Date: Mon, 19 Jun 2000 08:35:31 -0700 From: Lindsay X-Mailer: Mozilla 3.0 (Win16; I) To: aussie-weather at world.std.com Subject: aus-wx: Cent Tablelands rain Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Monday 9am: Some moderate to heavy showers here in Blackeath overnight. 9mm in the gauge this morning. Temp at 9am = 5 Anybody more in the know than me got some thoughts on this change due in Thursday? Much cold air with it? Here's hoping the ski-fields get some more snow and maybe out west of us too. Lindsay Pearce +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ From: Matthew John Piper To: aussie-weather at world.std.com Subject: aus-wx: Sydney blanketed in Fog Date: Mon, Jun 19 2000 11:40:58 GMT+1100 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi Everyone, Here in Sydney this morning it has been exceptionally foggy. Currently at 10:37am there is still an almost complete white out in the city. I can hardly see the building next to me the fog is so thick. I would presume that the airport would be closed because of it and it doesnt look like lifting anytime soon. Matthew Piper This message was sent through MyMail http://www.mymail.com.au +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ X-Sender: carls at ford.ace-net.com.au Date: Mon, 19 Jun 2000 01:50:46 +1000 To: Aussie Weather List From: Carl Smith Subject: aus-wx: SUMMARY: April Tropical Cyclone Summary - Part 2 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY APRIL, 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.) SPECIAL NOTE: The April summary is being issued in two installments. This second installment covers the Australian Region and the South Pacific Ocean. The first installment, covering the South Indian Ocean west of 90E, was issued on 8 May. *********************************************************************** TROPICAL CYCLONE NAMES FOR 2000 ATLANTIC AND NORTHEAST PACIFIC BASINS ATLANTIC EASTERN CENTRAL NORTH PACIFIC NORTH PACIFIC ----------------------------------------------------------------------- Alberto Leslie Aletta * Miriam Upana Beryl Michael Bud * Norman Wene Chris Nadine Carlotta Olivia Alika Debby Oscar Daniel Paul Ele Ernesto Patty Emilia Rosa Huko Florence Rafael Fabio Sergio Ioke Gordon Sandy Gilma Tara Kika Helene Tony Hector Vicente Lana Isaac Valerie Ileana Willa Joyce William John Xavier Keith Kristy Yolanda Lane Zeke * = name has already been assigned to a tropical cyclone *********************************************************************** APRIL HIGHLIGHTS --> Tropical Cyclone Hudah strikes Madagascar and Mozambique --> Severe Tropical Cyclone Rosita strikes Western Australia --> Two small midget cyclones form in Coral Sea--one hits Queensland *********************************************************************** ACTIVITY BY BASINS ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico Activity for April: No tropical cyclones *********************************************************************** NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180 Activity for April: No tropical cyclones *********************************************************************** NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180 Activity for April: No tropical cyclones *********************************************************************** NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea Activity for April: No tropical cyclones *********************************************************************** SOUTH INDIAN OCEAN (SIO) - South Indian Ocean West of Longitude 90E Activity for April: 1 moderate tropical storm 1 subtropical cyclone (of at least gale force) 1 intense tropical cyclone (from March) NOTE!!! The South Indian Ocean basin was covered in the first installment of the April summary and was issued on 8 May. *********************************************************************** AUSTRALIAN REGION (AUG) - From Longitude 90E Eastward to Longitude 160E Activity for April: 2 tropical LOWs 2 tropical cyclones of storm intensity 2 severe tropical cyclones (hurricanes) The primary sources of information for Australian Region tropical cyclones are the warnings and bulletins issued by the three TCWCs at Perth, Darwin, and Brisbane. Information gleaned from JTWC's warnings is used as a supplement for times when it was impossible to obtain Australian bulletins and for comparison purposes. References to sustained winds should be understood as being based on a 10-min averaging period unless otherwise noted. Matthew Saxby, a tropical cyclone enthusiast from Queanbeyan, New South Wales, Australia, typed up the tracks for the cyclones and LOWs in the Australian Region. Also, Carl Smith, another dedicated tropical cyclone enthusiast from the Gold Coast of Queensland, sent reports he had written for some of the cyclones; and Jeff Callaghan of the Brisbane TCWC sent me a considerable amount of information on Cyclones Tessi and Vaughan and the two Coral Sea LOWs at the end of the month. A special thanks to all these folks for their assistance. A description of the Australian Cyclone Severity Scale can be found in Chris Landsea's FAQ on HRD's website: on Michael Bath's Australian Severe Weather site: or on the Australian Bureau of Meteorology's official website: Click on the link 'Cyclone Severity Categories' Carl Smith has a website on which he has placed his full reports on the various cyclones in the Australian Region this season, as well as map animations which he has created for the storms. The URL is: Links to various reports and map animations can be found under the link 'TC Reports & Map Animations'. Australian Region Activity for April ------------------------------------ April turned out to be one of the most active months of the 1999 - 2000 season in the Australian Region. Two very intense tropical cyclones, Paul and Rosita, formed in the Perth AOR with Paul moving harmlessly out into the Indian Ocean while Rosita made landfall near Broome as a severe Category 4 cyclone. Very early in the month two midget cyclones, Tessi and Vaughan, popped up in the Coral Sea and menaced the Queensland coast with Tessi causing substantial damage in the Townsville area while Vaughan collapsed and dissipated very quickly near Cairns. Late in the month and into early May, two tropical LOWs formed in the Coral