From: Gary Padgett To: Multiple recipients of list WX-TROPL Subject: SUMMARY: August Tropical Cyclone Summary Date: Friday, September 25, 1998 9:26 AM MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY AUGUST, 1998 (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.) *********************************************************************** AUGUST HIGHLIGHTS --> United States struck by hurricane and tropical storm --> Eastern Pacific continues active --> First two Western Pacific typhoons of year develop *********************************************************************** 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 included in last month's summary. I will include this glossary from time to time, primarily in "lean" months without a lot of tropical cyclone activity to cover. But if anyone missed it last month and wishes to receive a copy, send me an e-mail privately and I'll forward them a copy. *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for August: 3 tropical storms 2 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. Also, a special thanks to Eric Blake, a graduate student at Colorado State University and owner of the Atlantic Tropical Weather Center website, for passing along some buoy and ship reports from Hurricane Bonnie. Tropical Storm Alex (TC #1) 27 July - 2 August ---------------------------- As the month of August opened, the Atlantic's first tropical storm of the season was battling rather strong vertical shear east of the Leeward Islands. Although Alex was near its peak intensity of 45 kts on 1 Aug, the system began to weaken rapidly and dissipated on 2 Aug to the northeast of the Leewards. The history of Tropical Storm Alex was covered in its entirety in the July summary and its complete track given in the accompanying tracking file for July. Hurricane Bonnie (TC #2) 19 - 30 August ------------------------- A tropical wave left the west African coast during the second week of August and moved slowly across the Atlantic. A large, broad circulation resembling a monsoon gyre accompanied the wave for several days. By 19 Aug the cloud pattern had become more consolidated over the northwest portion of the system so TPC/NHC issued the first depression advisory on the system at 2100 UTC, locating its broad center about 925 nm east-southeast of San Juan, Puerto Rico. The depression continued moving to the west-northwest at a pretty good clip, and the first reconnaissance flight into the system on 20 Aug found flight-level winds to 61 kts north of the center; therefore, the depression was upgraded to Tropical Storm Bonnie at 2100 UTC about 375 nm east of San Juan. Bonnie initially moved rather rapidly west-northwestward, passing about 100 nm north of San Juan around 1800 UTC on 21 Aug. The storm steadily increased in intensity with winds reaching hurricane force around 22/0600 UTC. Bonnie was centered at that time about 250 nm northwest of San Juan. The hurricane's forward motion slowed considerably on 22 and 23 Aug, and the track became more of a north- westerly one. Late on 22 Aug an Air Force Reserves reconnaissance flight measured a central pressure of 962 mb, which represented a drop of 15 mb in 8 hours. By 1200 UTC on 23 Aug Bonnie's pressure had dropped to 957 mb and the MSW had increased to 100 kts, making Bonnie a Category 3 hurricane on the Saffir/Simpson scale. The storm was centered at that point about 500 nm east-southeast of Miami. The lowest pressure in Bonnie's history came on the evening of 23 Aug when a reconnaissance flight measured a central pressure of 954 mb. Bonnie was a large hurricane by Atlantic standards. From the time the storm reached its peak intensity until landfall, gale-force winds covered an area over 300 nm in diameter, and hurricane-force winds eventually covered an area nearly 150 nm in diameter before the hurricane made landfall. Hurricane Bonnie continued on a steady northwesterly course toward the U.S. East Coast, gradually becoming more northerly early on 26 Aug. The eye of Hurricane Bonnie reached the Cape Fear, North Carolina, area late in the afternoon of 26 Aug and then turned to more of a general northeasterly course which allowed the center to "slide" along the coast, gradually moving inland. The hurricane's forward motion also slowed after making landfall, creating the potential for some very serious flooding from heavy rainfall. Bonnie's center gradually acquired a more east-northeasterly component of motion which allowed it to more or less skirt the coastal plain. The storm exited the state near Nag's Head on the Outer Banks around 28/0000 UTC--a little more than 24 hours after first touching