MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY JULY, 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.) *********************************************************************** JULY HIGHLIGHTS --> North Pacific quite active --> Twin typhoons affect several East Asian nations --> Rare Central North Pacific storm forms --> Hawaii affected by dying Eastern Pacific hurricane *********************************************************************** ***** Topic of the Month for July ***** SEASONAL STATISTICS FOR THE EASTERN NORTH PACIFIC The material presented below was compiled by John Wallace, a student at the University of Texas in San Antonio. John became very interested in tropical cyclones during the exceptionally active 1995 Atlantic hurricane season, and as he puts it, "started me on a crash course in tropical meteorology readings"--much the same experience I had had 30 years earlier, although it only took the very average 1963 season to get me started. John relates that after coming across the annual seasonal summary articles in _Weatherwise_, he was surprised to learn that the Northeast Pacific basin usually saw much more tropical cyclone activity than the Atlantic; yet, only rarely did one find articles written about tropical cyclones in this basin. At about the same time, John became familiar with the seasonal forecasts of Dr. Gray and the CSU team and decided that the Net Tropical Cyclone (NTC) activity index was an ingenuous way to measure the overall "punch" (or lack thereof) of a season's activity. So John gained access to the Best Track database for the Northeast Pacific and tabulated some statistics for this basin and calculated the NTC and Maximum Potential Destruction (MPD) according to Dr. Gray's formulae. The remainder of this article is as I received it from John with some minimal editing by myself. ----------------------------------------------------------------------- The first version of this table, with commentary, was completed in mid-1999. In it I used a 1975-1997 baseline and used "Named Tropical Cyclone Days" instead of Gray's canonical Named Storm Days--similar, except that the depression stage was included. As I didn't know the formula, I didn't calculate Maximum Potential Destruction (MPD). Gary Padgett was the first to review it, and he commented favorably though he considered it unwise to include the depression stage of storms. He also stated that reconnaissance data gave NEP data high reliability going back to 1971. I had limited the first study to the beginning of the use of the Dvorak technique (1975). Finally, he explained how to calculate MPD and Hurricane Destruction Potential (HDP). Buoyed by the new info, but also disheartened by its imperfections, I let the project rest for awhile, and when I resumed it I got rid of cyclone days and replaced it with storm days, extended the baseline back to 1971 and forward to 1999, and included the MPD. Unfortunately, HDP was too tedious to calculate with the available tools. A full description of the eight 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 MPD: Maximum Potential Destruction NTC: Net Tropical Cyclone Activity (%) Eastern North Pacific Seasonal Parameters 1971 - 1999 YEAR NS H IH NSD HD IHD MPD NTC 1971 18 12 6 83.75 38.50 6.00 122 111 1972 12 8 4 80.25 33.75 4.50 82 85 1973 12 7 3 61.75 28.50 7.25 89 78 1974 17 11 3 62.00 22.25 2.50 94 79 1975 16 8 4 68.25 26.75 5.50 90 85 1976 14 8 5 58.00 22.50 9.75 95 89 1977 8 4 0 20.50 5.25 0.00 31 23 1978 18 13 6 97.25 48.25 14.75 128 138 1979 10 6 4 33.75 13.75 3.25 72 56 1980 14 7 3 48.25 22.75 2.75 71 66 1981 15 8 1 57.00 18.00 1.00 68 58 1982 19 11 5 93.25 37.25 7.50 115 111 1983 21 12 8 109.50 47.50 16.00 151 150 1984 18 12 6 95.50 44.25 14.50 133 133 1985 22 12 8 101.75 44.50 8.50 140 134 1986 17 9 3 62.00 28.25 6.75 89 86 1987 18 9 4 69.25 24.75 7.75 102 92 1988 13 6 2 54.75 21.00 3.50 76 61 1989 17 9 4 67.25 27.25 5.75 95 88 1990 20 16 6 120.25 58.25 20.25 157 166 1991 14 10 5 86.25 44.00 14.00 102 119 1992 24 14 8 135.00 57.00 18.25 172 172 1993 14 10 8 79.25 45.50 15.25 137 130 1994 17 9 5 89.25 35.75 18.00 135 123 1995 10 7 3 51.75 22.25 9.00 75 74 1996 9 5 2 32.00 13.00 3.25 54 46 1997 17 9 7 72.50 33.50 15.00 138 120 1998 13 9 6 62.75 33.00 10.75 98 102 1999 9 6 2 46.50 23.50 6.00 57 61 Avg. 15.6 9.3 4.6 73.3 32.0 9.0 104 100 The NTC was calculated using the 1971-1999 averages of NS, H, IH, NSD, HD, IHD. The rounded averages of 16 NS, 9 H, 5 IH, 73 NSD, 32 HD, and 9 IHD were used for the calculations; the difference between the rounded and decimal answers was found to be negligible. These figures only include storms that formed (or were classified as such) east of 140W, and for the entire lifetime of the storm--storms of Central North Pacific origin are not included. For all the parameters, the average NEP season has an NTC roughly 170% of the 1950-1990 Atlantic value. An interesting coincidence that I noticed is that there are several years in which the MPD and NTC match, or nearly so: 1972, 1983, 1984, 1986, and 1992 are some examples. ----------------------------------------------------------------------- As John notes above, he included only storms forming in the Eastern North Pacific proper (i.e., east of 140W), but in the NSD, HD, and IHD parameters included the entire lifetime of each storm, regardless of whether it was east or west of 140W (or 180 for that matter). I calculated two alternate sets of statistics for the basin: (1) including only storms forming east of 140W and including only the portion of tracks east of 140W for the various days parameters (2) including all storms forming east of 180 and including only the portion of tracks east of 180 for the various days parameters I found that my NTC1 values were just about all within 10% of John's except for 1992 and 1994 with the latter year showing the greatest divergence. This was due to the large number of ENP cyclones forming farther west than normal and moving into the CNP, most notably Category 5 hurricanes Emilia, Gilma, and John. But my NTC2 parameter matched John's almost exactly for 1994. My NTC2 parameter was most different from John's NTC in 1992, no doubt due to my inclusion of the intense CNP hurricanes Ekeka and Iniki. The only other year in which my NTC2 showed a difference of more than around 10% was 1988; due most likely to John's omission of CNP Hurricane Uleki. *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for July: No tropical cyclones