[Jyo_hurricane] Hurricane Bertha: July 7 Update B

Beautiful Bertha gets Bigger (how's that for a news headline? am I in
the wrong field? :) ) ... she has intensified and the NHS now agrees
with what I wrote earlier - she will continue to intensify and become a
cat 2 (wind range: 96-110mph). Their next advisory is at 5pm, but it
looks to me like she is already a cat 2. The last advisory at 11am had
her with 90 mph winds and she was a smaller, weaker storm at that point.
Her diameter has grown quite noticeably in the last few hours, with a
solid ring of convection around a very clearly defined eye - she really
is a good looking system. There is still wind shear to the north-east,
which is why if you see a satellite image of her (for example,

http://www.ssd.noaa.gov/goes/flt/t1/vis.jpg), you will see a stream of
activity extending off her north-east quadrant. But despite that and the
dry air surrounding her, the low wind shear around other parts of the
storm and the warm waters underneath are really kicking in.

This storm is great and well-timed for two reasons:
1. It demonstrates that we (as a hurricane science community) still do
not fully understand what makes tropical storms intensify because if we
did then the models would have forecast this intensity, but as late as
24 hours ago they were still predicting that today she would be a
Tropical Storm.
2. Although the models improve every year, this gives us a benchmark for
the rest of the season as far as the intensity models are concerned, and
for this year their forecasts may still be off within any 24-hour window.

She's at about 20N, 51.5W, moving W-NW at about 15mph with a central
minimum pressure of 975 mb. Interestingly, the circulation still does
not extend up through the entire troposphere. The troposphere is the
lowest section of our atmosphere and in the tropics it extends to about
16km above the earth's surface (oooh... aaah... science :) ). There is
now, however, a clear circulation (vorticity) at the mid-levels of the
troposphere. The really large storms have a clear circulation all the
way to the top boundary of the troposphere, which is called the tropopause.

I'll probably send out another update after the 5pm advisory is out.
Isn't this exciting? :)
J.

Blogs archived at: http://www.jyotikastorms.blogspot.com/
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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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