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Tropical Storm Ernesto Discussion Number   9
NWS National Hurricane Center Miami FL       AL052018
500 AM AST Fri Aug 17 2018

Ernesto is maintaining its strength and status as a tropical storm
despite being over very cool 21 deg C waters.  Deep convection
remains well organized in a curved band that wraps across the
eastern half of the circulation.  The system is likely benefiting
from a moist and unstable airmass, which seems to be the reason why
Ernesto has held onto tropical storm status longer than expected.
The initial wind speed is again held at 40 kt, using a blend of the
latest satellite intensity estimates.

The convective organization is not expected to last much longer as
Ernesto is tracking over steadily colder waters and will also be
moving into an environment of higher shear.  These hostile
environmental conditions should cause the system to lose its
tropical characteristics within the next 24 hours, when the
cyclone is forecast to be over SSTs of around 15 deg C.  The
post-tropical low is expected to gradually decay before it merges
with a frontal zone near the United Kingdom in about 48 hours.

Ernesto is now well embedded in fast mid-latitude flow, and the
latest initial motion estimate is northeastward at 22 kt.  An even
faster northeastward to east-northeastward motion is expected until
the system merges with the frontal zone.  The models remain tightly
clustered, and the NHC track forecast lies near the middle of the
guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  17/0900Z 45.6N  36.4W   40 KT  45 MPH
 12H  17/1800Z 47.8N  31.4W   40 KT  45 MPH
 24H  18/0600Z 50.4N  23.2W   40 KT  45 MPH...POST-TROPICAL
 36H  18/1800Z 52.5N  14.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
 48H  19/0600Z...DISSIPATED

$$
Forecaster Cangialosi

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