[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 222035
TCDAT3

TROPICAL STORM LISA DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016
500 PM AST THU SEP 22 2016

Strong vertical shear from an upper-level low near 24N 40W continues
to plague Lisa, with the low-level center located to the southwest
of the deep convection as seen in a 1749Z SSMIS overpass.  The
initial intensity remains 45 kt based on the earlier ASCAT data and
the latest Dvorak estimate from SAB.  UW-CIMSS analysis shows that
the shear is already over 40 kt and the SHIPS model shows it near or
above this value for the next 36 hours, which should result in
weakening.  The official forecast follows that trend and is close to
the latest SHIPS guidance through 48 hours.  After that time, Lisa
is expected to remain a 30-kt post-tropical cyclone through 5 days.
Even though the shear diminishes in about 72 hours, the mid-level
relative humidity remains below 50 percent, and it is assumed that
Lisa will be too weak to take advantage of the lower shear.

The initial motion estimate is 320/07.  Lisa is expected to continue
moving northwestward into a break in the subtropical ridge for the
next 48 hours.  Beyond that time, Lisa or its remnants should
recurve ahead of a large mid-latitude trough.  The new NHC track
forecast is basically an update of the previous one and is along the
eastern edge of the latest guidance envelope.  There continues to be
a fair bit of along-track spread in the guidance late in the period,
with the GFS now faster than the other guidance.  The NHC forecast
has been adjusted a little faster this cycle but is slower than the
GFS and close to the latest guidance from the Ocean Prediction
Center.

FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z 20.7N  34.5W   45 KT  50 MPH
 12H  23/0600Z 21.8N  35.6W   40 KT  45 MPH
 24H  23/1800Z 23.2N  37.0W   35 KT  40 MPH
 36H  24/0600Z 24.4N  38.5W   30 KT  35 MPH
 48H  24/1800Z 25.6N  40.1W   30 KT  35 MPH
 72H  25/1800Z 29.5N  41.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  26/1800Z 34.0N  38.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  27/1800Z 42.5N  30.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brennan
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