Sea, moved eastward into the Fiji AOR thereby receiving a number from the Nadi TCWC, then returned into Australian waters and approached the Queensland coast. Since reports of gales were widespread with these systems, I have given them special coverage below. Tropical Cyclone Tessi (TC-22P) 31 March - 2 April -------------------------------- A STWO issued by JTWC at 0600 UTC on 31 Mar indicated that an area of convection had formed in the Coral Sea well southeast of New Guinea or roughly 600 nm east of Cooktown, Queensland, and had persisted for twelve hours. Animated satellite imagery revealed persistent convection with some degree of organization. A 31/0000 UTC synoptic analysis indicated strong gradient flow southwest of the convection and CIMSS charts indicated low to moderate vertical shear. The disturbance was given a Fair potential to develop into a significant tropical cyclone. The Brisbane TCWC also began issuing gale warnings on the LOW at 31/0600 UTC. The developing tropical LOW continued to move west-southwestward toward the Queensland coast throughout 31 Mar, gradually getting better organized, and was upgraded to Tropical Cyclone Tessi with 40-kt winds at 0000 UTC on 1 Apr when the center was located approximately 530 nm east of Cooktown. A convective band had developed over the northeast quadrant, and a 31/2251 UTC SSM/I pass showed convection wrapping in toward the LLCC from the southwest. At 1200 UTC both JTWC and Brisbane were estimating winds at 40 kts and the cyclone's appearance continue to improve in organization. Cyclone Tessi continued moving at about 10 kts toward the Queensland coast and made landfall on 2 Apr around 2030 UTC about 20 nm south of Lucinda. This storm was a midget cyclone which formed in the low- level easterlies in the absence of any monsoon westerlies. According to a report on the storm from Jeff Callaghan of BoM Brisbane, at 2300 UTC on 31 Mar the radius of the 1008-mb isobar was about 165 nm. Twenty-four hours later the 1008-mb isobar had shrunk to a radius of 80 nm, and by the time of landfall had a radius of only 35 nm, thus indicating how environmental pressures around the vortex rose as the cyclone intensified. Tessi formed a small, compact radar eye with a diameter of about 5.5 nm when it was near the coast around 1800 UTC on 2 Apr. In the cyclone's southern semicircle gales were reported as far south as Gumlu (about 120 km southeast of Townsville), which would imply a gale radius of about 100 nm; however, on the northern side gales extended outward from the center only about 16 nm. At Gumlu an anemometer failed at 60 kts. (It was a pressure tube anemometer at a height of 6.5 m above the ground.) The Australian Institute of Marine Science (AIMS) maintains an AWS on Magnetic Island (about 15 km or 8 nm northeast of the Townsville Meteorological Office), and some data from this site was received later and passed along to me by Jeff. The AWS measured a 10-min avg easterly wind of 59 kts at 02/1600 UTC which, in conjunction with some other data, indicates that Tessi's center was about 40 km (22 nm) from Townsville at its closest approach. Tessi set several new weather records for the month of April at the Townsville Meteorological Office: highest wind gust (70 kts), highest daily rainfall (271.6 mm), and the highest monthly rainfall (539 mm as of 27 Apr). Normal daily rainfall records are taken from 9AM to 9AM local time; however, 423.4 mm was measured in the 24-hour period ending at 1AM (local time) on 4 Apr. The maximum wind gust occurred at 02/1540 UTC when the center of the cyclone was about 33 nm away. The worst wind damage in settled areas occurred just outside the eye in the area around Mutarnee, a small village 60 km northwest of Townsville. Many large trees were uprooted and the roof of a farmhouse was lifted off, battens and all, and deposited in a cane field about 60 m away. The most extensive tree damage was farther east in the normally uninhabited beach areas where some isolated beach huts were unroofed. The eyewall passed over this uninhabited area consisting mainly of marsh land. The damage in this vicinity was confined to the immediate coastal area. Bambaroo, which lies 14 km northwest of Mutarnee and a little farther inland, suffered no damage. After 2000 UTC the eye began to dissipate quickly and Tessi was rapidly weakening as the center made landfall. In the Townsville area the cyclone caused widespread wind damage, mainly to trees and power lines with about 35,000 persons left without power. Most structural damage was due to falling trees though there were isolated reports of roof damage attributed directly to the wind. Widespread flooding occurred with the associated downpour, and there was a severe landslide in one of the more affluent residential areas on Castle Hill. There was also some wave damage with several boats destroyed. Warnings from JTWC and Brisbane were in pretty good agreement with regard to position but not with intensity. As was the case with Cyclone Steve back in February, JTWC's peak MSW estimate was actually lower than Brisbane's maximum 10-min avg wind estimate. Brisbane was reporting 50 kts as the cyclone neared the coast whereas JTWC's peak MSW estimate was 45 kts. (The 02/1200 UTC JTWC warning did indicate that at least one Dvorak intensity estimate of 55 kts had been received.) Again, as with Steve, radar and synoptic observations along the coast seem to confirm that Tessi was somewhat stronger than its appearance in satellite imagery suggested. Tropical Cyclone Vaughan (TC-23P / TD-17F) 28 March - 7 April ------------------------------------------- Like Tropical Cyclone Tessi, Vaughan was a midget tropical cyclone which formed in the low-level easterlies in the absence of any monsoon westerlies. A very broad area of convection had developed northwest of Fiji by 0600 UTC on 27 Mar near 14S, 172E. Synoptic analysis indicated a weak LLCC associated with the convection with CIMSS charts indicating the area was under weak to moderate vertical shear. Twenty-four hours later the main area of convection was about 300 nm farther to the west, or about 600 nm west of Fiji. Animated multi- spectral satellite imagery depicted poorly-organized convection forming along the tail end of a weak shear line extending from New Caledonia to