TC KIRRILY (09S) REPORT

25th January to 1st February 2000

By Carl Smith
carls@ace-net.com.au


Click here for TC KIRRILLY map animation.

See notes at end for source information etc..

A developing 1002 hPa (MB) Tropical Low in the Indian Ocean SE of Christmas Island was first mentioned in an Australian Bureau of Meteorology (BoM), Perth, shipping warning issued at 2157 UTC 25 January 2000 when it was located at 13.6S 108.1E moving ESE at 11 knots (KT). The Joint Typhoon Warning Centre (JTWC), Pearl Harbor, issued a Tropical Cyclone Formation Alert at 262130 UTC saying that winds in the area were estimated to 25 to 30 KT with METSAT imagery at 261730 UTC indicating a circulation center was located near 15.7S 111.6E moving SE at 10 knots. A recent scatterometer image indicating a well defined Low Level Circulation Center (LLCC) associated with the convection and 200 MB analysis indicating that the convection was slowly moving under the axis of an upper level ridge which should provide good outflow. UW-CIMSS Wind Shear charts also indicated decreasing vertical shear in the path of the disturbance closer to NW Australia.

The first TC warning was issued by JTWC for TC 09S at 270900 UTC saying maximum sustained winds were 30 KT with gusts to 40 KT and it was near 17.2S 112.5E approximately 330 Nautical Miles (NM) NNW of Learmonth, Western Australia (WA), moving S at 05 KT, with animated multi-spectral imagery depicting new convection building over the LLCC and low level cloud lines were visible moving in toward the center from the SE. A mid-level High situated over SW WA was forecast to build NW over the Kimberley region by the 36 hour period causing 09S to track initially SSE then SW.

It was named TC Kirrily by the BoM in a shipping warning issued 0016UTC on the 28th saying that central pressure (CP) was 985hPa and it was located at 0000UTC near 18.0S 111.0E moving SW at 6 KT and was causing rough to very rough seas with moderate swell and 30/40 knot winds within 100 nautical miles of centre increasing to 50 knots within 30 nautical miles of centre. The first public TC Update was issued by the BoM at 8:45 am WST (280045 UTC) on Friday, 28 January 2000 saying TC Kirrily Severity Category (Cat) 1 was located about 550 kilometres (km) (295 NM) NW of Exmouth.

JTWC warning no 3 noted that TC Kirrily was near 18.2S 109.8S at 280600 UTC moving W at 9 KT with maximum sustained winds of 55 KT and gusts to 70 KT and had intensified. A 280314 UTC Tropical Rainfall Measuring Mission (TRMM) pass indicated the system was developing an eye and convective banding was surrounding about eight tenths of the vortex. BoM TC Update no 2 issued at 2:30 pm WST (280600 UTC) on the 28th indicated it was now a Cat 2 cyclone moving SW at 11 km/hr (6 KT). BoM only issued one further public TC Update, as it became clear that it was of no real threat to the WA coast.

By JTWC warning no 5 it was near 20.4S 107.6E at 290600 UTC moving SW at 10 KT with max sustained winds of 80 KT and gusts to 100 KT with a 13 NM cloud filled eye. A minimum CP of 965 kPa was indicated at 1100 UTC on the 29th when the BoM noted that it was near 20.7S 107.2E moving SW at 07 KT, and was causing very rough to high seas, heavy swell and 35/45 KT winds within 150 NM of centre increasing to 50/65 KT with high to very high seas within 30 NM of centre.

JTWC warning no 6 indicated it was near 21.6S 106.6 at 291800 moving SW at 09 KTS with max sustained winds of 70 KT and gusts to 85 KT and was dissipating as a significant TC over water. It was about 470 NM W of Learmonth WA with animated satellite imagery showing weakening of the system and elongation to the SE. A 291404 UTC SSMI pass indicated a very broad LLCC however convection was confined to the very center, and there was no longer any evidence af any type of eye. 200 MB analysis indicated the upper-level ridge axis remained S of the system, an upper level jet was evident to the SE, it was tracking WSW under the steering influence of a mid-level sub-tropical ridge to the S, and was moving into an increasing vertical wind shear environment.

Subsequent warnings issued by both centers indicated a continued weakening trend, with the final BoM shipping warning being issued at 2225 UTC on the 31st saying that the remains of Tropical Cyclone Kirrily with CP 999 hPa was located at 2200 UTC near 22.9S 104.9E moving NNW at 04 KT. The system was causing rough seas with moderate swell and 30/35 KT winds within 60 NM of centre, and winds were expected to ease below 34 knots in the next 3 to 6 hours as the cyclone dissipated.

The last warning was issued by JTWC at 012100 UTC when winds had weakened to 25 KT gusting to 35 KT and it was located near 21.8S 102.6E about 625 NM W of Learmonth WA moving NW at 6 KT, with 011730 infrared satellite imagery depicting a fully exposed LLCC.

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) Perth Tropical Cyclone Warning Centre and are Copyright Commonwealth of Australia 1999, Bureau of Meteorology - http://www.bom.gov.au. BoM information is used unless otherwise noted. </p>

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.</p>

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

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