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HURRICANE VANCE DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212014
100 AM PST TUE NOV 04 2014

Satellite images indicate that the anticipated weakening of Vance
has begun.  The cloud pattern has become decidedly less circular and
more ragged over the past several hours, and the overall coverage of
deep convection is gradually decreasing.  The current intensity is
set at 90 kt in agreement with a Dvorak estimate from TAFB, although
this may be generous given the most recent satellite presentation.
More than 30 kt of south-southwesterly vertical shear is currently
affecting the hurricane, and this shear is forecast to increase to
about 45-55 kt in 24 to 36 hours.   Vertical cross sections from the
latest GFS model forecast show that most of the tropical cyclone's
circulation above 500 mb is removed within the next 24 hours,
presumably due to the intense shear.  These very hostile dynamical
conditions should result in a rather rapid rate of weakening before
the tropical cyclone nears the Mexican coast.  The official
intensity forecast closely follows the latest SHIPS prediction.
Although Vance could weaken to a depression by the time it reaches
the coast, given the uncertainties in intensity prediction, it is
prudent to have a tropical storm watch at this time.

It is estimated that the low-level center is near the southwestern
edge of the main convective mass, and the initial motion estimate
of 025/11 kt is not much different from the previous package.
Vance is expected to continue moving north-northeastward to the
south and southeast of a mid-level trough over the next day or two.
The official track forecast lies between the latest GFS and ECMWF
predictions, and lies a little to the east of the multi-model
consensus.

Moisture from Vance and its remnants should spread northeastward
across Mexico and into the south-central United States during the
next several days.  This is likely to produce heavy rains over
portions of these areas through Thursday or Friday.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 18.4N 110.0W   90 KT 105 MPH
 12H  04/1800Z 19.8N 109.3W   70 KT  80 MPH
 24H  05/0600Z 22.0N 108.4W   50 KT  60 MPH
 36H  05/1800Z 24.1N 107.6W   30 KT  35 MPH
 48H  06/0600Z 26.0N 107.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  07/0600Z...DISSIPATED

$$
Forecaster Pasch

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