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Tropical Storm FLORENCE


Tropical Storm Florence Discussion Number  65
NWS National Hurricane Center Miami FL       AL062018
1100 AM EDT Sat Sep 15 2018

Florence continues to creep slowly westward and weaken across
eastern South Carolina. NOAA WSR-88D Doppler weather radar data
indicate strong winds near 60 kt still exist between 3000-10000 ft
within intense rainbands situated between the Cape Fear/Wilmington
area and Bogue Inlet, North Carolina. Although those velocity values
would typically correlate to 50-kt surface winds, those winds appear
to be associated with small mesoscale circulations and possible
supercell thunderstorms, and not the larger tangential wind field.
In contrast, surface observations during the past couple of hours
have only shown sustained winds of around 40 kt, so that is the
intensity used for this advisory. The estimated central pressure
of 995 mb is based on nearby surface observations across eastern
South Carolina.

Radar data and surface observations indicate that Florence has
turned more westward, and has slowed down even more, and the initial
motion estimate is now 270/02 kt.  The models remain in very good
agreement that a mid-level ridge currently centered over the upper
Midwest will slide eastward across the lower Great Lakes to near the
northeastern U.S. during the next 48 hours.  This feature is
expected to steer Florence and its remnants in a general westward
motion for the next 24 hours or so, followed by a turn toward the
northwest on Monday.  The ridge will continue to shift eastward and
weaken, allowing Florence's circulation to get caught up in the
faster mid-latitude westerlies and accelerate toward the northeast
on day 3 and toward the east-northeast on days 4 and 5 as an
extratropical low pressure system. The new NHC track is similar to
the previous advisory track, and lies near the consensus model

Florence's inner-core convection and wind field will continue to
weaken throughout the next 72 hours or so. However, the outer wind
field and an associated band of deep convection in the eastern
semicircle will likely produce sustained tropical-storm-force winds
for another 12 hours or so, with some high gusts continuing until
the band moves inland by late Sunday as per the latest the latest
NOAA HRRR and other mesoscale model runs. More importantly,
continued heavy rains will be produced by this band of convection,
which will exacerbate the already catastrophic flooding that is
occurring across much of southeastern North Carolina. The official
intensity forecast closely follows the Decay-SHIPS model guidance
and the intensity model IVCN through 72 hours, and then follows a
blend of the IVCN, HCCA, and FSSE consensus models on days 4 and 5
when the post-tropical cyclone is forecast to strengthen due to
baroclinic processes after moving over the relatively warm waters of
the northwestern Atlantic Ocean.

Although coastal storm surge flooding will gradually subside today,
especially after the midday high-tide period ends, extremely heavy
rainfall will continue to be a serious hazard associated with
slow-moving Florence.  More than two feet 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 today, 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 today.

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 west-central Virginia and far eastern West 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 today.

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  15/1500Z 33.6N  79.6W   40 KT  45 MPH...INLAND
 12H  16/0000Z 33.6N  80.5W   35 KT  40 MPH...INLAND
 24H  16/1200Z 34.4N  81.7W   25 KT  30 MPH...INLAND
 36H  17/0000Z 36.0N  82.8W   25 KT  30 MPH...INLAND
 48H  17/1200Z 38.0N  82.9W   20 KT  25 MPH...INLAND
 72H  18/1200Z 41.3N  76.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  19/1200Z 44.3N  63.4W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  20/1200Z 48.5N  49.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

Forecaster Stewart