Atlantic Activity for July -------------------------- No warnings were issued on any tropical systems in the Atlantic basin during July. A fairly vigorous disturbance noted over Africa on 7 Jul had moved off the coast by 0000 UTC on 9 Jul and displayed a quite well-organized cloud pattern somewhat similar to the monsoon depressions of the Western Pacific. However, this system did not develop any further. (Thanks to Mark Lander for supplying some satellite imagery of this disturbance.) For a two-week or so period around mid-month strong upper-level westerlies spread over much of the tropical cyclogenetical region of the Atlantic--likely related to circulation anomalies in the Southern Hemisphere--and no tropical wave had much of a chance to develop. By late in the month the shear had relaxed and a tropical wave crossing the Atlantic from around the 27th through the 30th displayed a fairly tight swirl of low and middle clouds but could not generate enough sustained central convection to allow further development. *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for July: 2 tropical depressions 2 tropical storms ** 1 hurricane ** - One of these storms weakened in the Central Pacific but later redeveloped into a tropical storm in the Northwest Pacific basin 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. A special thanks to John Wallace for writing up most of the report on Tropical Storm Upana-Chanchu. I added an introductory paragraph and wrote the portion covering the redevelopment of the system as Chanchu in the Northwest Pacific basin. Northeast Pacific Activity for July ----------------------------------- Tropical cyclone activity had been just about normal in the North- east Pacific basin during June, although Carlotta's intensity was very unusual for June but not unprecedented. However, July was a little less active than average with only two named storms and one hurricane forming east of 140W in the Eastern North Pacific proper--only half of the normal 4 storms and 2 hurricanes. In addition to these cyclones, a rare Central North Pacific tropical cyclone formed--the first named storm on record to form in that area during July since the era of satellite coverage began. At the end of June a westward-moving disturbance more than 1000 nm west-southwest of Cabo San Lucas became quite well-organized and was on the verge of being classified as a tropical depression on 1 Jul. However, the thunderstorm activity became somewhat sporadic and no advisories were issued at the time. The TWO for 1000 PDT on 2 Jul also indicated that the system was likely to become a tropical depression within the next 24 hours, but once more the trend toward increased organization levelled off and the system subsequently weakened. In addition to the two named storms (Daniel and Emilia), plus Upana in the Central Pacific, advisories were issued by TPC/NHC for two tropical depressions in the Eastern Pacific. The first of these, TD-04E, formed from a tropical wave that left the African coast on 20 Jun. The wave tracked uneventfully across the Atlantic for the next ten days. Upon entering the Eastern Pacific on the 30th, a weak tropical LOW formed along the wave axis. Development was apparently hindered by a well-defined upper-level LOW to the north. Conditions slowly improved as the LOW tracked westward, and it was upgraded to TD-04E at 2100 UTC on 6 Jul when it was located approximately 900 nm southwest of Cabo San Lucas, Mexico. However, the depression soon entered a hostile environment and had fallen apart by around 1500 UTC on the 7th. (Thanks to John Wallace for writing up some information on TD-04E.) TD-05E likely developed from a tropical wave which was identified on 9 Jul in the eastern Atlantic southwest of the Cape Verdes. This wave had entered the Pacific by 18 Jul and a 1010-mb LOW formed on the wave axis on 20 Jul. The LOW passed south of Socorro Island on the 21st, still continuing to show increased convective organization. Advisories were commenced on TD-05E at 2100 UTC on 22 Jul when it was centered about 375 nm west-southwest of Cabo San Lucas. However, even as it was upgraded the depression was beginning to move over cooler SSTs, and by 23/0300 UTC was already over 24 C water. The convection that had been present earlier quickly vanished and the depression was declared dissipated at 1500 UTC on the 23rd. Tropical Storm Upana-Chanchu (TC-01C/12W / TS 0007) 20 - 30 July ---------------------------------------------------- Upana: a Hawaiian name, is the transliteration of Urban Chanchu: submitted by the colony of Macau, is the Macanese word for pearl The first Central North Pacific tropical cyclone to be named in three years was a rather insignificant system to have had so many names and numbers. There seems to be pretty good evidence that the development just west of the Dateline on 28 Jul was a re-development of the former Upana, but perhaps there was sufficient enough doubt at the time that the responsible JTWC forecaster decided to assign a new number when that agency initiated warnings on the depression. It should be pointed out that the official policy of the ESCAP/WMO Typhoon Committee regarding "Dateline crossers" is that the original name assigned by either NHC or CPHC will continue to be applied whenever a cyclone moves west across the 180th meridian. However, warnings on the earlier Tropical Storm Upana had been dropped for several days, and with a new number assigned by JTWC, it seems likely that JMA decided assigning a new name was the best policy to follow in this case. Upana was the first Central Pacific storm on record to form in the month of July since good satellite coverage began in 1966. An unofficial contender for the title is Tropical Storm Emilia of 1982: the best track data indicates tropical storm intensity was reached just west of 140W. However, that figure is probably due to the vagaries of best track data versus real-time warnings since there is often an adjustment. In any case, Upana was the first official July storm forming in the CPHC's area of responsibility and receiving a Hawaiian name. Upana was also the first Central Pacific storm to form in almost three years--since Paka in 1997. The origin of Upana can be traced to a well-defined tropical wave that tracked off the African coast on 28 June. It initially had a strong mid-level circulation, but this quickly dissipated, and the disturbance tracked uneventfully across the Atlantic. Even in the