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Hurricane FERNANDA


Hurricane Fernanda Discussion Number  26
NWS National Hurricane Center Miami FL       EP062017
200 AM PDT Tue Jul 18 2017

Fernanda is gradually weakening.  The eye of the hurricane is no
longer apparent in satellite images, and dry slots are evident in
microwave images over the eastern portion of the circulation.  The
cloud pattern now consists of a fairly circular central dense
overcast with curved bands surrounding the convective mass.  The
Dvorak CI-numbers are 5.0/90 kt from TAFB and SAB, and the ADT
values from UW-CIMSS are similar.  Based on these estimates, the
initial intensity is lowered a little to 90 kt.

Fernanda is still over relatively warm sea-surface temperatures, but
it is headed for cooler waters, and by 24 hours it should be
crossing the 26 deg C isotherm.  These cooler waters combined with
drier air and a significant increase in southwesterly wind shear
that begins in a few days should cause the cyclone to steadily
weaken.  Fernanda is predicted to be a remnant low by the end of the
forecast period when the SHIPS model shows the shear increasing to
near 30 kt and the environmental mid-level relative humidity values
below 40 percent.  The NHC intensity forecast is similar to the
previous one and generally follows the intensity model consensus.

The track forecast philosophy for Fernanda remains unchanged.  The
hurricane continues to move northwestward at 8 kt toward a weakness
in the ridge caused by a mid- to upper-level trough to the northeast
of the Hawaiian Islands.  This general motion is expected to
continue for the next 24 hours or so.  After that time, the trough
is forecast to lift out, allowing the ridge to rebuild to the north
of the weakening system.  This pattern change should cause Fernanda
to turn westward to west-northwestward.  Only small changes were
made to the previous NHC track forecast, and the new one lies near
the middle of the guidance envelope.


INIT  18/0900Z 15.4N 132.8W   90 KT 105 MPH
 12H  18/1800Z 16.1N 133.7W   80 KT  90 MPH
 24H  19/0600Z 16.9N 134.8W   70 KT  80 MPH
 36H  19/1800Z 17.4N 136.1W   60 KT  70 MPH
 48H  20/0600Z 17.8N 137.6W   55 KT  65 MPH
 72H  21/0600Z 18.6N 140.6W   45 KT  50 MPH
 96H  22/0600Z 19.3N 143.7W   35 KT  40 MPH
120H  23/0600Z 19.9N 147.6W   25 KT  30 MPH...POST-TROP/REMNT LOW

Forecaster Cangialosi