Tuesday, August 21, 2012

Tropical Depression 9, Gulf of Mexico Blob & the Atlantic Blobette: August 21, 2012

I didn't forget about you all yesterday! :-) I couldn't quite get to a working computer because I was driving, from St. Petersburg (Florida, not Russia!) to Tallahassee, through the lovely lovely rain that was generated by a Gulf of Mexico blob. Blogging whilst driving is just right out. My boss thinks that British people drive faster on roads when it is raining. This is only apparently true during torrential downpours and when it is dark (i.e. almost zero visibility) and you are sitting in the back seat (which I try not to do when I'm driving). 

Hurricane Gordon became Tropical Storm Gordon and now is Gone Gordon.

Gulf of Mexico Blob:
I would attach the latest satellite image of this Gulf blob's convection if I could figure out how to do that from an iPad. Hmmm. Technically advanced am I, not. Well yesterday heavy convection extended across the Gulf from the southwest to the northeast and over Florida. This was because it was part of a front and had very strong wind shear (which has decreased since yesterday). It generated a lot of rain because the sea surface water temperature in the Gulf is a cozy 30-32 deg C and, in the area where this blob is, the upper 75-100m of the water is warmer than 26 deg C. It is close to the coast of Mexico, so it seems unlikely to develop into much and the circulation looks like it has diminished. It is worth keeping half an eye on it in case it does something sneaky before it gets to land (which looks like it will be Mexico, maybe close to Texas). Currently the NHC give it a 30% chance of developing in the next 48 hours.

Tropical Depression 9:
The NHC finally got around to declaring the Atlantic Blob a Tropical Depression. I think this is already a Tropical Storm (Isaac) and I'm sure they will call it later. (Not attached are the visible & Infrared (convection) satellite images from this system.) The circulation is good in the lower troposphere, and the convection has also improved. It is moving away from that dry, dusty air. I estimate the center to be around 15N, 53W, moving westward at 20mph (almost as fast as British drivers in the rain ;-)). The official forecast has it crossing the mid-to-northern end of the Lesser Antilles tomorrow, as I mentioned a few days ago. Officially the forecast is for it to become a hurricane in the Caribbean by Thursday morning, reaching Cuba by Sunday. At the moment the winds are 35mph (central pressure 1008mb). It is possible that it will become a hurricane by Thursday morning, but I think there is a good possibility that it will remain a Tropical Storm because there are factors for and against a faster intensification. From under the storm there are reasons for it not to get strong that quickly. First, it has to cross the islands which usually takes some steam out of the system. Second, there is no change in sea surface temperature or how deep the 26deg C isotherm is between now and then (it is 28 deg C with waters warmer than 26deg C in the upper 100m), which suggests a gradual increase in intensity instead of a quick increase. But in the atmosphere the wind shear is decreasing and it will have more-or-less moved away from the dry & dusty Saharan Air Layer. From a scientific/intensity forecasting point of view, it will be interesting to see how this pans out. The track once it gets into the Caribbean is a bit tricky because the front/Gulf blob I drove through yesterday is moving eastward and it will influence the track depending on where it is relative to the storm as the storm moves westward. I hope to have a better idea of this tomorrow.

Atlantic Blobette
Like TD 9, this is also being impacted by the dry air to its north. Its circulation in the lower half of the troposphere is as good as TD9 but, like it's predecessor, the main convection is on the southern side. The center is somewhere around 10N, 32W, heading west at around 15mph. The NHC give this a 60% chance of developing in the next 2 days. Given that it is farther south than TD9 was when it developed, water temperatures are 28 deg C, the upper 50-75m of the water is warmer than 26 deg C, and there is little wind shear, I think this is reasonable. 

I am in Tallahassee to attend a scientific meeting to discuss the research being done post Gulf oil spill. Oooh... real cutting edge science! It's pretty darn tootin' interesting! :-) 

More later my peeps!

Twitter @JyovianStorm

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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