Tropical Storm SIMON

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TROPICAL STORM SIMON DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192014
200 PM PDT THU OCT 02 2014

The center of Simon has either re-formed or has made a large wobble
during the past few hours, as a TRMM overpass at 1827 UTC suggests
the center is well southwest of the position seen in earlier SSM/IS
overpasses.  This requires a southward adjustment of the initial
position.  The new advisory position is still north of the TRMM
position, and an additional adjustment may be required later if no
subsequent northward wobble occurs.  The initial intensity is
increased to 45 kt based on satellite intensity estimates from TAFB
and SAB, along with CIMSS ADT and CIRA AMSU estimates.

The initial motion is a rather uncertain 280/8.  For the next day
or so, mid-level ridging to the north and northeast of the cyclone
should steer Simon generally westward to west-northwestward.  From
24-72 hours, the cyclone should turn more northward as it approaches
the western end of the ridge.  The guidance continues to show
significant divergence after that.  The GFS, GFDL, and HWRF, show a
northeastward turn between 72-120 hours and bring Simon close to
Baja California in 96-120 hours.  On the other hand, the the ECMWF
and UKMET show a generally northwestward motion that keeps the
center well away from land.  The track forecast compromises between
these extremes by showing a slow northward motion by 120 hours.  The
new forecast is shifted to the south and west of the previous
forecast based on current trends, and it is in best overall
agreement with the Florida State Superensemble.

Simon is forecast to remain in a light vertical wind shear
environment and over sea surface temperatures of 28-29C for the
next 48 hours, which should allow at least steady strengthening.
After that, movement over cooler water should cause weakening.  The
new intensity forecast is increased over the previous forecast in
best overall agreement with the SHIPS model, and it lies near the
upper edge of the intensity guidance.  An alternative forecast
scenario is that rapid intensification begins in the next 12-24
hours, with Simon becoming significantly stronger than forecast.
This scenario is supported by above average probabilities in the
Rapid Intensification Index of the SHIPS model, and by the TRMM
data, which suggests Simon is developing a small inner core.


FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 18.3N 108.0W   45 KT  50 MPH
 12H  03/0600Z 18.6N 109.2W   50 KT  60 MPH
 24H  03/1800Z 19.0N 111.0W   60 KT  70 MPH
 36H  04/0600Z 19.7N 112.6W   70 KT  80 MPH
 48H  04/1800Z 20.7N 114.1W   75 KT  85 MPH
 72H  05/1800Z 22.5N 115.5W   70 KT  80 MPH
 96H  06/1800Z 24.0N 116.0W   60 KT  70 MPH
120H  07/1800Z 25.0N 116.0W   45 KT  50 MPH

$$
Forecaster Beven

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