Saturday, August 18, 2012

Hurricane Gordon, Tropical Depression Helene, and the Atlantic Blob: August 18, Update A

I hope you are all having a jolly Saturday because the Atlantic certainly is!

Hurricane Gordon

Hurricane Gordon is now a nice looking storm and has had a good eye for most of today. Here is the latest satellite image of his convection:

Clearly we can see that his eye he is centered at around 34.3N, 34W (how symmetrical is that?!?), and officially he is zooming E at 22mph. I would more accurately say that he is now heading ENE, crossing the Azores islands tomorrow evening as I expected and also as forecast by the NHC – we agree on this. I don’t agree with their estimate of intensity. The central pressure is estimated to be 965mb, with winds estimated at 110mph which makes him a strong cat 2 storm (cat 2 range: 96-110mph). I think this is an overestimation of his winds. There are a number of clues that suggest this:
1. there is wind shear that is impacting him – you can see this because there are clouds streaming off to the northeast.
2. to the southeast and also in the northeast quadrant the convection is a little ragged.
3. there are NO very strong thunderstorms in this system, and I haven’t seen any whenever I looked during the day… there are no areas of ‘red’ or ‘grey’ that you have seen in other storm satellite images. An eye will develop when winds reach around 90-95mph (i.e. as a cat 1).
4. Sea surface temperatures are just about 26 deg C, with colder temperatures to be found about 25m under the surface
5. There is dry air to his south

I think he did become a strong cat 1 storm (cat 1 range: 74-95mph), and maybe a weak cat 2, but I wouldn’t say much about 100mph. The wind shear is increasing now, so I can’t see him getting any stronger especially as he will soon be over cooler waters of 25 deg C as well. Still, quite a nice looking storm.

Tropical Depression Helene

There not too much to say about the former Tropical Storm Helene. She was really short (she needs to get some of those 5 inch heels ;-)). She is now a low pressure system over Mexico with winds of 30mph, central pressure of 1009mb. Her winds never got above 45mph anyway, so she was barely a Tropical Storm (range: 39-73mph). My guess is that the NHC classified her as a Tropical Storm so they could issue specific warnings along the coast of Mexico… but I’m not sure that it had much more to it than we (or the Mexicans) get in normal summer storms as far as convection and thunderstorms. In fact, Nicaragua had more severe thunderstorms and rain today than Mexico got from Helene. She officially made ‘landfall’ just south of Tampico, Mexico this morning, but as a Tropical Depression with winds of 35mph. Anyway, the NHC have stopped reporting on this system, and this is my last entry too.

Atlantic Blob

The Atlantic blob’s circulation in the lower troposphere had improved this morning, but is not as strong at the moment. Same goes for its convection – stronger earlier today, but weaker at the moment. The NHC have given this a 60% chance, but I think it may already be close to a Tropical Storm. At the least it should be a Tropical Depression, given the circulation in the lower half of the troposphere. It is centered at around 15N, 33.3W, heading westwardish at 20mph. This one is moving along the southern edge of the dry, dusty Saharan Air Layer, which will inhibit its development a bit, but not as much as we’ve seen with other storms (like Florence). At the moment this will continue generally westward for the next few days, but it is not clear to me where it will be as it approaches the Caribbean – this one might be closer to the central-to-northern end of the island chain). At the moment it doesn’t look this will curve out to the Atlantic as quickly as Gordon did. The next name on the list is Isaac.

More tomorrow!
Toodle pip,

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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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