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Tropical Storm Fernanda Discussion Number   3
NWS National Hurricane Center Miami FL       EP062017
900 AM MDT Wed Jul 12 2017

Convection associated with Tropical Depression Six-E has become
better organized during the past several hours.  While the cyclone
is still being affected by northeasterly vertical wind shear, an
area of convection has formed over the low-level center and outer
convective bands are present in the southwestern semicircle.  An
average of various satellite intensity estimates is 35 kt, and based
on this the depression is upgraded to Tropical Storm Fernanda.

The initial motion is 270/9.  Deep-layer ridging north of the
cyclone is steering it generally westward, and the ridge is expected
to strengthen and build westward during the next 4-5 days.  Based
on this evolution, Fernanda should move generally westward or south
of westward through at least 72 hours, with a north of west motion
expected thereafter.  There has been little change in the guidance
since the previous advisory, and the new forecast track is similar
to, but slightly south of, the previous forecast.

The large-scale models suggest that the current shear should
subside over the next 24 h or so and then remain light through the
remainder of the forecast period.  That, combined with 28-29C sea
surface temperatures along the forecast track, should allow the
system to intensify.  As seen in the previous advisory, the new
intensity forecast calls for gradual strengthening during the first
24-36 h, followed by a faster rate of development from 36-72 h.
The new forecast is similar to the previous forecast and is in best
agreement with the intensity consensus.  It should be noted that
while the environment is not currently conducive for rapid
intensification, it may become more favorable once the shear
decreases.


FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 12.0N 111.5W   35 KT  40 MPH
 12H  13/0000Z 12.0N 112.9W   35 KT  40 MPH
 24H  13/1200Z 12.0N 114.8W   45 KT  50 MPH
 36H  14/0000Z 11.9N 116.6W   55 KT  65 MPH
 48H  14/1200Z 11.7N 118.7W   65 KT  75 MPH
 72H  15/1200Z 11.5N 123.5W   85 KT 100 MPH
 96H  16/1200Z 12.0N 128.0W   90 KT 105 MPH
120H  17/1200Z 13.0N 133.0W   90 KT 105 MPH

$$
Forecaster Beven

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