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Hurricane Gert Discussion Number   9
NWS National Hurricane Center Miami FL       AL082017
1100 PM EDT Mon Aug 14 2017

Satellite images show that Gert has developed an eye, although the
convection is weak in the western eyewall.  Still, microwave images
show a healthy inner-core structure, with plenty of deep convection
in the eastern eyewall.  Satellite intensity estimates unanimously
support making Gert a hurricane on this advisory, and the initial
wind speed is set to 65 kt, close to the TAFB figure.

Some light or moderate northerly shear is forecast to continue to
affect Gert for the next day or so, which might limit the
intensification rate.  On Wednesday, however, the shear is forecast
to drop off as Gert accelerates northeastward over warm waters with
a large increase in upper-level divergence also noted.  This is
typically a favorable environment for intensification, and the
official forecast is raised from the previous one, lying between
the model consensus IVCN and the higher corrected consensus aids.
Gert is expected to complete extratropical transition within 72
hours, then gradually weaken over the North Atlantic before it
merges with a larger extratropical cyclone in 4 to 5 days.

Gert continues to move northward at about 7 kt.  The storm is
expected to turn north-northeastward and begin to accelerate
Tuesday ahead of a shortwave trough approaching the northeastern
United States.  Like the last cycle, the track guidance continues to
be in excellent agreement, but is generally slower than before.
The new forecast is on the fast side of the guidance, assuming that
Gert is a strong hurricane that stays vertically coherent in the
faster mid/upper-level flow.

Swells from Gert are expected to spread northward along the
mid-Atlantic coast of the United States during the next few days.
These swells are likely to produce dangerous surf and rip current
conditions.  Please consult products from your local National
Weather Service office.


FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 31.2N  72.3W   65 KT  75 MPH
 12H  15/1200Z 32.3N  72.0W   70 KT  80 MPH
 24H  16/0000Z 34.3N  70.6W   75 KT  85 MPH
 36H  16/1200Z 36.6N  66.9W   85 KT 100 MPH
 48H  17/0000Z 39.3N  60.8W   90 KT 105 MPH
 72H  18/0000Z 46.0N  46.0W   70 KT  80 MPH...POST-TROP/EXTRATROP
 96H  19/0000Z 52.0N  37.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  20/0000Z...DISSIPATED

$$
Forecaster Blake

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