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Tropical Storm LESTER Forecast Discussion


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000
WTPZ43 KNHC 260851
TCDEP3

TROPICAL STORM LESTER DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132016
300 AM MDT FRI AUG 26 2016

While Lester continues to produce a large area of cold cloud tops,
recent microwave imagery suggests that the storm is being affected
by vertical wind shear and dry air entrainment that is displacing
the convection mostly to the east and northeast of the center.  A
recent ASCAT-B overpass indicated 45-50 kt winds about 40 n mi
northeast of the center, and based on this the initial intensity
remains 50 kt.

The microwave data show that Lester has moved westward for the
past several hours, with the initial motion now 280/6.  The cyclone
should turn west-northwestward later today as it moves toward a
weakness in the subtropical ridge.  After 12-24 hours, Lester
should resume a westward track with an increase in forward speed as
the ridge strengthens and builds westward.  The track model
guidance is in excellent agreement with this scenario, and the new
forecast track is near the center of the guidance envelope.  The
new forecast is a little to the south of the previous forecast
based on the current position and motion.

The dynamical models forecast the shear to decrease over the next
24 hours and remain low for the rest of the forecast period, which
should allow Lester to again intensify.  The forecast track keeps
the cyclone over relatively warm water for about 72 hours, so the
intensity forecast calls for gradual strengthening during that
time.  Subsequently, the waters cool a little along the forecast
track, and the intensity forecast thus shows some weakening.  The
new intensity forecast is similar to the previous forecast, except
slightly weaker during the first 24 hours due to the shear.


FORECAST POSITIONS AND MAX WINDS

INIT  26/0900Z 16.9N 114.5W   50 KT  60 MPH
 12H  26/1800Z 17.1N 115.5W   55 KT  65 MPH
 24H  27/0600Z 17.3N 116.9W   60 KT  70 MPH
 36H  27/1800Z 17.4N 118.7W   70 KT  80 MPH
 48H  28/0600Z 17.4N 120.8W   75 KT  85 MPH
 72H  29/0600Z 17.5N 126.0W   80 KT  90 MPH
 96H  30/0600Z 17.5N 131.5W   80 KT  90 MPH
120H  31/0600Z 17.5N 136.0W   75 KT  85 MPH

$$
Forecaster Beven