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Tropical Storm VANCE (Text)

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TROPICAL STORM VANCE DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP212014
200 AM PDT SAT NOV 01 2014

Vance's structure has been improving since the last advisory.  A
cluster of deep convection has developed near the center, and more
defined curved bands are forming on the outer edges of the
circulation.  The maximum winds are held at 35 kt based on a
consensus of subjective and objective satellite intensity estimates.

The first three days of the forecast are fairly straightforward.
Vance is expected to turn west-northwestward later today,
accelerate northwestward toward a deepening mid-level trough west of
110W by day 2, and curve toward the north on day 3.  The track
guidance remains tightly clustered but has shifted westward after
36 hours.  Therefore, the updated NHC track forecast is a little
left of the previous one from 36 to 72 hours.  While Vance turns
northward, light vertical shear, warm sea surface temperatures, and
a moistening mid-level troposphere should allow the storm to reach
hurricane strength in 2-3 days.  This part of the forecast closely
follows the SHIPS, HWRF, and Florida State Superensemble guidance.

The forecast is a little more complex after day 3.  Once Vance
begins to recurve, it will encounter southwesterly shear that
increases from 20-25 kt on day 3 to well over 40 kt on days 4 and
5.  This environment is likely to cause the cyclone to decouple,
with the mid-level circulation being sheared off toward Mexico and
the low-level circulation being left behind south of the Baja
California peninsula.  While the operational GFS brings Vance to
the coast of Mexico in 96 hours, the parallel run of GFS and the
ECMWF model have much slower and weaker solutions and do not bring
the surface center to the Mexican coast.  As additional support for
this scenario, most of the GFS and European ensemble members show
Vance lingering or even dissipating offshore.  At this time, the
operational GFS is considered an outlier solution, and the NHC
track forecast is closer to a blend of the European and parallel
GFS models.  Due to the shear, Vance is expected to weaken rapidly
after day 3, possibly becoming a remnant low near or offshore the
coast of Mexico by day 5.

FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z  9.4N 102.7W   35 KT  40 MPH
 12H  01/1800Z  9.7N 104.1W   40 KT  45 MPH
 24H  02/0600Z 10.5N 106.3W   50 KT  60 MPH
 36H  02/1800Z 11.6N 108.6W   55 KT  65 MPH
 48H  03/0600Z 13.2N 110.4W   65 KT  75 MPH
 72H  04/0600Z 17.1N 110.8W   65 KT  75 MPH
 96H  05/0600Z 20.5N 109.0W   35 KT  40 MPH
120H  06/0600Z 23.5N 106.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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