Pacific, the wave showed no signs of organization until it reached 138W, whereupon it transformed into a tropical LOW on 17 July. The LOW's organization increased steadily, and was sufficient to warrant its upgrade to Tropical Depression One-C at 0300 UTC on 20 Jul roughly 800 nm southeast of Hilo, Hawaii. The depression formed under a rare set of favorable conditions; its low latitude kept it just south of strong westerlies to its north as well as south of the cooler waters that usually weaken tropical cyclones east of Hawaii. The westward track was influenced by the strong subtropical ridge to its north which ensured it would present no threat to the Hawaiian Islands. Shear was favorably low, and SSTs were adequate; steady intensification seemed likely. A slightly improving satellite presentation warranted One-C's upgrade to Tropical Storm Upana at 2100 UTC on the 20th, roughly 650 nm south-southeast of Hilo. After its upgrade, Upana intensified only slightly over the next day to a 40-kt MSW with a CP of 1006 mb by 0900 UTC on the 21st. This was to be Upana's peak intensity, and was maintained for only a day. The storm generated strong, but ragged and ill-defined, convection, a fact exacerbated by its unusual westward track through the ITCZ. Upana's low latitude did not favor much intensification, and as the 21st wore on its organization steadily decreased as shear began to impinge on the system. Upana dropped below storm strength at 2100 UTC on the 22nd about 700 nm south-southwest of Lihue. Its dissipation seemed certain; the LLCC was exposed and devoid of deep convection. Surprisingly, the depression underwent a minor intensity fluctuation on the 23rd as strong convection redeveloped over the center. As shear was relatively low and Upana was entering warmer waters, re-intensification to tropical storm status was forecast. This, however, did not happen. The LLCC remained difficult to locate and the track was adjusted southward early on the 24th as the circulation dissipated and convection collapsed. The final advisory on Tropical Depression Upana was issued at 0900 UTC on 24 Jul with the center located roughly 425 nm south-southwest of Johnston Island. It is worth noting that the depression may in fact have dissipated earlier and redeveloped completely--a scatterometer pass near 0500 UTC on the 23rd indicated an open wave with no closed circulation. No damage or casualties are known from Upana; it was never less than 550 nm from Hilo. Following the issuance of the last advisory from CPHC, the post-Upana disturbance was not mentioned in the STWOs from Honolulu except that the Outlook for 4PM Hawaiian Standard Time on 26 Jul carried a short note that the remnants of Upana had moved west of the Dateline. A STWO issued by JTWC at 26/0600 UTC mentioned an area of convection located about 900 nm east of Kwajalein and moving westward. The next day satellite imagery depicted improving organization around a LLCC and a 26/2205 UTC TRMM pass revealed a partially-exposed LLCC with deep convection sheared just east of the center. A Formation Alert was issued by JTWC at 1330 UTC on the 27th, and warnings on TD-12W were begun at 28/0000 UTC. The depression was located about 500 nm east of Kwajalein or 300 nm east-northeast of Majuro when the first warning was issued. The system initially moved slowly to the west-northwest and gradually became better organized. At 1800 UTC on the 28th JTWC upgraded the depression to a 35-kt tropical storm located roughly 470 nm east- northeast of Kwajalein. This position represented a relocation of about 60 nm to the north-northeast of the previous warning position. JMA had also decided the system met tropical storm criteria and assigned the name Chanchu to the tropical cyclone. After being named Tropical Storm Chanchu moved primarily on a slow northward track. The 29/0000 UTC JTWC warning brought yet another relocation of 60 nm to the north-northeast of the previous position. Satellite intensity estimates were 35 and 45 kts so the MSW was increased to 40 kts--the maximum for the storm. (JMA's peak 10-min avg wind estimate remained at minimal tropical storm intensity of 35 kts.) Convection continued to organize around the LLCC for the next few hours and the 40-kt MSW was maintained through 0600 UTC. Chanchu was a small tropical storm with gales covering an area only about 100 nm in diameter. By 29/1200 UTC convection had weakened considerably and Chanchu's winds were dropped to 35 kts. Recent scatterometer and SSM/I passes did not reveal a LLCC. The final JTWC advisory was issued at 1800 UTC, placing the dissipating storm at a location about 500 nm north-northeast of Majuro. A SSM/I pass at 1824 UTC as well as another QuikScat pass did not show any evidence of a LLCC although low-level convergence was indicated. The weakening depression was forecast to track northwestward and dissipate within twelve hours. Hurricane Daniel (TC-06E) 23 July - 5 August -------------------------- For information on the origins of Atlantic and Northeastern Pacific tropical cyclones, I usually rely on a file created and maintained by John Wallace of San Antonio, Texas. John scans the Tropical Weather Discussions issued four times daily by TPC/NHC for the Atlantic and Eastern North Pacific and maintains a running log of all the tropical waves and LOWs referenced, naming the waves from phonetic alphabetical lists he has selected to avoid confusion. The vast majority of such waves can be traced back to western Africa or at least the eastern tropical Atlantic, but in the case of the pre-Daniel disturbance, John's log first references this tropical wave on 20 Jul when it was already located in the Pacific south of southeastern Mexico. So if this system had indeed originated on the Atlantic side of Central America, there apparently was not enough information to clearly piece together any possible earlier history of the wave. A 1009-mb LOW had formed on the wave axis by 22 Jul when it was located several hundred miles south of Manzanillo, Mexico. The first visible imagery on 23 Jul indicated that the disturbance had become organized enough to be classified as a tropical depression, so advisories were initiated on TD-06E. At 1200 UTC the depression was centered about 525 nm south-southwest of Manzanillo with 30-kt wind estimates from TAFB and SAB. Infrared imagery showed cold cloud tops to -80 C and outflow was good everywhere except on the eastern side. Intensification proceeded steadily