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HURRICANE SIMON DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192014
200 AM PDT SUN OCT 05 2014

Simon peaked around 0000 UTC based on various satellite intensity
estimates and microwave satellite imagery indicating that an eyewall
replacement was well underway at that time. Since then, more recent
conventional and microwave satellite imagery indicates that the
inner-core convection has eroded significantly, especially in the
southwestern semicircle, and that the eye is rapidly becoming less
distinct. The initial intensity of 100 kt, which could be generous,
is based on a blend of subjective and objective satellite intensity
estimates from TAFB, SAB, and UW-CIMSS.

The initial motion estimate is 320/09 kt. There is no significant
change to the previous forecast track or reasoning. A steadily
weakening Simon is forecast to move around the western periphery of
a deep-layer ridge that extends from central Mexico westward to
southern Baja California Sur for the next 48 hours, and then recurve
to the northeast as the cyclone comes under the influence of
mid-level southwesterly flow ahead of an approaching weak shortwave
trough. As the cyclone weakens and becomes more vertically shallow,
the system is expected to slow down until it reaches the latitude
of recurvature along 24N-25N, after which a gradual increase in
forward speed is expected. The official forecast track is just an
update of the previous advisory track and is close to the consensus
model TVCN.

Simon is now located over sub-26C sea-surface temperatures and is
heading for cooler water. The cyclone is expected to remain in
unfavorable oceanic and thermodynamic conditions for at least the
next 72 hours, during which time southwesterly vertical wind shear
is forecast to increase to more than 25 kt by 48 hours. These
hostile conditions are expected to result in rapid weakening of
Simon, with the cyclone becoming a remnant low pressure system by 96
hours, if not sooner. The new intensity forecast is a little lower
than the previous advisory, and essentially follows the intensity
consensus model IVCN.

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

FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 22.1N 116.7W  100 KT 115 MPH
 12H  05/1800Z 23.0N 117.3W   85 KT 100 MPH
 24H  06/0600Z 24.0N 117.6W   70 KT  80 MPH
 36H  06/1800Z 24.9N 117.5W   55 KT  65 MPH
 48H  07/0600Z 25.6N 117.1W   40 KT  45 MPH
 72H  08/0600Z 27.6N 115.6W   30 KT  35 MPH
 96H  09/0600Z 28.9N 114.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  10/0600Z 30.6N 112.8W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart

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