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Hurricane FLORENCE


Hurricane Florence Discussion Number  57
NWS National Hurricane Center Miami FL       AL062018
1100 AM EDT Thu Sep 13 2018

The satellite and radar presentations of Florence have improved
somewhat this morning, with a 20-25 nmi wide eye closing off in the
radar data from the Morehead City and Wilmington WSR-88D Doppler
weather radars. However, an Air Force Reserve reconnaissance
aircraft investigating the hurricane this morning has not yet found
any flight-level or SFMR winds to support more than about 80 kt at
the surface thus far, even though the pressure has decreased to 955
mb. The initial intensity has only been lowered to 90 kt, given
that there are peak Doppler velocity values up to 110 kt with
average values of 95-97 kt at 15,000 ft in the northern eyewall
region, an area of the hurricane that the reconnaissance aircraft
has not yet sampled. The upper-level outflow pattern remains quite

Florence has been gradually slowing down this morning, and the
initial motion estimate is now 315/09 kt. The subtropical ridge to
the northeast and east of Florence is now well-established between
Bermuda and the U.S. mid-Atlantic region and extends westward into
Virginia and the central Appalachians. This large-scale feature is
expected to keep the hurricane moving northwestward today, followed
by a turn toward the west at a much slower speed on Friday as the
ridge to the north of Florence weakens due to a weak shortwave
trough dropping slowly southward from the Ohio Valley. On days 3-5,
Florence is forecast turn toward the northwest and north around the
western periphery of the subtropical ridge, and move across western
South Carolina on Sunday, across western North Carolina and eastern
Tennessee on Monday, and then move up the spine of the Appalachians
as an extratropical low after the cyclone merges or interacts with a
frontal system. The new NHC forecast track is similar to the
previous one, and lies close to a blend of the consensus models

Florence is currently approaching the Gulfstream current, and the
hurricane is forecast to move over warmer and deeper waters in 6-12
hours, which could allow for some slight strengthening. Just prior
to landfall in about 24 hours, Florence is expected to weaken some
due to upwelling of the shallow coastal waters. After landfall
occurs, rapid weaning of the stronger inner-core wind field is
expected to due land interaction and Florence's slow forward speed
of 5 kt or less. However, intense rainbands are expected to develop
over the Atlantic waters and keep moving along the coast and inland,
likely producing strong wind gusts through Saturday night.

Aircraft and satellite wind data show that Florence remains a large
hurricane.  Life-threatening storm surge, heavy rainfall, and
damaging wind will cover a large area regardless of exactly where
the center of Florence moves.

Key Messages:

1. A life-threatening storm surge is now highly likely along
portions of the coastlines of South Carolina and North Carolina, and
a Storm Surge Warning is in effect for a portion of this area. The
greatest storm surge inundation is expected between Cape Fear and
Cape Hatteras, including the Neuse and Pamlico Rivers and western
Pamlico Sound.

2. Life-threatening, catastrophic flash flooding and prolonged
significant river flooding are likely over portions of the Carolinas
and the southern and central Appalachians through early next week,
as Florence is expected to slow down as it approaches the coast and
moves inland.

3. Damaging hurricane-force winds are likely along portions of the
coasts of South Carolina and North Carolina as soon as this evening,
and a Hurricane Warning is in effect. Strong winds could also spread
inland into portions of the Carolinas.

4. Large swells affecting Bermuda, portions of the U.S. East
Coast, and the northwestern and central Bahamas will continue this
week, resulting in life-threatening surf and rip currents.


INIT  13/1500Z 33.4N  75.5W   90 KT 105 MPH
 12H  14/0000Z 33.9N  76.6W   95 KT 110 MPH
 24H  14/1200Z 34.2N  77.8W   85 KT 100 MPH...NEAR THE COAST
 36H  15/0000Z 34.1N  78.7W   65 KT  75 MPH...INLAND
 48H  15/1200Z 34.0N  79.6W   45 KT  50 MPH...INLAND
 72H  16/1200Z 34.3N  81.8W   25 KT  30 MPH...INLAND
 96H  17/1200Z 36.9N  83.0W   25 KT  30 MPH...INLAND
120H  18/1200Z 40.3N  79.2W   20 KT  25 MPH...POST-TROP/EXTRATROP

Forecaster Stewart