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Tropical Storm Pilar Discussion Number   5
NWS National Hurricane Center Miami FL       EP182017
400 PM CDT Sun Sep 24 2017

Pilar continues this afternoon to be a problematic system.
Fortunately, a 1426Z GPM 36 GHz image suggested that the system's
center was very close to Cabo Corrientes at that time.  This
allowed for a somewhat better estimate of the initial position and
motion (350 degrees at 7 kt).  Pilar is being advected around a
deep-layer ridge located over central Mexico.  Despite the initial
continued movement at around 7 kt this afternoon, the guidance
insists that Pilar should soon slow down.  The official forecast
track is quite similar to the previous one, with a course along or
just west of the coast of southwestern Mexico.  Fortunately, the
model guidance came into better agreement with the track prediction,
though some of the model's trackers could not explicitly follow the
weak vortex beyond a day or so into the future.

Because of Pilar having some of its circulation over the high
terrain of southwestern Mexico, some weakening has likely occurred.
The initial intensity is reduced to 35 kt, based upon a blend of the
TAFB and SAB Dvorak classifications.  While the SSTs are warm and
the vertical shear is only moderate for the day or so, continued
interaction with land is likely to prevent any re-intensification.
After about 24 hours, the vertical shear should go way up, as Pilar
is affected by strong southerlies associated with a vigorous mid- to
upper-tropospheric trough over the southwestern United States.  The
official intensity forecast is closest to a blend of the LGEM
statistical scheme and the HWRF dynamical model, and is just
slightly below the previous advisory.  An alternative scenario is
for Pilar to dissipate substantially sooner because of the land
interactions.

FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 20.8N 105.8W   35 KT  40 MPH
 12H  25/0600Z 21.8N 106.0W   35 KT  40 MPH
 24H  25/1800Z 22.5N 106.2W   30 KT  35 MPH
 36H  26/0600Z 23.0N 106.5W   25 KT  30 MPH
 48H  26/1800Z 23.5N 107.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  27/1800Z...DISSIPATED

$$
Forecaster Landsea

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