the Cape Fear area. During the three days preceeding the hurricane's landfall the central pressure, as measured by reconnaissance flights, fluctuated generally between 960 and 965 mb. A slight weakening of Bonnie may have been caused by the slow, quasi-stationary movement on 23 and 24 Aug which would have allowed SST cooling due to upwelling. As the hurricane approached the coast, it appeared also to entrain some drier air which led to a somewhat ragged appearance in satellite imagery. However, through all this, reconnaissance flights continued to find flight-level winds between 100 and 120 kts. Dvorak intensity estimates during this time were significantly lower than those provided by aircraft, thus underscoring the great value of aerial reconnaissance, especially in hurricanes that are threatening populated areas. On 25 Aug at 1800 UTC ship ZCBK6, located about 70 nm southeast of Bonnie's center, reported a sustained wind of 70 kts from 200 degrees; while at the same time, ship C6T20, located roughly 80 nm south- southwest of the center, reported sustained 60-kt winds from 300 degrees. Both ships recorded a pressure near 991 mb. Around 1700 UTC on 26 Aug a NOAA research aircraft reported winds of 116 kts at the 2450 m flight level in the northeast quadrant of the hurricane. Also, a GPS dropwindsonde released during the afternoon by an Air Force reconnaissance plane measured 110 kts in the eastern eyewall not far above the surface. The automatic reporting station at Frying Pan Shoals (33.5N, 77.5W) reported sustained winds of hurricane force during Bonnie's passage. At 26/2100 UTC the center of Bonnie was about 30 nm northwest of the station, and the reported sustained wind was 65 kts (150 degrees). Pressure was 972.7 mb and the peak gust during the preceeding hour was recorded at 90 kts. By 0000 UTC on 27 Aug the center of Hurricane Bonnie was located about 40 nm north-northwest of Frying Pan. The sustained wind at this time was being reported at 70 kts (170 degrees), with a peak gust over the past hour of 83 kts and a pressure of 982.7 mb. (It should be noted that the elevation of the anemometer at Frying Pan Shoals is 44.2 m above MSL. Thanks to Eric Blake for passing this piece of information along.) While overland Bonnie was downgraded to a 55-kt tropical storm, but winds began to increase as the center approached the coast. During the evening of the 27th a reconnaissance flight measured winds of 82 kts at 3050 m, so Bonnie was once more upgraded to a hurricane at 28/0300 UTC. The storm was at this time located near Nag's Head or about 50 nm north-northwest of Cape Hatteras. At 27/2200 UTC Diamond Shoals Lighthouse (anemometer elevation 46.6 m) reported a sustained wind of 63 kts (190 degrees) with a peak gust over the preceeding hour of 76 kts. Chesapeake Lighthouse reported sustained winds of 68 kts and Cape Henry reported 70 kts, but the heights of these anemometers and the time of the reports are unknown to the author. Flight-level winds on the morning of 28 Aug were reported at 90 kts, but surface winds were estimated at only 55 kts. Bonnie was kept at hurricane intensity through the 1500 UTC advisory, but downgraded to a tropical storm at 2100 UTC when centered about 200 nm south of New York City. Apparently a strong southerly flow from over the Gulf Stream advected latent and sensible heat into the cyclone and allowed it to maintain its strength for awhile longer even though it was moving over cooler SSTs. Bonnie accelerated to the northeast, passing well to the south of the Canadian Maritimes. MSW had decreased to 45 kts by 29/2100 UTC, but were upped back to 50 kts based on observations from Canadian buoy 44137, Sable Island and a ship report. The center of Bonnie passed just south of Sable Island at 0200 UTC on 30 Aug. An oil rig just east of the island reported a 65-kt wind from an anemometer located 100 m above sea level. Bonnie had become sufficiently extratropical that TPC/NHC issued the last advisory on the morning of the 30th, placing the center of the storm about 150 nm south of Cape Race, Newfoundland, at 1200 UTC. Damage from Hurricane Bonnie was widespread, but not as major as had been anticipated. There were reports of downed power lines, uprooted trees, broken limbs, roof damage, and damage to crops (especially the tobacco crop); but the magnitude of the losses was not nearly as great as with Hurricane Fran in 1996. There doesn't seem to have been a whole lot of storm surge flooding damage along the beachfront. Bonnie dropped up to 254 mm of rain on eastern North Carolina which resulted in some flooding, but not to the degree which had been feared. The Governor of North Carolina, as quoted in the press, stated that losses would likely run between $1 and $2 billion--much of this being agricultural losses. The author was able to locate an account of two deaths attributed to Hurricane Bonnie. About 1 million persons in North Carolina and 300,000 in Virginia lost electrical power during the storm. I know this account of Hurricane Bonnie is exceptionally long, but I wanted to mention one other interesting feature. The first space- borne rain radar, located onboard the Tropical Rain Measuring Mission (TRMM) spacecraft (a joint U.S.