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TROPICAL STORM ESTELLE DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062016
900 AM MDT MON JUL 18 2016

Although the cloud tops are not as cold as they were yesterday, the
area of convection is a little more symmetric around the center
indicating that the northwesterly shear is relaxing.  A couple of
recent microwave images also show less tilt between the low- and
mid-level centers, however the inner core is still not well
organized. The initial wind speed is maintained at 60 kt, which is
a little above the latest Dvorak estimates.  An automated weather
station on Clarion Island, about 35 n mi north of the center,
recently reported a sustained wind of 51 kt with a gust to 71 kt.

The vertical wind shear over Estelle is forecast to become very
low later today, and remain light during the next few days.  Since
the tropical storm is forecast to remain over warm water for
another 36 hours or so, modest strengthening is still anticipated
and the NHC forecast and most of the guidance still calls for
Estelle to become a hurricane within the next 24 hours.  In
36 to 48 h, the cyclone will be moving over decreasing SSTs
which should commence the weakening process.  A faster rate of
weakening should begin by 72 hours, when Estelle moves over SSTs
below 24C and into a more stable airmass.

The initial motion estimate is 295/9 kt. Estelle should move
west-northwestward to the south of the subtropical ridge during the
next 3 to 4 days.  After that time, a weakness in the ridge caused
by a mid- to upper-low to the northeast of the Hawaiian Island
should cause the cyclone to turn northwestward by day 5.  The track
guidance is in good agreement, but most of the typically better
performing models are along the northern side of the guidance
envelope.  As a result, the NHC track forecast is a little north of
the multi-model consensus and is near a blend of the GFS, ECMWF, and
UKMET models.


FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 17.7N 114.9W   60 KT  70 MPH
 12H  19/0000Z 18.2N 116.3W   65 KT  75 MPH
 24H  19/1200Z 18.7N 118.2W   70 KT  80 MPH
 36H  20/0000Z 19.1N 120.2W   75 KT  85 MPH
 48H  20/1200Z 19.5N 122.5W   70 KT  80 MPH
 72H  21/1200Z 20.9N 127.5W   50 KT  60 MPH
 96H  22/1200Z 23.5N 132.5W   35 KT  40 MPH
120H  23/1200Z 27.5N 136.5W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

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