Official Discussion issued by the National Hurricane Center

Florence (AL062018) DATA RELEASED: 9/15/2018 3:00:00 AM UTC

Copy of official data

Tropical Storm Florence Discussion Number  63
NWS National Hurricane Center Miami FL       AL062018
1100 PM EDT Fri Sep 14 2018

Although we lost data from the Wilmington, North Carolina,
WSR-88D radar several hours ago, the radars from Raleigh and
Columbia have clearly shown Florence's center has moved into extreme
eastern South Carolina.  Reflectivities around the eye have been
decreasing, but there are still some strong spiral bands moving from
southeast to northwest across portions of southeastern North
Carolina.  Maximum Doppler velocities are 65-70 kt from 5000-7000
feet, and on this basis Florence's maximum surface winds are
estimated to be 55 kt.

Radar fixes indicate that Florence has turned west-southwestward
and has an initial motion of 255/4 kt.  A mid-level high centered
near Iowa and Missouri is expected to slide eastward to the north
of Florence over the next 48 hours, which should cause the storm to
maintain a slow motion and gradually turn toward the west and
northwest over the Carolinas.  For this period, the new official
forecast track has been shifted a bit southward to follow an
overall trend in the model guidance, but this isn't surprising
given what some of the models were showing last night.  After 48
hours, Florence is expected to get picked up by the mid-latitude
westerlies, accelerating north and northeastward to the western
Atlantic by day 5.  The NHC track forecast is fairly close to the
TVCN multi-model consensus and just a little south of the previous
forecast beyond 72 hours.

Florence's winds should continue to slowly decay as the center
ambles farther inland, but enough of the circulation should remain
over water to allow the cyclone to remain as a tropical storm for
the next 24 hours or so.  This thinking follows the global model
fields of the GFS and ECMWF models.  After 24 hours, most of
Florence's circulation should be inland, allowing the cyclone to
weaken to a tropical depression and eventually degenerate into a
remnant low over the Ohio Valley by day 3.  The remnant low is then
likely to become an extratropical low by day 4, and it forecast to
begin producing gale-force winds well east of New England to the
south of Atlantic Canada.

Although coastal storm surge flooding will gradually subside
tonight and Saturday, it cannot be emphasized enough that another
serious hazard associated with slow-moving Florence will continue
to be extremely heavy rainfall.  More than a foot of rain has
already fallen across portions of southeastern North Carolina, and
more rain is still to come, which will cause disastrous flooding
that will spread inland through the weekend.

Key Messages:

1. Life-threatening storm surge will continue along portions of
the North Carolina coast through tonight, and also along the Neuse
and Pamlico Rivers in western Pamlico Sound, where rainfall and
freshwater flooding will also contribute to high water levels.
Dangerous storm surge could also affect portions of the northeast
coast of South Carolina coast tonight.

2. Life-threatening, catastrophic flash floods and prolonged
significant river flooding are likely over portions of the
Carolinas and the southern to central Appalachians from western
North Carolina into southwest Virginia through early next week, as
Florence moves slowly inland.  In addition to the flash flood and
flooding threat, landslides are also possible in the higher terrain
of the southern and central Appalachians across western North
Carolina into southwest Virginia.

3. Tropical storm conditions will continue along the coast within
the tropical storm warning area and also well inland across portions
of South Carolina and North Carolina through Saturday.

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  15/0300Z 33.8N  79.1W   55 KT  65 MPH...INLAND
12H  15/1200Z 33.7N  79.6W   45 KT  50 MPH...INLAND
24H  16/0000Z 33.8N  80.5W   35 KT  40 MPH...INLAND
36H  16/1200Z 34.4N  81.8W   30 KT  35 MPH...INLAND
48H  17/0000Z 35.9N  83.1W   25 KT  30 MPH...INLAND
72H  18/0000Z 39.3N  81.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
96H  19/0000Z 41.0N  74.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  20/0000Z 43.5N  61.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

Forecaster Berg