Hurricane Florence Discussion Number  51
NWS National Hurricane Center Miami FL       AL062018
1100 PM AST Tue Sep 11 2018

Florence's eye became a little ragged in appearance on satellite
images a couple of hours ago, but recently it has become better
defined.  There has also been a little cooling of the tops
surrounding the eye.  These features suggest that Florence is
maintaining its intensity.  The current intensity is kept at 120
kt, which is a little above the adjusted flight-level winds from
the Air Force Hurricane Hunters and a little below the latest
SATCON estimate from UW-CIMSS.  Over the next couple of days, the
hurricane is expected to move over a warm ocean and through an
environment of low vertical shear.  This would allow some
additional strengthening until about 48 hours.  From that time
and up to landfall, the global models suggest some increase in shear
which would cause some weakening.  However, Florence is still likely
to remain a dangerous major hurricane when its center crosses the
coast.  The official intensity forecast is a blend of the
Decay-SHIPS and ICON intensity model consensus.

The initial motion estimate is west-northwestward, or 300/15 kt.  A
mid-level ridge to the northeast should continue to steer Florence
on a west-northwestward to northwestward heading until the
hurricane nears the coast.  The steering pattern from 72 hours and
beyond becomes more complicated and uncertain.  The latest GFS
model run shows a mid-level ridge building over the east-central
United States in 3-4 days.  This temporarily blocks the forward
progress of the hurricane and forces a southwesterly turn in the
model run.  Later in the period, the ridge rebuilds to the north of
Florence allowing the system to move inland.  The official track
forecast is somewhat to the left of the previous NHC track, but to
the right of the latest consensus predictions.  It should be noted
that, due to increased model spread, there is substantial
uncertainty in the 3-5 track forecast.

It is important for users to realize that significant impacts extend
well away from the center of Florence, and serious hazards such as
a dangerous storm surge and flooding rains will cover a large area
regardless of exactly where the center 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.  All
interests from South Carolina into the mid-Atlantic region should
complete preparations and follow any advice given by local
officials.

2. Life-threatening, catastrophic flash flooding and significant
river flooding is likely over portions of the Carolinas and
Mid-Atlantic states from late this week into 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, and a Hurricane Warning
has been issued for a part of this area.  Damaging winds could also
spread well inland into portions of the Carolinas and Virginia.

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


FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 28.4N  68.7W  120 KT 140 MPH
12H  12/1200Z 29.6N  70.8W  125 KT 145 MPH
24H  13/0000Z 31.4N  73.4W  135 KT 155 MPH
36H  13/1200Z 32.9N  75.5W  130 KT 150 MPH
48H  14/0000Z 33.8N  76.8W  115 KT 130 MPH
72H  15/0000Z 34.3N  78.2W   95 KT 110 MPH...INLAND
96H  16/0000Z 34.3N  79.7W   45 KT  50 MPH...INLAND
120H  17/0000Z 34.9N  82.5W   25 KT  30 MPH...INLAND

$$
Forecaster Pasch