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TROPICAL STORM LISA DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016
500 AM AST WED SEP 21 2016

Lisa's cloud pattern has gradually become better organized into a
comma-like shape, although the system still appears to be somewhat
elongated from southwest to northeast.  Upper-level outflow
remains weak over the southeastern quadrant of the circulation.
Dvorak classifications from both TAFB and SAB yield an intensity
estimate of 45 kt, and that value is used for the advisory.  The
storm has less than 24 hours before west-southwesterly shear
associated with an upper-level trough near 40W-50W longitude becomes
prohibitively large for strengthening.  Therefore, some slight
additional intensification could occur today, but beyond 24 hours
Lisa is forecast to steadily weaken.  By days 4-5, although the
shear is predicted to weaken when Lisa moves under the trough axis,
the cyclone should have been disrupted too much by the earlier
hostile environment to make a recovery.  The official forecast is
close to the LGEM guidance through 48 hours and a little below that
model thereafter.

The center is not easy to locate and the initial motion is a rather
uncertain 315/8 kt, which is partially based on continuity from
earlier estimates.  A weak mid-tropospheric ridge to the north and
northeast of Lisa should maintain a generally northwestward motion
through 72 hours or so.  Later in the forecast period, an
approaching trough in the westerlies, which is also expected to
accelerate Karl to the northeast, should cause Lisa to turn
northward over the eastern Atlantic.  The official track forecast
is similar to the previous one and is close to a consensus of the
ECMWF, GFS, and UKMET global models.

FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 17.5N  32.2W   45 KT  50 MPH
 12H  21/1800Z 18.2N  33.2W   50 KT  60 MPH
 24H  22/0600Z 19.1N  34.5W   50 KT  60 MPH
 36H  22/1800Z 20.1N  35.9W   45 KT  50 MPH
 48H  23/0600Z 21.3N  37.4W   40 KT  45 MPH
 72H  24/0600Z 24.1N  40.4W   30 KT  35 MPH
 96H  25/0600Z 27.5N  43.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  26/0600Z 32.5N  43.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Pasch

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