listing and plot of the analyzed "best track" as well as plots of meteorological information. After Joyce had formed in the eastern Atlantic on 26 September not all that far away from Hurricane Isaac--at 26/1200 UTC Joyce was only about 700 nm southeast of the hurricane--it seemed logical to think that the new storm would follow a track similar to Isaac's. However, a mid-level ridge which had built in behind the earlier storm kept Joyce moving on a westward track throughout its entire life. Probably the biggest question which has been raised regarding Joyce is: What caused the storm to dissipate in an environment where shear was not particularly great and there were plenty of warm SSTs? There seems to be a fairly good consensus of opinion that dry air entrainment was the major factor in Joyce's weakening when other factors seemed to be favorable for a major hurricane to approach the Lesser Antilles. Roger Edson argues that a lack of southwesterlies to the south of the cyclone, and hence a lack of tropical moisture from the equatorial region, was the major reason for the drier-than-normal environment surrounding Joyce. Hurricane Joyce was very similar in many regards to Hurricane Cora of August, 1978. Both storms formed in the same general area, reached an estimated peak intensity of 80 kts, weakened as they approached the Windward Islands, and dissipated in the southeastern Caribbean Sea. The annual seasonal summary article for 1978, as published in _Monthly Weather Review_ (April, 1979, Vol. 107, No. 4), coincidentally was also written by Miles Lawrence. To quote from that article: "Rapid dissipation as Cora moved into the southeast Caribbean is not an unexpected event in this area. The entrainment of continental air from South America limits convective processes in the storm and strong tradewind easterlies produced by the geographic heat low disrupt the low-level circulation. Large-scale criteria were generally favorable otherwise for intensification, and yet the circulation completely disappeared within 24 hrs, which indicates the significance of continental influences." Another interesting tidbit from Miles' earlier report was the state- ment that Cora was only the third Atlantic tropical cyclone to be upgraded to hurricane status solely on the basis of satellite pictures. Prior to 1978 the only Atlantic hurricanes so classified on the basis of satellite imagery alone were Doris and Gladys of 1975. It's rather interesting to realize that what is nowadays a routine occurrence was, less than a quarter-century ago, considered a new and novel thing. Hurricane Keith (TC-15) 28 September - 6 October ------------------------ Hurricane Keith was one of the two most intense hurricanes of the season, the other being Hurricane Isaac. Both hurricanes reached Category 4 status on the Saffir/Simpson scale with the MSWs peaking at 120 kts. While Isaac remained far out in the mid-Atlantic, Keith wandered slowly around the extreme northwestern Caribbean Sea, brushing coastal regions of Mexico's Yucatan Peninsula and Belize as well as some offshore islands before weakening and making landfall as a strong tropical storm. The storm later re-intensified over the Bay of Campeche and made a second landfall in northeastern Mexico as a strong Category 1 hurricane. The official storm report on Keith, prepared by Jack Beven, can be found at the following URL: . I recommend that interested readers first connect to TPC/NHC's website and read Jack's report, which contains a tabular listing and plot of the analyzed "best track" as well as plots of meteorological information. Several months ago I asked Eric Blake if he would consider writing a report on Keith for me. Eric agreed to do so, and the remainder of the discussion of this hurricane is Eric's report basically as he sent it with only minimal editing by myself. I'd like to extend a very special thanks to Eric for writing the summary for Hurricane Keith. Keith's origins can be traced to a tropical wave that emerged off the west coast of Africa on 16 September. The wave continued moving slowly westward without development as it encountered strong vertical shear. The first signs of significant development were on 27 September when convection flared near the center of the system in the western Caribbean Sea. Aircraft reconnaissance found a 1004-mb tropical depression on 28 September just east-northeast of the Honduran coast- line, moving slowly in a general northwesterly direction. The depression was under a well-defined upper anticyclone and it intensified into a tropical storm the next day. Keith then began a period of unexpected rapid intensification shortly after 1800 UTC on the 29th when it was only about 125 nm from land. Well-defined banding features were noted and it became a hurricane on the 30th. Its pressure fell from 1000 mb to 939 mb in about 36 hours and the storm reached its estimated maximum intensity of 120 kts on 1 October. During this intensification a large area of cloud tops with temperatures colder than -80 C were noted and a circular, 15-20 nm wide eye emerged. The hurricane continued to drift slowly to the west during this time, very near the coast of Belize with its dangerous eyewall over the coastal islands. There were also reports of the shallow Bay of Chetumal emptying with the constant north to northwest winds. The cyclone meandered for about two days off the Belize coast, drifting slowly and erratically in a general westward direction. The hurricane weakened gradually due to increasing easterly shear, some mixing of cooler water from well below the surface of the northwest Caribbean Sea, and increasing interactions of the inner core with land. Keith made a first landfall as a Category 1 hurricane on Ambergris Cay near 2300 UTC on the 2nd. However, this island likely received winds of Category 3 strength or higher as it was in the hurricane's powerful eyewall for about 24 hours before the hurricane weakened. Keith diminished further into a tropical storm as it drifted westward, crossing the Belize coastline with a MSW of 60 kts around 0300 UTC on the 3rd between Belize City and Chetumal, Mexico. The system continued to weaken as it headed inland, becoming a tropical depression at 1200 UTC on the 3rd. It changed direction slightly, moving more to the west-northwest. A ridge over the northern Gulf of Mexico was providing a stronger steering current, and a gradual acceleration took place over the next two days. The environment was favorable for re-intensification over the Gulf of Mexico, and Keith intensified into a strong Category 1 hurricane before landfall. Weather radar from Tampico indicated that the system was well-developed when it made landfall, with a pronounced eye and well-defined spiral bands. The hurricane moved ashore about 40 km north of Tampico, Mexico, around 1800 UTC on the 5th with maximum sustained winds near 80 kts. Media reports indicate that 19 people died as a result of the storm, with most of the deaths occurring in Belize and Nicaragua due to flooding. Keith's slow motion led to incredibly large rainfall totals, most notably over 813 mm at the Phillip Goodson International Airport in Belize City. It is likely that higher amounts fell to the east and north closer to the core of the stalled-out hurricane. The maximum intensity of Keith is not an easy thing to determine. Aircraft reconnaissance were only flying twelve-hour missions near the probable time of maximum intensity, common practice in the northwestern Caribbean. The Hurricane Hunter nearest the time of maximum intensity only recorded a flight level wind of 118 kts at 700 mb, which normally would not support an intensity of 120 kts in the best-track. However, a dropsonde indicated peak winds of 153 kts in the southeastern eyewall at a level of about 883 mb. This dropsonde did not report winds below 904 mb, though. In addition another sonde in the southwestern eyewall recorded a wind of 122 kts about 30 m off the surface, and a wind of 140 kts at a level of about 70 m. Unfortunately, neither of these dropsondes recorded winds near the surface. However, Keith's convection was very intense and it seems plausible that the strong winds at 30 m could have easily been transported to the surface. The maximum flight-level wind at 850 mb was 133 kts, which would reduce to about 115 kts at the surface. However, this maximum wind was recorded more than 16 hours AFTER the minimum pressure was recorded in Keith. It appears that the winds were actually increasing more at the surface than at the 700-mb level and the normal flight-level-to-surface reduction factors do not apply well to this hurricane, or perhaps any rapidly-developing storm. Another interesting point is that objective T-numbers on Keith exceeded 7.0 for a number of hours, equating to an intensity of 140 kts or higher. This seems unlikely given twelve-hour Air Force reconnaissance and is another example of the benefit of having some ground truth observations. The minimum pressure estimation of Keith requires some further explanation. The lowest central pressure reported by a dropsonde was 942 mb, but this sonde reported a surface wind exceeding 40 kts. This indicates that the sonde likely did not hit the area of lowest pressure, and the National Hurricane Center has estimated a minimum central pressure of 939 mb for the best-track database. It is also worth noting that this storm gave forecasters a hard time at the National Hurricane Center, especially while it was still in the Caribbean Sea. Most of the forecasts issued had an error in both intensity and track that were well above the ten-year mean. There does appear to be some similarities with Hurricane Mitch in 1998, which was in the same general location at the same basic time of year. A comparison between the two storms shows that forecasts for both storms were trying to take the storms too quickly to the north whereas both hurricanes were generally stationary in the northwestern Caribbean for a number of days, and neither was forecast to rapidly intensify. *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for September: 3 tropical storms 1 hurricane