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TROPICAL STORM KARL DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
1100 PM AST SUN SEP 18 2016

Karl is a poorly organized tropical storm.  Satellite data indicate
that the low-level center is exposed to the southwest of a few
patches of deep convection.  The initial intensity is again held at
35 kt, in agreement with the earlier scatterometer data and a Dvorak
classification from TAFB.  The cyclone continues to struggle in an
environment of southwesterly shear and dry air.  In fact, total
precipitable water imagery shows dry air wrapping around the west
and south sides of the circulation.  The models indicate that the
shear should lower on Monday, and remain relatively light during the
next several days.  Since Karl is expected to track over
progressively warmer waters, between 28-30 deg C, and move into a
more conducive atmospheric environment, strengthening seems likely.
The NHC intensity forecast is largely an update of the previous one,
but it is a touch lower at the 12-h point given the current poor
initial structure of Karl. This forecast is in best agreement with
the SHIPS model.

The system is moving westward at 13 kt, and that general motion
should continue for the next 12-24 hours as Karl remains on the
south side of a subtropical ridge over the central Atlantic.  A
west-northwestward motion is expected to begin by Monday night,
followed by a turn to the northwest by mid-week when the cyclone
moves toward a weakness in the ridge.  Although the models
agree on the overall scenario, there is a fair amount of spread by
the end of the forecast period.  The NHC track forecast is slightly
faster than the model consensus, giving a little more weight to the
GFS and ECMWF models.

FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 18.3N  46.3W   35 KT  40 MPH
 12H  19/1200Z 18.5N  48.3W   35 KT  40 MPH
 24H  20/0000Z 19.1N  50.9W   40 KT  45 MPH
 36H  20/1200Z 19.8N  53.4W   45 KT  50 MPH
 48H  21/0000Z 20.7N  55.9W   50 KT  60 MPH
 72H  22/0000Z 23.1N  60.9W   60 KT  70 MPH
 96H  23/0000Z 26.5N  65.0W   70 KT  80 MPH
120H  24/0000Z 28.8N  66.9W   80 KT  90 MPH

$$
Forecaster Cangialosi

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