538 
WTNT43 KNHC 120835
TCDAT3

Hurricane Helene Discussion Number  20
NWS National Hurricane Center Miami FL       AL082018
500 AM AST Wed Sep 12 2018

Earlier this morning, Helene looked quite ragged in IR imagery. The
eye became poorly defined and cloud tops were steadily warming.
However, beginning around 0500 UTC, a new burst of convection began
wrapping around the previously open western portion of Helene's
inner core. Objective and subjective Dvorak current intensity
estimates range from 77 to 91 kt, and the initial intensity is
therefore set at 80 kt as a blend of all of these data.

Despite the fact that Helene appears to be on the upswing at the
moment, the cyclone is still passing over sub-26 deg C waters and
all of the intensity guidance shows weakening for the next 24 h.
Beyond that time, there is still some spread among the intensity
models, though it has decreased since the last advisory. Helene will
begin interacting with a mid-latitude trough over the north-central
Atlantic, which will result in an increase in shear over the
hurricane. However, Helene will also begin to move over warmer
waters and could get some baroclinic support from the upper-level
trough. Overall the intensity guidance is a little lower than
before, and now the NHC intensity forecast is near the middle of the
intensity guidance envelope.

Once again, no meaningful change has been made to the NHC track
forecast which continues to closely follow the HFIP Corrected
Consensus. Helene is moving north-northwestward, and should
gradually turn northward, and eventually northeastward, as the
cyclone is steered between a mid-level ridge to the east and the
aforementioned mid-latitude trough to northwest. The global models
remain in fairly good agreement on the track of Helene, especially
through 72-96 h, when Helene is forecast to pass near the Azores,
and interests in those islands should closely monitor the progress
of Helene over the next several days.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0900Z 19.2N  35.7W   80 KT  90 MPH
 12H  12/1800Z 20.7N  36.6W   75 KT  85 MPH
 24H  13/0600Z 22.9N  37.2W   65 KT  75 MPH
 36H  13/1800Z 25.5N  37.3W   55 KT  65 MPH
 48H  14/0600Z 28.9N  36.9W   55 KT  65 MPH
 72H  15/0600Z 36.0N  34.3W   50 KT  60 MPH
 96H  16/0600Z 41.0N  28.5W   50 KT  60 MPH
120H  17/0600Z 45.5N  19.0W   50 KT  60 MPH

$$
Forecaster Zelinsky