Tropical Storm POLO
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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