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Tropical Storm KARINA (Text)

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TROPICAL STORM KARINA DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
200 AM PDT SAT AUG 16 2014

Karina continues to be affected by about 15 kt of easterly vertical
wind shear, with the low-level center located just to the northeast
of a burst of convection with cloud tops colder than -80C.
Satellite intensity estimates are 45 kt from TAFB and 35 kt from
SAB.  In addition, a recent ASCAT overpass showed 35-40 kt winds
about 40 n mi north of the center.  Based on these data, the initial
intensity remains 40 kt.

The initial motion is now 285/9, with Karina continuing to be
steered by a subtropical ridge to the north.  This ridge will build
westward during the next couple of days, followed by an
amplification of a ridge well north of the Hawaiian Islands.  These
developments should result in Karina turning westward later today
and then turning a little south of due west during the middle of the
forecast period. The steering current are expected to collapse after
72 hours as a mid/upper-level trough likely develops off the west
coast of North America and other areas of disturbed weather develop
east and west of the cyclone.  During this time, the GFS and
Canadian models forecast a loop back to the east, the ECMWF and
UKMET models forecast a slow westward motion, and the NAVGEM and GFS
ensemble mean forecast a slow northward motion.  The official
forecast track compromises between these forecasts by showing a
westward drift. Overall, the new track is again similar to the old
track and near the multi-model consensus.

The large-scale models forecast the shear to decrease during the
next 48 hours or so.  However, Karina will be moving over gradually
decreasing sea surface temperatures, and the forecast track keeps
the center near the 26C isotherm after 48 hours.  In the short
term, Karina is expected to weaken a little more.  While the
official forecast keeps the system as a tropical storm,  an
alternate scenario is shown by the SHIPS and LGEM models, which
forecast it to weaken to a depression.  After 48 hours, the
guidance suggests Karina could re-intensify if it is not absorbed
by one of the nearby disturbances.  The latter part of the official
forecast reflects this by showing modest strengthening.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 18.1N 122.9W   40 KT  45 MPH
 12H  16/1800Z 18.2N 124.4W   35 KT  40 MPH
 24H  17/0600Z 18.2N 126.4W   35 KT  40 MPH
 36H  17/1800Z 18.0N 128.4W   35 KT  40 MPH
 48H  18/0600Z 17.6N 130.1W   35 KT  40 MPH
 72H  19/0600Z 16.5N 132.5W   40 KT  45 MPH
 96H  20/0600Z 16.5N 133.5W   40 KT  45 MPH
120H  21/0600Z 16.5N 134.0W   45 KT  50 MPH

$$
Forecaster Beven

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