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Hurricane Florence Discussion Number 56
NWS National Hurricane Center Miami FL AL062018
500 AM EDT Thu Sep 13 2018
The satellite presentation of Florence has changed little overnight
with the eye waxing and waning in infrared imagery. The eye has
moved into NWS radar range and can be seen in radar data from
Morehead City and Wilmington NWS 88-D imagery. An 0616 UTC
AMSR2 microwave overpass indicated that the convection over the
southern and southeastern portions of the storm is still disrupted,
and that the eyewall was open to the southeast. An Air Force
Hurricane Hunter aircraft also reported that the eyewall was not
fully intact on its last pass through the storm just after that
time. The Air Force plane measured a peak 700-mb flight level wind
of 102 kt and peak SFMR winds of 85 kt during the mission. These
data suggest that the intensity may be slightly lower, but the
initial intensity has been maintained at 95 kt, since the plane
may not have sampled the strongest winds. Another Air Force
plane will be in Florence shortly, and should provide a better
assessment of the intensity of the hurricane. As mentioned in
the previous discussion, it appears that some southern shear has
caused the degradation of the inner core. The global models suggest
that this shear will relax today while Florence moves over warm
waters, however, given the current storm structure, little overall
change in strength is anticipated as Florence approaches the coast.
Gradual weakening should occur as the hurricane interacts with land
in 24-36 h, with a faster rate of weakening predicted once Florence
moves farther inland.
Florence is moving northwestward or 315 degrees at 13 kt. A
developing mid-level ridge over the north-central United States
should cause the forward speed of the hurricane to decrease today.
As the steering currents collapse tonight and Friday, Florence is
forecast to drift westward or west-southwestward and continue that
slow motion into the weekend. The global models predict that the
ridge will slide eastward over the weekend, which should allow
Florence to turn northwestward and northward by the end of the
forecast period. Although there is still some spread in the
guidance by 48 hours, with the GFS along the northern side of the
guidance envelope, and the ECWMF along the southern edge, the
various consensus aids have moved little. As a result, the new NHC
forecast track is very similar to the previous advisory.
Aircraft and satellite wind data show that Florence is a large
hurricane. Life-threatening storm surge, heavy rainfall, and
damaging wind will cover a large area regardless of exactly where
the center of Florence moves.
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 in these areas should complete preparations and follow any
advice given by local officials.
2. Life-threatening, catastrophic flash flooding and prolonged
significant river flooding are likely over portions of the Carolinas
and the southern and central Appalachians 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
is in effect. Strong winds could also spread inland into portions
of the Carolinas.
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.
FORECAST POSITIONS AND MAX WINDS
INIT 13/0900Z 32.8N 74.7W 95 KT 110 MPH
12H 13/1800Z 33.7N 76.1W 95 KT 110 MPH
24H 14/0600Z 34.2N 77.4W 90 KT 105 MPH
36H 14/1800Z 34.3N 78.4W 70 KT 80 MPH...INLAND
48H 15/0600Z 34.1N 79.2W 50 KT 60 MPH...INLAND
72H 16/0600Z 33.9N 81.2W 30 KT 35 MPH...INLAND
96H 17/0600Z 35.4N 83.3W 25 KT 30 MPH...INLAND
120H 18/0600Z 39.5N 81.0W 20 KT 25 MPH...POST-TROP/REMNT LOW