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Tropical Storm Helene Discussion Number  32
NWS National Hurricane Center Miami FL       AL082018
500 AM AST Sat Sep 15 2018

Helene appears to be maintaining its strength.  Recent microwave
images show that the storm has an eye feature, but the vortex is
significantly tilted in the vertical due to southwesterly shear.
Deep convection is most organized in bands to the north and west of
the center. Based on the tropical storm's appearance in microwave
images, the initial intensity is again held at 60 kt, near the high
end of the satellite intensity estimates. Helene is expected to
gradually weaken during the next few days due to the influences of
southwesterly shear, drier air, and much cooler SSTs along the
forecast track. These conditions should also cause Helene to lose
tropical characteristics, and the storm is forecast become
extratropical in 24 to 36 hours.

The tropical storm is moving north-northeastward at a fairly fast
pace, 19 kt.  The center of Helene is expected to pass to the west
of the Azores by tonight.  However, Helene has a fairly large wind
field, and tropical-storm-force winds are expected across the
western Azores as the storm passes by. A shortwave trough to the
northwest of the system is expected to approach Helene by tonight,
and that should cause the cyclone to turn northeastward and then
speed up in that direction as it heads toward Ireland and the United
Kingdom late this weekend and early next week.  The models are in
fair agreement, and only small changes were made to the previous NHC
track forecast.

Helene is expected to be a post-tropical cyclone when it approaches
Ireland and the United Kingdom in two to three days. Interests in
those locations should consult products from their local
meteorological service for information about potential impacts from
Helene.  Local forecasts and warnings for the UK can be found on the
website of the UK Met Office at https://www.metoffice.gov.uk/.
Local forecasts and warnings for Ireland can be found on the website
of Met Eireann at https://www.met.ie/.

FORECAST POSITIONS AND MAX WINDS

INIT  15/0900Z 37.7N  34.8W   60 KT  70 MPH
 12H  15/1800Z 39.7N  32.7W   60 KT  70 MPH
 24H  16/0600Z 41.8N  29.2W   55 KT  65 MPH
 36H  16/1800Z 44.1N  24.3W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  17/0600Z 46.7N  18.1W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  18/0600Z 55.8N   5.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  19/0600Z...DISSIPATED

$$
Forecaster Cangialosi

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