27 replies to this topic

[Somerset Squall]

Tropical Cyclone 20P has formed, continuing the active 2009/10 South Pacific season. The cyclone has formed from invest 98P, and is located west of TC 19P, and is near Vanuatu. 20P is moving generally westwards along the northern periphery of the same subtropical steering ridge influencing 19P. This steering ridge should soon be broken down by a trough, then 20P begin to turn towards the southwest in a few days time.

20P has some persistant deep convection over the small, well defined LLC. 20P's size should help it intensify quickly in an environment of low shear, warm sea temperatures and good outflow in all directions. Like 19P, JTWC are expecting 20P's intensity to rise to at least 100kts as it tracks deeper into the Coral Sea.

Attached Thumbnails

• 

[kold weather]

This one is well worth watching, the conditions aloft are going to become increasingly favourable for strengthening in the next couple of days. Right now there is some shear over it but its not enough to stop it from strengthening in otherwise very favourable conditions.

The ECM goes rather mental with this system and explodes it in response to those very favourable conditions aloft. The big uncertainty is going o lay with how quickly the ridge is broken down by the trough feature. The longer it takes the more threat it is to the Australia coast, esp northern portions of it, whilst if it breaks down quickly enough this may yet end up heading out to sea.

Still there is enough about this system to watch very closely, could have a big landfalling cyclone in 7-9 days time. The risk is there also for a really potent system, probably 120kts+.

Edited by kold weather, 11 March 2010 - 22:44 .

[cookie]

like Kold says needs to be kept an eye on

[cookie]

[kold weather]

Well TC Ului is still looking very good at the moment, deep convection now is over the center with Sat.Estimates now at 45-50kts, which seems about right given there is some real signs of banding occuring as well. This system really does look primed to explode and become a very powerful TC, the deep convection over the center with the banding under now what are very very favourable conditions screams possible RI.

Anyway the models still deepen this into a very impressive system, the ECM still creates a total beast which is reflected in the forecasts which now call for 125kts. The GFS is now inline to some degree with the ECM as well, with the 06z GFS now coming into line with the ECM as well. They do forecast a W/WNW track over the next 72hrs before the steering currents weakening and a steady WSW track develops instead. There was some disagreements about when this would happen and how sharp it will be and to some extent these disagreements are still there but agreement is somewhat stronger now on a risk to E.Australia.

OHC is very high and if anything increases in 48-72hrs time, shear is very low as well so there really isn't anything that I can see that will hold this system back. No doubts IMO that this will be a cat-4/5 SS scale system when it maxes out...and with SST's well above average right to the coast, good chances of this one being a biggie if it does make landfall.

[cookie]

[kold weather]

A slight dry slot there Cookie but that image shows the northern eyewall and where the developing eye is right now. Sat estimates already have this as a firm 65-70kt system, however it may be just a little weaker then that for now, I'd say 60kts is a pretty fair balance...

18z GFS a little further south on this run as the system takes a bigger dive to the SW/SSW between 108-168hrs before it bends back WSW.

[Somerset Squall]

Ului has rapidly intensified since last night, and has developed a small eye. Intensity has risen to 105kts, making Ului a cat 3 on the SS scale. Ului is expected to continue to rapidly intensify in very warm waters, low shear and good outflow. Ului is forecast to become a category 5 cyclone on the SS scale within the next 48hrs. It is still unclear whether Ului will reach Australia or whether it will curve southwards sooner taking the dangerous storm out to sea.

[Somerset Squall]

Ului continues to deepen, and is now a 125kt cat 4 storm on the SS scale. Cat 5 just around the corner at this rate!

[cookie]

this system is stunning

Quote

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 13 MAR 2010 Time : 223000 UTC
Lat : 12:47:26 S Lon : 161:50:25 E


CI# /Pressure/ Vmax
6.9 / 904.7mb/137.4kt


Final T# Adj T# Raw T#
6.9 7.1 7.1

Latitude bias adjustment to MSLP : +3.5mb

Estimated radius of max. wind based on IR :N/A km

Center Temp : -27.1C Cloud Region Temp : -81.8C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : WEST PACIFIC
Dvorak CI > MSLP Conversion Used : PACIFIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

[Somerset Squall]

Definitely agreed there Cookie, what a beauty!

