MARGINAL TROPICAL CYCLONE NONAME (06S) REPORT

18th to 23rd January 2000

By Carl Smith

carls@ace-net.com.au

See notes at end for source information etc..

During the 3rd week of January 2000, a Tropical Low formed in the Gulf of Carpentaria, NW of Weipa on Cape York Peninsula. It drifted slowly WNW into the Arufura Sea over the next few days, passing to the N of Arnhem Land and Darwin.

By the 18th, it had moved into the Timor Sea. BoM Darwin issued the first shipping warning at 1200 UTC, saying a Tropical Low 1000 hPa was centred within 90 nautical miles of 11 S 127.5 E moving west at 05 knots. Darwin BoM continued issuing shipping warnings until 1200 UTC on the 19th, when responsibility was handed to BoM Perth as it was by then off the Kimberley coast around 12.7 S 125.3 E moving southwest at 10 knots (KT).

Over the next couple of days, the low continued moving SW towards the Pilbara coast. JTWC issued the first TCFA on the 20th, however development was generally slower than either JTWC or the BoM expected, with JTWC issuing another TCFA later in the day.

The BoM issued the first tropical cyclone advice at 6:50 am WST (202230 UTC) on the 21st, sayingt 6:00 am a tropical low was estimated to be 380 kilometres northnortheast of Karratha and moving southwest at 28 kilometres per hour, and the first cyclone warning was issued by JTWC on the 21st at 0300 UTC, saying that TC 06S had developed in the SE Indian Ocean about 350 Nautical Miles (NM) NE of Learmonth, and tracked SW at 10 KT within the steering flow of a subtropical ridge to the SE.

The 1st BoM warning for coastal communities was issued at 3:50 pm WST (210750 UTC) on the 21st for areas between Roebourne and Exmouth, noting that 3 pm WST (210700 UTC) a tropical low with Central Pressure (CP) 1000 hPa was estimated to be 290 kilometres (155 NM) northnorthwest of Karratha and moving southsouthwest at 18 kilometres per hour (10 KT). At 210900 UTC JTWC noted that animated satellite imagery indicated a rapid weakening of TC 06S, and animated water vapour imagery revealed increasing vertical wind shear to the SE due to a mid-latitude trough and associated support of a strong upper level jet.

The difficulties JTWC had in tracking this marginal TC were revealed when they re-located it 60 NM ENE in a warning issued at 212100 UTC, also noting a fully exposed LLCC with deep convection to the SW based on DMSP night-time visible satellite imagery, and animated infared satellite imagery depicted increasing convection over the previous 6 hours.

Over the 24 hours, TC 06S continued it's WSW motion towards the Pilbara slowly deepening to 992 hPa, but never quite reaching TC strength according to BoM criterea. The only significant change being noted in a JTWC warning issued at 221500 UTC, saying that based on infrared satellite imagery it had taken a turn to the SE during the previus 6 hours, and it appeared that the low/mid level High over the Western Plateau had weakened and shifted further E than model guidence had previously indicated, due primarily to the sudden eastwards movement of a mid-latitude trough which had been quasi-stationary off the SW coast of Australia, and water vapour imagery indicated that the trough had also increased in amplitude.

The BoM issued it's final warning on this system at 9:50 am WST (230150 UTC) on the 23rd saying that at 9am WST (230100 UTC) a tropical low with CP 992 hPa with wind gusts to 70 km/hr (40 KT) was estimated to be 70 kilometres (40 NM) WNW of Port Hedland, moving southeast at 25 kilometres per hour (14 KT). JTWC issued it's final warning at 230300 noting that TC 06S was dissipating over land.


NOTES:

Note 1: Tropical Cyclone Advices and Shipping Warnings used as sources for meteorological information in this report were issued by the Australian Bureau of Meteorology (BoM) Darwin and Perth Tropical Cyclone Warning Centres and are Copyright Commonwealth of Australia 1999, Bureau of Meteorology - http://www.bom.gov.au. BoM information is used unless otherwise noted.

Note 2: BoM Perth WA issues warnings to the Australian public using kilometers for distances, kilometers per hour for maximum gust wind speeds, hPa for central pressure, and times are WST, which is Australian Western Standard Time = UTC + 8 hours. I have converted all these and added in them brackets, so changing to nautical miles (nearest 5 NM), knots (nearest 5 KT), hPa = MB, and times are also given in UTC.

Note 3: Joint Typhoon Warning Centre (JTWC), Pearl Harbour, tropical cyclone warnings were also used for extra meteorological information where indicated, and that material is copyright JTWC - http://www.npmoc.navy.mil/jtwc.htm.

END REPORT


Maintained by Carl Smith.
carls@ace-net.com.au

Carl Smith 1999 - 2000. All maps, images, and other information on these Web pages is copyright, either by Carl Smith, or by the agencies that produce the satellite images and other weather related information, as indicated in each case. It is essential to obtain permission in writing from the copyright owner before reproducing any of the information on this website in any form whatsoever except for fair purposes of review as permitted under copyright legislation.

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