Wednesday, July 09, 2008

Hurricane Bertha: July 9 Update C

Big Beautiful Bertha - she's now a large cat 2 with sustained winds of
105 mph and a minimum pressure of 970 mb (cat 2 winds: 96-110mph). She
is back on a NW track and is moving at 12 mph - so although the track
east of Bermuda is still looking like a good scenario I would make
preparations though (and I don't mean cruise preparations!) because she
will grow, and the track forecast is still dodgy after tomorrow - we now
need her to make that N-NW turn and sustain it, and the sooner the
better. She's at lat. 24.8N, 58.1W, still surrounded by dry air, but
hanging out over water temps of 27-28 degc C and in a low wind shear

Interestingly, for such a good looking and strong storm her clouds tops
are fairly "warm". What does that mean? It means that the tops of her
clouds are not as high up in the troposphere (the lowest section of our
atmosphere) as they could be. The troposphere is characterized by
cooler air temperatures the higher up you go. So the higher the clouds,
the colder their tops, and that's an indication of some very very strong
(or deep) convective activity (large thunderstorms etc). If you look at
a color infrared image of a hurricane (there are some in the "satellite"
link on left side of the NHS webpage), the coldest clouds tops are
indicated by red. The last time Bertha was this size a couple of days
ago, if I recall correctly, her cloud tops were cooler - and they
certainly were red when she was a cat 3. So she is not yet as deep into
the troposphere as she could be.

That's all for today (unless there's any major change tonight).

P.S. I know the blog/wrap-around text problem did not get resolved -
we'll try something else tomorrow. Oh well... it still looks nicer than
it did. :)

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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