and the system was upgraded to Tropical Storm Daniel on the second advisory. Six hours later the MSW was upped to 50 kts based on 45-kt satellite estimates from the three agencies and a report from ship PJPO of 26-kt winds and a SLP of 1004.8 mb from a point about 100 nm northwest of the center. A small, persistent cold CDO was positioned right over Daniel's center. By 24/1200 UTC Dvorak estimates had reached 65 kts and a 0835 UTC TRMM image depicted an eye-like feature, so Daniel was upgraded to a hurricane at 1500 UTC when it was centered approximately 650 nm south-southwest of Cabo San Lucas. The storm was moving to the west- northwest at 15 kts and appeared to be rapidly intensifying. By 0600 UTC on the 25th Daniel exhibited a classic appearance in satellite imagery with a 15-nm eye embedded in cold cloud tops. Intensity estimates from TAFB and SAB had reached T5.5, so the MSW was increased to 100 kts at 0900 UTC, thereby making Daniel a Category 3 hurricane on the Saffir/Simpson scale. The hurricane was centered more than 700 nm southwest of Cabo San Lucas and moving west-northwestward fairly quickly at 18 kts. Hurricane Daniel reached its peak intensity of 110 kts from 25/1800 to 26/0000 UTC with an estimated attendant CP of 952 mb. After peaking Daniel's eye became less distinct and the winds slowly decreased; however, the hurricane maintained an impressive inner core convective structure. There was a burst of cold convection (-80 to -82 C) in the southern eyewall on the morning of 26 Jul, indicating that slightly cooler SSTs had not affected the intensity of Daniel too much at that point. The hurricane experienced some weakening on 27 Jul as it continued westward, steered by a well-established mid-level ridge to the north. The eye appeared to expand and the MSW was decreased to 90 kts. By 28/0000 UTC the storm presented the appearance of a very well-organized hurricane with a round CDO and a distinct eye. T-numbers had reached T5.5 with objective numbers peaking at T6.0. With the storm near marginal SSTs, the MSW was set at 95 kts but the 0300 UTC discussion noted that winds might be 100 kts. However, six hours later, even with Daniel over SSTs near 25 C, the satellite signature had improved to the point that winds were increased again to 105 kts. TAFB's estimate as well as some objective Dvorak estimates were as high as 115 kts. Daniel at this time was moving slightly west-northwestward at around 16 kts due to some weak southerly shear and a mid- to upper- level trough passing to the north which acted to weaken the subtropical ridge. By 1800 UTC on 28 Jul the hurricane was definitely weakening and the MSW was decreased to 90 kts. Daniel was located about 875 nm east-southeast of Hilo, Hawaii, and was approaching 140W, so warning responsibility was handed to the Central Pacific Hurricane Center in Honolulu. After entering the Central North Pacific Daniel came under increased shear aloft and continued to weaken. The MSW was lowered to minimal hurricane intensity at 29/0600 UTC. The discussion from CPHC at 2100 UTC noted that some deep convection had redeveloped near the circulation center, and with Dvorak estimates of T3.5 and T4.0 from SAB and Honolulu, the hurricane intensity was maintained, even though the latest scatterometer data did not confirm the presence of a closed circulation. During the afternoon a reconnaissance airplane flew into the storm and found a CP of 995 mb with estimated maximum surface winds of 55 kts, so Daniel was downgraded to a 60-kt tropical storm at 0300 UTC on 30 Jul. The storm was then located about 400 nm east of Hilo, moving to the west-northwest. For the next day or so Daniel pretty much held its own with winds fluctuating around 50-55 kts. A reconnaissance flight around 1800 UTC on the 30th found winds to 50 kts and greater at flight level northeast of the center. The LLCC was beginning to separate from the deep convection and Daniel was beginning to move on a more westerly course that was projected to take the weakening storm across the central Hawaiian Islands. However, during the afternoon (local time) of 30 Jul, Daniel strengthened slightly and took a jog to the right, likely due to deep convection which had redeveloped to the north of the center pulling the storm northward and allowing a greater influence from upper-level winds with a southerly component. This jog was very significant in that it more or less assured that Daniel's center would remain north of the islands. A reconnaissance aircraft also indicated that the eye had reformed with deep convection covering the LLCC once more. The MSW estimate was upped to 55 kts in the 31/0300 UTC advisory. This re-intensification did not last long as Daniel began to present a sheared appearance. Winds were decreased to 50 kts at 0900 UTC and to 45 kts six hours later. But by 31/1800 UTC, Daniel had pulled another surprise and re-intensified significantly. The LLCC had once more moved beneath the upper-level cirrus dense overcast and convection was beginning to wrap around the center. CPHC increased the MSW estimate to 60 kts--just shy of hurricane force. The storm was centered roughly 125 nm northeast of Hilo at this time, still moving basically on a west-northwesterly track. This strong pulsation was apparently due to a favorable interaction with an upper-level trough to the west. An eye became apparent as the convection wrapped around the center. But, like the earlier intensification spurt, this one was also short-lived. By early afternoon (local time) on the 31st, the convection was collapsing and the eye feature had closed up. Thereafter, Daniel slowly weakened as it moved to the west-northwest and passed north of the Hawaiian chain. At 1200 UTC on 1 Aug the LLCC (which was exposed) was about 130 nm northeast of Honolulu while the nearest deep convection was about 100 nm to the north of the center. The MSW was down to 45 kts by this time. A reconnaissance flight a few hours earlier had found a CP of 1001 mb but maximum FLW of only 32 kts. During succeeding days convection would occasionally break out along the storm's northern flank, the result of which was to pull the system northwestward. Daniel gradually weakened over the next few days, although some convection would occasionally flare up near the LLCC despite its movement over cooler waters. The storm never really showed any significant signs of re-intensification but the persistent convection did serve to prevent Daniel from