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Tropical Storm POLO (Text)

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TROPICAL STORM POLO DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172014
200 AM PDT SUN SEP 21 2014

Polo has continued to be impacted by strong easterly wind shear of
around 25 kt, which has severely weakened the associated convection.
What little convection that does exist has been displaced into the
western quadrant. A 0413 ASCAT-B overpass indicated several 33-kt
wind vectors in the northeastern and southwestern quadrants. Since
some undersampling is possible, the initial intensity is being
maintained at 35 kt for this advisory, especially since some
convective redevelopment could return during the remainder of the
convective maximum period this morning while the cyclone is over
SSTs near 28C.

Now that Polo's low and upper-level circulations are beginning to
weaken and decouple, the cyclone has made a westward jog and the
initial motion is now 285/06 kt. However, the track forecast and
reasoning basically remain unchanged from the previous advisory.
Polo is expected to continue to weaken and become more vertically
shallow, being steered westward and eventually southwestward by a
strengthening low- to mid-level ridge located to the north of the
cyclone. The NHC forecast track is similar to the previous advisory
track and TVCE multi-model consensus.

Strong easterly vertical wind shear is forecast to continue for the
next 36 hours or so, which should cause Polo to continue to weaken.
The cyclone will likely become a tropical depression later today,
and degenerate into a remnant low on Monday, if not sooner.
Although the remnant circulation will be moving back over warm
water on Days 3 and 4, the surrounding airmass is expected to be
dry and more stable, which should inhibit any persistent convective
development from occurring.

Given that the size of Polo's wind field has decreased and that the
cyclone is also now moving away from Baja California Sur, the
Government of Mexico has discontinued the tropical storm watch for
Baja California Sur.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 21.6N 110.5W   35 KT  40 MPH
 12H  21/1800Z 21.9N 111.7W   30 KT  35 MPH
 24H  22/0600Z 22.1N 113.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  22/1800Z 22.0N 114.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  23/0600Z 21.5N 115.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  24/0600Z 20.3N 116.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  25/0600Z 19.0N 117.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  26/0600Z...DISSIPATED

$$
Forecaster Stewart

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