Tropical Storm KARINA

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TROPICAL STORM KARINA DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
200 AM PDT TUE AUG 19 2014

Karina continues to be a difficult puzzle to solve.  The
strengthening trend observed on Monday has ceased, and the cyclone
appears to have weakened a bit during the past few hours.  Water
vapor imagery suggests that the outflow from Tropical Storm Lowell
may be helping to produce southeasterly shear over Karina, and the
low-level center is now exposed to the east of a small area of deep
convection.  The initial intensity is lowered to 50 kt based on a
blend of CI numbers from TAFB and SAB, although this could be a
generous estimate.

Karina's sudden weakening has resulted in a significant change to
the intensity forecast.  The cyclone is expected to remain over
warm water for much of the forecast period, but the SHIPS
diagnostics indicate that easterly shear is likely to remain steady
or increase through the next 5 days.  In addition, Karina will
likely start to ingest drier, more stable air in a couple of days.
The intensity models no longer show strengthening, and in fact, the
Florida State Superensemble and HWRF models weaken Karina to a
tropical depression in about 72 hours.  The official forecast holds
Karina steady at 50 kt for 36 hours while the thermodynamics remain
favorable, followed by steady weakening through the end of the
forecast period.  This solution is very close to the SHIPS and LGEM
models, as well as the intensity consensus, but weakening could
definitely occur sooner than indicated.

Recent microwave fixes indicate that the initial motion is 255/6 kt.
Karina is forecast to move westward and slow down during the next
36-48 hours when it begins to feel the tug of larger Tropical Storm
Lowell to its east.  After 48 hours, Karina should begin moving
east-northeastward and pick up speed within the southern part of
Lowell's circulation.  The official forecast is essentially
unchanged during the first 48 hours.  However, the track guidance
has sped up after 48 hours, and the updated NHC forecast is faster
on days 3-5 to be closer in line with the multi-model consensus
TVCE.

FORECAST POSITIONS AND MAX WINDS

INIT  19/0900Z 15.7N 134.0W   50 KT  60 MPH
 12H  19/1800Z 15.7N 134.7W   50 KT  60 MPH
 24H  20/0600Z 15.7N 135.6W   50 KT  60 MPH
 36H  20/1800Z 15.7N 136.2W   50 KT  60 MPH
 48H  21/0600Z 15.6N 136.3W   45 KT  50 MPH
 72H  22/0600Z 16.0N 135.0W   40 KT  45 MPH
 96H  23/0600Z 17.0N 133.0W   35 KT  40 MPH
120H  24/0600Z 19.0N 130.5W   35 KT  40 MPH

$$
Forecaster Berg

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