weakening as rapidly as might be expected. By 1200 UTC on 3 Aug the convection within the circulation had all but collapsed and Daniel was downgraded to a tropical depression well to the northwest of Hawaii. The depression continued moving to the northwest until around 04/0000 UTC when it appeared to be turning to the north as it "punched" through the subtropical ridge. The steadily weakening depression moved generally northward along 170W but the system stubbornly clung to life for another day or so by generating a few sporadic thunderstorms mainly to the south of the center. Finally, by 0600 UTC on 5 Aug all deep convection had ceased within the LLCC and Daniel was declared dissipated about 600 nm northeast of Midway Island. Except for some wobbles in the vicinity of Hawaii, this long-lived and far-travelled hurricane followed a remarkably smooth and regular track for its entire life. Tropical Storm Emilia (TC-07E) 26 - 30 July ------------------------------- The origins of the Eastern Pacific's fifth tropical storm of the season were connected with a tropical wave first identified in the east-central tropical Atlantic on 14 Jul. The disturbance propagated westward, entering the Caribbean Sea on the 17th, and had emerged into the Pacific Ocean by around 22 Jul. On that day a 1010-mb LOW was noted south of El Salvador. The wave continued to move westward and by the early morning of 25 Jul had become somewhat more organized. Showers associated with the disturbance at this stage spread north- ward and led to some locally heavy rains over portions of southwestern Mexico. By 1200 UTC on 26 Jul the system had become organized enough that advisories were initiated on TD-07E. The depression was then centered about 540 nm south of Cabo San Lucas. Although deep convection had become less centralized over the previous six hours, the overall convective pattern had improved. A 0748 UTC TRMM overpass indicated a mid-level circulation in the 85 GHz channel that was about 60 nm north of the LLCC as seen in the 37 GHz channel. Even though satellite intensity estimates were below tropical storm strength at 1800 UTC, later visible imagery revealed that an inner convective region had formed with an outer band wrapped more than halfway around it. On this basis the depression was upgraded to Tropical Storm Emilia on the 2100 UTC advisory. While Emilia presented a very well-defined LLCC with a pattern resembling a banding-type eye, the convection was neither strong nor concentrated near the broad center. There were occasional bursts of deep convection, and the MSW estimate reached 45 kts by 27/0600 UTC but remained there until 1800 UTC when there was an improvement in the organization of Emilia. Dvorak intensity estimates at 1800 UTC were 50 kts and 55 kts from TAFB and SAB, respectively, so Emilia's winds were upped to 55 kts--the peak for the storm's history. The center was located approximately 300 nm south-southwest of Cabo San Lucas at this time. The storm maintained this intensity for about twelve hours as it moved northwestward at 12 kts, but by 0600 UTC on the 28th had begun to weaken. Most of the associated convection had dissipated, and even though KGWC gave Emilia a 65-kt estimate with 55 kts from the other agencies, the lack of convection and motion over cooler SSTs suggested a lower intensity so the MSW was dropped to 50 kts. Some deep convection subsequently returned to the central region of Emilia, but northeasterly shear kept it from wrapping around the LLCC. Since its inception Emilia had been moving on a fairly straight northwesterly track, but upon reaching the 20th parallel, the weakening cyclone turned abruptly to the west and followed a general westerly course for the rest of its existence. The effects of shear and motion over cooler waters caused the storm to begin weakening rapidly after 1200 UTC on 28 Jul. Winds were down to minimal tropical storm intensity by 29/0000 UTC but were held there for about 18 hours due to Dvorak estimates from KGWC, TAFB, and SAB of 35 kts, and also due to the possibility of a convective flare-up during the diurnal maximum. There was a flare-up near the center around 1200 UTC, but by the after- noon of the 29th the convection had diminished and Emilia was down- graded to a depression at 2100 UTC, and the final advisory was issued at 0300 UTC on 30 Jul, placing the dissipating center about 625 nm west-southwest of Cabo San Lucas. *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for July: 2 tropical depressions 4 tropical storms ** 2 typhoons ** - One of these, Chanchu, was a redevelopment of Tropical Storm Upana from the Central North Pacific. Another was a system for which no warnings were issued by any TCWC but was considered a tropical storm by Dr. Mark Lander of the University of Guam. 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 Activity for July ----------------------------------- After a quiet June in which no tropical depressions or storms entered warning status, the waters of the Northwest Pacific basin became quite active indeed during the month of July. Five tropical storms, including two which reached typhoon strength, were assigned names by JMA. One of these originated with a disturbance from the Central Pacific which had formerly been a tropical storm south of Hawaii. In addition to these, another small TUTT-spawned tropical cyclone formed early in the month but no warnings were issued for this system by any TCWC. Dr. Mark Lander of the University of Guam felt that this disturbance did reach minimal tropical storm intensity, and he has provided me with a track for the cyclone which is included in the accompanying tropical cyclone tracks file. In accordance with a procedure I developed last summer, I have dubbed this system with the Greek letter "Kappa". (I assign the next available Greek letter to any system which (1) appeared to have exhibited nominal tropical characteristics, (2) was not warned on by any TCWC, and (3) in the opinion of some experienced tropical meteorologist, likely reached minimal tropical storm intensity (1-min avg MSW of 34 kts or higher).) This system, plus all the officially named tropical storms, will be described in greater detail below. There were also two tropical depressions identified during the month which did not reach tropical storm intensity. The first of these, TD-07W (named Gloring by PAGASA), formed on 12 Jul about 225 nm east of Catanduanes Island in the Philippines. PAGASA and JMA