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TROPICAL STORM LISA DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016
1100 PM AST THU SEP 22 2016
Lisa continues to struggle in the face of strong deep-layer shear.
Although the cyclone continues to pulsate convection, several
microwave passes between 1900 and 2100 UTC indicate that the center
has become somewhat more removed from the deepest convection since
this afternoon. The initial intensity has been lowered to 40 kt, in
line with decreased Dvorak estimates from TAFB and SAB. A 2344 UTC
ASCAT-B pass missed the center of Lisa, but showed that 35 kt winds
are present 100-150 nm NE of the presumed center.
Lisa is forecast to remain in a high shear and increasingly dry
environment, so further weakening seems inevitable. The main
question is how quickly will the deep convection cease to exist.
The GFS and HWRF both show mid- to upper-level dry air cutting over
the circulation in about 36 to 48 hours, suggesting a complete lack
of deep convection in those models at that time. The official
forecast now calls for Lisa to become post tropical within 48 hours,
before being absorbed by an approaching front after 96 hours.
There is little change to the track forecast reasoning overall.
Lisa continues to move toward the northwest, or 320 degrees, at a
rather uncertain 8 kt. A lack of microwave or scatterometer data
over the center since 2100 UTC has made the center difficult to
locate and introduces some uncertainty to the forecast. Regardless,
Lisa should continue moving northwestward around a low- to mid-level
ridge, located east of the Azores, before recurving ahead of an
approaching front. The first 48 hours of the forecast are near a
consensus of the GFS and ECMWF models. The 72 and 96 hour points
incorporate guidance from the Ocean Prediction Center.
FORECAST POSITIONS AND MAX WINDS
INIT 23/0300Z 21.3N 35.2W 40 KT 45 MPH
12H 23/1200Z 22.4N 36.3W 35 KT 40 MPH
24H 24/0000Z 23.6N 37.8W 30 KT 35 MPH
36H 24/1200Z 24.7N 39.3W 30 KT 35 MPH
48H 25/0000Z 26.2N 40.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 26/0000Z 30.5N 41.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 27/0000Z 35.5N 37.0W 30 KT 35 MPH...POST-TROP/REMNT LOW