Ului has continued to rapidly intensify overnight and is now a legendary category 5 storm with sustained winds of 140kts. Further strengthening could occur through the next 72hrs as shear remains low, waters very warm, and outflow excellent in all directions. Ului will continue to move westwards along the northern side of a subtropical steering ridge to the south for the next 72hrs, and then in a similar process to what is going to happen to Severe Tropical Cyclone Tomas to the east, a trough will erode the ridge which will stop westwards movement. Unlike Tomas, Ului isn't likely to move southwards very quickly as it is much further north away from the mid-lattitude westerlies. Instead, Ului is likely to be left in a very weak steering environment and should only slowly drift southwards as a ridge builds to the northeast. Track speeds will be slow as the ridge will be near the equator, a long way from the storm. The proximity of the trough will hinder Ului's outflow, and this, coupled with possible upwelling of colder water due to slow motion, should cause a weakening trend to set in beyond 72hrs. It is still unclear if and where Ului will make landfall. Must be a very scary sight for Australia nonetheless!

EDIT: Looking at wikipedia I have just realised this is the first cat 5 cyclone (SS scale) since Percy in 2005.

Attached Thumbnails

• 

Edited by Somerset Squall, 14 March 2010 - 10:14 .

[cookie]

[hannegan]

I was in Queensland last week,the last thing they need is this,I'm hoping to be back up there next week however will probably stay on the periphery if it as expected intensifies! local forecasts currently predict it makes land on Wed south of Cairns

[Somerset Squall]

I would certainly do that too Hannegan, especially as it is still uncertain just where Ului will end up.

Ului has slightly weakened since yesterday but remains a powerful 130kt cat 4 system. Ului is still moving westwards for now but the southward turn should materialise soon for reasons I explained in my last post. What is uncertain is the tracking after this. Ridging looks like it will build in to the southeast of Ului again which would cause a turn back to the southwest beyond day 3. The timing of the turn will have a large effect on where on the Australian coast Ului will make landfall, or even the possibility the storm will miss land entirely. We shall see as always.

JTWC are indicating weakening to occur beyond 24hrs due to increasing shear, but contrastingly, BOM are keen to bring Ului back up to cat 5 status. This could be because BOM aren't keen on sending Ului very far south, thus keeping it away from the 20-30kts of shear a couple hundred miles south of the system. If the JTWC's track forecast materialises, then 20-30kts of shear is bound to weaken Ului considerably in the coming days. A lot of uncertainty; going to be an interesting watch. Hopefully, Ului will stay away from land!

[cookie]

thanks for the updates guys,

Ului is still a very powerfull system.

[Somerset Squall]

Ului has began the southward drift. Intensity has fallen further to 115kts due to moderate shear and surpressed outflow due to the proximity of the trough responsible for the breakdown of the subtropical steering ridge formerly moving Ului westwards. The track forecast has not changed in the last 24hrs, though don't be surprised to see Ului play some tricks in regards to intensity. In my opinion, Ului looks more impressive than 6hrs ago as the eye appears to be clearing out again and even shrinking a little. Whether this signifies short term re-intensification is unclear but it's well worth watching.

Track map from JTWC indicates a Queensland impact in about 96hrs:

[Somerset Squall]

Intensity has continued to fall, and Ului is now a 100kt cat 3. Continued restricted outflow and moderate shear has caused a loss of convection and the eye to become enlarged and rather rugged. Further weakening is expected as Ului is forced westwards by a strengthening subtropical ridge to the south. Ului should make landfall at cat 1 intensity on the SS scale, thankfully not the monster cat 5 that Ului was a few days ago!

[cookie]

you can see from this how far this has gone down.

[Somerset Squall]

Ului has FINALLY accelerated to the west. The slow motion over the last 48-72hrs caused significant upwelling of cold water to the surface which led to central convection loss which is turn has weakened Ului to 65kts. Moderate shear has impinged on the system over the last couple days, further adding to the weakening trend. Moderate shear is expected to persist until Ului makes landfall at moderate tropical storm intensity near Townsville and Mackay in around 36hrs time.

[cookie]