Tropical Storm SIMON

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TROPICAL STORM SIMON DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192014
800 PM PDT SUN OCT 05 2014

The cloud pattern associated with Simon continues to slowly degrade
this evening.  The cloud tops have gradually warmed and recent
microwave data indicate that the low-level center is located to the
southwest of the main convective mass due to moderate southwesterly
shear.  The latest Dvorak Data T-numbers from SAB and TAFB are
3.5, but current intensity numbers remain higher due to Dvorak
weakening constraints.  The initial wind speed has been lowered to
60 kt, closer to the data T-numbers and a little below what was
supported by the earlier NOAA aircraft data.

Increasing southwesterly shear, cooler sea surface temperatures,
and drier air should cause continued weakening during the next
couple of days.  Simon is forecast to become a tropical depression
within 36 hours and should degenerate to a remnant low by Tuesday,
before the center reaches the Baja California peninsula.  The
updated NHC intensity forecast is in good agreement with the
SHIPS/LGEM guidance and is close to the model consensus.

Simon is moving north-northwestward or 345 degrees at about 6 kt.
The cyclone should turn northward, then north-northeastward during
the next 24 hours around the western side of a mid-level high
located near the coast of southwestern Mexico.  Although the track
guidance generally agrees on this scenario, there continues to be
differences in how soon Simon or its remnants will reach the Baja
peninsula.  The GFS takes the cyclone across the Baja peninsula in
about 48 hours, while the ECMWF and UKMET shows this occurring about
a day later.  The NHC track forecast remains in between these
solutions and is close to the multi-model consensus.

Even if Simon or its remnant circulation does not make it across the
rugged terrain of the Baja California peninsula, moisture associated
with this system is expected to spread across the northern Baja
California peninsula, northwestern Mexico, and into the U.S. Desert
Southwest, which could trigger heavy rains in those regions during
the next few days.

FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 23.8N 117.6W   60 KT  70 MPH
 12H  06/1200Z 24.6N 117.6W   45 KT  50 MPH
 24H  07/0000Z 25.7N 117.3W   35 KT  40 MPH
 36H  07/1200Z 26.9N 116.8W   30 KT  35 MPH
 48H  08/0000Z 28.1N 115.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  09/0000Z 30.0N 114.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  10/0000Z...DISSIPATED

$$
Forecaster Brown

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