-Japanese venture), produced images of a tall chimney cloud in the eyewall of Bonnie on 22 Aug which reached about 59,000 ft (almost 18,000 m) into the atmosphere. According to Dr. Robert Simpson, a former director of TPC/NHC, such tall clouds are rarely seen in Atlantic hurricanes. Tropical Storm Charley (TC #3) 21 - 22 August ------------------------------- The origin of Tropical Storm Charley can be traced back to an area of disturbed weather that was tracked from the southeastern Gulf of Mexico into the central Gulf. By the afternoon of 20 Aug cloudiness and showers were becoming better organized. On the morning of 21 Aug an Air Force Reserves reconnaissance plane closed off a weak low-level center about 250 nm southeast of Corpus Christi, Texas. TPC/NHC issued the first depression advisory at 1500 UTC. The depression moved northwestward toward the Texas coast during the afternoon, and was upgraded to Tropical Storm Charley at 2100 UTC after a plane reported flight-level winds (450 m) of 42 kts northeast of the center and some oil rigs reported winds to 37 kts in a small area north of the center. Charley's peak intensity of 50 kts and lowest pressure of 1003 mb were reached around 22/0600 UTC while centered only about 20 nm off the southern Texas coast. A reconnaissance aircraft reported a maximum flight-level wind (1500 m) of 57 kts while wind estimates from the Corpus Christi (KCRP) WSR-88D ran from 60-65 kts between 1050 and 1350 m elevation. The Rockport ASOS reported a sustained wind of 36 kts with a gust to 42 kts at 22/0800 UTC. Tropical Storm Charley made landfall around daybreak near Port Aransas (near Corpus Christi) and was downgraded to a depression at 1500 UTC. While Charley's winds quickly abated, a serious flooding threat began to develop from the heavy rains. The remnants of Charley moved slowly westward over the next several days, causing very heavy rains over portions of southern Texas. Almost 460 mm fell in the vicinity of Del Rio, Texas--a city of 30,000 located about 150 miles (240 km) west of San Antonio. Just about the entire city was inundated--water reached a depth of 2.5 m in some streets. The latest account located by the author mentioned 17 known fatalities with perhaps 50 more unaccounted for in the Del Rio area and across the Rio Grande in Ciudad Acuna, Mexico. Hurricane Danielle (TC #4) 24 August - 5 September --------------------------- A strong tropical wave which left the west coast of Africa around 20 Aug began to show signs of increased organization by 23 Aug when located several hundred miles west-southwest of the Cape Verdes. The system became much better organized on 24 Aug and was classified as a tropical depression about 700 nm west of the Cape Verdes in a special advisory issued at 1530 UTC. Tropical Storm Danielle with 35-kt winds was christened six hours later. Danielle began as a very small, compact tropical cyclone. By the morning of 25 Aug satellite pictures showed a small pinhole eye so the storm was upgraded to a hurricane at 1500 UTC about 1100 nm west of the Cape Verdes. Danielle reached an estimated peak intensity of 90 kts on 26 Aug when its center was imbedded in some -70 deg C cloud tops, but weakened some during succeeding days as some southerly shear disrupted its cloud pattern. The first reconnaissance flight into the storm late on the 26th found flight-level winds of 77 kts over the northeast quadrant but only 37 kts over the southwest quadrant. This very asymmetric wind field was likely caused by a combination of the rapid forward translational speed--18 kts--and the large pressure gradient associated with a ridge to the north. The lowest central pressure measured at the time was 992 mb. Very early on 27 Aug another flight found 90-kt winds in the northeast quadrant in very deep convection with tops between -70 and -75 deg C. The minimum pressure was only 993 mb--somewhat high for such strong winds--but a situation which has been observed in compact hurricanes before. Hurricane Danielle moved on a fairly straight west-northwestward course from