[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 050856
TCDAT3

Tropical Storm Leslie Discussion Number  36
NWS National Hurricane Center Miami FL       AL132018
500 AM AST Fri Oct 05 2018

Leslie's structure has evolved somewhat just within the past 6
hours.  Deep convection has redeveloped near the low-level center,
although it is displaced a bit to the north due to some southerly
shear.  The cyclone's circulation remains quite large, and earlier
ASCAT data indicated that the radius of maximum winds is about
90-100 n mi away from the center.  Since there is some inner-core
convection again, the initial intensity remains 55 kt based on the
ASCAT data.

Leslie has gained some speed and has turned toward the
north-northwest, now with an initial motion of 345/12 kt.  A
general northward motion should continue for the next 12-24 hours,
but then Leslie will reach the mid-latitude westerlies and make an
abrupt turn toward the east by 36 hours.  After that time, Leslie
is expected to make some significant eastward progress, although
the global models are showing several shortwave troughs in the
westerlies imparting a southeastward motion on Leslie by days 4 and
5.  In fact, some of the models have shifted significantly
southward by the end of the forecast period, leaving the previous
official forecast near the northern edge of the guidance envelope.
Due to this shift, the new NHC track prediction has been adjusted
southward on days 3-5, although it does not yet show as much
southward motion as indicated by the normally reliable ECMWF, HCCA,
and TVCN multi-model consensus.

Leslie doesn't appear to have to contend with much shear during the
next 3 days or so, but with such a large wind field mixing the
ocean around it, marginal sea surface temperatures are likely to
keep the intensity steady.  By days 3 and 4, an increase in shear
could cause some slight weakening.  The models are in very good
agreement in showing little to any change in Leslie's intensity
during the next 5 days, and that is largely what is indicated in
the NHC forecast.

Large swells generated by Leslie are expected to continue during the
next few days across the southeastern coast of the United States,
Bermuda, the Bahamas, and the Greater and Lesser Antilles.  These
swells will also increase near the coasts of New England and
Atlantic Canada later today.  Please consult products from your
local weather office as these conditions could cause life-
threatening surf and rip currents.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 35.9N  58.3W   55 KT  65 MPH
 12H  05/1800Z 36.9N  58.4W   50 KT  60 MPH
 24H  06/0600Z 37.4N  57.6W   50 KT  60 MPH
 36H  06/1800Z 37.4N  55.8W   50 KT  60 MPH
 48H  07/0600Z 37.0N  53.7W   50 KT  60 MPH
 72H  08/0600Z 35.7N  49.7W   45 KT  50 MPH
 96H  09/0600Z 33.5N  45.5W   45 KT  50 MPH
120H  10/0600Z 31.5N  42.0W   50 KT  60 MPH

$$
Forecaster Berg
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