01 September 2004

Frances a major threat to most of Florida, Gaston becomes extratropical...

From Jonathan Vigh: 
Early this morning, the NHC wrote the last advisory on Gaston as the
system transitioned to extratropical status. Healthy winds will be
experienced to the right of the storm as it passes south of Newfoundland
into the open Atlantic. 

A couple of disturbances have come off of Africa in the past couple
days. One of these passed over the Cape Verde Islands and is moving into
the Atlantic at about 18N. The other has just come off of Africa and is
much further south, around 9N. Both have a chance of developing, but the
smart money is probably on the southern system. If it develops, it will
be named Ivan. 

Frances now poses a major threat to the southern East Coast of the
United States. The storm is currently passing just to the north of the
Turks and Caicos Islands, and is forecast to pass through the Central
Bahamas on a track towards Florida's east coast. The storm is still
being steered by a strong ridge to the north, and right now, most of the
forecast models keep the ridge in a configuration that would force the
storm to make landfall somewhere in Florida. The forecast is still
uncertain, and depends somewhat on a trough over the Western U.S. A
stronger, deeper trough would likely strengthen the ridge north of
Frances, forcing her to make landfall further south and west. A weaker,
faster trough could weaken the ridge and allow Frances to drift further
north before landfall -- this scenario would keep Northern Florida,
Georgia, and even South Carolina at risk. Potential landfall is still at
least 72 hours away (as soon as Saturday morning), but it is looking
more and more likely that Florida will bear the brunt of this storm.
Residents of Georgia and even South Carolina should still closely
monitor the progress of this storm however, because it would not take
much of a turn to bring the storm close enough for ill effects to occur.
All people in the potential risk area should remember that the storm is
not a point -- at landfall, Frances' hurricane-force winds could extend
out up to 120 mile from the center. This means that wherever she hits, a
large portion of coast will be affected. 

As in previous days, very interesting changes to the inner core have
been occurring, with eyewall cycles taking place roughly every 12 hours.
As of this afternoon, it appears that another eyewall cycle was
completing, leaving a large 30 nm eye. The eye will probably contract
soon, potentially strengthening the storm. The outflow is excellent,
with two well defined outflow channels to the north and south. The storm
has been modifying its own environment -- the upper level low to the
west of Frances has been filling and weakening with time, allowing the
storm to stay in a favorable low shear environment. Thus, no external
influences are likely to cause any drastic weakening of the storm before
landfall. If anything the storm could strengthen as it passes over the
very warm waters of the Gulf Stream, and is very likely to make landfall
with at least cat. 3 intensity. 

To have two cat. 4 hurricanes make landfall in the same state within a
month would be unprecedented. Sadly, areas that were walloped by
Charley, such as the Orlando area (which had at least $3 billion worth
of damage), may experience even more devastation from Frances. Most of
the Florida coast is very populated, so it would be very difficult for
this storm not to produce a tremendous amount of damage, possibly
comparable to the damage produced by Hurricane Andrew. Even the Tampa
Bay area could experience hurricane conditions under some track
scenarios. Anyone living in main part of Florida or southeast Georgia
should closely monitor this storm and keep an ear to local officials for
actionable statements. 

I have prepared a Frances-themed resource page with links to local
radars, satellite loops, and other storm information (some of these are
quite technical), which can be accessed at:

Please visit my tropical Atlantic headquarters.

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