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Hurricane Fernanda Discussion Number  23
NWS National Hurricane Center Miami FL       EP062017
800 AM PDT Mon Jul 17 2017

Fernanda's eye has - once again - become clear in the shortwave
infrared imagery with a slightly asymmetric ring of very cold cloud
tops surrounding the 15 nm eye.  A blend of the subjective Dvorak
fixes from SAB/TAFB along with the objective Advanced Dvorak
Technique gives 110 kt intensity, maintaining Fernanda as a Category
3 hurricane.

In the short term, the SSTs beneath Fernanda will gradually cool,
reaching 26C in about 36 hours.  By days 4 and 5, the vertical shear
should go up substantially due to Fernanda moving closer to a
tropical upper-tropospheric trough.  Thus the official intensity
forecast shows steady weakening with the system becoming a remnant
low around day 5.  This forecast is closest to a blend of the LGEM
and D-SHIPS statistical intensity schemes, as well as the HCCA
corrected consensus technique.  (The HWRF and COAMPS dynamical
models appear to hold on to too strong a system at days 3 and
beyond, based upon the environment that Fernanda is expected to
encounter.)

The hurricane is tracking toward the west-northwest at about 9 kt.
Fernanda is expected to turn slightly toward the northwest during
the next couple of days as it moves around the southwestern
periphery of a deep-layer subtropical ridge.  By days 3 to 5, the
system should turn back toward the west as it gets advected along in
the low-level flow as a weakening tropical cyclone.  The NHC
forecast is nearly unchanged from the previous advisory and is based
upon the TVCN multi-model consensus technique.

The initial wind radii were maintained based on the earlier 0542Z
and 0626Z ASCAT scatterometer overpasses.  The forecast wind radii
are based upon the RVCN multi-model consensus technique.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 13.7N 130.9W  110 KT 125 MPH
 12H  18/0000Z 14.4N 132.0W  100 KT 115 MPH
 24H  18/1200Z 15.3N 133.3W   90 KT 105 MPH
 36H  19/0000Z 16.1N 134.4W   80 KT  90 MPH
 48H  19/1200Z 16.8N 135.6W   70 KT  80 MPH
 72H  20/1200Z 17.5N 138.9W   50 KT  60 MPH
 96H  21/1200Z 17.9N 142.3W   35 KT  40 MPH
120H  22/1200Z 18.3N 146.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Landsea

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