[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 221435
TCDAT3

TROPICAL STORM LISA DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016
1100 AM AST THU SEP 22 2016

An ASCAT-A pass from 1138Z showed that the center of Lisa is located
near the southwestern edge of an area of bursting deep convection.
The ASCAT data showed a cluster of 40-45 kt winds north of the
center, so the initial intensity is set to 45 kt for this advisory,
which is also in agreement with the latest Dvorak current intensity
estimates of T3.0/45 kt from TAFB and SAB.  The restrengthening
appears to have occurred despite the shear increasing to 30-35 kt
based on the SHIPS model analyses and satellite analyses from
UW-CIMSS, and the upper-level outflow has improved somewhat during
the past few hours.  However, the separation between the convection
and the low-level center appears to be increasing, and Lisa will be
moving into a region of even stronger southwesterly shear in the
next 24 hours, which should result in weakening.  The shear is
forecast to relax late in the period, but it is unlikely that Lisa
will be able to recover and the cyclone is forecast to become a
remnant low in 3 to 4 days.  This is in agreement with the global
models, which show the system decaying by that time.  The new NHC
intensity forecast is a little higher than the previous one given
the higher initial intensity, and is closest to the statistical-
dynamical SHIPS and LGEM models.

Based on the ASCAT data and earlier microwave fixes, my best
estimate of the initial motion is 310/06, as the cyclone appears to
have slowed down some during the past few hours.  The track forecast
reasoning remains the same, however, with Lisa expected to move
northwestward into a break in the subtropical ridge for the next 48
hours.  After that time, Lisa or its remnants should recurve ahead
of a large mid-latitude trough.  The new NHC track forecast is an
update of the previous one through 72 hours and has been shifted a
bit to the right at days 4 and 5 following the latest model guidance
trends.  There is a fair bit of along-track spread in the guidance
late in the period, with the ECMWF much faster than the GFS and
UKMET.  The NHC forecast favors the slower solution, in agreement
with the latest guidance from the Ocean Prediction Center.

The initial and forecast 34-kt wind radii were adjusted based on
the above-mentioned ASCAT data.

FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 20.0N  34.0W   45 KT  50 MPH
 12H  23/0000Z 21.1N  35.1W   45 KT  50 MPH
 24H  23/1200Z 22.5N  36.4W   40 KT  45 MPH
 36H  24/0000Z 23.8N  37.6W   35 KT  40 MPH
 48H  24/1200Z 25.0N  39.0W   30 KT  35 MPH
 72H  25/1200Z 28.0N  41.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  26/1200Z 32.0N  39.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  27/1200Z 35.5N  37.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brennan
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