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Tropical Storm Fernanda Discussion Number   7
NWS National Hurricane Center Miami FL       EP062017
800 AM PDT Thu Jul 13 2017

Recent IR and WV images show that Fernanda has begun to establish
good outflow in all quadrants, indicating that the shear that
previously affected the tropical storm is diminishing. Recent SSMI
and SSMIS passes from 1016 and 1130 UTC, respectively, show that
that convection is wrapping all the way around a mid-level center,
but the low-level center remains displaced a little to the
north-northeast.  Dvorak estimates from TAFB and SAB have increased
to T 3.5 / 55kt, and the initial intensity has been increased to
that value.

Confirming what the satellite data suggests, the analyzed shear has
decreased below 10 kt.  Warm SSTs and sufficient moisture are also
contributing to an environment that is very conducive for continued
intensification.  The SHIPS-RII shows a greater than 50 percent
chance of a 30 kt increase in 24 hours and a 45 kt increase in 48
hours. This is a notable increase in the probabilities which have
doubled in the last 12 h.  Considering the convective structure
of the cyclone has improved over the past few hours, and the lack of
any obvious inhibiting environmental factors, rapid intensification
within the next 24 or 36 hours seems likely.  The intensity forecast
has been substantially increased for the first 48 hours and now
explicitly shows an increase of 30 kt within 24 hours. Fernanda is
forecast to be at or near major hurricane strength by tomorrow
evening, with conditions favoring additional intensification after
that. Near the end of the forecast period, the hurricane is
expected to encounter decreasing sea surface temperatures that could
cause slight weakening.  The intensity forecast is near the top of
the guidance envelope, close to the corrected consensus aids FSSE
and HCCA.

No major changes have been made to the track forecast. The
initial motion estimate remains 265/9 kt.  A deep-layer ridge
extending over a large portion of the eastern north Pacific will
steer Fernanda generally westward for the next 2-3 days.  Most of
the dynamical guidance still shows a slight weakening of the ridge
after about 3 days which would cause Fernanda to turn toward the
northwest.  The NHC forecast is very close to to the track
consensus TVCN and is nearly on top of the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 11.7N 115.0W   55 KT  65 MPH
 12H  14/0000Z 11.5N 116.4W   65 KT  75 MPH
 24H  14/1200Z 11.2N 118.3W   85 KT 100 MPH
 36H  15/0000Z 11.0N 120.3W  100 KT 115 MPH
 48H  15/1200Z 11.2N 122.4W  110 KT 125 MPH
 72H  16/1200Z 12.0N 126.9W  120 KT 140 MPH
 96H  17/1200Z 13.4N 131.0W  115 KT 130 MPH
120H  18/1200Z 15.0N 135.5W  105 KT 120 MPH

$$
Forecaster Zelinsky

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