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000
WTPZ42 KNHC 180850
TCDEP2

HURRICANE POLO DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172014
200 AM PDT THU SEP 18 2014

Polo has changed little in organization during the past several
hours.  Satellite imagery indicates a small central convective
feature, with an area of outer banding over the southeastern
semicircle.  Satellite intensity estimates from TAFB and SAB remain
65 kt, and that is the initial intensity.

The initial motion is 300/7.  A mid-tropospheric ridge extending
westward from northwestern mainland Mexico across the Baja
California peninsula should cause the tropical cyclone to move on a
west-northwestward or northwestward heading for the next several
days.  While the overall track forecast philosophy is unchanged, the
latest track guidance has shifted to the north since the previous
advisory due mainly to forecasts of a northwestward motion during
the first 24-48 hours.  The new forecast track lies parallel to but
a little north of the previous track in best agreement with the GFS
and ECMWF models.  However, the new track is south of the center of
the guidance envelope, as well as south of the consensus model TVCE.

Analyses from CIMSS at the University of Wisconsin show that
northeasterly vertical wind shear is increasing over Polo.  The
large-scale models forecast this to continue, with the shear
becoming quite strong after 24 hours.  The intensity guidance
responds to these developments by forecasting Polo to be weaker
than the guidance of 6 hours ago.  The intensity forecast follows
the trend of the previous forecast, with a little strengthening
during the first 24 hours followed by weakening as Polo encounters
the stronger shear and cooler water.  However, the forecast
intensities are lowered from 24-120 hours.  It should be noted that
the new forecast is at the upper-level edge of the intensity
guidance, and an alternative forecast scenario is that Polo does not
strengthen any more before the shear causes it to weaken.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0900Z 16.7N 105.0W   65 KT  75 MPH
 12H  18/1800Z 17.4N 105.8W   70 KT  80 MPH
 24H  19/0600Z 18.2N 106.8W   75 KT  85 MPH
 36H  19/1800Z 18.9N 107.8W   75 KT  85 MPH
 48H  20/0600Z 19.6N 108.8W   70 KT  80 MPH
 72H  21/0600Z 21.0N 111.0W   60 KT  70 MPH
 96H  22/0600Z 22.0N 113.0W   50 KT  60 MPH
120H  23/0600Z 22.5N 115.0W   40 KT  45 MPH

$$
Forecaster Beven



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