NOTE: Much of the information presented below was obtained from the TPC/NHC discussion bulletins issued with every regular advisory (CPHC for locations west of 140W.) All references to sustained winds imply a 1-min averaging period unless otherwise noted. Northeast Pacific Tropical Activity for September ------------------------------------------------- The average number of tropical storms forming in the Northeast Pacific basin in September is about three with two reaching hurricane intensity. This year four tropical cyclones formed during the month but only one became a hurricane, the other three systems being short- lived, minimal tropical storms. The hurricane, Lane, remained offshore but did, in its later stages, move somewhat farther north than usual, dissipating well to the west of San Diego, California. Tropical Storms Miriam and Norman, although weak, did produce some slight effects along portions of the Mexican coastline. Kristy was a very brief storm which was a minimal tropical storm for only about 18 hours on 2 September about halfway between Mexico and Hawaii. Tropical Storm Kristy (TC-13E) 31 August - 3 September ------------------------------- Tropical Storm Kristy was a short-lived, minimal tropical storm which blossomed briefly about halfway between Hawaii and Mexico. The storm was the easternmost developing disturbance associated with an outbreak of enhanced convective activity in the Central and Eastern North Pacific regions in late August, the others being Tropical Storm John and an unnamed system south of Hawaii for which no warnings were issued (which I dubbed "Mu" based on an opinion from Mark Lander that tropical storm intensity was likely reached). (See the August summary for discussions of those two systems.) The earliest mention by TPC/NHC of the pre-Kristy disturbance seems to have been in a Tropical Weather Outlook issued at 1700 UTC on 29 August. The system was located over 1100 nm southwest of Cabo San Lucas and contained minimal thunderstorm activity. Over the next couple of days the disturbance drifted slowly westward and gradually became better organized. Advisories were initiated on TD-13E at 2100 UTC on 31 August with the center located roughly 1425 nm west-southwest of Cabo San Lucas or about 1325 nm east-southeast of Hilo, Hawaii. The depression was sheared with the LLCC located to the northeast of the main area of convection, and the initial intensity was set at 25 kts. TD-13E remained essentially stationary for the next day or so, being embedded in a large col region in the subtropical ridge axis, and was slow to intensify. Last visible images on 31 August as well as a SSM/I overpass at 0605 UTC on 1 September showed a good mid-level circulation, but at the lower levels the circulation was broad with possible multiple vortices and little deep convection near the main circulation center. A large convective burst developed over the center around 01/0800 UTC which led to the MSW being bumped up to 30 kts. This burst soon faded away, but a second burst occurred during the morning and was a little better organized than the first with a weak banding pattern around the center. By 02/0000 UTC satellite intensity estimates from both TAFB and SAB had reached 35 kts, so the depression was upgraded to Tropical Storm Kristy at 0300 UTC. However, overnight the storm lost most of its deep convection and did not intensify beyond minimal tropical storm intensity. Convection fluctuated and remained somewhat disorganized, but by 02/1800 UTC the low-level center was completely exposed and Kristy was downgraded to a depression. The warning positions had suggested a slow westward drift, but visible images warranted a relocation of the center back eastward to near its point of origin. By 0000 UTC on 3 September the LLCC had become elongated and separated from a few spots of deep convection. The system appeared to be embedded in the ITCZ, and the final advisory was issued at 0300 UTC. Hurricane Lane (TC-14E) 5 - 14 September ------------------------ The final hurricane in the NEP basin this season formed from a tropical wave which left the coast of Africa around 19 August. The wave propagated westward across the Atlantic and Caribbean, reaching the Eastern Pacific by the 30th. A 1008-mb LOW had formed by 3 September southwest of the Gulf of Tehuantepec. Ship reports early on the 3rd indicated winds as high as 35 kts in squalls, but the low- level center appeared to be displaced well to the southeast of the strongest convection. The disturbance continued to move to the west- northwest off the southern Mexican coast, and by the afternoon of the 4th showers and thunderstorms had become more concentrated near the LOW which was located a couple hundred miles south-southeast of Manzanillo. Advisories on TD-14E were begun at 1500 UTC on 5 September as the system exhibited some banding features and strong convection near the estimated center which was located approximately 200 nm south-southwest of Manzanillo, Mexico. The depression was upgraded to Tropical Storm Lane on the next advisory with satellite intensity estimates solidly supporting tropical storm intensity; however, a ship with call sign VRUZ9 had recently reported winds of only 12 kts near the center, thereby casting some doubt upon the Dvorak intensity estimates. Lane continued to intensify in the near-term. Winds were up to 45 kts by 06/0300 UTC and were further increased to 50 kts at 0900 UTC. Ship VRUZ9 reported winds of 27 kts about 70 nm north of the center at 0000 UTC, so the strongest winds were confined to a very small area near the center. There was little evidence of any banding features, and Lane's center early on 6 September appeared to be near the northern side of a convective burst. Around 1200 UTC vessel ELX27 reported west winds of 30 kts and a pressure of 1003 mb about 80 nm south of the estimated position of the center. Some evidence of northeasterly shear was beginning to be seen over the storm which put a halt for the moment to the intensification process. Lane was embedded in a broad low- to mid-level tropospheric trough which extended westward from the coast of Mexico to near 120W. This steering environment caused the cyclone's westward progress to slow and come to a halt. Visible pictures around 1800 UTC revealed that the partially-exposed LLCC was located to the southeast of the previous position estimates. Tropical Storm Lane's appearance continued to deteriorate as it became trapped in a large ITCZ-like band of low-level cyclonic flow and convergence which competed with the storm's inflow. The northeasterly shear also was detrimental to the storm, and the MSW was lowered to 40 kts at 0300 UTC on the 7th as the convection near the center had become increasingly ragged. On infrared imagery Lane appeared as a broad circulation with several clusters of deep convection but without an inner core. Dvorak T-numbers had decreased to T2.5 from TAFB and SAB by 1200 UTC, so the MSW was lowered to 35 kts in the 1500 UTC advisory. Six hours later a banding feature west and south of the center had developed so the intensity was increased to 40 kts; however, at 0300 UTC on 8 September Lane was downgraded to a depression about 325 nm southwest of Manzanillo. The LLCC that was being followed had popped out from under the convection during the afternoon and progressively became less defined, eventually losing its identity within the broad area of low pressure. NHC decided to hang on to Lane as a tropical depression in the interest of avoiding potential confusion in case the larger LOW should consolidate into a tropical cyclone. That decision proved to be a good one as by 0600 UTC Dvorak numbers had jumped into the 45-55 kt range, based on the development of a large, cold CDO-feature. It was impossible to determine from infrared imagery if a LLCC had formed beneath the convection, but the CDO was impressive enough that Lane was re-upgraded to a 35-kt tropical storm. During the 48 hours from around 1200 UTC on 6 September through 1200 UTC on the 8th, Lane had described a somewhat erratically-shaped counterclockwise loop. By 08/1200 UTC the tropical cyclone was moving slowly northwestward under the steering influence of a large mid- and upper-level ridge over northwestern Mexico. The MSW was increased to 55 kts at 2100 UTC based on unanimous Dvorak estimates of T3.5 from the three agencies, and six hours later Lane was upgraded to a 65-kt hurricane about 350 nm south of Cabo San Lucas on the tip of the Baja California peninsula. A 25-nm cloud-filled eye had become visible on satellite images. The storm at this time was moving northwestward at 8 kts. The hurricane-force winds were confined to a very small area near the center, but based upon 0000 UTC ship reports from waters west of Manzanillo, the zone of gale-force winds was expanded out to 275 nm to the northeast--the coastal gales likely due to funneling effects of the high terrain. Lane at this time was a large storm in terms of gales: winds 34 kts or higher covered an area exceeding 500 nm in diameter. The rapid intensification trend which brought Lane up to hurricane force leveled off some. By 1200 UTC on 9 September the MSW was raised to 70 kts as the storm with its banding-type eye passed very near or over Socorro Island where a minimum pressure of 973.7 mb was reported. The hurricane reached its peak estimated intensity of 85 kts at 0000 UTC on 10 September when it was located approximately 200 nm southwest of Cabo San Lucas. The minimum estimated CP was 970 mb, and Lane at this time was sporting an eye 60 nm in diameter. Due to the large size of Hurricane Lane, squalls with strong gusty winds, heavy rain, high seas and pounding surf were forecast to occur along both coasts of the Baja and along the Mexican west coast north of Manzanillo. The peak intensity of 85 kts was maintained for 18 hours and then Lane began to slowly weaken as it began to approach and move over cooler SSTs. The MSW was dropped to 80 kts at 10/2100 UTC even though the storm's convective pattern had become more symmetric. The cloud tops were beginning to warm and Dvorak T-numbers were beginning