Sunday, September 09, 2012

Tropical Storm Leslie and Hurricane Michael: September 8, Update A

Chris K., who is on a Research Vessel in the Atlantic, said that although the forecast called for 7-10 ft seas yesterday, “instead it was flat calm” out there (she’s not complaining!). I also heard from Tom that there were no swells on St. Thomas either (although he’s pleased that Leslie is on the move away from the Caribbean). This suggests that either Leslie has weaker winds than the official forecast suggests or that the models that are being used to issue these forecasts need some work.

Tropical Storm Leslie
She’s officially at 30.1N, 62.6W, heading N at 8mph. Winds are officially 65mph, with a central pressure of 988mb, making her a strong Tropical Storm. Officially anyway.

I’m curious how, according to the NHC, she’s been heading north (360 deg) all day while they managed to move her central location almost 0.5 degrees West. As I said last night, I think she was moving NNW. Since then she made a shift to a more northward track and now, although I agree with the NHC on her current location, I think she has shifted again to a more NNE track. However, I think she’ll wiggle once again to the N/NNW before making her final curve to the N/NE.

Intensity-wise, I think her winds are a little weaker than 65mph. Although it looks like she has an eye in some satellite images, bewarned that it’s not actually an eye. Here's the visible satellite image from about 8 hours ago, in which you can see the 'eye':

It’s actually an area of dry air slap bang in the center. Here is the infra-red satellite image from 8 hours ago, and you can clearly see the dry air entering from the northeast:

Also, for your viewing pleasure, here is the latest infra-red satellite image… it looks like dry air is winning this game!

Her convection has decreased quite considerably, even in the last 8 hours. Bermuda is having a breezy night with some rain.  Even though the sea surface temperatures are warm enough to sustain her at 28 deg C, and the wind shear has decreased for now, it seems unlikely to me that she’ll get up to a hurricane at this point (still officially in the forecast for tomorrow evening). The circulation in the upper troposphere has already started to deteriorate and once she crosses Bermuda tomorrow the sea surface temperatures begin to decrease and wind shear picks up again.

I’m sure the rum will be safe. J

Hurricane Michael
Meanwhile, a short hop, skip and a jump away is Michael. I have to say that he’s a persistent little fellow. The eye returned after my last update and has remained all day. He is currently at about 33.5N, 42.6W, heading NNW at 6mph. Winds are now 100mph, with a central pressure of 975mb. I’d say the winds were closer 95mph because the convection is still pathetic (as you can see in the IR satellite image below), but 100mph is ok too… it’s still a weak cat 2 storm (range: 96-110mph). 

The forecast is for his intensity to decrease tomorrow to a cat 1. I think he’s borderline cat 1/cat 2 already and will continue to decrease in intensity. The NHC have said he’ll remain a hurricane until Monday.

More tomorrow when hopefully Long-lasting Leslie will have finally made it past Bermuda … and I might write about the latest Atlantic Blobette out of Africa.


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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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