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Tropical Depression Claudette Discussion Number 10
NWS National Hurricane Center Miami FL AL032021
1000 PM CDT Sat Jun 19 2021
Although the center is well inland, Claudette has become better
organized during the past several hours, with a large area of
convection forming close to the center in the northern quadrant.
In addition to this convection, a large area of rain bands is
present over the eastern semicircle from the northeastern Gulf of
Mexico northward into southeastern Tennessee Surface observation
indicate that the maximum winds have decreased a little more and
are now 25 kt, with these winds mainly over the Gulf of Mexico to
the south of the center. Surface observations also indicate that
the central pressure is 1005-1006 mb.
The initial motion is still northeastward, but is a little slower
than before, 050/12 kt. A turn to the east-northeast is expected
during the next 6-12 h as Claudette moves in the westerlies on the
north side of the subtropical ridge. This motion should take the
system across portions of the southeast U.S. during the next 36 h
or so and then over the western Atlantic and toward Atlantic
Canada with a significant increase in forward speed between 36-
72 h. The track forecast guidance remains tightly clustered and
has changed little since the last advisory. So, the new forecast
track is basically an update of the previous forecast, and it calls
for the system to be near the coast of North Carolina at about the
36 h point.
The intensity guidance continues to show a sizable amount of
spread. On one side, the GFS has an ill-defined system reaching
the Carolina coast in 36 h, with only minimal subsequent
intensification after Claudette moves into the Atlantic. On the
other side, the UKMET shows the central pressure falling below 1000
mb before the system reaches the Atlantic and winds exceeding 50 kt
once the system is over water. The ECMWF and Canadian models lie
between these extremes. The model forecasts do not show any strong
baroclinic forcing that would lead to the level of intensification
shown by the UKMET. On the other hand, the short-term trends in
the cyclone's organization currently favor the stronger model
forecasts. Given the uncertainty, the intensity forecast is not
changed much from the previous forecast, except for moving the time
of dissipation up by 24 h as Claudette gets absorbed into a large
extratropical low over eastern Canada. If the current trends
continue, or later GFS runs forecast a stronger system, the
intensity forecast could be adjusted upward in later advisories.
It should be noted that even the weaker GFS solution brings 30-35
kt winds to the North Carolina coast near the 36 h point, and a
tropical storm warning will likely be required for a portion of the
current watch area on the next advisory.
1. Claudette is expected to produce heavy rainfall and flash
flooding across portions of the Florida Panhandle, northern Alabama,
and Georgia through tonight, and into the Carolinas on Sunday.
Considerable flash, urban, and small stream flooding impacts are
possible across these areas.
2. Tropical storm conditions are possible along portions of the
North Carolina coast Sunday night and Monday, where a Tropical Storm
Watch is in effect. Tropical Storm Warnings will likely be
required for portions of this area early Sunday.
FORECAST POSITIONS AND MAX WINDS
INIT 20/0300Z 32.6N 87.0W 25 KT 30 MPH...INLAND
12H 20/1200Z 33.3N 84.7W 25 KT 30 MPH...INLAND
24H 21/0000Z 34.2N 81.0W 30 KT 35 MPH...INLAND
36H 21/1200Z 35.4N 76.6W 35 KT 40 MPH...INLAND
48H 22/0000Z 37.7N 71.9W 40 KT 45 MPH...OVER WATER
60H 22/1200Z 40.8N 66.7W 40 KT 45 MPH
72H 23/0000Z 44.5N 60.8W 45 KT 50 MPH...POST-TROP/EXTRATROP