to come down. Lane continued to slowly spin down as it moved on its north- westerly track well to the west of Baja California. The storm was downgraded to a 60-kt tropical storm at 1800 UTC on the 11th, and by 12/0000 UTC very little convection remained near the system's center. The MSW was lowered to 55 kts on the 0300 UTC advisory and continued to drop with each new advisory. The outflow pattern became increasingly asymmetric and northward-oriented--evidence of increased vertical shear over the system. A trough to the northwest of the storm caused Lane to recurve to the north and northeast. During the evening of the 12th a burst of convection occurred near the center of Lane despite its being located over 21 C waters. Water vapor imagery indicated that the burst was likely due to interaction with a negatively-tilted upper-level shortwave trough passing just southwest of the storm. Lane had weakened into a minimal tropical storm by 0600 UTC on the 13th when it reached the westernmost point of its track about 450 nm west of Punta Eugenia, Mexico. The system was downgraded to a depression at 1200 UTC, and the final warning on Lane was issued at 0300 UTC on 14 September with the center of the swirl of low clouds located about 250 nm west-southwest of San Diego, California. Moisture from Lane spread over portions of California, Nevada, and Oregon. Tropical Storm Miriam (TC-15E) 15 - 17 September ------------------------------- Tropical Storm Miriam was a short-lived, minimal tropical storm which brushed the tip of the Baja California peninsula. The Tropical Wave log prepared by John Wallace does not connect Miriam with a wave of African origin. The first mention of the pre-Miriam disturbance in a TWO from TPC/NHC was at 1700 UTC on 8 September. An area of disturbed weather was then located a few hundred miles south-southeast of the Gulf of Tehuantepec, so it seems very possible that a tropical wave from the Caribbean which had crossed Central America was the precursor of Miriam. The disturbance moved slowly westward for the next several days off the southern Mexican coast. On the 8th and 9th the system seemed to be getting better organized, but it ran into a less favorable environment on the 10th which put further development on hold for a few days. As late as 14 September upper-level winds were still somewhat hostile, but by the 15th conditions were becoming more favorable for development and convection had become more concentrated near the center. The first advisory on TD-15E was issued at 15/2100 UTC placing the center about 175 nm west of Manzanillo, Mexico--south of the mouth of the Gulf of California. Convection associated with the depression disappeared during the diurnal minimum but had begun to make a comeback early on the 16th. Satellite intensity estimates were 35 kts at 0600 UTC, but ship C6LF9, located near the center, reported only 20-kt winds and 1007.1 mb, so the depression was not upgraded at 0900 UTC. The system was upgraded to Tropical Storm Miriam at 1500 UTC with 35-kt winds although the appearance in satellite imagery was not much improved over that of the previous day. Miriam was located about 225 nm west-northwest of Manzanillo moving slowly north-northwestward in the general direction of Cabo San Lucas. Visible satellite images during the day showed an unimpressive-looking system with ragged convection. An upper-level cyclone over the central Baja was producing some southwesterly shear over the storm. The last visible pictures of the day revealed an exposed LLCC south of the previous position and southwest of the deep convection. Nonetheless, Dvorak classifications were slightly higher due to the certainty of the center, and Miriam's MSW was bumped up to 40 kts--the peak for the storm. The cyclone was centered about 125 nm southeast of Cabo San Lucas at this time and was moving north- westward at only 5 kts. Six hours later satellite intensity estimates were still 40 kts but the MSW was dropped back to 35 kts based on a QuikScat wind analysis. By 17/1200 UTC QuikScat data indicated no winds of tropical storm force associated with the system and Miriam was downgraded to a tropical depression near the tip of the Baja peninsula. Satellite imagery during the afternoon revealed that the circulation had dissipated in the southern Gulf of California and the final advisory on Miriam was issued at 2100 UTC. The remnants of the depression were still generating intermittent convection over the southern Gulf and adjacent land areas. Heavy rains in association with Miriam likely fell over portions of the Baja peninsula, but the author has learned of no damage or casualties resulting from this tropical cyclone. Tropical Storm Norman (TC-16E) 20 - 22 September ------------------------------- Like Miriam, Tropical Storm Norman was a minimal tropical storm which had a short career, but unlike the earlier storm, did make landfall in Mexico--twice, in fact. Again, as was the case with Miriam, I am unable, based on the information available to me, to say with certainty whether or not Norman developed from a tropical wave of African origin. The first mention of the pre-Norman system in a TWO from TPC/NHC (1100 UTC on 16 September) indicated that a westward-moving area of disturbed weather was located just southwest of the Gulf of Tehuantepec. This suggests that the disturbance likely did originate on the Caribbean side of Central America. By very early on the 19th disturbed weather extended along and just off- shore from an extensive area of the Mexican coastline: from the Gulf of Tehuantepec to Cabo Corrientes. A weak LOW was embedded in the disturbed area about 200 nm south of Manzanillo but was showing no imminent signs of development. However, during the morning convection began to increase and by afternoon was becoming fairly well-organized. The 4:00 PM PDT Tropical Weather Outlook indicated that a tropical depression could form within the next day or two. The first advisory on TD-16E was issued at 0300 UTC on 20 September. The initial location was roughly 150 nm south-southeast of Manzanillo. Outflow had improved and central deep convection had increased with a large area of very cold cloud tops of -85 to -88 C on the western side of the center. Embedded in a weak steering flow pattern, the depression was drifting northward at only 2 kts. At 1200 UTC ship 3ESU8 reported 38-kt winds and a SLP of 1001.5 mb, and at 1300 UTC ship LADQ4 reported winds to 39 kts and a SLP of 1003.0 mb. Therefore, TD-16E was upgraded to Tropical Storm Norman at 1500 UTC with the MSW estimated at 40 kts. The center of Norman was just south of the coast about 115 nm southeast of Manzanillo or about 75 nm west- northwest of Zihuatanejo. The cyclone still exhibited very cold cloud tops of -83 C and further strengthening was considered a possibility before landfall. Norman at this time was moving north-northeastward at 6 kts. At 1800 UTC Norman's center was difficult to pinpoint but was likely located on the Mexican coastline. Satellite intensity estimates from TAFB, AFWA, and SAB were 45 kts, 45 kts, and 35 kts, respectively, so the MSW remained at 40 kts. Almost immediately after making land- fall, Norman began to track to the west-northwest parallel to and just inland from the coast, likely due to a mid- and upper-level anticyclone located over Mexico. The cyclone was downgraded to a depression at 21/0300 UTC and never regained tropical storm intensity even though the center later re-emerged over water. Norman passed just to the north of Manzanillo around 0600 UTC on the 21st with peak sustained winds estimated at only 25 kts. By 22/0000 UTC the center of the depression had moved back over the Pacific near Cabo Corrientes and was moving at a slightly faster pace toward the northwest. The MSW was increased slightly to 30 kts after the system had moved back over water based on a 22/0105 UTC QuikScat pass. The QuikScat data showed westerly rain-contaminated winds of 35 to 40 kts south of the center, which equates to about 30-32 kts corrected surface winds. A large convective complex was noted north of the center and also inland over Mexico. While environmental conditions would have favored some re-intensification, interaction with the Mexican landmass inhibited any further strengthening of the depression. Norman turned to the north after 22/0600 UTC, and surface reports and first visible pictures on the 22nd indicated that the small circulation center was making landfall near Mazatlan. After moving inland Norman continued to move northward, and the final advisory was issued at 2100 UTC. Some media sources reported that at least 8 persons died in Mexico within 24 hours from a tropical depression on the Gulf coast and from Tropical Storm Norman on the Pacific coast. There was no tropical depression in the Gulf of Mexico during this period, but there was a disturbance in the Bay of Campeche which on 19 September did appear to be organizing rapidly at one point, prompting a reconnaissance flight into the area. This area weakened on the 20th as the outflow from Norman streamed across the region. In the city of Tapachula (in the state of Chiapas), four persons died in mudslides and rockslides. Tapachula lies along the extreme southeastern coast near the Guatemalan border, so these fatalities were not associated with Norman. Neither were two deaths which were reported in Veracruz state. However, there were two deaths by drowning reported in Guerrero state which were due to the heavy rains of Norman. The center of Norman made landfall in the state of Michoacan which lies just to the west of Guerrero. ************************************************************************* NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for September: 3 tropical storms ** 2 typhoons ++ 2 super typhoons ** - one of these was treated as a tropical storm only by JTWC, and another is included based upon Mark Lander's assessment that it reached tropical storm intensity ++ - one of these (Sonamu) was not upgraded to typhoon status by JMA NOTE: Most of the information on each cyclone's history presented in the narrative will be based upon