Tropical Cyclone Discussion
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WTPZ41 KNHC 310836

200 AM PDT FRI OCT 31 2014

Several overnight microwave images and ASCAT data indicate that the
center of Vance is located farther south and east than previously
estimated.  The center is near the southern edge of the large mass
of deep convection due to moderate south-southwesterly shear.  The
ASCAT data and Dvorak satellite intensity estimates support
maintaining an initial wind speed of 40 kt.  The shear and some dry
low- to mid-level air are expected to continue to affect the
tropical cyclone during the next 12 to 24 hours, and only gradual
strengthening is expected during that time. Environmental conditions
are forecast to become more conducive for strengthening over the
weekend, and most of the intensity guidance shows Vance becoming a
hurricane in 2 to 3 days.  By day 4, increasing southwesterly
upper-level flow ahead of a large mid-latitude trough is expected to
cause a significant increase in shear.  This should cause weakening
late in the period.  The NHC intensity forecast is similar to the
previous advisory and is near the model consensus.

Due to the center relocation, the initial motion is a highly
uncertain 245/3 kt.  Vance is expected to move west-southwestward
today around the southeastern portion of a mid-level ridge near the
southern Baja California peninsula.  The ridge is forecast to shift
eastward during the next several days while the aforementioned
trough approaches the west coast of California.  This should cause
Vance to turn west-northwestward, then northwestward over the
weekend.  After 72 hours, Vance is forecast to turn northward, then
northeastward ahead of the trough.  The track guidance remains in
agreement on this scenario but there remains some spread in the
timing of the northward turn, and the forward speed of Vance later
in the period. The updated NHC forecast is similar to the previous
track through 72 hours, but is a little faster than the previous
advisory at days 4 and 5.


INIT  31/0900Z 10.5N 101.0W   40 KT  45 MPH
 12H  31/1800Z 10.1N 101.6W   45 KT  50 MPH
 24H  01/0600Z  9.8N 103.1W   50 KT  60 MPH
 36H  01/1800Z 10.0N 104.8W   55 KT  65 MPH
 48H  02/0600Z 10.9N 106.8W   60 KT  70 MPH
 72H  03/0600Z 14.0N 110.0W   70 KT  80 MPH
 96H  04/0600Z 18.5N 109.0W   60 KT  70 MPH
120H  05/0600Z 22.5N 106.0W   40 KT  45 MPH

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