000
WTNT42 KNHC 232049
TCDAT2

TROPICAL STORM KARL DISCUSSION NUMBER  38
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL122016
ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM AST FRI SEP 23 2016

Satellite imagery contintues to show a well-developed outflow
pattern around Karl with the center noted on the southeastern edge
of the colder cloud tops.  Aircraft reconnaissance data has
indicated a gradual drop in pressure to 988 mb, based on a
dropsonde report of 989 mb with 12 kt of wind at the surface.  A
peak 850-mb flight-level wind of 62 kt was measured, which equates
to an surface intensity of 50 kt.  Reliable SFMR data also showed
maximum surface winds around 50 kt, and that will remain the
initial intensity.  Latest aircraft fixes had also indicated that
Karl was beginning to turn more northward as it moves around the
western edge of the mid-Atlantic subtropical ridge.

Karl is expected to remain over sea surface temperatures of between
29-30C for the next 24 hours or so while at the same time, some
brief relaxation in the vertical shear is forecast.  These
conditions should favor some continued slow strenghthening, which is
generally supported by a majority of models.  The models also
suggest that Karl could reach hurricane strength by 24 hours as the
system moves to the east of Bermuda.  Continued strengthening of
Karl is likely through 36 hours, then it is expected to gradually
transition to extratropical status by 48 hours as it becomes
absorbed by a rapidly approaching cold front.

The latest official forecast has shifted Karl slightly west of the
previous track during the next 12 hours, but otherwise, there are
no significant changes from the previous advisory.  Karl should make
a sharp turn and acceleration to the northeast beyond 12 hours as it
encounters increasing westerly flow in advance of an amplifying
upper trough and associated cold front across the northwest
Atlantic.  Karl should then become absorbed by another extratropical
low over the north Atlantic in 72 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 29.9N  65.1W   50 KT  60 MPH
 12H  24/0600Z 31.3N  64.3W   55 KT  65 MPH
 24H  24/1800Z 33.7N  60.8W   65 KT  75 MPH
 36H  25/0600Z 37.1N  54.0W   70 KT  80 MPH
 48H  25/1800Z 42.0N  44.6W   65 KT  75 MPH...POST-TROP/EXTRATROP
 72H  26/1800Z...DISSIPATED

$$
Forecaster Sullivan/Berg