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TROPICAL STORM KARINA DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112014
800 PM PDT SUN AUG 17 2014

Karina's cloud pattern has changed little in organization over the
past several hours.  The system remains a sheared tropical cyclone,
with all of the deep convection displaced to the west-southwest of
the low-level center.  The intensity is kept at 40 kt for this
advisory, which is only slightly above the most recent Dvorak
estimates and is consistent with earlier scatterometer data.  The
easterly shear over Karina is due to a combination of an
upper-level anticyclone to the north-northeast and the outflow from
a developing system to the east.  The global models indicate that
the anticyclone will shift eastward and weaken, which could
result in some decrease in shear.  However since Karina will be
traversing marginal sea surface temperatures during the next
several days, only slight strengthening is predicted.  This is the
same as the previous official wind speed forecast and very close to
the latest intensity model consensus.

The storm continues to move west-southwestward with gradually
decreasing forward speed, and the initial motion estimate is 255/10
kt.  A weak mid-level ridge to the north of the storm should
maintain a west-southwestward to westward heading for the next
couple of days.  However, the interaction with the developing
cyclone to the east and another, weaker, disturbance to the west of
Karina should result in a slowing of the forward motion.  Around
the end of the forecast period, a broad fetch of west-southwesterly
flow feeding into the larger cyclone to the northeast should cause
Karina to reverse its heading and move northeastward.  The new
official track forecast is somewhat farther west of the previous one
at days 2-5, but not as far west as the latest track model
consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 17.5N 130.4W   40 KT  45 MPH
 12H  18/1200Z 17.0N 131.7W   40 KT  45 MPH
 24H  19/0000Z 16.5N 133.0W   45 KT  50 MPH
 36H  19/1200Z 16.4N 134.0W   45 KT  50 MPH
 48H  20/0000Z 16.4N 134.8W   50 KT  60 MPH
 72H  21/0000Z 16.5N 136.0W   45 KT  50 MPH
 96H  22/0000Z 16.5N 136.5W   45 KT  50 MPH
120H  23/0000Z 17.5N 135.0W   45 KT  50 MPH

$$
Forecaster Pasch

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