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Tropical Storm KARINA (Text)

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TROPICAL STORM KARINA DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
800 PM PDT WED AUG 13 2014

Analyses from the University of Wisconsin indicate that about 15 kt
of east-northeasterly shear is affecting the cyclone, but recent
microwave images suggest that Karina is succeeding in maintaining a
tight inner core.  Maximum winds are held at 45 kt on this advisory
based on Dvorak estimates of T3.0/45 kt from TAFB and SAB and
T2.8/41 kt from the ADT.  Even though vertical shear is expected to
only gradually diminish during the next day or two, its easterly to
east-northeasterly direction should still allow strengthening during
that time.  In fact, the SHIPS rapid intensification index is
showing a 1 in 3 chance of a 25-kt increase in winds during the next
24 hours.  Since environmental conditions appear favorable for
continued strengthening, the NHC intensity forecast is near the
upper end of the guidance, closely following the SHIPS and FSU
Superensemble models during the first 3 days.  Only gradual
weakening is indicated on days 4 and 5, mainly due to less favorable
thermodynamic conditions.

Karina continues moving westward, or 275/13 kt, to the south of the
subtropical ridge.  The ridge is expected to continuing exerting
its influence for the next several days, and the track guidance is
tightly clustered on a westward trajectory through 48 hours.  The
spread in the guidance beyond 48 hours appears to be the result of
how Karina interacts with two adjacent disturbances.  The GFS shows
Karina interacting with a strengthening cyclone to its west, with
the resulting flow keeping it farther north and on the northern side
of the guidance envelope.  The ECMWF, on the other hand, shows more
interaction between Karina and a possible cyclone to its east, which
forces Karina southwestward and on the southern side of the guidance
envelope.  Due to the high uncertainty in how the pattern will
evolve by day 5, the official forecast maintains Karina on a general
westward, but decelerating, motion toward the end of the forecast
period.

FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 17.4N 114.1W   45 KT  50 MPH
 12H  14/1200Z 17.5N 116.0W   55 KT  65 MPH
 24H  15/0000Z 17.6N 118.3W   65 KT  75 MPH
 36H  15/1200Z 17.7N 120.6W   70 KT  80 MPH
 48H  16/0000Z 18.0N 122.8W   75 KT  85 MPH
 72H  17/0000Z 18.5N 127.0W   75 KT  85 MPH
 96H  18/0000Z 18.0N 131.0W   70 KT  80 MPH
120H  19/0000Z 17.5N 134.0W   65 KT  75 MPH

$$
Forecaster Berg

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