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Hurricane Leslie Discussion Number  61
NWS National Hurricane Center Miami FL       AL132018
1100 AM AST Thu Oct 11 2018

Leslie's structure has remained steady since last night. The
hurricane has a ragged banding eye surrounded by a somewhat patchy
central dense overcast. Recent Dvorak classifications from TAFB
and SAB are unchanged, and still support an initial intensity of
70 kt.

For days now, it has been clear that Leslie will accelerate
east-northeastward on the south side of a mid-latitude trough
moving across the North Atlantic. That acceleration is well underway
now, and the initial motion estimate is 060/14 kt. It has been
unclear, however, when (or if) Leslie could separate from this
trough and begin to drift southward over the eastern Atlantic. The
model spread has remarkably increased since yesterday, and nearly
1/3 of the members of the most recent GFS and ECMWF ensemble runs no
longer forecast Leslie to separate from the trough at all, instead
showing the cyclone approaching western Europe as an extratropical
low. Even the deterministic model spread has increased, and the
two NOAA regional hurricane models, the HWRF and HMON, are nearly
2300 miles apart at day 5. Through 48 h, the official track forecast
is very similar to the previous advisory, but it has been adjusted
eastward beyond that time, to bring it closer to the most recent
deterministic multi-model consensus. Confidence in the track
forecast is not high at 72 h and beyond, and it's possible that
large changes could still be required to future advisories.

Leslie should remain in a generally favorable environment for
strengthening during the next 24-36 h, and slight intensification
is still expected, though the official intensity forecast is now on
the high side of the guidance through this period. By 48 h and
onward, Leslie will be moving into a far more stable environment
and over cooler waters, so steady weakening is anticipated.  If
Leslie follows a track similar to the NHC forecast, it will likely
become a weak post-tropical low within 96 h. However, if Leslie
undergoes extratropical transition, its worth noting that the
maximum winds associated with the cyclone would likely be higher
than indicated here.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 29.1N  38.3W   70 KT  80 MPH
 12H  12/0000Z 30.3N  35.5W   75 KT  85 MPH
 24H  12/1200Z 31.7N  30.3W   75 KT  85 MPH
 36H  13/0000Z 32.8N  24.6W   70 KT  80 MPH
 48H  13/1200Z 33.2N  20.0W   60 KT  70 MPH
 72H  14/1200Z 31.3N  17.3W   40 KT  45 MPH
 96H  15/1200Z 29.1N  19.0W   30 KT  35 MPH...POST-TROPICAL
120H  16/1200Z 27.5N  24.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky

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