began issuing bulletins on Gloring, but JTWC did not initiate warnings until 0000 UTC on 13 Jul when the broad center of the depression was about 115 nm north-northwest of Catanduanes Island. The system moved generally in a westerly direction, crossing central Luzon between around 14/0600 and 1800 UTC. After emerging into the South China Sea, Gloring turned more to the northwest and weakened with the final JTWC warning placing the center about 250 nm northwest of Manila at 15/0000 UTC. As Tropical Depression 07W (Gloring) was crossing Luzon, another area of disturbed weather formed in the South China Sea to the west of Luzon. This area slowly consolidated into a tropical depression and JTWC initiated warnings on TD-08W at 0000 UTC on 16 Jul when the center was located roughly 235 nm south-southwest of Hong Kong. The depression moved on a north-northwesterly track which carried it inland into China about 140 nm west of Hong Kong around 17/0600 UTC. Based upon JTWC's warnings, winds never exceeded 25 kts in this system; however, JMA reported the 10-min avg MSW at 30 kts. By 1800 UTC the depression was dissipating inland in China north of Canton. Tropical Cyclone "Kappa" 1 - 5 July ------------------------ NOTE: No warnings were issued by JTWC nor JMA on this system. All the information contained below (except for some geographical references which I calculated) was supplied to me by Dr. Mark Lander of the University of Guam. A special thanks to Mark for sending me the information and track for this system. A small circulation formed in the eastern quadrant of a TUTT cell on 1 Jul about 325 nm northwest of Wake Island. Over the next day or so the small system tracked generally northward (or a little west of due north) until it reached a point roughly 600 nm northwest of Wake Island around 1800 UTC on 2 Jul. It then made a sharp turn to the east and convection began to increase around the center. By 1800 UTC on 3 Jul Mark estimates the MSW to have reached 35 kts with the center located approximately 625 nm north-northwest of Wake Island. Estimated peak intensity of 40 kts occurred around 04/1200 UTC when visible satellite imagery showed a partially-exposed LLCC tucked under the southwestern side of a CDO feature. "Kappa" continued to move in a general easterly direction and began to weaken rapidly on 5 Jul as it merged with an old frontal system. The final position in Mark's track places the dissipating center about 700 nm north- northeast of Wake Island at 05/1200 UTC. Typhoon Kirogi (TC-05W / TY 0003 / Ditang) 2 - 8 July ------------------------------------------- Kirogi: Korean word for a type of wild goose, submitted by the Democratic People's Republic of Korea (North Korea) After lying quiescent for over a month, the tropics of the Northwest Pacific basin became quite active in early July. Two twin typhoons were spawned on opposite sides of the Philippines with both moving on northerly, roughly parallel, tracks. Typhoon Kirogi was the stronger of the two and moved from its birthplace well east of the central Philippines to near the Japanese island of Hokkaido, brushing the southeastern corner of Honshu as it swept north-northeastward. An area of convection developed on 30 Jun about 350 nm east of the Philippine island of Mindanao. The convection persisted near a weak, mid-level circulation near the axis of the monsoon trough which extended from Mindanao eastward to Koror. CIMSS shear charts and a 200-mb analysis indicated a favorable environment for strengthening. The disturbance remained quasi-stationary in the general area for the next few days and slowly became better organized. A broad LLCC was evident in visible imagery on 1 July. JTWC issued a Formation Alert at 2300 UTC on 1 Jul as convection began to organize rapidly about the LLCC. The first warning on TD-05W was issued at 02/0600 UTC with the center located about 525 nm east of Catanduanes Island in the Philippines. PAGASA initiated warnings six hours later, naming the depression Ditang. The developing system began moving on a slow northerly track several hundred miles east of the Philippines. JTWC upgraded TD-05W to a tropical storm at 02/1800 UTC and PAGASA followed suit six hours later. The LLCC was still very broad but convection was wrapping around the southern and western periphery. JMA upgraded the depression to Tropical Storm Kirogi at 0600 UTC on 3 Jul with maximum 10-min avg winds of 40 kts. JTWC's 1-min MSW was 45 kts, which represents excellent agreement with JMA. Both JTWC and JMA upgraded Kirogi to a 65-kt typhoon at 03/1800 UTC with the storm centered roughly 450 nm east-northeast of Catanduanes Island. Animated satellite imagery revealed increasing consolidation with tightly-curved banding features. The storm exhibited good outflow in all quadrants and was continuing to be steered generally northward by a mid-level subtropical ridge to the east. Located within a favorable large-scale environment, Kirogi quickly intensified into a strong typhoon. JTWC's MSW estimate reached 100 kts at 0600 UTC on 4 Jul with animated visible satellite imagery depicting a large, rapidly intensifying system. Kirogi sported a 29-nm irregular eye with a convective band evident as far as 230 nm to the north of the LLCC. Kirogi reached its estimated peak intensity of 115 kts six hours later with the center approximately 470 nm southeast of Okinawa. A SSM/I pass at 04/0926 UTC depicted a 32-nm round eye with data from a TRMM pass indicating that the strongest banding lay to the east and south. Gales extended outward 165 nm to the east of the center and 115 nm elsewhere, while 50-kt winds reached out 85 nm to the east and 55 nm elsewhere. The estimated radius of 100-kt winds was 15 nm; hence, Kirogi was a fairly large typhoon. JMA's estimated peak 10-min avg wind was 85 kts while PAGASA reported 90 kts from 05/0000 through 05/1800 UTC. The JTWC warning at 05/0000 UTC noted that convection was symmetric around the 26-nm cloud-filled eye. Six hours later the MSW was still reported as 115 kts, but animated satellite imagery showed that the deep convection had weakened considerably over the past few hours. Apparently a mid-latitude trough to the northwest was having an adverse effect on Kirogi even though the outflow appeared to still be good in all quadrants. A 05/0914 UTC SSM/I pass depicted virtually all of the convective banding to be confined to the eastern half of the typhoon. By 1800 UTC the storm was continuing to show signs