JTWC's advisories, and references to winds should be understood as a 1-min avg MSW unless otherwise noted. However, in the accompanying tracking document I have made comparisons of coordinates with JMA (Japan) and the Philippines (PAGASA) when their positions differed from JTWC's by usually 40-50 nm or more. A special thanks to Michael V. Padua, owner of the Typhoon 2000 website, for sending me the PAGASA and JMA tracks. In the title line for each storm I plan to reference all the cyclone names/numbers I have available: JTWC's depression number, the JMA-assigned name (if any), JMA's tropical storm numeric designator, and PAGASA's name for systems forming in or passing through their area of responsibility. Northwest Pacific Tropical Activity for September ------------------------------------------------- An active September followed on the heels of an active August in the Northwest Pacific basin. Five tropical cyclones were named by JMA with four becoming typhoons. (This per JTWC's classification--JMA did not upgrade Sonamu to a typhoon.) Two of the typhoons, Saomai and Shanshan, reached super typhoon status as winds climbed to 130 kts. (Again, this based upon JTWC's 1-min avg MSW values.) Typhoon Saomai passed over Okinawa after weakening from super typhoon status and later made landfall in South Korea. Shanshan spent its entire life east of 165E--an unusual area for a super typhoon to occur. Early in the month Typhoons Saomai and Wukong and Tropical Storm Bopha were all progressing simultaneously for several days. Wukong passed over the extreme southern tip of Hainan Island and made landfall in Vietnam. Bopha followed a very unusual course, being driven southward by the large circulation of Super Typhoon Saomai. The storm moved almost due southward off the east coast of Taiwan and made landfall on the northern end of Luzon. Typhoon Sonamu was a very small typhoon which formed near Iwo Jima and moved northward, remaining east of Japan. Also around mid-month another small TUTT-induced system formed several hundred miles south- east of Japan. No warnings were issued on this system, but Dr. Mark Lander of the University of Guam believes that it reached tropical storm intensity. A track is included for this system, which I have designated with the Greek letter "Nu", in the cyclone tracks file. Finally, near the end of the month, another weak system formed to the north of Wake Island and was designated as Tropical Depression 27W by JTWC. JTWC later upgraded this system briefly to tropical storm status, but JMA carried it only as a depression; hence, it was not named. Super Typhoon Saomai (TC-22W / TY 0014 / Osang) 2 - 18 September ----------------------------------------------- Saomai: submitted by Vietnam, is the Vietnamese name for the planet Venus Saomai was a long-lived typhoon which became the year's third super typhoon in the NWP basin. The storm traced out a long trajectory from its point of origin well to the east of the Marianas which took it directly over Okinawa and eventually into South Korea. Saomai's peak intensity of 140 kts (per JTWC) was reached while southeast of Okinawa, but fortunately the storm had weakened considerably before striking the island, although it was still a potent typhoon. The daily STWO issued by JTWC on 1 September discussed an area of convection located approximately 700 nm east of Guam which apparently had persisted from the previous day. (Unfortunately, I cannot locate the STWO for 31 August.) Convection had been pulsating for a couple of days around a LLCC, but the center was too weak to maintain the convection. An upper-level ridge was over the area with a TUTT to the northwest. CIMSS analysis indicated weak vertical shear over the disturbance and the development potential was upgraded to Fair. A Formation Alert was issued for the system at 02/0130 UTC. Animated satellite imagery indicated improving organization during the previous six hours with convection developing west of the LLCC. Outflow over the disturbance was fair and vertical wind shear was weak. The first warning on TD-22W was issued at 12/1200 UTC, placing the center about 700 nm east-northeast of Guam. The system was smaller than average (about 130 nm in diameter), and a 02/1057 UTC SSM/I pass revealed deep convection increasing near the center and to the west. The environment was favorable for strengthening and JTWC upgraded the depression to a 35-kt tropical storm on the second warning (1800 UTC). The tropical cyclone moved on a straight westerly course on 3 September and began to intensify rather quickly. JMA upgraded the system to a tropical storm at 03/0600 UTC and assigned the name Saomai. By 1200 UTC Saomai had developed a central cold cover with temperatures to -84 C. Outflow was good over the system, and by 1800 UTC the storm was approaching typhoon strength with both JTWC and JMA estimating peak sustained winds of 55 kts (both 1-min and 10-min avg). JTWC upgraded Saomai to a typhoon at 0000 UTC on 4 September with the storm centered approximately 425 nm east-northeast of Guam. The MSW was increased to 70 kts at 0600 UTC since a 04/0236 UTC TRMM pass depicted a developing eyewall; however, infrared satellite imagery at this time did not reveal a warm spot (indicative of eye formation). Saomai continued to increase in intensity on the 4th with JMA upgrading the storm to a typhoon at 1200 UTC. By 1800 UTC the MSW reached an initial peak intensity of 90 kts (per JTWC) while JMA estimated the maximum 10-min avg winds at 70 kts. A warm spot had become evident in imagery; however, the storm was also showing some signs of increasing vertical shear caused by an upper-level anticyclone to the northwest of the typhoon. A TRMM pass at 04/2033 UTC indicated that much of the convection had been sheared to the south of the LLCC, although a narrow band of convection was wrapping into the center from the north. JMA downgraded Saomai to a tropical storm at 0600 UTC on the 5th when the storm was located about 85 nm northeast of Saipan (or about 200 nm northeast of Guam), and JTWC followed suit six hours later. By 1200 UTC Saomai was moving slowly southward, steered by a sub- tropical ridge to its southwest. This southward motion continued until around 0000 UTC on 6 September when the storm reached a point roughly 190 nm east of Guam. The MSW dropped to 55 kts (50 kts per JMA) and maintained this strength for the next 48 hours. A 06/0758 UTC Quik- Scat pass showed that the strongest winds were located in the southeast quadrant. By 0600 UTC the storm had embarked on a northwesterly track which it was to follow for over a week. Tropical Storm Saomai was located about 80 nm east of Saipan at 1800 UTC where a pressure of 991 mb and sustained winds of 15 kts were recorded. Convection was making a comeback with improved banding west and southwest of the center. A low- to mid-level ridge to the northeast of the system was the primary steering influence at this juncture. Around 0000 UTC on 7 September Saomai moved through the Marianas island chain, passing about 60 nm north of Saipan near Anatahan Island. The storm exhibited a partially-exposed LLCC on the northern edge of the convection. After passing the Marianas Saomai continued moving northwestward at around 12-14 kts with little change in intensity or structure. Outflow was good over the southern semicircle but an upper-level LOW to the northeast was inhibiting outflow on the northern side. By 08/0000 UTC the storm's organization had increased and a CDO about 140 nm in diameter had formed. JTWC re-upgraded Saomai to a typhoon, placing the center approximately 400 nm south of Iwo Jima. (JMA, however, did not upgrade the storm to typhoon intensity for another 24 hours.) Hints of a developing eye were seen around 0600 UTC, and JTWC had increased the MSW estimate to 85 kts by 1800 UTC. Deep convection was present over the LLCC and a large inflow was evident in satellite imagery. Typhoon Saomai continued to intensify on 9 September as it plodded in the direction of Okinawa. A 22-nm irregular eye had become visible by 1200 UTC and the MSW was upped to 100 kts. The 1800 UTC warning further increased the winds to 120 kts around a well-defined, 15-nm diameter eye surrounded by intense convection. (JMA's maximum 10-min avg wind estimate had reached 90 kts by this time.) Saomai reached its peak estimated intensity of 140 kts at 1200 UTC on 10 September when the 20-nm eye was centered 280 nm east-southeast of Okinawa. (JMA's maximum 10-min avg wind at this time was 100 kts.) 50-kt winds extended 70 nm to the northeast of the center and 55 nm elsewhere while gales covered an area almost 350 nm in diameter. Super Typhoon Saomai possessed a broad circulation with a fairly tight, intense inner core. The typhoon continued to make a beeline for Okinawa but very fortunately began to slowly weaken. The MSW was lowered to 130 kts at 11/0000 UTC, and by 1800 UTC on the 11th was down to 110 kts. (JMA was reporting 90 kts.) At 1800 UTC Saomai was centered 100 nm east-southeast of Naha Airport, moving toward the west- northwest at 6 kts. A TRMM pass at 11/1647 UTC depicted an intense, symmetric system with a 33-nm circular eye, and animated satellite imagery revealed concentric eyewall development. Typhoon Saomai continued to slowly weaken as it approached and crossed Okinawa. By 12/0000 UTC the eye had become cloud filled and defined solely by the convective bands. Kadena AB (WMO 47931) was reporting northerly sustained winds of 27 kts with gusts to 44 kts. A 12/0045 UTC SSM/I pass depicted a concentric eyewall with strong banding to the south. At 0755 UTC Kadena AB was reporting northerly winds of 48 kts with gusts to 76 kts and a SLP of 958 mb. The 20-nm eye was centered at 12/0600 UTC only about 15 nm southeast of Okinawa (presumably Naha Airport, since the previous JTWC warnings had used that site as a reference point), and the estimated MSW was 100 kts. (JMA's maximum 10-min avg wind had dropped to 75 kts by this time.) The storm crossed over the central part of the island during the late afternoon (local) of 12 September. At 0830 UTC the exact center of Saomai's eye was located