Sunday, August 26, 2012

Tropical Storm Isaac: August 26, Update C

I’ve been eating a banana and chocolate ice cream and analyzing the latest pressure field data. Hmm… tomorrow it looks like Isaac will have a room to move in a slightly more north/NW direction compared to the current forecast center of cone (i.e. the right edge of the cone), which actually brings him a couple of inches closer to west Florida and Tampa Bay. Currently it doesn’t look like any of the computer models show a west Florida landfall, so I think he’ll just slow down a bit more because the high pressure is now developing on his west as well which means he can’t move too much in that direction either.

The NHC say his center is at 24.2W, 82.9W, currently heading WNW at 14mph. I can see this in the radar imagery from Key West, however the main convection is north of this. The satellite imagery is not as clear as to where the center is (it may be a little north), so I’ll go with the radar and NHC location. They kept his winds to 65mph for now, central pressure 993mb, but I think his convection and structure has improved enough in the past few hours to upgrade him to a weak cat 1 storm (range: 74-95mph). This is because he is still over the Loop Current and it’s deep warm water and he has moved away from the dry air. If he does move in a more north/NW direction tomorrow he will move away from the Loop Current a little quicker, so he might weaken again. He still has some wind shear and although the circulation over the entire troposphere is strong it is not as well-structured in the lower half of the troposphere because he is still being impacted a little by Cuba.

Isaac’s future forecast track is very tricky, and will become trickier if he slows down much more or stalls. From the NHC 11pm advisory: “THERE IS AN UNUSUALLY LARGE SPREAD IN THE TRACK GUIDANCE AFTER 24 HOURS.  THE SPREAD OF LANDFALL LOCATIONS ALONG THE NORTHERN GULF COAST RANGES FROM THE TEXAS/LOUISIANA BORDER EASTWARD TO THE ALABAMA/FLORIDA BORDER”. The latest forecast track shifted slightly to the west as expected, but I’d have to say that at this point that shift means about as much as a the collected works of Shakespeare does to a cat. Everyone should prepare, and we’ll just have to figure this out a day at a time (alas!).

More tomorrow morning.


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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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