its point of origin to its point of recurvature on 31 Aug about 325 nm east of Cape Canaveral, Florida, passing about 250 nm north of Puerto Rico early on 28 Aug. The hurricane weakened along the way, partly due to the aforementioned shear, and partly due to moving over patches of water whose SSTs had been cooled several degrees by Bonnie's recent passage through the same area. However, after recurving to the northeast, Danielle began to undergo a modest strengthening once more. The minimum pressure of 965 mb was measured around 1800 UTC on 1 Sep when the hurricane was centered about 300 nm west of Bermuda. Attendant MSW was estimated at 85 kts after a reconnaissance flight found 94-kt winds at flight level. The hurricane's closest approach to Bermuda came around 02/0600 UTC when the center was about 175 nm northwest of the island. The area of gale-force winds had expanded considerably, especially to the south- east of the eye. An observation from Bermuda at 02/1100 UTC reported sustained winds of 34 kts with a gust to 47 kts. After passing Bermuda Danielle began to accelerate rapidly off to the northeast. The storm passed about 400 nm south of Halifax, Nova Scotia, around 1800 UTC on the 2nd. A Canadian buoy (ID 44141 at 42.1N, 56.2W) recorded a 66-kt wind and a pressure of 976 mb at 0700 UTC on 3 Sep. At 0900 UTC a pressure of 962 mb, 54-kt winds, and 16 m seas were reported from the same buoy. Around mid-day Danielle passed south of another Canadian buoy (ID 44138 near 44.3N, 53.7W) which reported winds of 45 kts, a pressure of 972 mb, and 12 m seas. On 3 Sep Danielle transformed into a very vigorous extratropical cyclone with the last TPC/NHC advisory placing the center about 150 nm southeast of Cape Race, Newfoundland. The deep extra- tropical storm continued rapidly eastward across the North Atlantic, passing well north of the Azores by early on 5 Sep. Since Danielle continued as a tropical entity for only three days into the month of September, I have chosen to report its entire history in this summary issue. The accompanying tracking file contains the complete track of Hurricane Danielle, including its extratropical stage through 0600 UTC on 5 Sep. Except for its brush with Bermuda, Danielle did not affect any populated areas. It is likely that any affects experienced in Bermuda were very minimal. Tropical Storm Earl (TC #5) 31 August ---> ---------------------------- Tropical Storm Earl, which later became Hurricane Earl, developed from a tropical wave which had moved off the coast of western Africa around mid-August. This wave followed the wave which produced Bonnie but preceeded the disturbance from which Danielle developed. The system had gotten better organized by 22 Aug and had moved into the eastern Caribbean by 23 Aug, but its development began to be hindered by the outflow from Hurricane Bonnie, located to the northwest. The wave weakened and continued slowly across the Caribbean during the ensuing week. By 31 Aug the main area of disturbed weather associated with the wave had moved into the southwestern Gulf of Mexico. During the afternoon a reconnaissance plane flew into the broad area of low pressure in the southwestern Gulf. Even though the circulation was broad and disorganized, the plane found a peak wind of 43 kts at 450 m and a pressure of 1002 mb. The disturbance was upgraded directly to Tropical Storm Earl at 31/2100 UTC. Earl proved to be a very unusual tropical cyclone that was very difficult to track. The saga of Earl will continue in next month's summary. No track is given in the accompanying tracking document for this month. *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for August: 1 tropical depression 1 tropical storm 3 hurricanes 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. Hurricane Estelle (TC-06E) 29 July - 8 August --------------------------- Hurricane Estelle had developed on 29 Jul about 150 nm south- southwest of Acapulco, Mexico, and had reached hurricane intensity on 31 Jul about 500 nm south of Mazatlan. (A few more details of Estelle's early history were covered in the July summary.) During its life Hurricane Estelle followed a fairly straight general west- northwesterly course from its point of origin south of Mexico to its point of dissipation well to the northeast of Hawaii. By 0000 UTC on 1 Aug Hurricane Estelle was passing about 450 nm south of Cabo San Lucas with MSW estimated at 75 kts. Late that day a well-defined eye surrounded by a ring of intense convection had appeared. Estelle reached its peak intensity of 115 kts with an attendant estimated central pressure of 948 mb at 0600 UTC on 2 Aug when located