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Hurricane Fernanda Discussion Number  22
NWS National Hurricane Center Miami FL       EP062017
200 AM PDT Mon Jul 17 2017

The eye of Fernanda is not as distinct as it was over the
past day or so and appears cloud-filled at times in satellite
images. The cloud tops surrounding the eye, however, remain very
cold and the extent of the area of deep convection has grown since
yesterday. In addition, the convective pattern remains fairly
symmetric due to the light wind shear conditions. The Dvorak
classifications from TAFB and SAB were both 5.5/102 kt, and the ADT
values from CIMSS at the University of Wisconsin are a little
higher. Based on these estimates, the initial wind speed is held at
105 kt. Fernanda is beginning to pull away from the warmest waters,
and it is expected to track over progressively cooler waters during
the next few days. These less favorable oceanic conditions combined
with a drier and more stable air mass and an increase in westerly
wind shear should cause Fernanda to steadily weaken through the
forecast period. The NHC intensity forecast is an update of the
previous one and is in good agreement with the consensus models.

Fernanda continues to move to the west-northwest at 10 kt, steered
by the southwestern periphery of a mid-level ridge. The track
forecast philosophy remains unchanged. A trough to the northeast of
the Hawaiian Islands is expected to erode the western portion of the
ridge and should cause Fernanda to move west-northwestward to
northwestward at a slower pace during the next few days. After that
time, the trough is expected to lift out allowing a ridge to rebuild
to the north of the tropical cyclone. This should cause the system
to turn toward the west by the end of the forecast period. The
track models are tightly clustered, and only small changes were made
to the previous NHC track forecast.

The initial 34-kt wind radii were adjusted based on a 0542 UTC
ASCAT-B overpass.

FORECAST POSITIONS AND MAX WINDS

INIT  17/0900Z 13.4N 130.1W  105 KT 120 MPH
 12H  17/1800Z 14.1N 131.3W  100 KT 115 MPH
 24H  18/0600Z 15.0N 132.7W   95 KT 110 MPH
 36H  18/1800Z 16.0N 133.8W   85 KT 100 MPH
 48H  19/0600Z 16.7N 135.0W   75 KT  85 MPH
 72H  20/0600Z 17.6N 138.0W   60 KT  70 MPH
 96H  21/0600Z 17.9N 141.5W   45 KT  50 MPH
120H  22/0600Z 18.2N 145.2W   35 KT  40 MPH

$$
Forecaster Cangialosi

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