of weakening with the MSW lowered to 100 kts. The deepest convection was located in the southeastern quadrant only. Kirogi was by this time moving on a north-northeasterly heading from which it never deviated. Winds had dropped to 85 kts by 06/0000 UTC and were down to 75 kts (per JTWC) by 1200 UTC, but the storm's intensity then levelled off and Kirogi maintained 75-kt winds for a day and a half. The typhoon passed about 375 nm west of Iwo Jima around 0600 UTC on the 6th. This location was also approximately 350 nm east of Okinawa. By 1200 UTC Kirogi was beginning to accelerate some on its north-northeasterly heading, and had also become quite a large typhoon. Winds of 50-kts covered an area 300 nm in diameter while gales covered an area almost 500 nm in diameter. Even though Kirogi had lost much of its earlier punch, it remained a well-organized typhoon with a ragged, cloud-filled eye visible much of the time as it accelerated toward Japan. The JTWC warning at 0600 UTC on 7 Jul noted that animated satellite imagery revealed a 13-nm eye with a band of heavy convection closing in to make a concentric eye- wall. By 1800 UTC Kirogi was located about 90 nm south of Tokyo and moving north-northeastward at 26 kts. The MSW were estimated at 70 kts from both JTWC and JMA with a synoptic pressure report of 973 mb. A 200-mb analysis indicated that a mid-latitude trough was situated about seven degrees west of the typhoon with southerly divergent flow of 10-20 kts over the system. The weakening Kirogi passed near Choshi on Cape Inubo as it brushed southeastern Honshu. By 08/0000 UTC the storm was located approximately 80 nm east- northeast of Tokyo with 65-kt winds and was beginning to transition into an extratropical system, although a 07/2117 UTC SSM/I pass indicated a CDO with the LLCC about 30 nm into the convection. Thereafter, Kirogi continued to weaken as cold air advection and cooler SSTs caused the convection to weaken. The storm continued moving north-northeastward east of Honshu and by 1800 UTC on the 8th had completed extratropical transition just southeast of the island of Hokkaido. While Typhoon Kirogi was gaining strength east of the Philippines, a monsoon depression in the South China Sea, later to become Typhoon Kai-tak, was slowly consolidating and was accompanied by a large area of gales before any warnings were issued. Heavy rains during this time led to disastrous flooding and landslides in the Philippines. There were some press stories circulating which stated that Typhoon Kirogi had struck the Philippines or had caused great damage to the nation. This is erroneous--the typhoon was never closer to the Philippines than about 450 nm and could not have had any significant impact in the country. However, Kirogi did leave behind some damage and fatalities in Japan. There were three persons reported killed and some cities were flooded and homes buried in landslides. At least 300 homes in the Tokyo metropolitan area were flooded, and downed power lines led to about 20,000 homes being without electricity for as long as four hours. Before reaching Honshu the storm had struck the Izu island chain south of Tokyo where a shrine festival hall and three homes were demolished by landslides on the island of Kozushima. One press report mentioned winds to 68 kts in Japan, but the location of this report isn't clear, nor was it stated if it were a sustained wind or peak gust. Typhoon Kai-tak (TC-06W / TY 0004 / Edeng) 3 - 11 July ------------------------------------------- Kai-tak: contributed by Hong Kong, China, is the name of the old airport in Hong Kong which was closed in 1998 An area of persistent but disorganized convection developed on 2 Jul in the central South China Sea about halfway between Luzon and Vietnam. A QuikScat pass and synoptic reports indicated that a broad, weak circulation was associated with the convection. The area had drifted northward some by 3 Jul, and a synoptic analysis and visible satellite imagery revealed a developing LLCC. PAGASA initiated warnings on Tropical Depression Edeng at 03/0000 UTC with the center located approximately 425 nm south-southeast of Hong Kong. Edeng moved slowly northeastward toward the northern tip of Luzon. JTWC issued a Formation Alert at 03/2300 UTC with the LLCC estimated about 150 nm northwest of Manila. The system had exhibited improved organization with a band of convection wrapping into the eastern quadrant of the LLCC. Edeng was located in a favorable environment for intensification underneath the axis of the subtropical ridge. JMA began issuing bulletins on the system at 0000 UTC on 4 Jul with the broad center located about 100 nm south-southwest of Laoag on the island of Luzon. JTWC followed suit and initiated warnings on TD-06W six hours later. The center of the depression remained quasi- stationary over the next couple of days over or near northern Luzon, thereby slowing its intensification, even though convection gradually became better organized. At 1200 UTC on 5 Jul PAGASA upgraded Edeng to a tropical storm with 35-kt winds centered about 35 nm north of Laoag. Six hours later both JTWC and JMA had classified the system as a tropical storm with JMA assigning the name Kai-tak. Even though Kai-tak had developed slowly, once it moved out over the Luzon Strait, the storm began to intensify rather quickly. By 0600 UTC on 6 Jul the convection had increased in areal coverage and had consolidated around the LLCC. MSW were estimated at 60 kts by both JTWC and JMA, and Kai-tak was upgraded to typhoon intensity at 1200 UTC by JMA. The center of Kai-tak was located approximately 150 nm northwest of Laoag at this time. (JTWC upgraded the storm to a typhoon at 1800 UTC.) Typhoon Kai-tak remained quasi-stationary in the Luzon Strait just off the northern end of Luzon for several days. At 1200 UTC on 8 Jul, just before the by-then weakening typhoon began to move decidedly to the north-northeast, the center of Kai-tak was located only about 90 nm north of where it been 72 hours earlier when it had first been upgraded to a tropical storm by PAGASA. From comments in some of the JTWC warnings, it appears that Kai-tak's slow motion was caused by the combination of a subtropical ridge building in from the east of the storm and a ridge located to the north. The typhoon reached its estimated peak intensity of 75 kts (per both JTWC and JMA) from 07/0600 through 08/0000 UTC. Interestingly, PAGASA reported a 10-min avg wind of 90 kts during