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Subtropical Storm Ernesto Discussion Number   6
NWS National Hurricane Center Miami FL       AL052018
1100 AM AST Thu Aug 16 2018

Convection developed closer to the center of Ernesto early this
morning, suggesting that the system was attempting to make the
transition to a tropical cyclone, but that area of convection has
weakened within the past couple of hours.  Patches of deep
convection continue over the outer portion of the circulation, and
a very recent ASCAT overpass continues to show a rather large radius
of maximum winds, indicating that Ernesto remains a subtropical
cyclone.  The ASCAT data showed a large area of 35-40 kt winds over
the eastern and southeastern portions of the circulation, so the
initial wind speed has been increased to 40 kt.

Ernesto has likely reached its peak intensity since it will be
moving over much cooler SSTs later today, and the cyclone is
expected to lose its subtropical characteristics late tonight or
early Friday.  The post-tropical cyclone should be able to maintain
its intensity due in part to its expected fast forward speed over
the North Atlantic.  The global models indicate that the system will
merge with a frontal zone as it approaches Ireland and the United
Kingdom late Saturday.

Ernesto has turned northeastward and is beginning to accelerate,
and is now moving at around 14 kt.  The cyclone should be fully
embedded within the mid-latitude westerlies within the next 24
hours, and a significantly faster northeastward to
east-northeastward motion is expected over the next couple of days.
The track guidance continues to be in good agreement, and the new
NHC official forecast is essentially an update of the previous
advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 42.0N  43.2W   40 KT  45 MPH
 12H  17/0000Z 43.9N  40.4W   40 KT  45 MPH
 24H  17/1200Z 46.7N  35.0W   40 KT  45 MPH...POST-TROPICAL
 36H  18/0000Z 49.5N  28.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  18/1200Z 52.0N  19.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  19/1200Z...DISSIPATED

$$
Forecaster Brown

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