[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 201503 CCA
TCDAT3

TROPICAL STORM LISA DISCUSSION NUMBER   4...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132016
1100 AM AST TUE SEP 20 2016

CORRECTED LISA TO BE TWELFTH NAMED STORM

The cloud pattern of the cyclone has steadily improved, with long
curved bands having developed in the northern semicircle since the
previous advisory. Although Dvorak satellite classifications from
TAFB and SAB were 30 kt at 1200Z, recent UW-CIMSS ADT values have
increased to 35 kt and AMSU intensity estimates range from 35-45 kt.
Therefore the initial intensity has been increased to 35 kt, which
is a compromise of these estimates, making the cyclone the twelfth
named storm of the 2016 hurricane season.

Visible satellite imagery indicates that Tropical Storm Lisa is now
moving northwestward or 305/10 kt. Water vapor imagery and
satellite-derived winds indicate that a large mid-latitude trough
extends from near the Canary Islands southwestward into the tropics,
which has created a break in the subtropical ridge along 30W-40W
longitude. Lisa is forecast to move generally northwestward toward
the break in the ridge for the next 4 days, followed by a northward
turn as the cyclone moves around the western periphery of the ridge
axis. The latest model guidance remains in good agreement on this
track scenario, and the new NHC forecast track is just a little to
the right of the previous advisory track, mainly to account for the
more northward initial position, and lies close to the consensus
model TVCN.

Lisa has about 48 hours remaining to strengthen while the vertical
wind shear and upper-level outflow pattern remain favorable, and
sea-surface temperatures are above 27 deg C. However, a marginally
moist mid-level environment and the large size of the cyclone are
expected to prevent any rapid strengthening from occuring. After
that time, the atmosphere is expected to become quite hostile,
characterized by southwesterly shear of 25-30 kt and much drier
mid-level air, resulting in steady weakening from 72-120 hours.
Although the dynamical guidance continues to forecast some
relaxation of the shear toward the end of the period, the cyclone
will likely be too degraded to recover. The official intensity
forecast is close to the SHIPS model through 48 hours, and then lies
closer to the LGEM guidance after that.

FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 15.3N  30.4W   35 KT  40 MPH
 12H  21/0000Z 16.2N  31.5W   35 KT  40 MPH
 24H  21/1200Z 17.3N  33.2W   40 KT  45 MPH
 36H  22/0000Z 18.2N  35.0W   45 KT  50 MPH
 48H  22/1200Z 19.1N  36.4W   50 KT  60 MPH
 72H  23/1200Z 21.7N  39.0W   40 KT  45 MPH
 96H  24/1200Z 24.5N  41.4W   30 KT  35 MPH
120H  25/1200Z 28.3N  43.6W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart
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