000
WTPZ41 KNHC 152034
TCDEP1

Hurricane Fernanda Discussion Number  16
NWS National Hurricane Center Miami FL       EP062017
200 PM PDT Sat Jul 15 2017

A recent AMSU pass indicates that Fernanda continues to have a
double eyewall structure, with the inner eye about 20 n mi in
diameter and the outer eye about 60 n mi across.  The appearance of
Fernanda in geostationary satellite images remains impressive with a
small distinct eye surrounding by a ring of cold cloud tops.
The cold cloud tops, however, are not quite as expansive as they
were earlier.  Accordingly, the latest satellite intensity estimates
have decreased slightly and range from 105 to 125 kt, and based on
these data, the initial wind speed is lowered a little to 115 kt.
It should be noted that it is common for hurricanes that undergo
eyewall replacement cycles (ERC) to weaken during the beginning of
the process.

Assuming the ERC completes, Fernanda has an opportunity to
restrengthen during the next day or so while it remains in
favorable atmospheric conditions and over warm water.  After that
time, steady, or even rapid, weakening is expected as the hurricane
moves over cooler water and into a drier and more stable air mass.
An increase in southwesterly shear should aid in the weakening
process toward the end of the forecast period. The NHC intensity
forecast is at the high end, or slightly above, the guidance in the
short term, but then falls in line with the intensity model
consensus after that.  This forecast is a tad lower than the
previous one.

A mid-level ridge located over the western United States is steering
Fernanda westward, or 280 degrees, at 11 kt. A west-northwestward
motion is expected to begin tonight and continue for the next
several days while the hurricane moves toward a weakness at the
western periphery of the ridge. The track models remain in good
agreement, and the NHC track forecast lies near the middle of the
guidance envelope, in best agreement with the various consensus
models.

FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 11.4N 124.0W  115 KT 130 MPH
 12H  16/0600Z 11.9N 125.8W  125 KT 145 MPH
 24H  16/1800Z 12.7N 128.2W  125 KT 145 MPH
 36H  17/0600Z 13.4N 130.4W  120 KT 140 MPH
 48H  17/1800Z 14.1N 132.3W  105 KT 120 MPH
 72H  18/1800Z 15.7N 135.5W   80 KT  90 MPH
 96H  19/1800Z 16.8N 138.3W   60 KT  70 MPH
120H  20/1800Z 17.3N 141.6W   50 KT  60 MPH

$$
Forecaster Cangialosi