Sunday, August 15, 2010

The northern Gulf Blob formerly known as Tropical Depression 5: August 15, Update A

You know sometimes there is a glitch in The Matrix? In ancient times it was also known as 'Deja Vu'? Well, we've got one! The phrase "I'm not dead yet" (Monty Python) springs to mind yet again - this time with Tropical Depression 5.
I know, I know, we thought we'd seen the last of this one about four days ago. Well apparently that was just to lull us into a false sense of security. Although it did go over land (southern US states) ... it's back. There's a lot of convection that has flared up as the remnants of this depression moved in a southwestward direction and back towards the Gulf. The convection is currently over Alabama, Mississippi and Louisiana, with some over Florida and Georgia. Circulation (vorticity) is pretty strong for a storm that's coming *off* the land - it's got a nice structure in the lowest half of the troposphere (up to about 5km above the earth's surface). In the last few hours, the portion of the storm that is over water began to look like a real tropical storm, as opposed to a blob. It has some nice outflow in the southern flanks. (I'll have to explain this outflow business one day, but it be bed time here so that can wait).
Looking at the closest buoys (e.g. from NOAA's National Data Buoy Center, the buoy at Orange Beach, Alabama:, the highest wind speeds that I can see at the moment are only around 24 mph, so it's not yet a Tropical Storm (TS wind range: 39-73 mph), but I think it could certainly be re-classified as a Tropical Depression. If it is, I'll have a proper look at all the stuff (wind shear etc). For now, this is just a heads up (although if you are in the rainy bits, you might want to stick your head down until you get to a drier spot ;-) ).  
I don't think this will get very strong because it is also interacting with land, but if it continues to move offshore then there's a chance for some intensification. However, despite it's current 'weak' state there are some *very* strong thunderstorms in this system - both on and off-shore - which will bring a lot of rain, strong gusts of wind, lightning etc. I hope all of you in in the Gulf (and southern) states have your rain hats, brollies, wellington boots, and canoes ready...  
That's it for today from this side of the pond. We'll see what tomorrow brings.
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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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