about 550 nm southwest of Cabo San Lucas. By the afternoon of 3 Aug the hurricane had weakened considerably as it passed into a region of cooler SSTs (25-26 deg C). The hurricane was downgraded to a 60-kt tropical storm at 04/0600 UTC, and was downgraded to a depression 30 hrs later when located over 1300 nm west of Cabo San Lucas. Estelle had been a large and powerful hurricane, so it took several days for the circulation to spin down. The weakening depression was still close to tropical storm intensity when it crossed 140W into the Honolulu area of warning responsibility around 1800 UTC on the 6th. Further weakening ensued and the final advisory was written by the CPHC at 1800 UTC on 8 Aug, locating the weak center about 400 nm north- northeast of Hilo. The remnants were tracked westward for several more days to near 23N, 170W (about 625 nm west of Lihue, Hawaii) at 15/0000 UTC. Tropical Storm Frank (TC-07E) 6 - 10 August ------------------------------ A tropical disturbance several hundred miles south-southwest of Cabo San Lucas showed increased signs of organization on 6 Aug, and at 1800 UTC the first depression advisory was written by TPC/NHC, placing the poorly-defined center about 75 nm southwest of Socorro Island. Observations from Socorro and a ship 150 nm south of the center helped to confirm that a surface circulation existed, although it was elongated along a north-northeast/south-southwest axis. Initially, this system was not expected to intensify into a tropical storm. The depression began tracking in a general northward direction. At 07/1800 UTC Socorro Island, located then about 120 nm south- southeast of the center, reported south winds at 25 kts, with 1008.7 mb following a 3-hr pressure rise of 3.1 mb. Visible and infrared satellite imagery showed better organization as the day progressed, and the depression was upgraded to Tropical Storm Frank at 08/0300 UTC after the T-number from TABF had reached 2.5 and several ships about 100 nm northeast of the center reported winds of 25 to 33 kts. At 0000 UTC Frank's center was estimated to be about 150 nm southwest of Cabo San Lucas. Tropical Storm Frank remained a minimal tropical storm as it trekked northward. The center passed about 140 nm west of Cabo San Lucas around 1200 UTC on 8 Aug. It was initially believed that the center of Frank made landfall on the Baja coast at 09/0600 UTC about 125 nm southeast of Punta Eugenia, but later satellite fixes indicated the center was about 100 nm to the west. The 09/1200 UTC analyzed position was estimated to be about 50 nm south-southwest of Punta Eugenia. At this time Frank consisted of a low- to mid-level circulation without much deep convection. The weakening depression turned more to the northwest (which was what most models had predicted all along) and had dissipated by 0000 UTC on 10 Aug about 125 nm west- northwest of Punta Eugenia. The lowest central pressure in Frank was estimated to have been 1001 mb on 8 Aug about the time the center was due west of Cabo San Lucas. Rainfall from the tropical storm affected portions of north- western Mexico and the southwestern United States, but the author has not learned of any significant damage or any casualties resulting from these rains. Hurricane Georgette (TC-08E) 11 - 17 August ----------------------------- The first advisory on TD-08E was issued by TPC/NHC on 11 Aug at 0900 UTC, locating the center about 550 nm southwest of Manzanillo, Mexico, at 0600 UTC. In contrast to several of this season's North- eastern Pacific hurricanes, Georgette moved on more of a northwesterly course throughout its life which carried it to a fairly high latitude well west of the Baja California peninsula. The depression was upgraded to Tropical Storm Georgette at 11/1800 UTC and to a hurricane with 65-kt winds at 1200 UTC on 12 Aug when centered about 575 nm west-southwest of Manzanillo. Georgette continued moving northwestward and reached its estimated peak intensity of 100 kts and 960 mb pressure at 14/0600 UTC. At this point the hurricane was located about 570 nm west-southwest of Cabo San Lucas. According to a TPC/NHC discussion, Georgette represented an excellent example of a banding-type hurricane. At 0900 UTC on 13 Aug the discussion bulletin mentioned that the system had a small CDO which, when combined with the principal convective band, appeared in infrared imagery in the shape of the number "6". At the time of its peak intensity, Georgette featured a large eye--around 35 nm in diameter--which was surrounded by a ring of deep convection, but with little deep convection elsewhere. By early on 15 Aug Georgette was beginning to rapidly