about 6 nm east-southeast of Kadena AB, and by 1500 UTC had moved to a position about 36 nm north-northwest of the base. Yoron Island (WMO 47942), north of Okinawa, reported sustained winds (1-min avg) to 65 kts. By 1800 UTC the storm was centered about 65 nm west-northwest of Naha Airport with the MSW estimated at 90 kts (per JTWC). Yoron Island, which was located beneath a strong convective band, reported 63-kt sustained winds (1-min avg) and a SLP of 980.2 mb around 1800 UTC. Kadena AB reported peak gusts to 45 kts and a pressure of 971.7 mb, and was still reporting sustained winds of 28 kts (10-min avg) and gusts to 42 kts at 0000 UTC on the 13th. The heaviest precipitation was confined to the eastern semicircle of the typhoon at this time. After passing Okinawa Typhoon Saomai continued moving rather slowly to the northwest through a weakness in the subtropical ridge. The storm remained in a more or less steady state intensity-wise on 13 and 14 September with the MSW in the 85-90 kt range (per JTWC) and the maximum 10-min avg winds estimated at around 70-75 kts by JMA. At 13/0600 UTC the typhoon's center was located about 320 nm south of Cheju Island, South Korea. A buoy (WMO 22001), located approximately 30 nm north of the center, reported 54-kt sustained winds and a SLP of 962 mb. Six hours later the same buoy was about 15 nm east of the typhoon's center and was reporting 45-kt sustained winds and a SLP of 968 mb. By 1800 UTC Saomai had slowed some in its forward motion and was moving westward at 5 kts. Infrared imagery revealed an irregular, ragged eye, and microwave imagery indicated a thin eyewall with a larger band of convection south of the center. Saomai reached the westernmost point of its long track at around 0600 UTC on 14 September when it was located approximately 185 nm east of Wenchou, China. The storm had intensified slightly from 85 to 90 kts, and began to turn slowly to the north due to a mid-latitude trough to its northwest. Infrared imagery showed that the system was beginning to elongate along a north-south axis. Vertical shear was still weak but forecast to increase as the storm moved farther to the north. By 14/1800 UTC Saomai was indeed beginning to weaken as evidenced by warming of the cloud tops and deterioration of the eye. Microwave imagery revealed a partially-exposed LLCC with convection being advected northward. After recurvature the weakening storm initially moved slowly east-northeastward, then began to accelerate to the northeast. At 1200 UTC on the 15th Saomai passed about 300 nm east of Shanghai, moving north-northeastward at 20 kts with winds of minimal typhoon intensity. Cloud tops had continued to warm and what significant convection remained was isolated near the center of the low-level circulation, although SSM/I imagery showed a very weak convective band in the southeastern quadrant. By 1800 UTC Saomai's center was approximately 80 nm southwest of Pusan, South Korea, and continuing to accelerate toward the coast. JMA had downgraded the typhoon to a tropical storm, and while JTWC was still maintaining Saomai as a minimal typhoon, the remarks in the warning indicated that the storm was beginning to undergo extra- tropical transition. Animated water vapor imagery depicted cold air associated with a major short-wave trough pushing into the system from the coast of China. Saomai made landfall around 2030 UTC at a point approximately 95 km west of Pusan. At 2100 UTC Pusan reported 36-kt sustained winds from the south with a pressure of 979.5 mb. JTWC issued their final warning on the system at 0600 UTC on 16 September with the now-extratropical system located over the Sea of Japan about 170 nm northeast of Seoul, South Korea, and tracking rapidly just east of due north at 28 kts. What convection remained was displaced north of a fully-exposed LLCC. The extratropical remnants of Saomai continued to move northward over the western Sea of Japan, passing back inland near Vladivostok, Russia, and remained identifiable over eastern Siberia for a few more days. Strangely, I cannot locate any references to any damage or casualties caused by this typhoon. If any should become available later they will be reported in a future summary. I did receive some rainfall amounts from Patrick Hoareau of Rennes, France. Naha (on Okinawa) recorded 183 mm in the 48 hours ending at 13/0000 UTC. Dinghai, in China's Zhejiang province, measured 102 mm in the 18 hours ending at 13/0600 UTC--slightly more than half the monthly average of 190 mm. Kaesong, North Korea, recorded a 24-hour total of 147 mm from 15/0000 to 16/0000 UTC. Also, the lowest pressure measured during Saomai's passage across Okinawa that I could find referenced in warnings from JTWC was 958 mb. I seem to recall an e-mail which mentioned a 952-mb reading, but I can not find any record of this in my files. If anyone can confirm this, I'd appreciate it if they would let me know. NOTE: In looking through my files I discovered an e-mail from Mark Lander--which he posted late on 2 September--in which he disagreed with the warning intensity reported in the JTWC warnings for the early part of Saomai's history. I overlooked this when I prepared the September cyclone tracks file back in October. I am including here Mark's preliminary best track which he prepared for Saomai from 02/0000 to 03/0000 UTC. DATE TIME (UTC) LAT LON MSW-1 min (kts) ------------------------------------------------------------- 00 SEP 02 0000 16.1 N 158.6 E 25 (JTWC: none) 00 SEP 02 0600 16.2 N 157.3 E 35 (JTWC: none) 00 SEP 02 1200 16.2 N 156.5 E 40 (JTWC: 25 ) 00 SEP 02 1800 16.3 N 155.7 E 45 (JTWC: 35 ) 00 SEP 03 0000 16.3 N 154.8 E 55 (JTWC: 35 ) Tropical Storm Bopha (TC-24W / STS 0015 / Ningning) 5 - 12 September --------------------------------------------------- Bopha: submitted by Cambodia, is the name of a flower which is used as a little girl's name Tropical Storm Bopha certainly had the most unusual track of any NWP basin tropical cyclone so far this year. The storm formed several hundred miles to the southeast of Okinawa and ahead of the intensifying Saomai. The storm moved west-northwestward and passed near Okinawa just as Saomai was beginning to rapidly deepen into a super typhoon. The large circulation of the intense Saomai drove Bopha on a very unusual southward course parallel to the east coast of Taiwan and eventually into northern Luzon. I am unable to trace the origin of Bopha with certainty due to some missing STWOs. The storm may be related to a disturbance which was mentioned on 1 September, located about 450 nm southeast of Okinawa. Animated visible satellite imagery showed disorganized convection sheared to the west of a LLCC. I do not have the STWO for the 2nd, but the STWO for 3 September indicates that this area of convection had dissipated. No tropical disturbance was mentioned in the STWO for 4 September except the pre-Wukong system in the South China Sea. Unfortunately, I am missing the STWO for the 5th, which was the day that PAGASA initiated warnings on a tropical depression about 500 nm southeast of Okinawa at 0600 UTC, assigning the name Ningning. JMA began including information on the depression in their High Seas Bulletins at 1200 UTC while at the same time PAGASA upgraded Ningning to a tropical storm. JTWC issued a Formation Alert for the system at 05/1600 UTC, followed by the first warning on TD-24W at 1800 UTC. JTWC estimated the MSW at 25 kts, while JMA reported the maximum 10-min avg wind at 30 kts and PAGASA at 35 kts. JMA upgraded the system to Tropical Storm Bopha at 06/0000 UTC when it was centered approximately 550 nm southeast of Okinawa. The system initially moved slowly northeast- ward before curving to the northwest as it came under the steering influence of a low- to mid-level ridge to its northeast. It is interesting that JTWC's intensity estimates were well under those from JMA during the early portion of Bopha's history. JTWC finally upgraded Bopha to a tropical storm at 07/0000 UTC when the system was centered approximately 475 nm east-southeast of Okinawa. The remarks in the JTWC warning indicate that the warning intensity (35 kts) was based upon satellite current intensity estimates ranging from 25 to 55 kts--JMA's 10-min avg wind estimate at the time was 50 kts. Animated satellite imagery depicted a fully-exposed LLCC with convection sheared about 30 nm to the north. A 200-mb analysis indicated that Bopha was under moderate vertical shear beneath the subtropical ridge axis. By 1800 UTC the tropical storm was centered about 200 nm east- southeast of Okinawa and moving west-northwestward at 16 kts. The center was still exposed and satellite intensity estimates ranged from 35 to 55 kts, but the MSW was increased to 45 kts, likely influenced by a report of 38-kt sustained northerly winds from a ship west of Bopha's center. Over the next 12 hours the convection increased in areal extent and became more concentrated over the LLCC, and at 0600 UTC on the 8th Bopha reached its peak intensity of 55 kts (per JTWC). (JMA's estimated maximum 10-min avg wind remained at 50 kts during this period.) The storm was centered at this time about 50 nm south- east of Naha, Okinawa, where 30-kt sustained east-northeasterly winds were reported at the airport (WMO 47936). Bopha continued moving to the west-northwest, passing just to the south of Okinawa. Kadena AB reported a peak wind of 40 kts at 0926 UTC (not sure if this reading is sustained or a gust). By 1800 UTC the cyclone was centered about 125 nm west of Okinawa--this proved to be the northernmost point of its track. Six hours later Bopha was moving south-southwestward at 5 kts due to the influence of the larger and steadily-intensifying Typhoon Saomai, located then about 700 nm to the east-southeast. The tropical storm was also beginning to weaken. Microwave imagery showed a ring of weak convection about the system with some stronger cells wrapping into the LLCC, and QuikScat data indicated very weak winds in the southeast quadrant and an elongation of the wind field. Bopha continued to move south-southwestward roughly parallel to the east coast of