Wednesday, August 27, 2008

TS Gustav: August 27 Update B

Well, I suppose this wasn't too bad as "eeek-there's-a-storm-out-there"
days go ;) - Gustav has weakened further and is now a very weak TS with
max. winds of 45 mph (TS range: 39-73 mph). He continued to interact with
Haiti, and also Jamaica and Cuba a bit, during the day and there was some
small wind shear - both of which impacted his intensity more than the
really warm waters underneath.

There is still some circulation in the system, but it is in the lower part
of the troposphere and is not as strong as it was earlier. The center of
circulation is difficult to find, which is not unusual in a very weak
system. The official NHC center is at 18.8N, 75.4W, but I really can't
tell where it is from the satellite images.

He started the day moving NW, then WNW, then W... and the 11pm advisory
says he is now moving W-SW at 8mph. He did slow down to a forward speed of
3mph in the afternoon, so he is still is between Haiti and Jamaica/Cuba.
The main convection is to the south and east parts of the storm. But
again, it is also much less that earlier in the day. And the rain over
Haiti has almost ended (hurray).

The W-SW movment is very interesting to me - it suggests he is following
the southward expansion of the high I mentioned earlier instead of
stalling. If he continues in that direction and the high remains in place,
it will takes him closer to crossing the Yucatan Peninsula than coming
into the Gulf! (but for everyone in the Gulf states, I would get ready
anyway). Hypothetically, if at this moment in time this storm was already
in the Gulf then I would say he's heading for NW Florida/AL, but he is
days away from being in the Gulf and everything can change.

A lot of you have asked about these 'magical' pressure maps I keep
yabbering on about (and I'm sure some of you use the word 'yabbering' or
the American equivalent... ;) ). I generally look at the 500 mb pressure
field, which is the pressure field about half way up in the troposphere
(the lowest part of the atmosphere). I get those fields twice a day from:

Item 4. is the 500 mb field, and a) is the version I am currently looking
at to get a broad overview of the pressure fields. This is at a very
coarse resolution, so it really only gives a general idea of what is going
on, but that's what I use initially. When a storm gets closer to the US, I
look at b), which has finer scale resolution.

Now you can all follow along as I say things like 'the high pressure moved
southward today', 'the high pressure expanded westward', 'the high
pressure had a shot of scotch and then fell over' etc... ;)

Tomorrow should be interesting in both intensity (which is much weaker
than forecast) and track (which I am very excited about with the southward
movement - one of these days I'll figure out why :)).

As Arnold S. said in Terminator: "I'll be back" :)

Night night,

Blogs archived at:
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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