30 August 2004

Gaston rains itself out, Hermine may brush Massachusetts, Frances getting stronger, faster...

From Jonathan Vigh: 
Tropical Depression Gaston continued to rain itself out today over North
Carolina and southern Virginia. Over the last 24 hours, 2-5" of rain has
fallen over central North Carolina and southeastern Virginia. Wind gusts
up to 45 mph were reported near the NC/SC border. Gaston will continue
its plodding trek through Eastern Virginia and the Del Marva peninsula
and gradually lose its identity as it tangles with an approaching cold
front. An alternate scenario is that Gaston moves out over open (but
cold) waters and attempts a come-back, perhaps as an extratropical

Tropical Storm Hermine lost its head and is running towards
Massachusetts. Vertical wind shear at midlevels separated Hermine's low
level center from the deep convection this morning. The system is still
at tropical storm strength, however, and may brush southeast
Massachusetts overnight. Therefore, the National Hurricane Center has
issued a tropical storm warning for this area. 

At 21Z, Hermine was at 38.4N 71.3W, or 210 miles south-southwest of
Nantucket, Massachusetts, moving north at 18 kt. Winds are at 45 kt and
the estimated central pressure is 1008 mb.

With Gaston and Hermine soon to be gone, all eyes turn towards Hurricane
Frances. The storm fought through mild southerly wind shear yesterday,
but now appears to be under little if any vertical wind shear. Frances
has a healthy appearance in the satellite imagery this afternoon: the
outflow is good in all directions and expanding in time, a sign that the
environment is favorable for intensification. Indeed, at 18Z, recon
aircraft found that the pressure had fallen to 948 mb (down from as high
as 958 mb overnight). The aircraft also found a an 18 nm inner eye with
an outer eyewall 48 nm in diameter.  Frances appears to be nearing the
end of another eyewall cycle today, and the storm will probably
strengthen as the outer eyewall contracts. At this point, there do not
appear to be any factors that would cause substantial weakening of
Frances, so the official forecast calls for a dangerous 120 kt storm in
five days. 

Frances will pass north of the Lesser Antilles overnight. Sustained
tropical storm force winds are likely in this area, and there is a
possibility that the northernmost islands (Anguilla, Virgin Gorda) could
experience hurricane conditions. Tropical storm warnings are in effect
for the northern U.S. and British Virgin Islands, Culebra, Vieques, and
Puerto Rico. If the storm stays on track, tropical storm force winds
should remain close to or offshore of northeast Puerto Rico. The Bahamas
will likely be the first to feel Frances' full fury. A strong ridge is
forecast to continue to steer Frances on a west-northwest course towards
the southeast U.S. Coast, possibly making a landfall as early as
Saturday morning. At this point in time, there does not appear to be any
trough that could recurve the storm before landfall. If the ridge
weakens towards the end of the week, Frances could travel further north
and hit North Florida, Georgia, or even South Carolina by Sunday or
Monday. Alternatively, if the ridge strengthens, Frances could make a
quick left turn into South or Central Florida by Saturday morning. Since
any potential landfall is at least 5 days away, there is still much
uncertainty -- the storm could even miss the U.S. entirely, although the
chance of that happening seems to be decreasing with time. Residents in
these areas should closely monitor Frances progress this week and
remember that 4 and 5 days forecasts typically have track errors of a
couple hundred miles.

At 21Z, Frances was at 19.5N  60.0W, with maximum sustained winds of 110
kt. She has also increased her forward motion, moving westward at 13

Please visit my tropical Atlantic headquarters.

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