Friday, July 11, 2008

Hurricane Bertha: July 11 Update A

There wasn't much change in Bertha's track or intensity yesterday... she
has winds of about 85mph and is therefore still a mid-sized cat 1 (wind
range: 74-95mph), and she continues to move in a NW direction.

She did slow down, and is now chugging along at about 6mph, which
indicates that she continues to bump up against a higher pressure region
in front of her (was it the Little Engine That Could that went slowly up
the hill or was it Thomas the Tank Engine?). Although there is still an
eye, it is not as well formed as it was 24 hours ago. But there is good
circulation in this system, now extending into the higher levels of the
troposphere (lowest level of the atmosphere). Despite the nice
circulation the convective activity is not very well distributed and
this morning it is mostly on the west side. Without better observations,
the best guess (mine, the NHC, the models) is that she will remain a cat
1 today.

She's currently at about 28.2N, 61.7W and the computer models are in
agreement that she will continue her NW track until she is at about 30N.
After that point they diverge, but all remain on the east side of
Bermuda. Some even forecast that she will stall. The NHC will probably
issue a Tropical Storm Watch for Bermuda later today.

I am waiting for her to get to about 30N before I can assess which of
the three scenarios I presented yesterday will really kick in. Until
then, she's going NW and towards Bermuda.

She is in a region of low wind shear, and also over water temperatures
of about 27-28 deg C. But just north of 30N, she will encounter warmer
temperatures of 28-29 deg C.

There is insufficient data to be able to make a really good call on her
track at this point - and this is the problem with both the track and
intensity forecasts. There are not enough observations at a high enough
resolution. With the right type of data at the right resolution,
hurricane forecasts would be much improved... and then you'd all have
more time to do interesting things like washing your hair or watching
the grass grow instead of reading this blog :)

For those wondering what those hardy Bermudians are going to do about
their research cruise - last I heard it had been pushed back to Sunday.
Maybe I'll get an update today... and if they do go out, we might get
some live "in the field" reports. I suppose it's one way to lose weight...

More later,

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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 I "run away,
run away" (Monty Python), I'll let you know.

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