27 August 2004

Frances intensifies into 3rd major hurricane of the season, TD7 forms off SC coast...

From Jonathan Vigh: 
August 2004 will go down in the history books as the first August (since
the era of reliable records) that three major hurricanes have formed in
the same month. Even more remarkable is that fact that in no modern
hurricane season has ever had three major hurricanes before September
(including the months of June and July). For all of this to happen in
just one month is pretty remarkable. Finally, on the subjects of
records, only two other Augusts have ever had 6 or more tropical storms
(1990 had 6 storms; and 1995 had 7 storms, 5 of which were hurricanes!).
This record may also be in jeopardy (see below). Thanks to Phil
Klotzbach for providing these statistics.

At 21Z today, Frances was upgraded to a category 3 hurricane with winds
estimated at 100 kts. This is a day ahead of schedule according to
yesterday's forecast. Indeed, Frances has intensified rapidly since it
was first numbered less than 3 days ago. 

To summarize, here is the intensity history of Frances:
 21Z August 24 just a tropical disturbance, numbered at 03Z
 21Z August 25 Frances becomes a named storm, 35 kts, 1005 mb
 21Z August 26 Frances becomes a hurricane, 70 kts, 983 mb
 21Z August 27 Frances obtains 'major' status, 100 kts, 962 mb

Of course, the intensity is only estimated. The storm will probably not
be investigated by reconnaissance aircraft until about midday Sunday. By
that time, Frances is forecast to be a cat. 4 hurricane. There are
several factors in favor of further strengthening (persistence -- it has
a good trend going, the warmer SSTs along its forecast track, and the
fact that its outflow is excellent and still improving), but Frances
could also come under some vertical wind shear in a couple days as it
passes through a weak trough axis. If this happens, the storm could
weaken in the intermediate time frame, then strengthen later next week.
It may never hit that shear, however, as a small upper low appears to be
pinching off to the northwest -- this may protect the storm somewhat. In
that case, the intensity could be dictated by internal storm dynamics.
Regardless, this storm will be very interesting to follow. 

Frances is presently located at 15.7N 49.8W and traveling NW at 12 kts.
All the forecast models show a left turn in a couple days, and the storm
is forecast to pass a couple hundred miles to the north of the Leeward
Islands and then continue passing the Greater Antilles at a comfortable
distance (Puerto Rico and the Dominican Republic). If the left turn is
sharper than forecast, these locations could be threatened by a very
serious storm. Anyone in these locations should watch the storm closely
over the weekend. This could be a bad time to start a long sailing trip.
For the long time frame (5 days), the storm may be starting to menace
the Turks and Caicos Islands. There is no use in speculating where
Frances might go beyond 5 days. Beyond this time frame, there are lots
of factors (in general, chaos) that almost always ruin even the most
sophisticated model forecasts. Residents of the United States can rest
in peace this weekend. 

Don't make the mistake of keeping all eyes (pun intended) on Frances --
some excitement is happening right off the South Carolina coast!
Tropical Depression 7 formed today, just 140 miles southeast of
Charleston (31.6N 78.1W). The storm apparently formed when the remnants
of a cold front received a bit of a kick from a small upper level
disturbance. Deep thunderstorms have been cycling in this area for the
past couple days and voila! a tropical depression formed. The depression
is forecast to strengthen slowly and drift westward or northward toward
the coast, making landfall as a minimal tropical storm. The main threat
from this storm will be heavy rains, especially because it is moving so
slowly. Always remember to never drive through flooded roadways -- it's
just not worth the risk.

And if that wasn't enough to keep track of, a tropical disturbance south
of Bermuda may be showing signs of organization. If it continues to
organize, it may be numbered as TD 8 in the next day or two. 

Will August break the record of 7 named storms (1995)? Where will
Frances go? Can she reach the elusive cat. 5 status? Stay tuned . . .
Please visit my tropical Atlantic headquarters.

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