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HURRICANE LESTER DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132016
800 AM PDT SAT AUG 27 2016

Lester has been slowly strengthening.  Since the last advisory, the
eye has cleared out, warmed and become better defined.  The cyclone
has also been maintaining a compact and fairly symmetric central
dense overcast but with no prominent banding features.  Satellite
classifications are T4.5/77 kt and T5.0/90 kt from TAFB and SAB,
respectively.  A blend of these is used to raise the initial
intensity estimate to 80 kt.

Lester's heading has become more westerly during the past several
hours, and the initial motion estimate is 275/08.  A strong
subtropical ridge should hold sway to the north of Lester for at
leastthe next 3 days, keeping the cyclone on a nearly due-west
course. The track guidance is tightly clustered during this time,
resulting in a high confidence forecast. After 72 hours, the model
spread increases, with the GFS-based solutions on the northern
side of the guidance envelope and the ECMWF to the south.  The
differences between the models are related to their handling of a
mid-latitude trough approaching the California coast, which could
weaken the ridge to the north of Lester.  The ECMWF maintains a
stronger ridge and thus depicts a more westerly track, while the
GFS-based guidance shows Lester gaining more latitude as a result of
a weaker ridge.  The new NHC track foreast is adjusted slightly
north of the previous one from 72-120 hours and is close to a
consensus of these models.

Global models forecast a nearly uniform easterly flow at all levels
over Lester throughout the forecast period, implying a low-shear
environment for the foreseeable future.  Sea surface temperatures
should gradually decrease along Lester's track but be warm enough to
support additional intensification, except perhaps when it
encounters a pocket of somewhat cooler waters between 130W and 140W
in 2 to 4 days.  The main issue governing Lester's intensity is
likely to be the dryness of the air surrounding it, with both the
GFS and ECMWF models indicating unusually dry air affecting the
cyclone during the period.  The NHC intensity forecast calls for
only modest intensification the next day or two, during a time when
environmental conditions appear most optimal.  After that time, the
extremely dry conditions and more marginal SSTs suggest that a slow
weakening would be the best forecast.  The new intensity forecast is
lower than the previous one throughout the period.  The NHC forecast
is above the multi-model consensus in the short term and generally
near it after 72 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 18.0N 118.4W   80 KT  90 MPH
 12H  28/0000Z 18.0N 119.9W   85 KT 100 MPH
 24H  28/1200Z 18.1N 122.4W   90 KT 105 MPH
 36H  29/0000Z 18.2N 125.1W   90 KT 105 MPH
 48H  29/1200Z 18.4N 128.0W   85 KT 100 MPH
 72H  30/1200Z 18.6N 133.7W   80 KT  90 MPH
 96H  31/1200Z 18.6N 138.7W   75 KT  85 MPH
120H  01/1200Z 18.7N 143.5W   70 KT  80 MPH

$$
Forecaster Kimberlain

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