Tropical Storm POLO

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TROPICAL STORM POLO DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172014
200 AM PDT FRI SEP 19 2014

Polo is showing a sheared cloud pattern this morning, with the
low-level center located near the northern or northeastern edge of
the convection.  This is consistent with analyses of 20-25 kt of
easterly vertical wind shear impacting the cyclone.  Satellite
intensity estimates are 55 kt from TAFB and 65 kt from SAB, and a
04Z ASCAT overpass showed 50-55 kt winds.  Based on these, the
initial intensity remains 60 kt.

The initial motion is 315/7.  Global models continue to forecast a
ridge of high pressure to develop westward from northern Mexico
during the next several days.  This should cause the track of Polo
to gradually bend toward the west-northwest. By late in the forecast
period, the weakening cyclone should be drifting westward and
southwestward in the shallow low-level flow.  The track guidance
shows little change from the previous advisory through 96 hours, and
then shows a more southwestward drift than forecast earlier.  The
new official forecast follows this, and it is in best agreement with
the consensus model TVCE.

The large-scale models forecast the shear to continue through the
forecast period as Polo moves over progressively cooler sea surface
temperatures.  This should lead to a gradual weakening as shown by
all of the intensity guidance.  The new intensity forecast is
similar to that of the previous advisory, calling for Polo to
weaken to a tropical depression by 96 hours and to degenerate to a
remnant low by 120 hours.


FORECAST POSITIONS AND MAX WINDS

INIT  19/0900Z 18.9N 107.1W   60 KT  70 MPH
 12H  19/1800Z 19.6N 107.9W   55 KT  65 MPH
 24H  20/0600Z 20.4N 108.9W   55 KT  65 MPH
 36H  20/1800Z 21.0N 110.1W   50 KT  60 MPH
 48H  21/0600Z 21.7N 111.5W   45 KT  50 MPH
 72H  22/0600Z 22.5N 114.0W   35 KT  40 MPH
 96H  23/0600Z 22.5N 116.5W   30 KT  35 MPH
120H  24/0600Z 22.0N 117.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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