Saturday, August 04, 2012

TS Ernesto, TS Florence and the small Atlantic Blob: August 4, Update A

I thought I’d take the day off yesterday as nothing much was happening out there so I figured you wouldn’t miss me…. J Hurray, it’s the weekend and that means more than one update a day. How lucky for you! ;-)

TS Ernesto
Honestly Ernesto, you really have to change out of that teeny-weeny yellow polka dot bikini if you want to be a taken seriously as a proper hurricane! ;-)

Ernesto crossed into the Caribbean, close to St. Lucia, yesterday morning as a weak Tropical Storm with winds of 45mph (TS range: 39-73mph) and his winds at the moment are still officially only around 50mph, central pressure 1008mb. His circulation is good in the lower half of the troposphere, but he is interacting with the South America landmass which is they only reason I can see to explain why he isn’t a hurricane yet (other than his attire of course ;-)). There is very little wind shear, not much dry air around him now, and sea surface temperatures are 28 deg C, with the upper 75-100m of the ocean warmer than 26 deg C. All of these are conducive to strengthening. Actually, I think he is stronger than the official 50mph wind speed suggests. You can see the strong convection in this satellite image (large area of red, with some gray):

I think he’s a strong Tropical Storm, with winds closer to the 60-70mph range.    

As we expected, he is taking a southern path and the NHC have been slowly, but consistently, revising their center of cone forecast track southwards. Currently they are showing landfall in the Yucatan Peninsula on Weds morning. The current center looks like it is still a bit too far north (to me), but the Yucatan landfall is more reasonable than the earlier tracks they had. He is officially at 14.4N, 68.7W heading WNW at 18mph. I think his center may be slightly south of this, closer to 14.1N.   

TS Florence
Beautiful little Florence left the coast of Africa a couple of days ago, and she looked good as she left. By the time she got to the Cape Verde Islands region she had good circulation in the lower half of the atmosphere and good convection on the southern side of the system. The NHC upgraded her to Tropical Depression 6 yesterday and then to Tropical Storm Florence this morning. I agree with this upgrade. J (see, it *is* possible to agree ;-) ).  Her convection is limited on the northern side because there is a lot of dry and dusty Saharan air to the north which is getting in the way of her blossoming. Sea surface water temperatures, at 27 deg C, are certainly warm enough to sustain her, with the upper 50m of water warmer than 26 deg C.

You can see she is now at 15N, 30W from this satellite image (heading WNW at 16mph):

She is still fairly weak, with official winds estimated to be 45mph, central pressure estimated to be 1002mb. I will figure out her track for the next update.  

Small Atlantic Blob
There is a blob that’s been doing a tour of the beaches and is moving towards Florida from the Bahamas region. This really is a blob, in the blobbiest sense of the word (i.e. a mass of clouds). There is a little circulation, but it is in the very lowest part of the troposphere (not even covering the lower half). People can expect a few buckets of rain though because it is near the Florida Current/Gulf Stream, which is rather toasty warm and has a lot of warm water in the upper 100-125m of the ocean. Just have your umbrellas polished and ready to use if you need.

More on all of the above later. Must go and do weekend things now, like umm… having another cup of tea. J


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DISCLAIMER: 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 "run away, run away" (Monty Python), I'll let you know.

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