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Subtropical Storm Leslie Discussion Number   3
NWS National Hurricane Center Miami FL       AL132018
1100 PM AST Sun Sep 23 2018

There has been little change in the organization of the subtropical
cyclone over the past several hours.  Patches of deep convection
continue to develop over the southeastern portion of the circulation
but there is a lack of convective banding elsewhere. The initial
intensity remains 35 kt, which is based on a partial ASCAT pass that
detected 25-30 kt winds over the northwestern portion of the storm
this evening.  Leslie is not forecast to strengthen over the next
day or so due to dry air and moderate vertical shear.  By 48 hours,
some increase in wind is predicted as Leslie interacts with an
approaching baroclinic zone.

Leslie jogged west-southwestward for a few hours this evening, but
has since turned southwestward and slowed down.  The system is
forecast to move little over the next 24 hours, then begin a faster
eastward motion on Monday night and Tuesday as a mid-latitude trough
and associated cold front digs southeastward over the central
Atlantic. The global models indicate that the front will overtake
Leslie in about 48 hours, and the NHC forecast calls for the system
to become an extratropical low at that time.  The evolution of the
system becomes even more complex after that, as the GFS shows Leslie
being absorbed by a new non-tropical low pressure area to the north,
while some of other global models maintain post-tropical Leslie as
the primary low pressure area.  For now, the NHC forecast maintains
continuity with the previous advisories and calls for the system to
merge with the larger front/low by 72 h, but there is a high level
of uncertainty in the exact evolution and structure of the system.
Regardless of the details of the evolution, a large non-tropical
low pressure area with gale- to storm-force winds is expected to be
over the east-central Atlantic later this week.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0300Z 33.3N  48.5W   35 KT  40 MPH
 12H  24/1200Z 33.1N  48.5W   35 KT  40 MPH
 24H  25/0000Z 33.1N  47.8W   35 KT  40 MPH
 36H  25/1200Z 32.9N  46.0W   35 KT  40 MPH
 48H  26/0000Z 33.1N  43.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  27/0000Z...MERGED WITH FRONT AND LARGER LOW

$$
Forecaster Brown

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