Fiji with a weak LLCC centered over Vanuatu. The disturbance was located under the subtropical ridge axis and a 27/1855 UTC QuikScat pass showed convergent flow north of the shear line. Fiji began mentioning the system in their daily Tropical Weather Summary at 28/1800 UTC, numbering it as Tropical Disturbance 17F. The area remained quasi-stationary for a couple of days roughly 150 nm south-southwest of Port Vila in Vanuatu. The STWO issued by JTWC at 29/0600 UTC indicated that convection was still poorly organized and displaced east of the LLCC which was located within a northwest- southeast oriented surface trough under moderate vertical shear. Convection increased some on 30 Mar with a 200-mb analysis indicating a diffluent region over the area. JTWC upgraded the development potential to Fair while Nadi classified the system as a tropical depression and issued three gale warnings, mainly in the anticipation that gales would develop. On 1 Apr the depression began to move slowly to the northwest toward an environment more favorable for intensification. Early on 2 Apr the system showed some signs of weakening and JTWC downgraded the development potential to Poor. However, by 1800 UTC animated satellite imagery showed convection rapidly building over the LLCC so the development potential was once more upgraded to Fair. The Nadi TCWC issued a new gale warning at 02/2100 UTC with the center of the depression located on the boundary of the Brisbane AOR. JTWC issued a Formation Alert at 1930 UTC, noting that the system was quite small in areal extent (90 nm) with maximum winds estimated at 20-25 kts. A 200-mb analysis indicated that the system was moving under the subtropical ridge. Brisbane took over warning responsibility as the depression crossed 160E and forecast gales to 40 kts in the southern semicircle. JTWC issued their first warning at 03/0000 UTC with MSW estimated at 35 kts. TC-23P was a small, symmetrical system with associated cloud lines moving in toward the center from the northwest. The LOW continued to display increased convective organization and Brisbane named the system Tropical Cyclone Vaughan at 1800 UTC with peak 10-min avg winds estimated at 40 kts. By 04/0000 UTC deep convection had organized around the LLCC, and Brisbane increased the maximum winds to 50 kts while JTWC's estimated MSW jumped to 55 kts based on current intensity estimates of 35 and 55 kts. Vaughan at this time was located about 575 nm east-northeast of Cairns, moving west at 11 kts. In their 1200 UTC warning JTWC decreased the MSW to 45 kts but Brisbane maintained Vaughan's intensity at 50 kts. Convection had weakened significantly earlier but had made a comeback during the previous six hours. At 0000 UTC on 5 Apr JTWC further dropped the MSW to 40 kts while Brisbane increased the 10-min avg estimate to 55 kts! The center of the cyclone by this time was located about 350 nm east-northeast of Cairns and moving toward the west-southwest at 10 kts. Animated infrared imagery indicated that convection was cycling between periods of intensification and weakening. At 1200 UTC JTWC reported the MSW at 35 kts while Brisbane maintained Vaughan's intensity at 55 kts. Animated infrared and microwave imagery indicated that the convection had essentially dissipated between 0000 and 1200 UTC. Around 1400 UTC there was a massive blowup of convection over the center with cloud tops colder than -80 C. Willis Island and Cairns radars showed an eye developing shortly afterward as did TRMM 85 GHz data from a pass at 2132 UTC. At 1700 UTC Holmes Reef (WMO 94289) reported gales when the center was about 80 nm distant. BoM Brisbane thought that Vaughan was rapidly intensifying to hurricane intensity and upped the 10-min avg winds to 60 kts at 1800 UTC. JTWC, however, only increased their 1-min avg MSW estimate from 35 to 40 kts. This intensification was short-lived, however, as the mid-level vortex (which was being steered by a 500-mb ridge) left the low-level center behind. Vaughan rapidly collapsed just off the Queensland coast east of Cooktown. The maximum 10-min avg wind estimate dropped from 55 kts at 06/0100 UTC to 30 kts at 0600 UTC. While JTWC tracked a low-level center inland through 07/0000 UTC, information from Jeff Callaghan indicates that coastal observations showed a 500-mb center southwest of Cairns at 06/1100 UTC while reports from Bougainville Reef (WMO 95288) placed the low-level center still out to sea near that station. The JTWC warning issued at 06/1200 UTC mentioned that a 06/1120 UTC SSM/I pass depicted extremely sparse deep convection with no clearly discernible LLCC. It is obvious that there were greatly divergent interpretations of satellite imagery of Tropical Cyclone Vaughan by the different warning agencies, and by other interested parties. Pete Donaldson, of the Central Pacific Hurricane Center, sent around a visible satellite image taken at 04/2130 UTC in which he felt that a small, cloud-filled eye could be seen near the center of a small CDO, and that this feature represented the LLCC of Vaughan rather than exposed outside of the CDO. Roger Edson, however, disagreed with this assessment, stating that he could not see any sign of an eye in the image in question. Roger supplied a TRMM 37 GHz image from 04/1300 UTC (courtesy of Jeff Hawkin's NRL Tropical Page) which showed the center of the circulation near the edge of a large convective area. Roger contended that the 2130 UTC visible image revealed a partially-exposed LLCC on the southern edge of the CDO with the same low-level cloud lines seen consistently throughout the day. One final e-mail from Pete implied that Mark Lander was in agreement with the assertion that a tiny and indistinct eye had been visible intermittently from 04/2130 UTC through at least 05/0332 UTC, but the author personally has not received any e-mail from Mark concerning this cyclone. Based upon the intensity estimates from Brisbane and JTWC, it seems fairly obvious that the Brisbane TCWC must have felt that the center of Vaughan was imbedded within the CDO while the JTWC analysts interpreted the imagery more in line with Roger's assessment since their MSW estimate was lowered during the period in question. Dvorak numbers from KGWC also indicated a weakening system during this time frame. The other