this period which would correspond to a 1-min avg MSW of about 105 kts. In the cyclone tracks file, I normally use the higher 10-min avg MSW value that I have access to, but in this case, I reported JMA's lower value since it was much more in line with JTWC's MSW, although it should be pointed out that a 75-kt 10-min avg MSW would imply a 1-min avg MSW of 85 kts. By 0000 UTC on the 8th satellite imagery depicted weakening convection around a 15-nm eye, possibly due to upwelling of cooler water as a result of the very slow movement of the system. At this point JTWC still forecast Kai-tak to take off toward the north and intensify, but by 0600 UTC it was evident the typhoon had weakened considerably. Virtually all the convection around the exposed LLCC had dissipated and the MSW was decreased to 65 kts. There was still, however, a fair amount of convection over the periphery of the storm. Kai-tak was able to maintain minimal typhoon intensity for another 24 hours as it began to move north-northeastward toward southern Taiwan. The storm scooted up the east coast of the island, being located about 50 nm northeast of the southern tip of Taiwan at 0000 UTC on 9 Jul. At this juncture some convection had begun to wrap in towards the center and a banding eye was becoming evident, but this trend was reversed, apparently due to interaction with the mountainous island. At 0600 UTC Kai-tak was downgraded to a tropical storm when it was located about 45 nm southeast of Taipei. (JMA had down- graded the system twelve hours earlier.) By the time the storm was passing Taipei it was moving northward at 18 kts, being steered by a combination of a mid-level HIGH to the east and a mid-latitude trough over southeastern China. After brushing Taiwan Kai-tak continued rapidly northward with a slight jog to the north-northwest toward eastern China with most of the convection over the western portion of the system. As the storm neared China there was an increase in convection north of the center. Animated water vapor imagery showed good outflow to the north and south of the center and a 200-mb analysis revealed upper-level diffluence above Kai-tak. At 09/1800 UTC the storm was centered about 35 nm east-southeast of Wenchou and by 0000 UTC on the 10th was skirting the Chinese coast about 50 nm south-southeast of Shanghai. The MSW estimate was decreased to 45 kts at this time and the storm continued to weaken as it pulled away from the coast and sped north- ward into the Yellow Sea. By 0600 UTC Kai-tak's center was located about 85 nm northeast of Shanghai and moving northward at 22 kts. Convection was beginning to weaken and the storm was downgraded to a depression at 1200 UTC and forecast to transition into an extratropical system. The final JTWC warning at 11/0000 UTC placed the system in the far northern reaches of the Yellow Sea just west of the northern part of the Korean peninsula. During the time that Kai-tak was brewing as a monsoon depression in the South China Sea, gales existed for several days just south of the system. This regime helped to bring very heavy rains to portions of the Philippines which led to widespread damage and many fatalities. Contrary to what was widely reported in the press, Typhoon Kirogi, several hundred miles to the east, was not responsible for the situation in the Philippines except that perhaps inflow into the typhoon helped to enhance the monsoon a bit. In the 72 hours ending at 0000 UTC on 6 Jul Baguio City had recorded 570 mm, the monthly average being 1074 mm. (Thanks to Patrick Hoareau for sending this information along.) The number of fatalities is not altogether clear. One press report indicated that 27 lives had been lost in the flooding and landslides in the northern and central portions of Luzon. Over 400,000 persons were driven from their homes by the flooding which left hundreds of villages and many towns under 1 to 2 metres of water. Hundreds of houses were damaged and in many cases totally destroyed. The water level behind the Ambuklao and Binga dams came to within less than 1 metre of reaching the spillover level. Crops (especially rice) and fishponds in many areas were damaged. An unusual tragedy in Manila claimed over a hundred lives. A city garbage dumpsite, covering about 0.1 square miles in area but with garbage piled up to seven stories high, was weakened by the heavy rainfall and collapsed onto an area of shanties, huts, and lean-tos. As the garbage slid over the homes, it caught fire, burning and burying many people alive. Three days after the slide the number of dead was placed at 137 with 150 or more still believed buried. Tropical Storm Tembin (TC-09W / TS 0005) 17 - 23 July ----------------------------------------- Tembin: Japanese word for balance (a weighing device) Tropical Storm Tembin was a fairly weak tropicavel behind the Ambuklao and Binga dams came to within less than 1 metre of reaching the spillover level. Crops (especially rice) and fishponds in many areas were damaged. An unusual tragedy in Manila claimed over a hundred lives. A city garbage dumpsite, covering about 0.1 square miles in area but with garbage piled up to seven stories high, was weakened by the heavy rainfall and collapsed onto an area of shanties, huts, and lean-tos. As the garbage slid over the homes, it caught fire, burning and burying many people alive. Three days after the slide the number of dead was placed at 137 with 150 or more still believed buried. Tropical Storm Tembin (TC-09W / TS 0005) 17 - 23 July ----------------------------------------- Tembin: Japanese word for balance (a weighing device) Tropical Storm Tembin was a fairly weak tropical storm which formed near the northern Mariana Islands in mid-July and moved almost due northward, recurving just east of Honshu. An area of convection developed on 16 Jul over the northern Marianas. Animated satellite imagery and CIMSS products indicated that the region was under the divergent quadrant of a TUTT with a possible anticyclone developing over the convection. Synoptic observations indicated a weak LLCC. JMA began issuing bulletins on a new tropical depression at 0000 UTC on 17 Jul with the weak center estimated to be just west of the northernmost Marianas. JTWC issued a Formation Alert at 0100 UTC, noting that the disturbance had consolidated and was intensifying. =========================================================================== =Published with permission @ Typhoon2000.com WxSite.= 10.04.00 .