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TROPICAL STORM HERMINE DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092016
400 PM CDT WED AUG 31 2016

The system appears better organized on satellite images than it was
yesterday, with more evidence of convective banding features.
However, based on the NOAA Hurricane Hunter data the center is
still situated near the northern edge of the main convective cloud
mass.  Also, data from the aircraft show a very asymmetric wind
field with all of the strong winds occurring over the eastern and
southeastern portions of the circulation.  The advisory intensity
is set to 40 kt based on SFMR-observed surface winds from the
Hurricane Hunters.  Hermine should be in an environment of
moderate west-southwesterly shear until it nears the coast, when
the dynamical models show increasing shear.  The official intensity
forecast has been nudged upward a bit, and there is a distinct
possibility that Hermine could become a hurricane before landfall.
The predicted extratropical transition of the system is based on
the latest global model forecasts, which show the cyclone becoming
embedded within a front over the eastern United States by 72 hours.

The aircraft data show a rather broad area of light winds near the
center, making the actual center fixes a little uncertain.
However, the best estimate of initial motion is north-northeastward
or 030/6 kt.  A developing mid-level trough over the southeastern
United States should cause Hermine to move north-northeastward at
increasing forward speed over the next couple of days.  The GFS and
ECMWF global models have shifted westward from their previous
predictions, and so has the new official forecast.  This required a
westward extension of the hurricane watch and tropical storm
warning along the Florida panhandle.  Later in the forecast period,
there is significant uncertainty in the track of the system, which
will depend on how the post-tropical cyclone interacts with a
mid-tropospheric cutoff low that develops over the northeastern
United States.  The new official forecast keeps the cyclone closer
to the east coast from 72-120 hours in deference to the latest GFS
solution.

It is important not to focus on the forecast landfall point of this
system.  In addition to the normal uncertainty in track and
intensity forecasts, dangerous storm surge flooding is likely to
extend along the Gulf coast well to the east and south of
the path of the center.

FORECAST POSITIONS AND MAX WINDS

INIT  31/2100Z 25.5N  87.4W   40 KT  45 MPH
 12H  01/0600Z 26.5N  87.3W   45 KT  50 MPH
 24H  01/1800Z 28.1N  86.3W   50 KT  60 MPH
 36H  02/0600Z 30.0N  85.0W   60 KT  70 MPH
 48H  02/1800Z 32.0N  82.9W   50 KT  60 MPH...INLAND
 72H  03/1800Z 36.5N  77.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  04/1800Z 39.0N  74.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  05/1800Z 39.5N  72.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

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