[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 110849
TCDAT3

Hurricane Leslie Discussion Number  60
NWS National Hurricane Center Miami FL       AL132018
500 AM AST Thu Oct 11 2018

The cloud pattern of Leslie has not changed significantly
overnight.  The hurricane has a large and ragged eye with deep
convection most organized on its east side.  The Dvorak CI-numbers
are unchanged at 4.0/65 kt from TAFB and 4.5/77 kt from SAB, and
based on these data, the initial intensity is held at 70 kt.

Leslie will remain in low wind shear conditions and over relatively
warm waters for another day or two, so little change in strength is
expected during that time.  Thereafter, the hurricane is forecast
to move over waters as cool as 24 deg C and into an atmospheric
environment of stronger shear and drier air.  All of these
conditions point to a weakening trend, which is likely to begin by
the weekend.  Most of the guidance shows a cold front approaching
Leslie, but not quite merging with it so extratropical transition is
not expected. However, it seems likely that Leslie will lose its
convection and become a weaker post-tropical low in about 4 days.
This scenario is supported by the latest runs of the GFS, ECMWF, and
HWRF models.

Leslie has made the expected east-northeastward turn with the latest
initial motion estimated to be 065/9. This east-northeastward motion
with an increase in forward speed is forecast to continue for the
next 2 days while the steering pattern holds.  After that time,
however, it becomes much less clear.  The models continue to
struggle and keep changing their tune cycle to cycle on whether or
not Leslie continues east-northeastward toward Morocco or Portugal,
or gets left behind and moves west-southwestward due to a building
ridge.  The ensemble members of both the GFS and ECMWF favor the
left behind (or southwestward) solution, and the NHC track forecast
continues to lean in that direction.  This forecast does show Leslie
moving farther east before it makes the southwestward turn to be in
better agreement with the latest consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  11/0900Z 28.4N  40.1W   70 KT  80 MPH
 12H  11/1800Z 29.3N  37.8W   75 KT  85 MPH
 24H  12/0600Z 30.9N  33.3W   75 KT  85 MPH
 36H  12/1800Z 32.1N  27.5W   70 KT  80 MPH
 48H  13/0600Z 32.7N  22.3W   70 KT  80 MPH
 72H  14/0600Z 31.3N  18.7W   50 KT  60 MPH
 96H  15/0600Z 29.0N  19.5W   35 KT  40 MPH...POST-TROPICAL
120H  16/0600Z 27.5N  24.5W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Cangialosi
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