instance where JTWC's and Brisbane's intensities were greatly divergent was the eleventh-hour blowup of convection beginning around 05/1400 UTC (mentioned above) shortly before the cyclone began to collapse. A Satellite Bulletin from KGWC at 05/2120 UTC noted that convection had developed rapidly near the center during the past 4 to 6 hours but the T-number was 2.0. It seems likely that the appearance of an eye on the Willis Island and Cairns radars (also mentioned above) was the primary basis for Brisbane's increasing the intensity of Vaughan to 60 kts. The author would like to point out that the above discussion of the varying interpretations of satellite imagery by the warning agencies involved and by other tropical meteorologists should not be construed as criticism of any person or warning center, nor as an attempt to imply who may or may not have been correct in their assessment of Vaughan's intensity. Rather, my purpose was simply to underscore the inherent uncertainty often encountered in estimating the intensity of tropical cyclones by remote sensing, especially with midget cyclones such as Vaughan (and also Tessi). Perhaps some more studies will be made of this interesting tropical cyclone in an attempt to better estimate its actual intensity. If I should receive any further information on Tropical Cyclone Vaughan, I will report it in a future summary. Severe Tropical Cyclone Paul (TC-24S) 13 - 22 April -------------------------------------- The most intense tropical cyclones in the South Indian Ocean this season seem to have come in pairs: Leon/Eline and Hudah both formed in the western portion of the Australian Region and moved on westerly trajectories for thousands of miles, eventually wreaking much havoc in Madagascar and Mozambique; John and Rosita formed in the Timor Sea and struck the Western Australian coastline as intense cyclones; and Norman and Paul both formed off northwestern Australia, moved westward out into the Southeast Indian Ocean while attaining great intensity, and then weakened just shy of reaching the boundary of the Southwest Indian basin. A STWO issued by JTWC on 10 Apr at 1800 UTC indicated that an area of convection had formed about 160 nm west of Darwin (near 12S, 128E). Animated infrared satellite imagery indicated improving convective organization, and a QuikScat pass indicated a broad LLCC with a secondary center over land near 17S, 127E. A 200-mb analysis indicated a favorable environment for strengthening. By 12 Apr the area of convection had moved westward over the Timor Sea with deep convection beginning to wrap into the LLCC. CIMSS analysis indicated the system was under an upper-level anticyclone with weak vertical shear and the system was given a Fair potential for development. JTWC issued a Formation Alert at 1730 UTC. At this time convection was starting to wrap around the northwest quadrant and maximum winds were estimated at 25-30 kts. Both Perth and JTWC initiated warnings on the intensifying system early on 13 Apr. At 0100 UTC the first shipping warning from Perth placed the center of the LOW about 500 nm north of Exmouth. The LLCC was still partially exposed with bands of convection wrapping in from the west side. The LOW tracked west-southwestward fairly quickly (at 18 kts) and at 1000 UTC was upgraded to Tropical Cyclone Paul with 45-kt winds and located about 450 nm north-northwest of Exmouth. Convection continued to consolidate around the LLCC and by around 14/0000 UTC Perth and JTWC were estimating the MSW at 50 kts (10-min avg) and 55 kts (1-min avg), respectively. Paul was moving westward at 13 kts at this time, but the cyclone's motion began to tend more to the west-northwest with time. The storm underwent a period of rapid intensification on the 14th with Perth assessing the peak 10-min avg winds at 70 kts at 1000 UTC, and JTWC's MSW estimate reached 90 kts at 1200 UTC. A 10-nm diameter eye had become apparent in infrared imagery by this time. Paul's center was located approximately 300 nm south-southeast of Christmas Island at the time it reached severe tropical cyclone (hurricane) intensity. The intensification trend continued with Paul reaching its estimated peak intensity of 110 kts (10-min avg) and 125 kts (1-min avg) around 1000 UTC on 15 Apr. Steered by a strong subtropical ridge to the south, the cyclone was moving on a west-northwesterly track at this time and was centered roughly 350 nm east-southeast of Cocos Island. A SSM/I pass at 15/1108 UTC indicated a well-defined eye 10-nm in diameter with a banding feature wrapping in toward the LLCC from the south. At Paul's peak intensity gales extended outward 120 nm to the south and 75 nm elsewhere. The radius of 100-kt winds was estimated to be 20 nm. The minimum central pressure in the storm's history per Perth's analysis was 920 mb from 15/1000 UTC through 16/2200 UTC. Paul maintained its peak intensity through around 2200 UTC on 16 Apr. Even as early as 16/0000 UTC the eye had become cloud-filled and the cyclone's appearance was less symmetric. By 1200 UTC eye temperatures had cooled somewhat and cloud tops had warmed. The storm began to track slightly to the west-southwest as indirect interaction with Tropical Storm Innocente (TC-26S) southeast of Diego Garcia had weakened the peripheral ridge situated between the two systems. Severe Tropical Cyclone Paul passed about 125 nm south of Cocos Island around 0700 UTC on 17 Apr. Winds were down to 100 kts at this time (120 kts MSW from JTWC) and the storm began to weaken fairly quickly thereafter. The JTWC warning at 17/1200 UTC noted that the intense convection was confined to the northwest quadrant. By 17/2200 UTC Perth's intensity estimate had dropped to 90 kts. JTWC reported the MSW at 105 kts at 18/0000 UTC and the warning noted that SSM/I imagery indicated a very tightly-wrapped LLCC but with the intense convection limited to the well-defined eyewall. Paul's forward motion had become quite slow, generally toward the west. By 19/0000 UTC satellite imagery revealed that the cyclone was becoming elongated along a northwest-southeast axis. The Perth TCWC dropped the 10-min avg winds to 55 kts at 1000 UTC and JTWC's MSW estimate had fallen to 65 kts by 1200 UTC. Paul's center was located about 200 nm southwest of Cocos Island at this time. The storm