weaken as it moved over 23 deg C SSTs. At 0600 UTC the storm, still with 85-kt winds, passed about 725 nm west of Cabo San Lucas, moving northwest- ward. Georgette was downgraded to a tropical storm at 16/0000 UTC and to a depression 18 hrs later. The last advisory, at 0300 UTC on the 17th, placed the dissipating center about 650 nm west-southwest of Punta Eugenia on the west coast of the Baja. Tropical Depression (TC-01C) 16 - 19 August ----------------------------- The only tropical cyclone thus far this season to form in the area of warning responsibility of the CPHC in Honolulu began to take shape on 15 Aug. A disturbance about 800 nm east-southeast of Hilo, located on a northward bulging ITCZ, began to get better organized, and TD-01C had formed by 1200 UTC on 16 Aug. Ship reports of 30 kts and visible satellite pictures confirmed that a closed circulation had developed. Infrared pictures indicated that a convective band was trying to wrap around the east side of the center. The depression, with 30 kts winds, was initially forecast to reach tropical storm intensity, but this never materialized. (Had this system become a tropical storm, its name would have been Upana--a Hawaiian name.) The tropical depression moved generally westward as vertical shear inhibited development. Deep convection followed a diurnal pattern, increasing to a maximum during the night and weakening during the daytime hours. MSW were decreased to 25 kts by 17/1200 UTC, and the last advisory was written at 0000 UTC on the 19th placing the weak center about 325 nm south of Hilo. Hurricane Howard (TC-09E) 21 - 29 August -------------------------- On the afternoon of 20 Aug satellite pictures indicated that an area of disturbed weather about 375 nm south of Acapulco had become significantly better organized. The previously exposed low-level center had become positioned under deep convection associated with a primary banding feature to the east. A ship report of 40-kt winds and a 1005 mb pressure from just north of the center at 21/0000 UTC led to the system being upgraded directly to Tropical Storm Howard. Howard moved generally on a west-northwestward course for most of its life. The storm strengthened quite rapidly, reaching hurricane intensity at 1800 UTC on 21 Aug about 350 nm south-southwest of Acapulco. Hurricane Howard began to deepen explosively during the morning of 22 Aug. MSW increased from an estimated 95 kts at 1200 UTC to a peak of 130 kts only 12 hrs later. Minimum central pressure was estimated at 930 mb with an eye diameter of 11 nm. Hurricane Howard was the strongest hurricane seen in the Northeastern Pacific basin thus far this season. After reaching its peak intensity Howard slowly weakened, with estimated MSW dropping to 105 kts by 24/1800 UTC. At this point the eye was quite large with an apparent double structure. It is possible that there was a mesocyclone rotating around the north side of the center. Satellite imagery, however, showed that Howard made somewhat of a comeback on the 24th. The eye at this time was very large--about 50 to 60 nm in diameter. The storm presented a distinct doughnut-like appearance in satellite pictures. Winds reached 125 kts once more at 0600 UTC on 25 Aug when the hurricane was centered about 600 nm southwest of Cabo San Lucas. The eye at this time was about 30 nm in diameter with a 60 nm-wide ring of surrounding convection of -70 to -75 deg C cloud tops. By this time, however, Howard was approaching SSTs of 25 deg C, and a fairly rapid weakening trend soon set in. The hurricane was downgraded to a tropical storm at 0000 UTC on 28 Aug when located about 950 nm west-southwest of Cabo San Lucas, and was further reduced to depression status at 29/1200 UTC. The final advisory at 1800 UTC placed the weakening depression far to the west of the Mexican coast, near 20N, 133W. The remnants of Howard drifted westward into the Central North Pacific area on 31 Aug and occasionally produced some limited convective activity into the first couple of days of September, but showed little indication of re-intensifying. On 2 Sep the weak system appeared to merge into the ITCZ several hundred miles to the southeast of Hawaii. *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for August: 1 tropical storm ** 2 typhoons ** ** This based upon JTWC's classifications--JMA did not classify Otto as a typhoon. 