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Hurricane FERNANDA


Hurricane Fernanda Discussion Number  15
NWS National Hurricane Center Miami FL       EP062017
800 AM PDT Sat Jul 15 2017

An AMSR2 overpass around 0925 UTC shows that Fernanda is
undergoing an eyewall replacement cycle (ERC).  Based on the 36 GHz
composite image from that pass, the inner core at that
time consisted of a very small, 10 nm-wide, inner eyewall surrounded
by a 30 nm-wide outer eyewall.  An earlier WindSat pass at 0149 UTC
suggests that the ERC began about 12 hours ago.  This is
consistent with a warming trend observed in the cloud top
temperatures that began a little before 0000 UTC yesterday.  The
initial intensity has been decreased to 120 kt, based on a blend of
Dvorak estimates from TAFB, SAB, and the UW-CIMSS ADT.

Assuming a typical ERC weakening period of about 15 hours, the
hurricane could reintensify later today, once the outer eyewall
contracts.  The environment should support intensification for
another 24 hours or so, and the forecast reflects this.  Additional
ERCs could lead to fluctuations in intensity that aren't explicitly
shown in the forecast.  After about 36 hours, the hurricane will
become embedded in a drier and more stable environment, so steady
weakening is anticipated.  The new forecast is similar to the
previous one, despite the weaker initial intensity, and is above
most of the intensity guidance for the first 36 hours.  It is close
to the intensity consensus by the end of the forecast period.

Fernanda is beginning to make a long-anticipated turn toward the
west-northwest and the initial motion is now just north of due
west, or 275/11.  Almost no change has been made to the track
forecast, which remains on top of the various multi-model consensus
aids.  A west-northwest to northwest motion is expected for the
next several days while the cyclone moves along the southwestern
periphery of a deep-layer ridge.  The track guidance is still
tightly clustered, and confidence remains high in the track


INIT  15/1500Z 11.0N 123.0W  120 KT 140 MPH
 12H  16/0000Z 11.5N 124.8W  130 KT 150 MPH
 24H  16/1200Z 12.3N 127.3W  130 KT 150 MPH
 36H  17/0000Z 13.0N 129.7W  125 KT 145 MPH
 48H  17/1200Z 13.8N 131.9W  120 KT 140 MPH
 72H  18/1200Z 15.3N 135.3W   95 KT 110 MPH
 96H  19/1200Z 16.5N 138.0W   70 KT  80 MPH
120H  20/1200Z 17.0N 141.0W   50 KT  60 MPH

Forecaster Zelinsky