[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 050851
TCDAT5

Hurricane Dorian Discussion Number  48
NWS National Hurricane Center Miami FL       AL052019
500 AM EDT Thu Sep 05 2019

Dorian continues to exhibit a large eye of about 50 n mi in
diameter on satellite and radar images.  Earlier data from
hurricane hunter aircraft indicate little change to the minimum
central pressure, and flight-level winds still support an intensity
close to 100 kt at this time.  Dorian should soon begin to
experience increasing southwesterly shear, which should lead to at
least slow weakening during the next couple of days.  The official
forecast maintains the cyclone at hurricane strength through 72
hours, which is in general agreement with the LGEM guidance and on
the high side of the guidance suite.  By 72 hours, the global models
show Dorian becoming embedded within a baroclinic zone, and
simulated satellite imagery from the ECMWF model depicts a highly
asymmetric cloud pattern.  Therefore, the NHC forecast shows the
system becoming extratropical by that time.

Dorian's initial motion is about 010/6 kt.  The hurricane is
currently moving through a break in the subtropical ridge.  Within
a day or so, the cyclone should turn northeastward with increasing
forward speed in response to a broad mid-tropospheric trough to the
north.  The official track forecast remains in good agreement with
the dynamical model consensus.  The forecast track and wind radii
now require the issuance of a tropical storm watch for extreme
southeastern New England.

The center of Dorian is still expected to move very near or over
the coastline of the Carolinas and the southern Mid-Atlantic
states.  Residents of these areas should already be prepared for
damaging winds, life-threatening storm surges, and flooding rains.


Key Messages:

1. Life-threatening storm surge and dangerous winds are expected
along portions the coasts of South Carolina and North Carolina, and
portions of southeast Virginia and the southern Chesapeake Bay,
regardless of the exact track of Dorian's center.  Water levels
could rise well in advance of the arrival of strong winds.
Residents in these areas should follow advice given by local
emergency officials.

2. Flash flooding will become increasingly likely across the eastern
Carolinas today.  There is a high risk of flash flooding over
coastal sections of the Carolinas where life-threatening flash
flooding is expected.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 31.7N  79.5W  100 KT 115 MPH
 12H  05/1800Z 32.7N  78.9W   95 KT 110 MPH
 24H  06/0600Z 34.2N  77.2W   90 KT 105 MPH
 36H  06/1800Z 36.1N  74.5W   85 KT 100 MPH
 48H  07/0600Z 38.3N  70.8W   80 KT  90 MPH
 72H  08/0600Z 46.0N  61.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  09/0600Z 53.0N  52.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  10/0600Z 58.0N  38.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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