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Tropical Storm FLORENCE


Tropical Storm Florence Discussion Number  62
NWS National Hurricane Center Miami FL       AL062018
500 PM EDT Fri Sep 14 2018

Florence's satellite appearance continues to be quite impressive
with well-established outflow and a nearly symmetrical cloud
pattern. In radar imagery, however, the inner-core convection has
continued to weaken and the echoes are now more stratiform in
nature, while outer banding remains rather vigorous, especially
south of Cape Lookout and Morehead City, North Carolina. An eye is
no longer evident, and the pressure has continued to rise to a
now estimated to be 972 mb based on nearby surface observations. Air
Force Reserve aircraft data, NOAA Doppler weather radar velocity
data from Wilmington, and nearby surface observations indicate that
Florence's intensity has decreased to 60 kt, tropical storm status.

Florence has turned westward and the motion estimate is now 270/03
kt. The new 1200Z global and regional model guidance is in good
agreement on Florence moving slowly in a general westward direction
for the next 48 hours or so, followed by a northward motion on day 3
as the system moves around the western periphery of a narrow
subtropical ridge. On days 4 and 5, the cyclone is forecast to turn
northeastward and accelerate ahead of an approaching shortwave
trough and frontal system, and emerge off the northeast U.S. coast
as an extratropical low. The new official forecast track is very
similar to the previous advisory, and is lies near the northern
and eastern edge of model guidance envelope, is closer to the
TVCA/TVCN consensus models.

Florence is expected to only slowly weaken overnight due to its
proximity to the warm Atlantic where convective bands are expected
to continue to develop and propagate inland in the eastern and
southern portion of the circulation, which will act to bring down
some of the stronger winds aloft. It is worth noting that the last
reconnaissance pass indicated 700-mb flight-level winds of 77 kt
just east of Charleston, South Carolina, so it won't take much
convection to bring down some of those stronger winds to the
surface as gusts. More rapid weakening is forecast over the weekend
as Florence moves westward across the higher terrain of central
and northwestern South Carolina. The official intensity forecast
follows the weakening trend of the previous advisory, and is similar
to an average of the GFS- and ECMWF-based Decay SHIPS models.

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 16 inches of rain has
already fallen in many areas across 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, mudslides 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.

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  14/2100Z 34.0N  78.6W   60 KT  70 MPH...INLAND
 12H  15/0600Z 33.9N  79.3W   50 KT  60 MPH...INLAND
 24H  15/1800Z 33.9N  80.3W   40 KT  45 MPH...INLAND
 36H  16/0600Z 34.4N  81.4W   25 KT  30 MPH...INLAND
 48H  16/1800Z 35.5N  82.6W   25 KT  30 MPH...INLAND
 72H  17/1800Z 38.5N  82.6W   20 KT  25 MPH...POST-TROP/INLAND
 96H  18/1800Z 41.5N  76.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  19/1800Z 44.0N  64.5W   30 KT  35 MPH...POST-TROP/EXTRATROP

Forecaster Stewart