Taiwan, passing about 175 nm east of Taipei at 09/0600 UTC. The storm continued to weaken as it experienced shear from Typhoon Saomai. By 0000 UTC on 10 September the storm was located about 120 nm east-northeast of the southern tip of Taiwan. Winds had dropped to 40 kts, but the JTWC warning remarked that the system had moved into a more favorable environment. Convection became better organized with a deep convective band on the western and southern sides spiraling toward the center, and the MSW was upped to 50 kts at 0600 UTC and briefly to 55 kts once more at 1200 UTC. Bopha was at this time located about 115 nm north of Port San Vicente, Luzon, still moving south-southwestward at 11 kts. However, as the cyclone approached northern Luzon, it ran into increasingly stronger vertical shear and began to weaken. At 0000 UTC on the 11th the center had just about reached the coastline of north- eastern Luzon, and the MSW had dropped to 45 kts (40 kts per JMA). The system was being sheared apart with the upper-level clouds streaming to the west-southwest while the LLCC had begun to move to the south-southeast. The JTWC warning for 11/0600 UTC indicated that a synoptic report of 40-kt winds had been reported near the center (which was over Luzon), but the location wasn't specified. Bopha was downgraded to a tropical depression (by both JTWC and JMA) at 1200 UTC when the center was near Ilagan. The dissipating depression subsequently turned eastward and moved back out over the Philippine Sea with the final JTWC warning at 12/0000 UTC placing the center about 125 nm east of Casiguran. Typhoon Wukong (TC-23W / TY 0016 / Maring) 2 - 10 September ------------------------------------------ Wukong: submitted by China, is the king of the monkeys. Featured in the classic novel _Journey to the West_. While Super Typhoon Saomai and the weaker Tropical Storm Bopha were dancing about in the open Pacific, Typhoon Wukong formed in the South China Sea and pursued a fairly straight track westward across the southern tip of Hainan Island and into northern Vietnam, becoming a respectable 95-kt (per JTWC) typhoon along the way. An area of convection formed on 1 September approximately 360 nm north-northwest of Palau. Animated visible satellite imagery showed disorganized convection sheared to the west of a LLCC. As noted in the discussion of Tropical Storm Bopha above, I am missing the STWO for the 2nd. However, PAGASA initiated warnings on the disturbance at 02/0000 UTC, placing the center about 350 nm east-northeast of Catanduanes Island and naming it Maring. Maring initially jogged to the north, then took off on a westerly track towards Luzon. That the system was poorly-organized and difficult to track is evidenced by several huge "jumps" (i.e., relocations). At 03/0000 UTC Maring was relocated approximately 180 nm to the west-northwest of its previous warning position. The STWO issued by JTWC at 0600 UTC also mentions this relocation to a position about 140 nm east of Luzon. JTWC at this time was not treating the system as a depression but did assign a Fair development potential. The PAGASA warning on Maring at 1200 UTC placed the broad center about 75 nm east-southeast of the northeastern tip of Luzon, but at 1800 UTC the depression's center was relocated to a position 200 nm to the west-northwest, or about 75 nm north-northwest of Laoag on north- western Luzon. And at 0000 UTC on 4 September Maring was relocated yet again to a position approximately 165 nm west-southwest of Laoag. In the meantime, the STWO from JTWC at 04/0600 UTC indicated that the disturbance east of Luzon from the previous days had dissipated. The remarks indicated that a LLCC had developed in the South China Sea about 180 nm west of Luzon. This location is very near PAGASA's 0600 UTC position for Tropical Depression Maring. Whether this South China Sea circulation (which ultimately became Wukong) is the same disturbance noted east of the Philippines a few days earlier or a completely new development is perhaps open to question. As the day progressed the system appeared to weaken and PAGASA issued a final warning at 04/1800 UTC. However, six hours later JMA began treating the system as a tropical depression in their High Seas Bulletins, and JTWC issued a Formation Alert at 05/0300 UTC, noting that convection had intensified over the previous few hours near a partially-exposed LLCC. JTWC issued the first warning on TD-23W at 0600 UTC on the 5th, locating the center about 350 nm south-southeast of Hong Kong and essentially stationary. Also at 0600 UTC PAGASA re-initiated warnings on Maring, upgrading it to a 35-kt tropical storm. The system was located in an environment of moderate easterly vertical shear, so intensification proceeded at a slow rate. A low- level ridge to the south steered Maring/23W on a slow easterly track initially, but after around 1800 UTC the system began to move to the north. JMA upgraded the system to a tropical storm at 06/0000 UTC, naming it Wukong. JTWC still had the MSW assessed at 30 kts while PAGASA was reporting a peak 10-min avg wind of 40 kts. At this stage Wukong exhibited a broad LLCC with a strong band of convection and strongest winds to the south of the center. JTWC classified Wukong as a tropical storm at 0600 UTC on the 6th when the system was centered approximately 300 nm southeast of Hong Kong. The storm was moving to the north-northwest at 5 kts and gradually turned to a westward track as a subtropical ridge to the north began to build. By 1200 UTC CIMSS satellite-derived winds products indicated weak vertical shear with good diffluence over the area, and significant intensification was not long in coming. The MSW was up to only 40 kts at 1800 UTC (although JMA's 10-min avg wind estimate was 50 kts), but convection had begun to increase in areal extent and consolidate around the center. However, at 0000 UTC on 7 September JTWC abruptly upgraded Wukong to a 65-kt typhoon located about 235 nm south-southeast of Hong Kong. Animated satellite imagery indicated that the system had rapidly gained in organization, and a 06/1934 UTC TRMM pass depicted tightly curved convective bands. The storm by this time was tracking westward at 9 kts, a course from which it never significantly deviated for the rest of its life. Although Wukong had rapidly strengthened from a minimal tropical storm into a typhoon, the intensification trend levelled off and the system remained a minimal typhoon for the next 24 hours. (JMA upgraded Wukong to a typhoon at 07/1800 UTC.) Overall organization improved even though convection weakened slightly. A 07/1311 UTC SSM/I pass depicted eyewall convection around the system except for the southern quadrant with a convective band to the southwest. Typhoon Wukong passed about 200 nm due south of Hong Kong at 0000 UTC on 8 September. Animated water vapor imagery revealed good outflow aloft over the storm and the organization was improving. JTWC increased the MSW to 75 kts at this time and to 90 kts at 0600 UTC. (JMA's 10-min avg wind estimate rose to its peak value for the storm's history--75 kt--at 0600 UTC.) A TRMM pass at 08/0224 UTC revealed a ragged eyed 45 nm in diameter. The typhoon exhibited a slight weakening around 1800 UTC, losing its eye feature in infrared imagery. JMA decreased the intensity to 70 kts but JTWC maintained the MSW at 90 kts. As Wukong continued on toward the southern tip of Hainan Island it re-intensified some, reaching its peak intensity of 95 kts (per JTWC) at 09/0000 UTC as it neared the island. The estimated MSW was based on satellite intensity estimates of 90 and 102 kts. Microwave imagery indicated a well-defined center with deep convection consolidated in the southern semicircle. By 0600 UTC on the 9th Wukong was located over the extreme southern tip of Hainan and moving westward at 10 kts. The storm was beginning to weaken and the MSW was lowered to 75 kts. (JMA downgraded Wukong to a 60-kt tropical storm at 0600 UTC.) Wukong's intensity continued to decrease further as it plodded westward across the Gulf of Tonkin, and JTWC dropped the MSW to 65 kts at 1200 UTC. By 0000 UTC on the 10th the storm was nearing the coast of northern Vietnam, and although microwave imagery indicated the redevelopment of a large eye, Wukong was downgraded to a 60-kt tropical storm. All the convection was located along the southern side of the LLCC. The tropical cyclone made landfall and began to weaken quickly. At 10/0600 UTC JTWC issued their final warning, placing the center of Wukong about 150 nm south of Hanoi. The MSW was estimated at 45 kts, based on a synoptic report of 40 kts just north of the center. JMA issued one more bulletin, down- grading the storm to a depression. The remnants of Wukong continued moving westward toward central Laos and northeastern Thailand. Media reports indicate that Wukong left 5 dead with one person missing in Hainan province. Over 2700 homes and 70,000 hectares of crops were destroyed while 240,000 hectares of crops were damaged and nearly 2.5 million persons adversely affected by the typhoon. In Vietnam's Ha Tinh province, where the storm made its final landfall, two persons were reported killed and 69 injured. Wukong's heavy rains and 60-kt winds destroyed nearly 3000 homes--leaving 10,000 homeless-- and blew the roofs off 5000 others. In addition 11,000 hectares of rice were submerged, power lines downed, and some sea dyke systems breached by the torrential rains and storm surge. Tropical Cyclone "Nu" 13 - 18 September --------------------- The discussion of this system is based almost completely upon information supplied by Dr. Mark Lander of the University of Guam, who supplied the track for this cyclone which was included in the global cyclone tracks file. Mark's track first defines a weak tropical depression at 0600 UTC on 13 September about 425 nm north- west of Wake Island. Over the next day or two the system moved rather quickly to the northwest, gradually turning to the north- northwest. By 15/0000 UTC the cyclone had reached its point of recurvature about 700 nm east of Tokyo. In Mark's opinion the system had reached tropical storm intensity