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Tropical Storm FLORENCE


Tropical Storm Florence Discussion Number  66
NWS National Hurricane Center Miami FL       AL062018
500 PM EDT Sat Sep 15 2018

Florence's center has continued its slow...and I do mean s-l-o-w...
westward trek across eastern South Carolina, with little change in
the overall structure of the wind field both overland and over
water. NOAA WSR-88D Doppler weather radar data, surface
observations, and a 1527Z ASCAT pass indicate that Florence is
still producing a significant fetch of tropical storm force winds
within and adjacent to the the two bands of convection that are
currently located between the Cape Fear/Wilmington area and Bogue
Inlet, North Carolina. The ASCAT pass contained numerous 40-45 kt
wind vectors, and the NOAA NOS observing site at Johnny Mercer Pier
in Wrightsville Beach, North Carolina, has been reporting sustained
winds of 38-41 kt and gusts to 46-48 kt during the past few hours
during the passage of light to moderate rain showers. Therefore, the
initial intensity is being maintained at a conservative 40 kt for
this advisory. The estimated central pressure of 997 mb is based on
nearby surface observations across eastern South Carolina.

The initial motion remains 270/02 kt. The new 12Z model guidance
remains in excellent agreement on a mid-level ridge currently to the
northwest and north of Florence moving steadily eastward during the
next 48 hours, which will keep the broad cyclone moving slowly
westward to west-northwestward during that time. By 48 hours and
beyond, the ridge is forecast to continue to shift eastward to near
the northeast U.S. coast and weaken, which will allow Florence and
its remnant circulation to move slowly northward into the
mid-latitude westerlies by Tuesday. By days 3-5, the global models
diverge on where and how fast Florence's then extratropical
circulation moves. Due to the significant spread in the guidance,
the official forecast track lies close to the consensus model
TCVA/TVCN and the previous advisory track forecast.

Florence's inner-core convection and wind field will steadily weaken
throughout the next 48 hours or so. However, the outer wind
field and an associated band of deep convection in the eastern
semicircle should continue to produce tropical-storm-force winds
for another 12 hours or so over water and near the coast, with
occasional strong wind gusts occurring over land. The official
intensity forecast is close to an average of the Decay-SHIPS and
LGEM, and the IVCN consensus intensity model guidance through 72
hours, and then follows a blend of the IVCN, HCCA, and FSSE
consensus models at 96 and 120 hours when the post-tropical cyclone
moves back over water and strengthens some due to baroclinic

Although coastal storm surge flooding will continue to subside
tonight and Sunday, torrential rainfall will continue to be a
serious hazard associated with slow-moving Florence.  More than two-
and-a-half 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 farther inland
through the weekend.

Key Messages:

1.  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.

2.  Water levels along the coast will gradually subside through

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  15/2100Z 33.6N  79.9W   40 KT  45 MPH...INLAND
 12H  16/0600Z 33.9N  80.9W   35 KT  40 MPH...INLAND
 24H  16/1800Z 35.1N  82.6W   25 KT  30 MPH...INLAND
 36H  17/0600Z 37.0N  83.2W   25 KT  30 MPH...INLAND
 48H  17/1800Z 38.8N  82.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  18/1800Z 41.4N  74.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  19/1800Z 43.3N  60.8W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  20/1800Z 47.0N  47.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

Forecaster Stewart