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. Also, as announced earlier in a separate posting, a column of 10-min avg MSW is included--the values being obtained from either PAGASA's or JMA's advisories. A special thanks to Michael V. Padua, owner of the Typhoon '98 webpage, for sending me the PAGASA tracks. Also some information, primarily on the pre-depression stages of the various cyclones, was taken from the Monthly Report of the RSMC, Darwin, Northern Territory, Australia. A special thanks to Sam Cleland for forwarding that report to me. In the title line for each storm I plan to reference all the cyclone names/numbers I have available: JTWC's depression number and name (if any), JMA's tropical storm numeric designator, and PAGASA's name for systems forming in or passing through their area of responsibility. Typhoon Otto/Bising (TC-04W / STS 9802) 1 - 5 August ---------------------------------------- A tropical LOW developed in the Philippine Sea from a mesoscale convective complex in early August. This was west of a TUTT which helped to provide favorable upper-level divergence over SSTs exceeding 30 deg C. A scatterometer pass at 01/1411 UTC indicated winds of around 30 kts. JTWC issued the first depression advisory at 0000 UTC on 2 Aug, locating the center about 325 nm east of Manila. (It should be noted that PAGASA issued the first bulletin on Tropical Depression Bising 12 hrs earlier. The companion tracking file reflects this.) Tropical storm intensity was reached at 1200 UTC on 2 Aug about 215 nm east of Manila. Initially, Otto/Bising was a small system with gales covering an area less than 100 nm in diameter. After drifting very slowly westward during the formative stages, the storm began to moved northward, then north-northwestward in the general direction of Taiwan. JTWC upgraded Otto/Bising to a minimal typhoon at 03/1200 UTC when the center was about 125 nm north-northeast of the northern tip of Luzon. (It should be noted that JMA never assigned typhoon status to this system, but treated it as a severe tropical storm.) Otto/Bising remained a rather small system with storm-force winds covering an area less than 40 nm in diameter and gales extending out from the center no more than 65 nm. The typhoon reached the southeast coast of Taiwan about 100 nm south-southwest of Taipei around 0600 UTC on 4 Aug, moving north-northwestward. Otto weakened briefly to a tropical storm after crossing the island, but regained minimal typhoon intensity shortly before reaching the coast of China. Typhoon Otto appeared to make landfall in Fukien Province, near Fuchou. (Please forgive me if this spelling is incorrect or has changed--these names were taken from an old atlas.) The system weakened rapidly and began to dissipate once inland. For some comments regarding the possible impact of Otto on the severe river flooding occurring in China, refer to the discussion on Tropical Storm Penny which follows. Tropical Storm Penny/Klaring (TC-05W / STS 9803) 6 - 11 August ------------------------------------------------- As Typhoon Otto was crossing the Chinese coast, another tropical LOW formed in the Philippine Sea in a manner similar to the pre-Otto disturbance. JTWC issued the first depression advisory at 06/0600 UTC locating the center about 425 nm east-southeast of Manila. Mid-level steering had a pronounced easterly component and the depression moved northwestward toward the northern tip of Luzon. PAGASA issued the first advisory at 07/0000 UTC, naming the system Klaring, while JTWC upgraded the system to Tropical Storm Penny at 1800 UTC when the storm was centered about 175 nm northeast of Manila. Penny/Klaring crossed over the northernmost end of Luzon into the South China Sea and temporarily weakened into a depression. JTWC upgraded the system back to tropical storm status at 1800 UTC on 18 Aug. After reaching the South China Sea, Penny/Klaring moved on a general west-northwesterly course until it was about 115 nm south of Hong Kong. At that point the storm turned to more of a westerly track and reached an intensity of 50 kts at 10/1200 UTC when located about 150 nm southwest of Hong Kong. Shortly afterward, Penny turned to the north and made landfall in southern China just east of the Luichow Peninsula. Peak intensity of 55 kts was reached shortly before landfall. Once inland the storm began to quickly weaken and dissipate. Massive flooding along the Yangtze River and perhaps other rivers in China had been in progress for several weeks before the arrival of Otto and Penny. The author scanned several press articles covering the flooding but was unable to find any details of specific effects of these two tropical systems. No doubt the flooding was exacerbated to some degree from the rainfall attending Otto and Penny, but it is probably impossible to specify exactly the magnitude of their effects. Typhoon Rex/Deling (TC-06W / TY 9804) 24 August ---> -------------------------------------- What was to become the Northwestern Pacific's longest-lived cyclone to date this season began in a weak monsoon trough which extended from China to the Philippine Sea during an active phase of the Intraseasonal Oscillation (ISO). A LOW formed in the trough on 22 Aug, but the first depression advisories were not issued until 0000 UTC on the 24th when both JTWC and JMA began issuing advisories. TD-06W was initially located about 375 nm south-southeast of Okinawa. (PAGASA initiated advisories on the depression at 0600 UTC and named it Deling, but the system moved north of 25N and out of their AOR within 24 hours.) The tropical depression moved slowly to the north-northeast and was upgraded to Tropical Storm Rex at 25/0000 UTC. Rex's northeastward motion came to a halt around 1800 UTC that day when centered about 350 nm east-southeast of Okinawa. The storm began to drift a little south of due east for a couple of days, during which time it strengthened into a typhoon. Estimated MSW reached 100 kts at 1200 UTC on 27 Aug when Typhoon Rex was located about 100 nm west-northwest of Iwo Jima. Rex began to curve to the north on the 27th and reached its peak intensity of 115 kts about 150 nm north-northwest of Iwo Jima at 0600 UTC on 28 Aug. By 30/0600 UTC the MSW had come down a bit to 90 kts and Rex began to drift to the east-northeast from a position about 350 nm south- southeast of Tokyo. This slow east-northeastward motion continued through 0600 UTC on the 31st, after which Rex began to drift on an unusual east-southeastward course. At 0000 UTC on 1 Sep Typhoon Rex was still a 90-kt typhoon located about 500 nm southeast of Tokyo. Next month's summary will continue the saga of Typhoon Rex as well as provide some more details on the atmospheric circulation features which led to Rex's most unusual track. *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for August: No tropical cyclones *********************************************************************** SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E Activity for August: No tropical cyclones EXTRA FEATURE - NAMES FOR THE 1998-1999 SEASON The tropical cyclone season in the South Indian Ocean is considered to run from 1 August to 31 July of the following year. The names for the upcoming season are: Alda, Birenda, Chikita, Davina, Evrina, Francine, Genila, Helvetia, Irina, Jocyntha, Kristina, Lina, Marsia, Naomie, Orace, Patricia, Rita, Shirley, Tina, Veronique, Wilvenia, Yastride *********************************************************************** AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E Activity for August: No tropical cyclones NOTE: I had planned to include some comments by Dr. Jack Beven of TPC/NHC and Dr. Greg Holland of Australia's Bureau of Meteorology regarding an interesting hybrid storm system along the New South Wales coast. Due to the great length of this summary, I am going to hold this for a couple or three months until we reach a month without quite so much tropical cyclone activity to cover. *********************************************************************** SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E Activity for August: No tropical cyclones *********************************************************************** 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) The files will be named with an obvious nomenclature--using August as an example: aug98.tracks 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 August summary is the eleventh cyclone summary in this series; the first one covering the month of October, 1997. If anyone did not receive any of the previous summaries, they may be downloaded from the aforementioned FTP site at HRD. The summary files are catalogued with the nomenclature: aug98.sum, for example. Back issues can also be obtained from the following websites (courtesy of Michael Bath and Michael V. Padua): (since January only) The preliminary storm reports for all the 1997 Atlantic and Eastern North Pacific tropical cyclones are available on the Tropical Prediction Center's website: . These reports include the analyzed best-track for each cyclone. The staff of JTWC is also working on an on-line version of their Annual Tropical Cyclone Report for 1997. It is still under construction, but the best-track files are already available for 1997 Northwestern Pacific and North Indian Ocean cyclones. The URL is: Prepared by: Gary Padgett E-mail: garyp@alaweb.com Phone: 334-222-5327 *********************************************************************** ***********************************************************************