at this point. A visible picture taken at 14/2230 UTC shows a small, bright convective area with very pronounced spiral bands feeding into the CDO. Mark estimates that the MSW was 40 kts around this time. An intermediate STWO issued by JTWC at 14/2300 UTC mentioned this area and indicated that it appeared to be developing rapidly. The system was given a Fair development potential and a Formation Alert was issued at 15/0000 UTC. A recent QuikScat pass supported the existence of a LLCC beneath the convection with winds of 20-25 kts. However, the small cyclone turned toward the east-northeast and quickly weakened. Mark's track weakens the system to 30 kts by 1200 UTC, and JTWC cancelled the Formation Alert at 1800 UTC. Convection had decreased significantly and the exposed LLCC had moved north of the upper-level ridge axis beneath moderate westerlies. The weak system continued moving generally eastward for about 24 hours and then sprang back to life with another burst of convection. Mark estimates that the system had regained tropical storm intensity by 1200 UTC on 16 September and that it reached its peak MSW of 45 kts at 1800 UTC when it was centered approximately 900 nm east of Tokyo. An infrared image taken at 1130 UTC reveals a circular area of cold cloud tops seemingly over or very near the LLCC. Following this flare-up the system began to weaken again and drifted toward the south and later toward the west-southwest. The final entry in Mark's track at 0600 UTC on 18 September places the dissipating center about 950 nm east- southeast of Tokyo. Typhoon Sonamu (TC-25W / STS 0017) 14 - 21 September ----------------------------------- Sonamu: Korean word for pine tree, contributed by the Democratic People's Republic of Korea (North Korea) An area of convection formed on 13 September roughly 400 nm south- west of Iwo Jima and by early on the 14th had moved to a position approximately 200 nm southwest of the island. JTWC issued a Formation Alert at 0430 UTC for the system as convection had become increasingly organized. Synoptic and scatterometer data indicated a possible LLCC beneath the convection. Vertical wind shear was weak and the environment was favorable for strengthening. By 0600 UTC animated satellite imagery indicated that the system was organizing quite rapidly and warnings were initiated on TD-25W. The depression was moving east-northeastward at 9 kts in the general direction of Iwo Jima. The MSW was increased to 30 kts at 1200 UTC and to 35 kts at 1800 UTC when the cyclone was centered about 130 nm southwest of Iwo Jima. (JMA had designated the system as a depression at 1200 UTC but did not upgrade it to a tropical storm until 0600 on the 15th.) The minimal tropical storm was being steered northeast- ward by a low-level ridge to the south but was forecast to begin tracking northward after about twelve hours due to the influence of a subtropical ridge to the east. JTWC increased the MSW to 40 kts at 15/0000 UTC, and JMA upgraded and named the system Sonamu at 0600 UTC. By this time Sonamu was located about 75 nm south of Iwo Jima and the expected northward turn was taking place. The storm was rather small with the radius of gales estimated to be only 50 nm. Animated satellite imagery around 1800 UTC indicated a possible developing eye and also a deep convective band developing southeast of the vortex center; therefore, the MSW was upped to 60 kts (JMA's maximum 10-min avg wind estimate was 50 kts). Tropical Storm Sonamu continued to move toward the north-northeast and had reached a position about 25 nm east of Iwo Jima by 0000 UTC on 16 September. Animated satellite imagery depicted a tiny cloud-filled eye only 3 nm in diameter with an associated primary spiral band wrapping in toward the LLCC from the southwest. JTWC upgraded Sonamu to a 65-kt typhoon based on the formation of the eye and satellite intensity estimates of 55 and 77 kts. At 15/2300 UTC Iwo Jima reported sustained winds of 21 kts (10-min avg) from the northwest with gusts to 33 kts. (JMA increased their maximum 10-min avg wind estimate to 55 kts, which was the peak for the storm's history--that agency did not upgrade Sonamu to a typhoon.) By 0600 UTC Typhoon Sonamu was located about 80 nm north-northeast of Iwo Jima and moving northward at 12 kts. The island was then reporting sustained southwest winds of 22 kts (10-min avg) with gusts to 31 kts. The MSW was increased to 70 kts at 1200 UTC based upon satellite imagery which revealed improving organization. The typhoon was centered about 30 nm northwest of Chichijima Island which was reporting 35-kt sustained winds (10-min avg). Sonamu continued to track toward the north, accelerating to 20 kts by 17/0000 UTC when it was centered about 300 nm south-southeast of Tokyo. Most of the deep convection was to be found in the northeast quadrant while the southwest quadrant was virtually convection-free. JTWC bumped the MSW up to 75 kts at 0600 UTC on the 17th--this was the storm's peak intensity per that agency's analysis. Animated visible satellite imagery revealed improving organization and a 13-nm irregular eye. Sonamu by this time was located about 200 nm southeast of Tokyo and moving north-northeastward at 21 kts. The translational speed had increased to 29 kts by 1200 UTC as the typhoon passed 170 nm east of Tokyo. Sonamu was maintaining its intensity and exhibited a banding eye with tightly curved bands. The storm continued to move rapidly north-northeastward in advance of a major shortwave trough over South Korea and eastern China. Sonamu was able to maintain its intensity due to its tracking beneath an upper-level ridge axis, but by 1800 UTC deep convection was beginning to weaken as the storm moved over 20 to 22 C SSTs. The MSW was still estimated to be 75 kts at 0000 UTC on the 18th, but visible satellite imagery depicted a mid/high cloud shield extending several hundred miles northwest of the vortex center, indicative of an extratropical system. An upper-level wind analysis at 17/1800 UTC indicated that Sonamu was situated beneath the polar front jet with winds of 60 kts from the southwest. In addition water vapor imagery indicated a cold air tongue pushing in toward the vortex from the southwest. Almost no convection was left and JTWC declared Sonamu to be extratropical at 18/0000 UTC and issued their final warning, placing the center about 240 nm northeast of Misawa, Japan. The vigorous storm, however, was still estimated to be packing winds of 75 kts (55-kt 10-min avg wind from JMA) even as it transitioned into an extratropical cyclone. The extratropical storm raced rapidly to the northeast for the next 24 hours, passing through the Aleutian Island chain into the Bering Sea where it became quasi-stationary and remained for several more days while slowly filling. Super Typhoon Shanshan (TC-26W / TY 0018) 17 - 27 September ------------------------------------------ Shanshan: contributed by Hong Kong, China, is a fairly common pet name for young girls An area of convection formed on 15 September near 15N just west of the Dateline. A QuikScat pass indicated a developing LLCC with 20-kt sustained winds. JTWC issued a Formation Alert at 16/0230 UTC as imagery indicated that deep convection was increasing near the LLCC and low-level cloud lines were becoming evident west of the center. The disturbance developed slowly and a second Formation Alert was issued 24 hours later. The first warning on TD-26W was issued at 1200 UTC on the 17th, placing the center about 450 nm southeast of Wake Island or about 400 nm north of Majuro Atoll in the Marshall Islands. Convection was becoming better organized and a 17/0640 UTC QuikScat pass indicated 20-25 kt winds near the LLCC. The depression continued to slowly strengthen and JTWC upgraded the system to a 40-kt tropical storm at 0000 UTC on 18 September. Satellite current intensity estimates were 30 and 45 kts, and animated imagery depicted rapid consolidation of the deep convection during the previous three hours with a 34-nm CDO over the LLCC and a spiral band wrapping into the center from the east. (JMA began issuing bulletins on the system at 18/0000 UTC but did not upgrade it to a tropical storm until 1200 UTC.) The cyclone's center at 0000 UTC was located about 390 nm southeast of Wake Island (or 475 nm north of Majuro) and was tracking west-northwestward at 7 kts within a weakness in the subtropical ridge. The MSW was increased to 50 kts at 0600 UTC and to 55 kts at 1200 UTC when JMA upgraded the system to a tropical storm and named it Shanshan. Convective organization had continued to improve with an increase in spiral banding wrapping in toward the LLCC. A TUTT north- west of Shanshan was helping to enhance the outflow. Expanding areal coverage of the deep convection with cooling cloud top temperatures was observed over the next 18 hours, and JTWC upgraded Shanshan to a typhoon at 0600 UTC on the 19th when the storm was centered roughly 200 nm southeast of Wake Island. Shanshan jogged northward a bit about this time but soon resumed a slow, northwesterly motion. Hints of a developing eye were seen at 1200 UTC, and by 1800 UTC a 25-nm irregular, cloud-filled eye had developed. The typhoon was then located about 175 nm east of Wake Island, and JTWC increased the MSW estimate to 90 kts while JMA upgraded Shanshan to a typhoon with maximum 10-min avg winds of 70 kts. By 0600 UTC on the 20th Shanshan's winds had climbed to 100 kts (per JTWC's warnings). The typhoon displayed a 7-nm diameter eye, and animated water vapor imagery depicted good outflow aloft with a mid- level ridge building northeast of the storm. Typhoon Shanshan continued to intensify as it tracked slowly northwestward. The MSW reached 125 kts at 1800 UTC when the eye was centered approximately 120 nm north-northeast of Wake Island. However, satellite imagery revealed that the southern half of the eyewall had collapsed and the storm's intensity plateaued at 125 kts for about 18 hours. But by 1200 UTC on 21 September Shanshan had begun to strengthen again and JTWC increased the MSW to 130 kts, thus qualifying Shanshan for super typhoon status. The storm had excellent outflow in all quadrants and a 25-nm round eye. Six hours later Shanshan reached its peak estimated intensity of 135 kts, based upon satellite current intensity estimates of 127 and 140 kts. The 17-nm diameter eye was then centered about 275 nm north-northwest of Wake Island and was moving north-northwestward at 8 kts under the steering influence of a mid- level HIGH situated to the northeast. 