[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 202042
TCDAT3

TROPICAL STORM LISA DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016
500 PM AST TUE SEP 20 2016

During the past six hours, a central dense overcast (CDO) feature
has developed over and to the east of Lisa's low-level center. The
upper-level outflow has also improved, albeit elongated northeast-
to-southwest.  The initial intensity has been increased to 40 kt,
which is a blend of a Dvorak satellite intensity estimate of T2.5/35
kt from TAFB, a UW-CIMSS ADT values of T2.9/43 kt, and a 1611Z AMSU
estimate of 44 kt.

The initial motion estimate is 315/10 kt. Lisa has made a jog to the
right of the previous forecast track and model guidance, which is
most likely due to the center reforming closer to the strongest
convection. Other than shifting the forecast track to the right of
the previous advisory track to account for the more eastward initial
position, the forecast rationale remains unchanged. The latest NHC
model guidance continues to indicate a steady northwestward motion
for the next four days toward a break in the subtropical ridge
between 30W-40W longitude.  On day 5, Lisa is expected to move
northward as the ridge erodes eastward. The new NHC forecast track
lies down the middle of the tightly packed guidance envelope through
day 4, and then follows a blend of the ECMWF and HWRF models on day
5 since those models maintain the cyclone longer.

Lisa has another 36 hours or so to strengthen some more before the
large-scale environment becomes very unfavorable, which will be
characterized by southwesterly vertical wind shear of 25-30 kt,
drier and more stable air, and SSTs less than 27 deg C. It is
possible that Lisa could end up being a little stronger between the
24- and 36-hour forecast periods. By 48 hours, however, steady
weakening is expected to ensue, with Lisa becoming a remnant low
pressure system by 120 hours. The intensity forecast closely follows
the intensity consensus model IVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 16.4N  31.0W   40 KT  45 MPH
 12H  21/0600Z 17.2N  32.1W   45 KT  50 MPH
 24H  21/1800Z 18.1N  33.6W   50 KT  60 MPH
 36H  22/0600Z 19.0N  35.0W   50 KT  60 MPH
 48H  22/1800Z 20.0N  36.5W   45 KT  50 MPH
 72H  23/1800Z 22.7N  39.2W   35 KT  40 MPH
 96H  24/1800Z 25.2N  42.0W   30 KT  35 MPH
120H  25/1800Z 29.2N  44.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart
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