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Tropical Storm Gert Discussion Number   5
NWS National Hurricane Center Miami FL       AL082017
1100 PM EDT Sun Aug 13 2017

Gert continues to gradually become better organized on satellite
imagery.  A large curved band feature has formed in the eastern
semicircle, with very deep convection.  It still appears the center
is on the northwest side of the convection, somewhat displaced to
the north of the mid-level center.  Intensity estimates are a little
higher than the last advisory, so the wind speed is raised to 40 kt.
Gert should remain in a light-to-moderate northerly wind shear
environment for the next couple of days, with anomalously warm SSTs
and increasing mid-level moisture in the forecast path.  Almost all
of the historically reliable guidance now show Gert becoming a
hurricane in a couple of days under these moderately favorable
conditions, and so does the official forecast. The latest NHC
prediction is raised from the previous one but remains below the
model consensus, closest to the LGEM model.  Gert should rapidly
weaken as it undergoes extratropical transition in 3-4 days over the
cold north Atlantic waters.

Gert is moving north-northwestward at 8 kt on the southwestern
periphery of a subtropical ridge.  A northward turn is expected
on Monday while the system rounds the western side of the ridge, and
Gert is expected to be about midway between Bermuda and North
Carolina on Tuesday.  After that time, a progressively faster motion
to the northeast and east-northeast is forecast as the system
becomes embedded in the mid-latitude westerlies until it dissipates
in about 5 days.  The guidance has shifted a little bit to the west
after recurvature, so the official forecast is moved in that
direction.

FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 28.8N  71.9W   40 KT  45 MPH
 12H  14/1200Z 30.0N  72.1W   50 KT  60 MPH
 24H  15/0000Z 31.6N  72.1W   55 KT  65 MPH
 36H  15/1200Z 33.6N  71.2W   60 KT  70 MPH
 48H  16/0000Z 36.0N  68.5W   65 KT  75 MPH
 72H  17/0000Z 41.0N  55.5W   65 KT  75 MPH
 96H  18/0000Z 48.0N  41.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  19/0000Z...DISSIPATED

$$
Forecaster Blake

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