Wednesday, September 22, 2010

Post-Ex-Igor, Tropical Storm Lisa and the Caribbean Blob: September 22, Update A

Aww... northeastern Canada took a bit of a beating from the extratropical Igor/low front morphed storm. It looks like it might be the storm of the century for them! It caused a lot of damage and certainly will be talked about, probably for the next 100 years. Even though it was a lot weaker than when it passed Bermuda, the northern latitudes are not as used to such storms on an annual basis. The Canadian Broadcasting Corportation has post-storm updates and photos posted at  I believe the little bit of remaining rain and the still rather strong winds have now shifted towards Greenland.
Tropical Storm Lisa:
Lisa has been spinning her wheels all day! ;-) She's been stuck more-or-less in the same spot for over 24 hours, resulting in a decrease in underlying sea surface temperatures from about 26-27 deg C to 25-26 deg C (an estimate). Her convection has decreased since yesterday. Officially her current location is 17.7N, 30.5W and she's moving E at 3mph and officially winds have been kept at 45 mph, making her a very weak Tropical Storm (range: 39-73mph). Her estimated central pressure is 1002mb. I think it is possible that she is moving NE, and is at something like 17.9N, 29.6W. The circulation (vorticity) is interesting. She still has the vorticity I would associate with a Tropical Storm in the lowest levels of the troposphere, but at mid-levels it looks like she is now connected to a low pressure front that extends off to the northeast. You can see this in satellite images. I've included a picture on the blog site... because I can :-) (it just tickles me that I can put pictures on there. It's the little things in life. ;-)). In the picture (taken by the METEOSAT-8 satellite) Lisa is the red dot (heavy convection) at about 18N, 30W (this was taken at 18:00 UTC, which is 1pm in the afternoon EST). The front is marked by the stream of blue and yellow convective area streaming off to the northeast. There's a chance she'll head northeast and get absorbed into that front. The NHC forecast has her moving NW and dissipating in the mid-Atlantic by Monday.

Caribbean Blob:
The chance of this developing into a tropical cyclone in the next 2 days is now officially 60%. The vorticity has slowly improved in the lower half of the troposphere today but it is just clipping the northern edge of South America, which I think is one reason it has been slow to develop. The other reason is that there is a bit of wind shear. It is difficult to tell if it will get a chance to fully develop in the Caribbean because if it continues to go west it will reach Central America and possibly cross into the Pacific before it forms into a proper storm. Yesterday I was thinking that it might head north towards the Hispaniola/Cuba region, but I see today that there are a line of clouds and thunderstorms that stretch from this blob towards Cuba, so maybe that is what I was seeing. Whether the area of higher vorticity follows that or not, I can't tell yet. It needs to move away from land really before it can develop.
Umm, gosh... I think that's it for today. All this time left! I can go and stare at a wall now. How exciting! ;-)
A bientot,

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These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I was there and was going to "run away, run away" (Monty Python), I'll let you know.

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