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Hurricane Gert Discussion Number  13
NWS National Hurricane Center Miami FL       AL082017
1100 PM EDT Tue Aug 15 2017

Gert looked a bit ragged in satellite imagery earlier this evening,
with the eye disappearing and microwave data showing the center to
be in the northwest portion of the convective mass.  Since then, the
cloud pattern has become better organized, with a well-defined
convective band now present around the center. Satellite intensity
estimates from TAFB and SAB have increased to 77 kt, and thus the
initial intensity is increased to 75 kt.

Gert continues to recurve into the westerlies between the
subtropical ridge and a baroclinic zone extending from North
Carolina to Nova Scotia, and the initial motion is now 035/13.  The
hurricane should accelerate northeastward during the next 24-48 h,
passing well south of the Canadian Maritimes and Atlantic
Provinces.  After that, the cyclone will then likely slow down and
turn more northward by day 4 as it interacts with a large
baroclinic low moving eastward from northeast Canada.  The track
guidance remains tightly clustered, and the new forecast track is
little changed from the previous track.

Conditions appear conducive for additional strengthening during the
next 24 h as Gert remains over warm water and in a light/moderate
vertical shear environment.  The new intensity forecast raises the
peak into to 85 kt, which is on the low side of the intensity
guidance.  After that time, Gert should move over cooler water and
begin to merge with the above-mentioned baroclinic zone.  The
cyclone is now forecast to become extratropical in 48 h, to
persist as an extratropical low through 96 h, and then be absorbed
by the baroclinic low by 120 h.   As mentioned in the previous
advisory, the large-scale models suggest the possibility that Gert
may survive as its own entity beyond 96 h, and a 120 h point could
be added in later advisories.

Swells from Gert should spread northward along the mid-Atlantic
coast of the United States during the next few days, with the first
impacts expected to occur tonight.  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  16/0300Z 34.8N  70.3W   75 KT  85 MPH
 12H  16/1200Z 36.3N  67.6W   80 KT  90 MPH
 24H  17/0000Z 38.5N  62.2W   85 KT 100 MPH
 36H  17/1200Z 41.1N  54.8W   75 KT  85 MPH
 48H  18/0000Z 44.9N  46.8W   65 KT  75 MPH...POST-TROP/EXTRATROP
 72H  19/0000Z 53.0N  35.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  20/0000Z 55.5N  31.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  21/0000Z...ABSORBED BY EXTRATROPICAL LOW

$$
Forecaster Beven

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