continued to steadily deteriorate. A 19/2310 UTC SSM/I pass depicted a partially-exposed LLCC with weak convection located south to west of the center. Perth wrote their final shipping warning at 20/0400 UTC as gales were no longer forecast. JTWC continued to issue warnings on Paul through 21/1200 UTC. Upper-level south- easterlies generated by a ridge southwest of Paul continued to displace convection to the northwest of the LLCC. A TRMM pass at 21/0821 UTC depicted a broad, exposed LLCC with associated isolated convection located 45 nm to the east and 130 nm to the northwest of the center. JTWC's final warning at 1200 UTC placed the weakening center about 335 nm southwest of Cocos Island with 35-kt winds and moving slowly westward at 5 kts. The remnants of Paul continued to drift westward across 90E and occasionally some convection would flare up, but the system never made any serious attempt at re-intensification. Severe Tropical Cyclone Rosita (TC-27S) 15 - 21 April ---------------------------------------- Back in December Severe Tropical Cyclone John ushered in the cyclone season in Western Australia with a bang, making landfall west of Port Hedland near Whim Creek as a Category 5 cyclone on the Australian Cyclone Scale. In April Cyclone Rosita concluded the season with only a slightly lesser bang, moving inland near Broome as a Category 4 cyclone. The Perth TCWC mentioned a tropical LOW in their daily Tropical Weather Outlook issued at 0400 UTC on 15 April. The weak LOW was located about 360 nm north of Broome. In their STWO at 1800 UTC, JTWC indicated that convection had persisted for over twelve hours and that animated water vapor imagery showed improving outflow. A 15/1008 UTC QuikScat pass revealed a well-defined LLCC. Perth began issuing regular shipping warnings at 0400 UTC on the 16th with the LOW's center located about 300 nm to the west of its position of 24 hours earlier. The LOW drifted very slowly during the next day or so. At 1600 UTC Perth relocated the center to about 85 nm southeast of the previous warning position. JTWC issued a Formation Alert at 17/0000 UTC with the system exhibiting a partially-exposed LLCC located on the northern edge of the deep convection. Infrared satellite imagery depicted steadily improving organization with some deep convection beginning to wrap into the LLCC from the northwest. The first warning from JTWC was issued at 0600 UTC for a 35-kt system drifting slowly southward at 3 kts. Deep convection had increased in areal coverage with two symmetric areas of convection to the north and south of the LLCC. Perth upgraded the LOW to Tropical Cyclone Rosita with 45-kt winds at 17/1000 UTC, placing the center about 275 nm northwest of Broome. JTWC upped their MSW estimate to 50 kts at 1800 UTC, noting that Rosita had intensified rapidly and had moved southwestward at 14 kts during the previous six hours. After this initial rapid intensification, Rosita's winds reached a plateau for about a 24-hour period. The cyclone moved very slowly to the south, later turning to the southeast. Around 18/0600 UTC the cyclone was moving through a weakness in the subtropical ridge and still exhibited a partially-exposed LLCC although with good upper- level outflow. Convection continued to increase in organization around the LLCC and at 2200 UTC Perth abruptly increased the maximum 10-min avg wind estimate to 70 kts with Rosita's center located about 135 nm west-northwest of Broome. JTWC increased their MSW estimate to 90 kts at 19/0600 UTC with the cyclone now moving east-southeastward at 6 kts. A 14-nm diameter eye had formed and a 19/0126 UTC SSM/I pass indicated deep convection within the eyewall. Severe Tropical Cyclone Rosita reached its peak intensity of 105 kts (10-min avg) with an attendant CP estimated at 930 mb at 1000 UTC on 19 April when the cyclone's center was only 70 nm west-northwest of Broome. JTWC assigned a peak MSW (1-min avg) of 125 kts just before the cyclone made landfall at 1630 UTC about 25 nm south-southwest of Broome, tracking east-southeastward at 9 kts. A 19/1548 UTC TRMM pass showed a symmetric eyewall with a banding feature west of the eye. A loop from the Broome radar indicated a slight decrease in intensity but very little change in the eyewall structure in the 1-1/2 hours following landfall. Rosita weakened rapidly following landfall and Perth issued the last advice at 20/0400 UTC, placing the weakening system with 35-kt winds about 135 nm southeast of Broome. JTWC issued its final warning at 0600 UTC, noting that the only deep convection remaining was confined to a small area just south of the LLCC. At 0400 UTC on 21 Apr Rosita was a rain-bearing depression located about 450 nm south of Darwin and moving east-southeastward. Broome fortunately escaped the worst of Rosita's fury. The maximum wind gust recorded in the town was 77 kts compared to 130 kts (likely estimated) near the cyclone's center. Seas off the coast were mountainous with residents saying they had not seen such conditions in 14 years. About 250 people were relocated from the Bidyadanga Community, south of Broome, to Port Hedland. In the Broome area most power lines were down, and several boats broke loose from their moorings at the height of the storm. At Broome's only banana plantation, the crop was almost completely lost with only about 10 plants left out of 18,000. (Most of the information in this paragraph was taken from an Australian Broadcast Corporation news bulletin and passed along to the author by Carl Smith.) Coral Sea Tropical LOWs (TD-21F & TD-20F) 26 April - 2 May & 28 April - 2 May ------------------------------------------ During the final days of April and into early May, two tropical LOWs (i.e., depressions) performed an interesting dance around the Coral Sea. Gale-force winds were reported in the southern semicircle of both systems due to a tight pressure gradient with a HIGH to the south, but neither acquired the structure of a tropical cyclone. (This was consistent with satellite intensity estimates from JTWC and KGWC with a Dvorak T2.0 being the highest rating given to either LOW.) The lion's share of the information given below on these LOWs was provided by Jeff Callaghan of the Brisbane TCWC with some supplemental data from Matthew Saxby of Queanbeyan, NSW. A special