Thursday, July 22, 2010

Tropical Depression 3 & Gulf of Mexico Blob: July 22, Update A

Tropical Depression 3:
Woo hoo... we have the third Tropical Depression of the season! :-)
Our rainy little western Atlantic blobette got upgraded to a Tropical Depression today (one, two, three... aww! ;-)). A Tropical Depression is when the system has 'closed' circulation but winds are less than 39 mph. For this TD, maximum winds are currently 35mph and central pressure is 1006mb. A plane was out there this afternoon and found it wasn't strong enough (yet) to be a Tropical Storm (TS wind range: 39-73 mph). I'd agree with this because from the satellite images it looks like it's still struggling. Convection, although looking good earlier today, has decreased over the last few hours.
It's visiting the Bahamas (how nice). The NHC have the center of circulation at 22.7N, 75.4W moving NW at 14mph. I agree with the NW movement, but I might have had one too many glasses of wine because that doesn't look quite like the location of the center to me. From satellite images, I think the center is somewhere around 22.8N, 74.9W. This suggests that the forecast track may be to the right (northern edge) of the current cone, which means it's currently heading towards the east coast of Florida. BUT, the forecast from the NHC is that the pressure patterns that are steering this will change (based on models), and it will begin heading WNW tomorrow, bringing it to the southern tip of Florida, the Keys and then into the Gulf eventually - but only as a very weak Tropical Storm. Bear in mind is that this is a weak system, and it's typically harder to forecast the track of weak systems because it's difficult to find the center.
Wind shear died down a bit today, which is what gave this system a chance, but it looks like it might pick up again. Sea surface water temperatures are around 28-29 deg C, but temperatures warmer than 26.5 deg C don't extend very deep because the water depth is pretty shallow. I think that if this system is going to pick up any strength it will be when it's close to or over the Florida Current system, but that's a day or two away and it depends on atmospheric conditions at the time.
The other factor that may be contributing towards inhibiting it is Saharan Dust. It's difficult to see in the satellite images because of the all the clouds (go figure!), but there is a lot of dust blowing off Africa at the moment, and extending across the Atlantic. I got this from Gene S. today:
"I  have been in Marathon Fla (in my boat) for more than a week due to 25 mph wind out of the east. We have been having one heck of a dust storm since last Friday. visibility has been way down ..and air temp is hot and humid as the dickens.  We can smell the dust. Last Sat it was so bad in Stuart, Fla that African dust made the front page of the news paper."
Gulf of Mexico Blob:
This rather large beasty is over the Bay of Campeche, near Mexico. Convection with this system has been very strong - poor Mexico is getting lashings of rain with a dollop of thunder and lightning! Water temperatures are over 29-30 deg C here and wind shear is weak. The circulation is as strong in the lower half of the troposphere as that in the TD, so I would have thought this was also a TD by now. It is close to Mexico, so there's a chance it will make landfall without getting to that status. 
That's all for today folks. Oh, my cat would like to add: 'mggggreee333eeezz'. I think it means 'stop writing and give me some food before I fall asleep'. ;-)
Until tomorrow amigos!
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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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