Thursday, September 11, 2008

Hurricane Ike: September 11 Update B

From the 5pm (EDT) advisory, Ike's center is somewhere around 26 N,
89.4 W, although there is no clearly visible eye. He has an estimated
central pressure of 950 mb (from aircraft data) and officially he is
heading WNW at 10mph. They said he made a NW 'jog' earlier today, but it
looks like he's still heading more NW than WNW to me, and they have
adjusted the track to reflect a slight northward shift in the 5pm
advisory (taking him to Galveston now) - so the official WNW heading
does not quite match up.

He is a bit of a gargantuan storm in area, but not in intensity - it
looks like he is covering almost 2/3 of the Gulf! But he does not appear
to be greater than a cat 2 with winds still near 100 mph. The cold cloud
tops have decreased (for now) and his convection is not evenly
distributed in all quadrants. It looks like wind shear from the
northwest is the main culprit for his ragged, asymmetric appearance in
the Infra-red images (the satellite images that show convective
activity), plus there is some dry air that is helping to keep him from
developing on the west side. Most of the cloudiness is to his east and
south - this part is still over the Loop Current (see
for Loop Current explanation) - where the warm water is very deep as well.

I talked about cold cloud tops a while ago and I'm *sure* everyone who
was reading back then remembers word-for-word what I wrote ;), but for
the new readers this is why cloud top temperature is important (adapted
from Bertha, July 9 Update C from web blog): Warm cloud tops 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 (think of
how it gets colder the higher up a mountain you are). 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.

I also wrote a little 'Satellite Imagery Primer' earlier this season.
For part one read this entry:
If that hasn't bored you ;) then for part deux, read this entry:

Back to Ike. It is still difficult to asses his exact landfall location
I'm afraid. I will send out another update later today if there is any
better indication, but at the moment it could still be anywhere along
the Texas coast (north of say South Bird Island) to Louisiana near the
Texas border - so keep an eye on the entire cone, not just the center
track. Storm surge (see previous entry for monitoring this yourselves)
along the eastern and northeastern side of the Gulf has diminished, but
it is about 6 ft above normal in Shell Beach, LA, and still rising. Texas, we have storm surge at the moment of about 2 ft
above normal water levels in the Galveston and NE Texas area, and just
over 1 ft above normal in the Corpus Christi area.

If you are reading this and are in Corpus Christi, Houston, and esp.
Galveston - stop reading and go and get ready and pay attention to your
Emergency Managers! If you have any specific questions, drop me a line.

If there's anything new to report, I'll send out another update later.
Otherwise tomorrow my friends.

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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