thanks to Jeff and Matthew for sending me the information. Over the period 26-27 Apr a large 1034-mb HIGH moved into the Tasman Sea. A marked upper-level trough extended into far northern Queensland and a small tropical LOW formed under a diffluent wind pattern between upper northwest winds ahead of the trough and upper-level southeasterly flow towards New Guinea. The intense pressure gradient between the LOW and the HIGH generated gales in the Cairns area. The LOW became quasi-stationary for a time on 27 Apr roughly 150 nm north of Cairns and became quite deep as a 26/2300 UTC RAWIN showed winds to 52 kts at 850 and 800 mb. Above 600 mb winds turned northwesterly under the influence of the upper-level trough and convection which had formed moved off to the southeast, preventing further development. Green Island AWS (WMO 95289) reported almost continual gales from 26/0530 to 27/1248 UTC with a maximum 10-min wind of 43 kts, and Low Isle AWS (WMO 94285) reported continual gales from 26/1700 to 27/1100 UTC with a peak 10-min wind of 41 kts. A trawler with a crew of 3 sank near Norman Reef northeast of Cairns but the crew was rescued. A family of 6 was rescued by helicopter from a remote beach 32 km southeast of Cairns after the heavy seas forced them to beach their power boat. In addition the chopper crew rescued 13 people from a flooded campground west of Cairns. The diffluent pattern east of the upper-level trough which helped to form the Cairns LOW moved out into the Coral Sea and triggered a mass of convection. A surface LOW formed to the west of this convection and by 28/0000 UTC QuikScat data indicated gales under the convection to the east. The LOW moved towards the southeast as the mid- to upper-level trough became quite involuted to the south. The LOW passed to the north of Ile Loop AWS (WMO 91574) where east-southeast winds of 36 kts were reported at 29/0700 UTC, and later near Ile Surprise AWS (WMO 91570) where winds reached 32 kts at 1100 UTC. The lowest pressure of 998.3 mb was recorded at 1600 and 1700 UTC. With a 1034-mb HIGH centered over Auckland, a huge area of gales and near- gales were being directed from the Dateline towards the east coast of Australia. The center of the LOW moved east of 160E after 0000 UTC on 29 Apr, reaching its easternmost location of 162E between 1200 and 1800 UTC. The TCWC at Nadi, Fiji, issued gale warnings on the system during this time and numbered it as Tropical Depression 20F. The cyclonic portion of the mid-level involution began moving north towards the LOW and the steering mechanism became the deep ridge to the south, thus turning the LOW westward toward Australia. Some intensification occurred as the mid-level LOW began to couple up with the low-level center. The system passed to the north of Cato Island (WMO 94394) where gales were reported generally between 2000 UTC on 30 Apr and 0200 UTC on 1 May. The peak 10-min avg wind recorded was 44 kts at 30/2300 UTC while the lowest pressure of 999.5 mb occurred at 01/0200 UTC. The LOW was becoming almost vertically stacked and was probably near peak intensity as it went past Cato Island. Many ships reported gales with several reporting 10-min mean winds as high as 45 kts on 1 May. Several locations along the Australian coast reported winds in excess of gale force. The highest 10-min avg wind appears to have been recorded at Double Island Point AWS (WMO 94584): 43 kts at 01/0351 UTC, while the highest gust recorded was 57 kts at Cape Moreton AWS (WMO 94594) at 01/0832 UTC. The Toowoomba AWS (WMO 94551), which is inland, reported mean winds of 33 kts with gusts to 41 kts at 1341 UTC on the 1st. A visible satellite image of the LOW at 01/0131 UTC shows an exposed LLCC off the Queensland coast with an extensive area of lower clouds and fairly shallow convection to the southeast. Fortunately the LOW made landfall as a weak system and caused little wind damage and no heavy rain. There was serious beach erosion on Fraser Island and in the Sunshine and Gold Coast tourist areas. Peak wave heights of 7.4 m were reported on the Gold Coast and reached 8.1 m and 9.7 m at Tweeds Head and Brisbane, respectively. Turning back to the Cairns LOW of 26-27 Apr--after the 27th this first LOW became detached from the surface trough and was tracked as a vorticity feature on satellite imagery moving initially northwestward but later turning eastward. QuikScat winds at 29/2007 UTC showed gales on its southern side with a center near 13S, 153E. The small LOW was rapidly moving within the deep westerlies north of the deep cyclonic circulation to its south. It made it as far east as 161E by 2100 UTC on 30 Apr where Fiji designated it as Tropical Depression 21F. The LOW then moved around the periphery of the larger circulation and headed westward toward Australia. Just as the other LOW (TD-20F) was weakening and crossing the coast, TD-21F replaced it about 110 nm north of Cato Reef at 02/0000 UTC. The LOW kept the gales going to the south for another 24 hours before it too made landfall as a weak system about 80 nm (150 km) north of where the first LOW had landed. *********************************************************************** SOUTHWEST PACIFIC (SWP) - South Pacific Ocean East of Longitude 160E Activity for April: 3 tropical depressions 1 tropical cyclone of gale intensity Most of the information presented below was taken from the operational warnings and advisories issued by the Fiji TCWC at Nadi. References to sustained winds imply a 10-minute averaging period unless otherwise noted. Also, the basic definition of a cyclone in WMO Region 5 (Australia and the South Pacific) has the unique requirement that a depression must have gale-force winds more-or-less completely surrounding the center before the system is named as a tropical cyclone. Hence, often gales of 35-40 kts may be present in one or two quadrants but the system is not considered a tropical cyclone. Last season Fiji initiated their own numbering scheme for tropical disturbances (01F, 02F, etc) that form in the Nadi AOR. Some of the numbered disturbances never warrant depression status. The report on Tropical Cyclone Neil was written by Alipate Waqaicelua, Chief Forecaster at the Nadi TCWC, with only minimal editing by myself. A very special thanks to Alipate for sending me the