[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 030252
TCDAT5

Hurricane Dorian Discussion Number  39
NWS National Hurricane Center Miami FL       AL052019
1100 PM EDT Mon Sep 02 2019

Dorian continues to pummel Grand Bahama Island this evening.  The
hurricane still has an impressive presentation in satellite and
radar images, however, there have been occasional dry slots
observed in the western part of the eyewall.  Both the NOAA and
Air Force Hurricane Hunters provided excellent data in Dorian this
evening, and based primarily on the flight-level wind data from the
aircraft, the initial intensity of Dorian is set to 115 kt.  The
westernmost outer rain bands are reaching the east coast of south
Florida and producing gusty winds.

The major hurricane has been stationary much of the day.  The reason
the cyclone has moved very little is because it is caught in weak
steering currents between high pressure ridges to its east and
northwest and a trough to its north.  This weak flow should result
in a very slow and likely erratic northwest drift through at least
early Tuesday.  After that time, the models are in general agreement
that the ridge to the east and trough to the north will amplify.
This change in the steering pattern should cause Dorian to move a
little faster to the north on Wednesday and to the northeast on
Thursday and Friday.  The NHC track forecast remains consistent and
continues to show the core of Dorian offshore, but dangerously close
to the east coast of the U.S. from Florida to North Carolina during
the next 3 days or so. This track forecast is largely an update of
the previous one and it is in good agreement with the various
consensus models.  Users are reminded that the hurricane is not a
point, and that life-threatening storm surge and hurricane-force
winds extend far from the center. Regardless of the exact forecast
track, Dorian is likely to produce strong winds and a
life-threatening storm surge along a portion of the U.S. east coast
from Florida through the Carolinas.

The intensity models are in agreement that Dorian should slowly
lose strength during the next several days due to a gradual
increase in wind shear and perhaps drier air.  Regardless of the
details of the intensity forecast, the bottom line is that Dorian is
expected to remain a powerful hurricane as it tracks very near the
east coast of the U.S. from Florida to North Carolina during the
next few days.  The NHC intensity forecast is the same as the
previous one and close to the HCCA and IVCN guidance.


Key Messages:

1. Devastating 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 hurricane-force 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. Heavy rains, capable of producing life-threatening flash floods,
are expected over northern portions of the Bahamas and coastal
sections of the southeast and lower mid-Atlantic regions of the
United States through Friday.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 26.9N  78.5W  115 KT 130 MPH
 12H  03/1200Z 27.1N  78.7W  115 KT 130 MPH
 24H  04/0000Z 27.9N  79.1W  110 KT 125 MPH
 36H  04/1200Z 29.2N  79.7W  110 KT 125 MPH
 48H  05/0000Z 30.6N  79.7W  105 KT 120 MPH
 72H  06/0000Z 33.7N  77.3W   90 KT 105 MPH
 96H  07/0000Z 38.0N  71.0W   80 KT  90 MPH
120H  08/0000Z 45.4N  61.5W   70 KT  80 MPH...POST-TROP/EXTRATROP

$$
Forecaster Cangialosi
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