Wednesday, August 12, 2009

TD 2: August 12 Update A

I expect the NHC will upgrade TD 2 to Tropical Storm Ana in the next
advisory at 11am EST (or later today). She certainly looks like one. I
think we have our first named storm of the season birling away out there,
but for now I'll continue to call her a TD.

There is some pretty strong convection, and good circulation (vorticity)
in the lower half of the troposphere. The wind speed range for a Tropical
Storm is 34 kt (knots) to 63 kt, or 39-73 mph. (1 knot = 1.15 mph). From
satellites, it looks like she has winds in the lower end of that range.

Although water temperatures are 27-28 deg C, there are some factors that
will inhibit her development. Dry air to the north and west combined with
a bit of wind shear should keep her at the lower end of the TS range for
another day, if not longer.

The center of circulation is at about 14.6N, 34.9W, with a central
pressure of 1006 mb, and she's moving at ~12 mph in a general westward
direction along the southern edge of a high pressure system. She did move
west-southwest as I thought yesterday, and the official track was adjusted
slightly southward. But in the next day or so, I think she'll begin to
take a more west-northwestward track. This is based on the pressure fields
which, alas, are not very detailed out over the Atlantic. The computer
models also indicate that she'll begin moving WNW, passing north of the
Caribbean. At the moment this seems reasonable to me, but everyone from
the Caribbean to Bermuda to the eastern side of the US should keep an eye
on this one as things do have that annoying tendency to evolve, especially
when you aren't looking!

I am ignoring the other practically non-existent blobs from yesterday for
now. Because I can. :)

Until tomorrow, or later, or possibly the day after tomorrow...

p.s. Weather here: cloudy and sunny, a little breezy, with possible rain.
I think that covers most summer-time eventualities. :)

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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,
hypothetically, I was there and I was, hypothetically, going to "run away,
run away" (Monty Python), I'd let you know.

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