Official Discussion issued by the National Hurricane Center

Florence (AL062018) DATA RELEASED: 9/14/2018 3:00:00 AM UTC

Copy of official data

Hurricane Florence Discussion Number  59
NWS National Hurricane Center Miami FL       AL062018
1100 PM EDT Thu Sep 13 2018

Radar imagery and data from an Air Force Reserve Hurricane Hunter
flight indicate that Florence has an inner eye that is open on the
east side, and a secondary wind maximum that has already begun to
spread inland across southeastern North Carolina.  The highest
flight-level wind (102 kt) was actually measured within the outer
band that is moving onshore in the Wilmington area.  However, the
highest SFMR-measured wind was 73 kt, and the highest land
observation so far was a sustained wind of 72 kt at Cape Lookout,
North Carolina.  On top of that, NOAA Doppler radar velocities have
been running around 100 kt at about 5,000 feet.  All of these data
support reducing the initial intensity to 80 kt, but based on the
higher flight-level winds, the gust factor is being set a little
higher than is typical for an 80-kt hurricane.

Florence has been wobbling a little since the previous advisory,
but the 12-hour motion is northwestward, or 305/5 kt.  Nearly all
of the track models agree that Florence will turn westward or
west-southwestward during the next 36 hours, bringing the
hurricane's center inland over extreme southern North Carolina and
extreme eastern South Carolina Friday and Friday night.  After 48
hours, Florence is expected to recurve across the western Carolinas
and the central Appalachian Mountains around a western Atlantic
ridge.  No major changes were required to the NHC official track
forecast, and it is generally close to the multi-model consensus
aids.  It should be noted that the ECMWF, HCCA, and Florida State
Superensemble still take Florence on a more southern track,
straddling the coast of South Carolina before turning inland.
While that is not shown by the official forecast, it cannot yet be
ruled out as a possibility.

Florence's intensity is not likely to change much in the 12 hours
or so it has left over water.  Once the center moves inland, the
intensity is forecast to decrease.  However, since a good portion
of Florence's circulation will remain over water for the next 36-48
hours, the NHC intensity forecast is a blend of the regular SHIPS
model (which assumes a storm staying over water) and the Decay-SHIPS
model (which assumes the storm has moved inland).  Based on that,
Florence should weaken to a tropical storm just after 24 hours and
then below tropical storm strength after 48 hours.

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 already occurring along
portions of the North Carolina coast and will continue through
Friday.  This surge is also likely along portions of the South
Carolina coast.  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 occurring along portions of
the North Carolina coast and are expected to spread to portions of
the South Carolina coast on Friday.  Strong winds could also spread
inland into portions of the Carolinas over the next couple of days.

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  14/0300Z 34.0N  76.8W   80 KT  90 MPH
12H  14/1200Z 34.2N  77.6W   75 KT  85 MPH
24H  15/0000Z 34.0N  78.5W   65 KT  75 MPH...INLAND
36H  15/1200Z 33.8N  79.2W   50 KT  60 MPH...INLAND
48H  16/0000Z 33.8N  80.2W   40 KT  45 MPH...INLAND
72H  17/0000Z 35.5N  82.9W   25 KT  30 MPH...INLAND
96H  18/0000Z 39.5N  82.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  19/0000Z 44.0N  72.5W   25 KT  30 MPH...POST-TROP/INLAND

Forecaster Berg