[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 031451
TCDAT5

Hurricane Dorian Discussion Number  41
NWS National Hurricane Center Miami FL       AL052019
1100 AM EDT Tue Sep 03 2019

Recent radar and aircraft data show that Dorian has finally begun to
move northwestward, but dangerous winds and life-threatening storm
surge will continue over Grand Bahama Island for much of today.  The
eye has become cloud filled in infrared and visible satellite
imagery.  While aircraft and radar data indicate that the eye has
increased in size, it is also a bit more ragged.  Recent reports
from reconnaissance aircraft and data buoys indicate that overall
wind field of the hurricane is slowly expanding, while the peak
winds have come down a little more.  The latest reports from the
aircraft support an initial intensity of 95 kt.  As Dorian moves
near the east coast of Florida during the next day or two, little
overall change in intensity is anticipated.  After that time,
increasing shear should result in a gradual decrease in the peak
wind speed while the hurricane gains latitude and grows in size.
The official forecast is in good agreement with the intensity
consensus models.

The initial motion estimate is 320/2 kt.  A shortwave trough moving
into the Great Lakes region is forecast by the global models to
amplify a deep-layer trough along the east coast of the United
States on Wednesday.  This should allow Dorian to begin moving
slightly faster toward the north-northwest during the next 36 hours,
followed by a northward and then northeastward motion near or over
the coasts of South and North Carolina.  After moving offshore of
the Outer Banks, Dorian should get caught in the mid-latitude
westerlies and accelerate northeastward.  The NHC track is along the
western edge of the interpolated track models through 36 hours,
closer to what is depicted in the various global fields. After that
time, the official forecast is near a blend of the faster GFS and
slower ECMWF models.

Although the official forecast does not show Dorian making landfall
along the Florida east coast, the increasing size of Dorian's wind
field along with any deviation to the left of the forecast track
will bring hurricane-force winds onshore along portions of the
Florida east coast.

The new forecast has necessitated numerous changes to watches
and warnings along the southeastern United States coast.

Key Messages:

1. Dangerous winds and storm surge will continue to affect Grand
Bahama Island for several more hours.  Everyone there should remain
in shelter.

2. Life-threatening storm surge and dangerous winds are expected
along portions of the Florida east coast and the coasts of Georgia
and South Carolina, regardless of the exact track of Dorian's
center. Water levels could begin to rise well in advance of the
arrival of strong winds. Residents in these areas should follow
advice given by local emergency officials.

3. The risk of life-threatening storm surge and hurricane-force
winds continues to increase along the coast of North Carolina.
Residents in these areas should follow advice given by local
emergency officials.

4. The flash flood threat will increase today and tonight along the
Florida peninsula, then spread up the southeast and mid-Atlantic
coast during the middle and latter part of the week.

FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 27.1N  78.6W   95 KT 110 MPH
 12H  04/0000Z 27.9N  79.0W   95 KT 110 MPH
 24H  04/1200Z 29.2N  79.4W   95 KT 110 MPH
 36H  05/0000Z 30.7N  79.8W   95 KT 110 MPH
 48H  05/1200Z 32.1N  79.2W   95 KT 110 MPH
 72H  06/1200Z 35.3N  75.0W   85 KT 100 MPH
 96H  07/1200Z 40.5N  66.5W   75 KT  85 MPH
120H  08/1200Z 48.0N  57.5W   65 KT  75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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