Tropical Storm KARINA

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TROPICAL STORM KARINA DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
800 AM PDT FRI AUG 15 2014

Karina is displaying quite vigorous convection with very cold cloud
tops, but almost exclusively in the southwestern semicircle - a
classic symptom of moderate vertical shear.  The 15-20 kt deep layer
shear continues to cause some weakening as the TAFB and SAB Dvorak
and CIMSS AMSU estimates suggest an intensity of around 55 kt. The
CIMSS ADT, on the other hand, does not recognize the shear pattern
in the deep convection and is likely substantially too high.  The
current intensity is analyzed at 55 kt.

The short-term trend in intensity - primarily driven by the hostile
vertical shear - suggests some further weakening, which is
consistent with all the intensity guidance.  The official intensity
forecast out through two days is thus slightly below that from the
previous advisory.  In about 36 hours, the shear should abate some,
but the SSTs and atmospheric instability should decrease along the
forecast track.  The guidance responds by making almost no change to
the intensity out through three days.  At days four and five, some
of the guidance suggests a re-invigoration of Karina.  However,
because of the rather high uncertainty of Karina's position and
possible interaction with other disturbances, the intensity forecast
shows no change at the long-lead predictions.

The initial motion is now 280/10.  Karina remains on the south side
of a mid-level ridge that extends from the southwestern United
States westward over the Pacific.  This feature should steer the
storm generally westward for the next couple of days with a slight
turn toward the west-southwest by day three.  After that time, the
guidance becomes divergent, partly due to how the models show Karina
interacting with other nearby tropical disturbances.  The ECMWF
model forecasts a low pressure area east of Karina causing the
cyclone to turn farther west-southwestward.  The UKMET and NAVGEM
also show a low to the east. However, they forecast it to have less
influence on Karina, with the UKMET showing a continued westward
track and the NAVGEM showing a turn toward the north.  The new GFS
has changed and now also shows a northward turn at day five.  Given
the uncertainty, the new forecast track shows a west-southwestward
turn at day three followed by a westward shift by day five in best
agreement with the variable consensus model. The new forecast track
is nearly the same as the previous advisory, except slightly slower
to the west at days four and five.

FORECAST POSITIONS AND MAX WINDS

INIT  15/1500Z 17.4N 120.2W   55 KT  65 MPH
 12H  16/0000Z 17.8N 121.9W   50 KT  60 MPH
 24H  16/1200Z 18.1N 124.1W   45 KT  50 MPH
 36H  17/0000Z 18.4N 126.2W   45 KT  50 MPH
 48H  17/1200Z 18.4N 128.2W   45 KT  50 MPH
 72H  18/1200Z 17.7N 131.6W   45 KT  50 MPH
 96H  19/1200Z 17.5N 134.5W   45 KT  50 MPH
120H  20/1200Z 17.5N 135.5W   45 KT  50 MPH

$$
Forecaster Landsea

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