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TROPICAL STORM ESTELLE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062016
300 AM MDT SAT JUL 16 2016

Satellite imagery this morning indicates a slight increase in
organization since the previous advisory, with a complex of
convective bands present over the western semicircle and the
southeastern quadrant of the cyclone.  However, there is no
concentration of convection near the center at this time.
Subjective satellite intensity estimates are 45 kt from TAFB and 35
kt from SAB.  In addition, there are recent AMSU intensity
estimates near 40 kt.  Thus, the intensity is raised to 40 kt.

The initial motion is 295/9.  Estelle is on the south side of the
subtropical ridge, which should steer the cyclone generally
west-northwestward for 72 hours or so.  Beyond that time, the
dynamical models diverge somewhat on the evolution of the ridge.
The GFS shows a weaker ridge due to a developing trough over the
northeastern Pacific, with Estelle continuing west-northwestward.
The ECMWF shows a stronger ridge with Estelle turning more
westward.  Overall, the center of the guidance envelope has shifted
a little to the north through the first 72 hours and a little to
the south from 72-120 hours.  The new forecast track is just north
of the previous track, lying south of the center of the envelope
through 72 hours and lying north of it from 72-120 hours.

The dynamical models suggest that Estelle will be in a light wind
shear environment for the next several days, so the intensity
forecast is dependent on the sea surface temperatures.  If Estelle
follows the forecast track, it should move north of the cold wake
left by previous tropical cyclones and remain over 27C sea surface
temperatures through about 72 hours.  Based on this, the intensity
forecast calls for a peak of 85 kt at 72 hours, which is higher
than the SHIPS model and lower than the Florida State
Superensemble.  After that time, the sea surface temperatures
decrease along the forecast track, and Estelle should weaken as a
result.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 15.6N 109.0W   40 KT  45 MPH
 12H  16/1800Z 16.0N 110.1W   45 KT  50 MPH
 24H  17/0600Z 16.3N 111.6W   55 KT  65 MPH
 36H  17/1800Z 16.7N 113.2W   65 KT  75 MPH
 48H  18/0600Z 17.1N 114.7W   75 KT  85 MPH
 72H  19/0600Z 18.0N 118.0W   85 KT 100 MPH
 96H  20/0600Z 18.5N 121.5W   80 KT  90 MPH
120H  21/0600Z 19.5N 126.0W   65 KT  75 MPH

$$
Forecaster Beven

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