Topic: 1st Low of the 2009/2010 Australian season : Tropical Cyclone Laurence

[Paul D]

Hardly even 24hrs and Laurence is back.

IDW24100
Australian Government Bureau of Meteorology
Western Australia

Media: The Standard Emergency Warning Signal should NOT be used with this
warning.


TOP PRIORITY FOR IMMEDIATE BROADCAST

TROPICAL CYCLONE ADVICE NUMBER 64
Issued at 11:55 am WST on Saturday, 19 December 2009
BY THE BUREAU OF METEOROLOGY
TROPICAL CYCLONE WARNING CENTRE PERTH

A Cyclone WARNING continues for coastal areas from Cape Leveque to Bidyadanga.

A Cyclone WATCH continues for coastal areas from Bidyadanga to De Grey.

At 11:00 am WST Tropical Cyclone Laurence was estimated to be
140 kilometres north of Broome and moving
west northwest at 8 kilometres per hour.

Tropical Cyclone Laurence has rapidly redeveloped after moving off the west
Kimberley coast.

GALES are occurring at offshore islands and may develop along the coast between
Cape Leveque and Beagle Bay this afternoon as the system continues to intensify.
GALES may extend further down the coast to Broome and Bidyadanga later today or
early on Sunday. As the system moves south westwards GALES could extend further
down the coast to De Grey by Monday morning. The system is expected to take a
more southerly track on Monday and then south eastwards towards the north
Pilbara coast on Tuesday.

Heavy rainfall is expected to continue today in coastal parts of the west
Kimberley with 24 hour falls in excess of 100mm possible.

FESA-State Emergency Service advises as a precautionary measure the following
community alerts:
BLUE ALERT: People in the communities from Cape Leveque to Bidyadanga, including
Broome, Beagle Bay, One Arm Point, Djarindjin and Lombadina need to prepare for
cyclonic weather and organise an emergency kit including first aid kit, torch,
portable radio, spare batteries, food and water.
Communities in northern Pilbara should listen for the next advice.


Details of Tropical Cyclone Laurence at 11:00 am WST:
.Centre located near...... 16.7 degrees South 122.3 degrees East
.Location accuracy........ within 20 kilometres
.Recent movement.......... towards the west northwest at 8 kilometres per hour
.Wind gusts near centre... 100 kilometres per hour
.Severity category........ 1
.Central pressure......... 990 hectoPascals

[Richary]

Silly thing, I know it is following the forecast tracks after it crossed the coast and went back out to sea, but was really hoping it would head inland and give some badly needed moisture to feed into parts of SA and maybe western NSW.

[Colin Maitland]

Laurence has been a interesting cyclone to watch. Maybe they should have called him Cyclone Yo Yo.

Latest data on the storm system has Laurence regenerating of the WA coast and he is expected to make an impact on land near Pilbara as a Cat 4 cyclone around Tuesday.

Data from BOM

The circulation has excellent structure through depth, vertical wind
shear is low and oceanic heat content is high so the system is expected to
rapidly intensify in the next 12-24 hours. Very deep convection is evident about
the centre particularly in the western eye-wall region with tightening curvature
near the centre indicated from Broome radar and latest microwave imagery.


 

[Carlos E]

This indeed has been an interesting Cyclone to track, especially so early.

I'm pretty certain that Laurence is now rapidly intensifying. Early signs of an eye can be seen on IR imagery. On Broome/Port Hedland radar show the eyewall a lot more thick and stable than 12 hours ago, more so in the northeast quadrant.

Edit: Laurence is a strong Category 4 system, and will probably make landfall at that strength, after which it will finally dissipate.

Details of Severe Tropical Cyclone Laurence at 8:00 am WST:
.Centre located near...... 19.0 degrees South 120.4 degrees East
.Location accuracy........ within 20 kilometres
.Recent movement.......... towards the south at 6 kilometres per hour
.Wind gusts near centre... 260 kilometres per hour
.Severity category........ 4
.Central pressure......... 939 hectoPascals

[Colin Maitland]

Laurence is now a CAT 5 system as it approaches the Northern WA coastline.

