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Tropical Storm SIMON Forecast Discussion

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WTPZ44 KNHC 021445

800 AM PDT THU OCT 02 2014

First-light visible imagery shows that Simon is gradually becoming
better organized.  The center is under a ragged central dense
overcast, and outer bands are occurring in all quadrants except the
north.  Satellite intensity estimates from TAFB and SAB are 35 kt,
while recent AMSU and SATCON estimates from CIMSS are 35-40 kt.
The initial intensity remains 35 kt, but this could be a little

The initial motion is 295/9, and this general motion is expected to
continue for the next 2 days or so while the storm is steered by
mid-level ridging to its north and northeast.  The model guidance is
in fair agreement during that time period, and the NHC track
forecast remains near the middle of the guidance envelope.  The
guidance continues to show significant divergence after 48 hours.
The GFS, GFDL, and HWRF, show a northeastward turn between 72-120
hours, while the the ECMWF and UKMET show a generally northward
motion.  In addition, the NAVGEM shows a west-northwestward motion
through the entire forecast period.  The track forecast compromises
between these extremes by showing a slow northward motion by 120
hours.  Overall, the new forecast is similar to, but faster than,
the previous forecast.  However, it is notably slower than the
consensus model TVCE from 72-120 hours.

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.  This should allow at least steady strengthening, and
there is an above normal chance for rapid strengthening as shown by
the Rapid Intensification Index of the SHIPS model.  After 48 hours,
the center is expected to move over cooler sea surface temperatures
and into an area of westerly shear.  These conditions should cause a
weakening trend, albeit at a slower rate than seen during Rachel a
few days ago.  The new intensity forecast is increased above that of
the previous forecast and is in best overall agreement with the
SHIPS model.


INIT  02/1500Z 18.4N 107.1W   35 KT  40 MPH
 12H  03/0000Z 18.9N 108.4W   40 KT  45 MPH
 24H  03/1200Z 19.3N 110.3W   50 KT  60 MPH
 36H  04/0000Z 19.8N 112.0W   60 KT  70 MPH
 48H  04/1200Z 20.4N 113.5W   70 KT  80 MPH
 72H  05/1200Z 22.5N 115.5W   70 KT  80 MPH
 96H  06/1200Z 24.0N 115.5W   60 KT  70 MPH
120H  07/1200Z 25.0N 115.5W   45 KT  50 MPH

Forecaster Beven

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Page last modified: Thursday, 02-Oct-2014 14:45:27 UTC