Tropical Storm SIMON

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TROPICAL STORM SIMON DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192014
800 AM PDT FRI OCT 03 2014

First-light visible imagery and a 1205 UTC SSMI/S overpass indicate
that Simon has become a little better organized.  The storm has a
central dense overcast with outer bands present in all quadrants,
and the microwave data shows a mid-level eyewall forming near or
over the low-level center.  However, the cloud pattern continues
to show some signs of easterly shear.  Satellite intensity
estimates are 55 kt from TAFB and SAB, and recent CIMSS ADT, AMSU,
and SATCON estimates are 50-55 kt.  The initial intensity is thus
increased to 50 kt.

The initial motion is now 285/8.  Simon should move generally
west-northwestward for the next 36 hours or so as it is steered by
the subtropical ridge to the north and northeast.  After that time,
the track guidance becomes very divergent.  The GFS, GFS ensemble
mean, and UKMET forecast Simon to recurve through a break in the
ridge near 115W and move inland over Baja California and
northwestern Mexico. The ECMWF and the NAVGEM show Simon moving much
farther west, with a northward turn delayed until the cyclone is
west of 120W. Given the magnitude of the disagreement, the official
forecast will follow the trend of the previous forecast in showing
a slow northward to northeastward motion from 72-120 hours.  The new
forecast track is and update of the previous track and similar to,
but slower than, the Florida State Superensemble.

Simon will be moving over warmer water with SSTs near 28-29C during
the next 24-36 hours while the deep-layer vertical shear is
expected to be light.  This should allow continued strengthening
until the cyclone encounters cooler waters in 36-48 hours.  The new
intensity forecast is similar to the previous forecast and is in
best agreement with the SHIPS model.  There are two major sources
of uncertainty in the intensity forecast.  The first is that rapid
intensification is still a possibility during the next 24 hours or
so, although the probabilities shown in the SHIPS Rapid
Intensification Index are slowly decreasing.  Second, how much cool
water Simon will encounter is dependent on the track. The GFS track
would keep the storm over relatively warm water, while the ECMWF/
NAVGEM track would take it over much cooler water.


FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 18.6N 109.8W   50 KT  60 MPH
 12H  04/0000Z 19.1N 111.4W   55 KT  65 MPH
 24H  04/1200Z 19.6N 113.3W   65 KT  75 MPH
 36H  05/0000Z 20.5N 115.0W   75 KT  85 MPH
 48H  05/1200Z 21.5N 116.1W   75 KT  85 MPH
 72H  06/1200Z 23.0N 116.5W   60 KT  70 MPH
 96H  07/1200Z 24.5N 116.0W   50 KT  60 MPH
120H  08/1200Z 25.5N 115.0W   35 KT  40 MPH

$$
Forecaster Beven

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