[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 161451
TCDAT2

TROPICAL STORM KARL DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
1100 AM AST FRI SEP 16 2016

Karl remains a sheared tropical cyclone this morning with all
of its deep convection in the northeastern quadrant due to shear
related to its interaction with a mid- to upper-level trough.  The
initial wind speed is kept at 40 kt for this advisory, a compromise
between lower Dvorak estimates and higher, but noisy, scatterometer
values.   Vertical shear is expected to decrease in about 36 hours,
and, despite a somewhat dry environment, warming sea surface
temperatures should allow for at least gradual strengthening.  The
intensity models continue to trend higher at the end of the
forecast period, and the official forecast follows this trend.  This
forecast is remains close to the SHIPS and LGEM models.

The center of Karl has become a little distorted due to the shear
and convection, but it still seems to be moving about 280/11.
Karl is forecast to turn more to the west and south-of-west this
weekend as the subtropical ridge strengthens to the north of the
cyclone. However, the current interaction of Karl with the mid- to
upper-level trough has not been well forecast, and Karl probably
will not get as far to the south as expected yesterday. In a few
days, the storm should move to the west-northwest and eventually
more to northwest around day 5 as it reaches the edge of the ridge.
The new forecast is close to a blend of the ECMWF and GFS, plus
their respective ensemble means, ending up a little north of the
previous NHC prediction at long range.


FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 18.4N  34.3W   40 KT  45 MPH
 12H  17/0000Z 18.5N  36.2W   40 KT  45 MPH
 24H  17/1200Z 18.4N  38.8W   40 KT  45 MPH
 36H  18/0000Z 17.9N  41.5W   40 KT  45 MPH
 48H  18/1200Z 17.7N  44.0W   45 KT  50 MPH
 72H  19/1200Z 18.3N  49.0W   50 KT  60 MPH
 96H  20/1200Z 20.0N  54.0W   60 KT  70 MPH
120H  21/1200Z 22.5N  58.5W   70 KT  80 MPH

$$
Forecaster Blake
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