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Hurricane FLORENCE


Hurricane Florence Discussion Number  27
NWS National Hurricane Center Miami FL       AL062018
1100 PM AST Wed Sep 05 2018

It appears that southwesterly shear is finally affecting Florence.
The cloud pattern has become asymmetric this evening, with the
northeastern quadrant growing at the expense of the southwestern
one, along with warming cloud tops noted across the central dense
overcast.  Satellite intensity estimates are a bit lower than
before, so the initial wind speed is reduced to 110 kt.

The current shear is forecast to persist by the global models during
the next day or two until an upper-level low cuts off to south of
Florence, which will likely reduce the shear.  This, in combination
with much warmer waters in the path of the hurricane, should set the
stage for restrengthening. At long range, a rather large upper-level
anticyclone is forecast to form near Florence, which would provide
ample opportunity for the hurricane to regain its former strength
and grow in size.  Thus, the official forecast shows slow weakening
in response to the initial shear, then levels off, with a
significant increase in strength predicted by day 5.  This solution
is very close to the previous NHC advisory, but not quite as high as
the HWRF and HMON models at long range.

Florence has been moving more to the right during the past several
hours, likely due to the vortex attempting to stay vertically
aligned in the face of the southwesterly shear, but a longer-term
motion is 310 degrees at 10 kt. A mid-level ridge is forecast to
strengthen to the north and northwest of Florence, causing the
hurricane to turn west- northwestward by Friday and even westward by
the weekend.  It appears that a mid-latitude trough over the
northwestern Atlantic in a few days will likely miss Florence, with
the only perceivable effects on the hurricane being a decrease in
forward speed.  The net result is that the model guidance continues
to trend westward at long range, and the official forecast follows
suit, lying just north of the model consensus in deference to the
ECMWF deterministic model and ensemble mean.

It should be noted that there is still considerable model ensemble
spread for Florence's track beyond day 5. Given the large
uncertainty at these time ranges, it is far too soon to speculate
what, if any, impacts Florence may have on the U.S. East Coast next
week. Regardless of Florence's eventual track, large swells
emanating from the hurricane will reach Bermuda beginning on Friday,
resulting in life-threatening surf and rip currents on the island.
Swells from Florence could also reach the U.S. East Coast by early
next week.


INIT  06/0300Z 23.4N  47.2W  110 KT 125 MPH
 12H  06/1200Z 24.2N  48.4W  105 KT 120 MPH
 24H  07/0000Z 25.0N  49.9W  100 KT 115 MPH
 36H  07/1200Z 25.5N  51.6W   95 KT 110 MPH
 48H  08/0000Z 25.7N  53.2W   95 KT 110 MPH
 72H  09/0000Z 26.1N  55.7W  100 KT 115 MPH
 96H  10/0000Z 27.2N  58.1W  105 KT 120 MPH
120H  11/0000Z 29.0N  62.0W  115 KT 130 MPH

Forecaster Blake