Latest stats and Data from BOM concerning the storm:

At 11:00 am WST Severe Tropical Cyclone Laurence was estimated to be
75 kilometres north of Wallal and
240 kilometres east northeast of Port Hedland
moving south southeast at 6 kilometres per hour.

Severe Tropical Cyclone Laurence is intensifying as it moves southwards towards the Eighty Mile Beach area of the Pilbara-Kimberley coast. Residents are warned of a period of VERY DESTRUCTIVE winds with gusts to 285 kilometres per hour developing during this afternoon. People in the area are specifically warned of the VERY DANGEROUS STORM TIDE expected as the cyclone centre approaches the coast. Tides may rise significantly above the normal high tide mark with
DAMAGING WAVES and DANGEROUS FLOODING.


Details of Severe Tropical Cyclone Laurence at 11:00 am WST:
.Centre located near...... 19.1 degrees South 120.5 degrees East
.Location accuracy........ within 20 kilometres
.Recent movement.......... towards the south southeast at 6 kilometres per hour
.Wind gusts near centre... 285 kilometres per hour
.Severity category........ 5
.Central pressure......... 929 hectoPascals

[Carlos E]

This site is almost directly in the path of Laurence. Although it's being blasted from the southeast side of the eyewall (the southwest is typically the strongest side with our Cyclones if memory serves me right).

Pressure is down to 952.1hPa.

[Carlos E]

Eh, I honestly thought it was the left side for our Cyclones, right side for Northern Cyclones. Learn something new everyday.

Pressure is now at 936. I think the eye is almost over the site at this point.

Edit: Fixed a typo.

[Paul D]

Looking at the obs for Mandora and the radar it looks like it just clipped the east edge of the eye, with Wallal Downs almost the same but on the west side. Max gusts stated so far 204km/hr around 4:35pm.

[Paul D]

As the pressure was dropping, at around 935hPa the wind speed & gusts peaked around 4:35pm 145km/h(77kts)speed 204km/h(110kts)gusts
but then seemed to ease back (still a bit choppy though) around the time of the lowest pressure bettween the 928.8hPa, 928.4hPa readings, to near 106km/h(57kts)wind speed 165km/h(89kts)gusts (5:18pm)then they increased steadily again with the pressure to be at 6:08pm 939.6hPa windspeed 158km/h(85kts)and gusts to 211km/h(114kts) before starting to ease again.
Could that be interpreted as a slice through the eye wall from outer to inner and back out again?

Cheers Paul

[Richary]

Interesting how the wind direction seemed to go quite random for a while there after about 6pm.

[Colin Maitland]

Laurence is still a Cat 3 cyclone after crossing the coast and continues to head inland (7.15am 22/12/09). He is expected to weaken as he tracks Southeast, but due to the flat terrain in Northern WA his weakening will be "somewhat slower than normal" according to the latest update from BOM.

BOM have stated,

  Model guidance indicates that despite increasing shear from 500-200 the low to mid levels will remain coherent and together with the rapid translation this is likely to result in a system capable of producing severe wind gusts and
significant rain a long way across the continent.

It is impressive to observe the track map, if the models hold true, you will notice that approximately 700km inland he is still a cat 1 cyclone. I think you have to go back to the 1978/79 season before you find a cyclone so deep inland. But I can't, at this stage, find if any of the cyclones were able to keep their intensity that many kilometers over land.

The synoptics indicate that Laurence will become a low and track right over the interior to the NSW/VIC coast over the coming next few days

Col

[Paul D]

If I remember right Vance got to within 70km's of Kalgoorlie before being downgraded to a low, but then Vance was a lot bigger system on crossing the coast, your right Col it'll be interesting to see how far Laurence goes relative to it's size.

Paul

[Colin Maitland]

Your right Paul, that is awesome, Cyclone Vance, March 1999

Thanks

Col

[Paul D]

Looks like Laurence didn't quite make it to Giles, now to see how much rain the system produces over the next couple of days..

Cheers
Paul