50-kt winds extended outward 90 nm to the northeast and 50 nm elsewhere while gale-force winds covered an area about 320 nm in diameter. (The peak 10-min avg wind estimate from JMA was 95 kts from 21/1200 through 22/0600 UTC. Super Typhoon Shanshan maintained its peak intensity for about twelve hours and then began to slowly weaken. At 0600 UTC on the 22nd the MSW was decreased slightly to 130 kts as the storm turned to a northerly course. Six hours later Shanshan was moving slowly to the north-northeast and convection was beginning to weaken. The storm was downgraded from super typhoon status with the MSW being estimated at 115 kts. A 22/0939 UTC SSM/I pass depicted concentric eyewalls with convective bands north of the eye. The typhoon passed about 900 nm west of Midway Island around 1800 UTC, still slowly weakening. At 0000 UTC on 23 September the MSW was still estimated at 100 kts although there was little convection in the southwestern quadrant. By 0600 UTC Shanshan was beginning to experience increased vertical shear from the southwest, and the forward motion had increased slightly to 14 kts. Six hours later the MSW was down to 90 kts (JMA's maximum 10-min avg wind estimate was 75 kts) and Shanshan's translational speed had increased to 17 kts. A 23/1342 UTC TRMM pass revealed an exposed LLCC with all the convection to the north of the center. By 24/0000 UTC Shanshan was a minimal typhoon moving quickly north- eastward at 24 kts and was beginning to undergo extratropical transition as it merged with a mid-latitude system to the north- northwest. The final JTWC warning at 24/0600 UTC indicated that the storm had become fully extratropical at a position about 600 nm west- northwest of Midway. The winds were estimated at 60 kts and the storm was moving northeastward at 33 kts. JMA was still treating Shanshan as a minimal typhoon, but six hours later issued their final bulletin and declared the storm to be extratropical. Over the next few days the storm continued to move northward in the vicinity of the Dateline, eventually turning northeastward and weakening to a 40-kt gale by 27 September a few hundred miles south of the Aleutian Islands. While Super Typhoon Shanshan did not significantly affect any land areas, it was notable for the location in which it occurred. According to Mark Lander, who reviewed some studies of typhoon climatology, it is highly likely that Shanshan was the first known storm to reach super typhoon intensity north of 20N and east of 155E. Tropical Storm (TC-27W) 28 - 30 September ----------------------- Tropical Storm 27W was a short-lived tropical cyclone which popped up in the waters north of Wake Island and moved northward for a couple of days before dissipating. JMA treated the system as a tropical depression only; therefore, no name was assigned. However, as was the case with the other unnamed tropical storm (TS-28W in early October), there were a couple of synoptic ship observations which seem to support minimal tropical storm intensity. The cyclone had its beginnings in an area of convection which developed about 200 nm north- northwest of Wake Island on 27 September. A 27/1009 UTC SSM/I pass (85 GHz data) indicated increasing organization with some banding features developing, so JTWC upgraded the development potential to Fair in a special STWO at 1400 UTC. This trend continued throughout the day and a Formation Alert was issued at 2200 UTC. The LLCC appeared to be embedded in the eastern extension of a monsoon trough. JTWC issued the first warning on TD-27W at 1800 UTC on 28 September. The depression was moving northward at 9 kts with increased convective organization and cooling cloud tops. The system was upgraded to a 35-kt tropical storm at 29/0000 UTC when it was located about 500 nm north of Wake Island. Satellite intensity estimates were 30 kts, but a ship about 40 nm northwest of the LLCC reported winds of 35 kts. The tropical storm was located in a moderate vertical shear environment and the deeper convection was sheared northeast of the center. Another 35-kt ship report six hours later (from 60 nm northwest of the center) sufficed to keep the system classified as a tropical storm for one more warning cycle. An approaching mid-latitude trough was creating the shear and also was steering the system to the north-northeast. The center was exposed with the deeper convection about 17 nm northeast of the LLCC. The system was downgraded to a tropical depression at 29/1200 UTC as it continued moving to the north-northeast and began to merge with the frontal boundary ahead of the trough. By 1800 UTC on 30 September the system had become extratropical and the final warning was issued placing the center about 600 nm north of Wake Island or 775 nm west of Midway. *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for September: No tropical cyclones NOTE: A low-pressure area which persisted in the Bay of Bengal for several days in late August and early September moved inland near the head of the Bay on 1 September. A bulletin from the IMD on 2 September mentioned that a depression had formed over land and at 02/0300 UTC was centered near 24N, 85W. This location is well inland to the northwest of Calcutta and about 70 km south of Gaya. No references were made to this system in any STWOs issued by JTWC and no track was included in the accompanying cyclone tracks file. *********************************************************************** SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E Activity for September: No tropical cyclones *********************************************************************** NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E Activity for September: No tropical cyclones *********************************************************************** NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E Activity for September: No tropical cyclones *********************************************************************** SOUTH PACIFIC OCEAN (SPA) - South Pacific Ocean East of Longitude 160E Activity for September: No tropical cyclones *********************************************************************** EXTRA FEATURE In order to shorten the amount of typing in preparing the narrative material, I have been in the habit of freely using abbreviations and acronyms. I have tried to define most of these with the first usage in a given summary, but I may have missed one now and then. Most of these are probably understood by a majority of readers but perhaps a few aren't clear to some. To remedy this I developed a Glossary of Abbreviations and Acronyms which I first included in the July, 1998 summary. I don't normally include the Glossary in most months in order to help keep them from being too long. If anyone would like to receive a copy of the Glossary, please e-mail me and I'll be happy to send them a copy. *********************************************************************** AUTHOR'S NOTE: This summary should be considered a very preliminary overview of the tropical cyclones that occur in each month. The cyclone tracks (provided separately) will generally be based upon operational warnings issued by the various tropical cyclone warning centers. The information contained therein may differ somewhat from the tracking and intensity information obtained from a "best-track" file which is based on a detailed post-seasonal analysis of all available data. Information on where to find official "best-track" files from the various warning centers will be passed along from time to time. The track files are not being sent via e-mail. They can be retrieved in the following manner: (a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206] (b) Login as: anonymous (c) For a password use your e-mail address (d) Go to "data" subdirectory (Type: cd data) (e) Set file type to ASCII (Type: ascii) (f) Transfer file (Type: get remote_file_name local_file_name ) (The files will be named with an obvious nomenclature--using September as an example: sep00.tracks) (g) To exit FTP, type: quit Both the summaries and the track files are standard text files created in DOS editor. Download to disk and use a viewer such as Notepad or DOS editor to view the files. The first summary in this series covered the month of October, 1997. If anyone wishes to retrieve any of the previous summaries, they may be downloaded from the aforementioned FTP site at HRD. The summary files are catalogued with the nomenclature: sep00.sum, for example. Back issues can also be obtained from the following websites (courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael Pitt, and Rich Henning): OR Another website where much information about tropical cyclones may be found is the website for the UK Meteorological Office. Their site contains a lot of statistical information about tropical cyclones globally on a monthly basis. The URL is: TROPICAL CYCLONE REPORTS AVAILABLE I have discovered that JTWC now has available on its website the complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999 season for the Southern Hemisphere). Also, ATCRs for earlier years are available also. The URL is: Also, TPC/NHC has available on its webpage nice "technicolor" tracking charts for the 1999 Atlantic and Eastern North Pacific tropical cyclones; also, preliminary storm reports for all the 1999 Atlantic and Eastern North Pacific cyclones are now available. In addition storm reports are now available for some of the Atlantic tropical cyclones in 2000. The URL is: Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays) *********************************************************************** *********************************************************************** Uploaded: 04:27 UTC 02.02.01 / Typhoon2000.com