summary and the cyclone's track. Southwest Pacific Activity for April ------------------------------------ Several tropical systems roamed the waters of the South Pacific east of 160E during April but most were quite weak. The only named cyclone was Neil, which formed around mid-month near Fiji and caused some heavy rains and marginal gales in the islands before moving off to the south- southeast. A system on 5 and 6 Apr was referred to as a tropical depression in two Tropical Disturbance Summaries but was not assigned a number. This depression formed just east of the Dateline east of Fiji and appeared to have been severely sheared with little real potential for development. No track is given for this system. A disturbance formed west of Tahiti from an upper-level cutoff LOW on 10 Apr and moved west-southwestward for a couple of days. This LOW was designated 18F but was never referred to as a tropical depression. Finally, at the end of the month two tropical LOWs (depressions) from the Australian Region moved eastward across 160E and were numbered 20F and 21F before moving back westward into Brisbane's AOR. Since the primary impact of these LOWs was to Australia, they are covered in the discussion of activity for the Australian Region. Tropical Cyclone Neil (TC-25P / TC-19F) 15 - 17 April ---------------------------------------- Tropical Cyclone Neil was the sixth cyclone to form in RSMC Nadi's AOR this season. A disturbance was first identified embedded in a slow-moving trough of low pressure just northeast of Fiji around 12/1200 UTC. At this stage the trough, along with the disturbance, was drifting slowly southwestward towards Fiji. After 13/0600 UTC the system had developed into a tropical depression while located some 60 nm northeast of Vanuabalavu island with convection immediately around the centre increasing. Though it was then located just south of the 250-mb ridge, shear was still minimal. Overall organisation had not changed much by 14/0000 UTC, even though deep convection appeared weakly sheared to the east. Twenty-four hours later, the depression had moved further southwest with convection increasing and becoming better organised around the LLCC. Good outflow in certain sectors was also established as the system was now located under the 250-mb ridge axis with good diffluent flow over it. A warm SST of around 30 degrees Celsius certainly enhanced the system's potential to reach tropical cyclone intensity within the next 24 hours. At 15/1200 UTC, in the second Tropical Disturbance Advisory issued by RSMC Nadi, the potential for development to a cyclone within 12 to 24 hours was raised to "high" as all factors became more favourable, though convection was still undergoing some diurnal variation. At this time the depression was located about 60 nm southeast of Kadavu and slow-moving, but anticipated to move further southwards. Through the early hours of the morning of the 16th, (Local) the depression further intensified with convective tops cooling and organisation improving significantly. At 15/1700 UTC, the depression was named Tropical Cyclone Neil while located some 80 nm southeast of Kadavu and still slow-moving. Through the 16th (Local), Neil was subjected to increasing westerly shear as it began to move southward at about 06 kts which effectively displaced the deep convection about 30 to 40 nm southeast of the LLCC. Shear was reinforced by a deep 250-mb trough upstream of the cyclone. After 16/0600 UTC it was apparent that shear over the system was only going to increase further and that the steering field would move it rapidly into cooler waters, thus demolishing any organisation that would have prevailed. Hence, at 16/1200 UTC, the system was downgraded to a tropical depression with gales confined to within 120 nm of the centre only in the southern semicircle, enhanced by an intense surface HIGH cell to the south. Former Tropical Cyclone Neil finally exited Nadi's AOR after 17/1800 UTC as a depression with gales still confined to the southern semicircle. Damage attributed to Neil was minimal, with only marginal gales reported over the two southern-most islands in Fiji: Kadavu and Ono-i-Lau. Torrential rain was experienced over some parts of Fiji while strong winds affected most places. There was one fatality due to drowning, but not directly associated with the cyclone. *********************************************************************** 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 the July, 1998 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 receiving it and wishes to obtain a copy, send me an e-mail privately and I'll forward them a copy. *********************************************************************** AUTHOR'S NOTE: This summary should be considered a very preliminary overview of the tropical cyclones that occur in each month. The cyclone tracks (provided separately) will generally be based upon operational warnings issued by the various tropical cyclone warning centers. The information contained therein may differ somewhat from the tracking and intensity information obtained from a "best-track" file which is based on a detailed post-seasonal analysis of all available data. Information on where to find official "best-track" files from the various warning centers will be passed along from time to time. The track files are not being sent via e-mail. They can be retrieved in the following manner: (a) FTP to: hrd-type42.nhc.noaa.gov [140.90.176.206] (b) Login as: anonymous (c) For a password use your e-mail address (d) Go to "data" subdirectory (Type: cd data) (e) Set file type to ASCII (Type: ascii) (f) Transfer file (Type: get remote_file_name local_file_name ) (The files will be named with an obvious nomenclature--using April as an example: apr00.tracks) (g) To exit FTP, type: quit Both the summaries and the track files are standard text files created in DOS editor. Download to disk and use a viewer such as Notepad or DOS editor to view the files. The first summary in this series covered the month of October, 1997. If anyone wishes to retrieve any of the previous summaries, they may be downloaded from the aforementioned FTP site at HRD. The summary files are catalogued with the nomenclature: apr00.sum, for example. Back issues can also be obtained from the following websites (courtesy of Michael Bath, Michael V. Padua, Tom Berg, Michael Pitt, and Rich Henning): Another website where much information about tropical cyclones may be found is the website for the UK Meteorological Office. Their site contains a lot of statistical information about tropical cyclones globally on a monthly basis. The URL is: TROPICAL CYCLONE REPORTS AVAILABLE I have discovered that JTWC now has available on its website the complete Annual Tropical Cyclone Report (ATCR) for 1999 (1998-1999 season for the Southern Hemisphere). Also, ATCRs for earlier years are available. The URL is: Also, TPC/NHC has available on its webpage nice "technicolor" tracking charts for the 1999 Atlantic and Eastern North Pacific tropical cyclones; also, preliminary storm reports for all the 1999 Atlantic and Eastern North Pacific cyclones are now available. The URL is: Prepared by: Gary Padgett E-mail: garyp at alaweb.com Phone: 334-222-5327 (nights & weekends) / 850-882-2594 (weekdays) *********************************************************************** *********************************************************************** +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ Date: Mon, 19 Jun 2000 13:37:42 +1000 From: Matthew Smith X-Mailer: Mozilla 4.73 [en] (Win98; U) X-Accept-Language: en To: aussie-weather at world.std.com Subject: aus-wx: Photo Gallery's Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi Everyone ! The Sydney Storm Chasers Photo Gallery is now finished, with a selection of myself, Daniel Weatherhead and James Harris's best photographs, mostly storms and clouds, but a few scenery and sunset ones as well. http://www.sydneystormchasers.com/gallery/index.htm Matthew Pearce's forecasts are on hold for a couple of weeks, as he has uni exams and other work commitments at The Weather Channel taking up his time, These will resume once he has some spare time after the exmas. (The link is on the front page of the site) A snow chase report from the other week will be in a week or so, with plenty of photographs of the snow around Oberon (Central Tablelands of NSW) before the big dump cut roads a couple of hours after we left. Jane and Ben, well done on your sites ! each is growing with new info every week or 2! Keep up the good work :) Enjoy ! Matthew Smith Sydney Storm Chasers http://www.sydneystormchasers.com ASWA Committee Memner http://www.severeweather.asn.au +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ From: Blair Trewin Subject: Re: aus-wx: Another abnormally cool day over Australia To: aussie-weather at world.std.com Date: Mon, 19 Jun 2000 15:36:33 +1000 (EST) X-Mailer: ELM [version 2.5 PL2] Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com > > On Tue, 13 Jun 2000 12:41:55 +1000 (EST), Blair Trewin > wrote: > > >Monday was another abnormally cool day over Australia, with a > >national high of only 28.4 degrees - as discussed in earlier postings, > >this is only 0.4 degrees above the record. > > > >Even stranger, said national high was at Gingin, just north of > >Perth - remarkably far south for a national high at this time of > >year. Perth Airport itself got to 26, not a record but the highest > >this far into winter (the June record of 27.8 was set on 5/6/1975). > > > Blair, according to my (far from perfect) database, records were > broken for June maxima on the 12th at several locations in WA: > > Pearce RAAF: 27.0 (previously 26.6) > Albany AP: 25.0 (previously 24.8) > Katanning PO: 23.2 (previously 22.6) > Lake Grace PO: 24.2 (previously 23.8) > Pingelly 23.5 (previously 23.4) > Wagin 23.5 (previously 23.2) > > Pearce and Albany are rounded, so the jury is still out, but the > others seem real enough. All have 35 to 45 years computerised record > apart from Pingelly and Wagin which are about 25 years. > > Any thoughts? > > Laurier A lot of old WA data has been digitised in recent years but hasn't made it onto the 'Extremes' pages yet. Katanning is the only one of these sites significantly affected by this (there is now data going back to 1907 there). Katanning's JUne record is 24.1 on 10 June 1940. Lake Grace's is 24.3 on 7 June 1998 (surprised you missed this, given that it's mentioned on your news page!). Katanning had also had a 22.8 that day, although the 2000 value topped that there. The other four seem genuine enough. As far as I can tell, the WA sites that have additional data digitised (start date in brackets) are Broome PO (1897), Port Hedland PO (1912), Marble Bar (1901), Carnamah (1940), Nabawa (1912 - now closed), Morawa (1925), Mullewa (1925), Wongan Hills (1949), Walebing (1907 - now closed), Bridgetown, Cape Leeuwin, Donnybrook, Esperance PO, Mt. Barker (all 1907), Esperance Downs (1951 - now closed), Cunderdin (1950), Kellerberrin (1910), Merredin (1907), York PO (1934), Corrigin (1948), Katanning (1907), Lake Grace (1956), Narrogin (1913), Wanderin (1901), Salmon Gums (1932) and Southern Cross (1907). I'll get back to you on the pressures when I've got them straightened out myself. Blair Trewin +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ From: "Karratha Weather" To: Subject: aus-wx: Severe Wind Warning for SW WA including Perth! Date: Mon, 19 Jun 2000 16:46:58 +0800 X-Mailer: Microsoft Outlook Express 5.00.2615.200 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com

Hey all

Looks like Perth and surrounding areas are in for a wild time in the next 24hrs. Wind gusts are expected to get to around 120km/h with a strong front to move through early tomorrow :)

BUREAU OF METEOROLOGY
WESTERN AUSTRALIAN REGIONAL OFFICE

PRIORITY
FOR IMMEDIATE BROADCAST

SEVERE WIND WARNING
Issued at 3:45 pm WST on Monday, 19 June 2000

For the Lower West, South West, and adjacent parts of the Great Southern and
Southern Coastal Districts, including the Perth metropolitan area, Mandurah,
Bunbury and Albany for Tuesday morning.

An approaching cold front is expected to cause wind gusts to 120 kilometres per
hour to develop in the early hours of Tuesday morning.

The State Emergency Service advises that people should secure loose objects and
stay indoors when gales develop. Boat owners should ensure that small craft are
securely moored.

The next advice will be issued at 9:30pm.

Batten down the hatches ! :)

Regards

Jason

Karratha W.A

http://www.wn.com.au/karrathaweather/