Official Discussion issued by the National Hurricane Center

Leslie (AL132018) DATA RELEASED: 9/29/2018 5:00:00 PM UTC

Copy of official data

Tropical Storm Leslie Discussion Number  14
NWS National Hurricane Center Miami FL       AL132018
500 PM AST Sat Sep 29 2018

Leslie has continued to take on more tropical characteristics over
the past few hours. Anti-cyclonic outflow is now present to the
northeast and southeast of Leslie and its primary convective band.
Late-arriving AMSU data from 1316 UTC also indicated that Leslie has
developed a deep-layer warm core structure. Based on these factors,
Leslie has been designated as a tropical storm.  The initial
intensity is set at 45 kt, based on a blend of recent satellite
intensity estimates from TAFB and the UW-CIMSS SATCON.

Leslie continues to move slowly southwestward with an initial motion
of 225/5 kt. The guidance is in very good agreement that this
general motion will continue for another 24 h or so, before the
cyclone becomes nearly stationary by early next week. An approaching
mid-latitude trough is still expected to eventually cause Leslie to
turn toward the north or northeast, perhaps over its own track, in 4
or 5 days. Only minor adjustments were made to the NHC track
forecast, which remains close to the various track consensus aids.

The NHC intensity forecast has not been changed in any significant
way and remains near the intensity consensus, but slightly favors
the regional hurricane models.  Leslie is currently located over
fairly cool SSTs, and its slow motion could cause further ocean
cooling. This could particularly be an issue in a few days when the
tropical storm is expected to become nearly stationary. The
ocean-coupled regional models (HWRF, HMON, COAMPS-TC) continue to
indicate that Leslie will struggle to intensify much over the next
few days, despite a fairly favorable upper-level environment. On the
other hand, some of the uncoupled global models and the SHIPS and
LGEM models suggest that more intensification will occur and that
Leslie could become a hurricane in a few days. Highlighting the
potential importance of SSTs in this case, the SHIPS and LGEM models
began using daily SST fields at 18Z, which show nearly 2 deg C
cooler SSTs along the track of Leslie, and those models now show
much less intensification than they did before.

Large swells generated by Leslie when it was a strong extratropical
low will affect Bermuda, the east coast of the United States, and
most of the Greater and Lesser Antilles through the weekend. These
swells could cause life-threatening surf and rip currents.


INIT  29/2100Z 34.1N  51.3W   45 KT  50 MPH
12H  30/0600Z 33.6N  52.0W   45 KT  50 MPH
24H  30/1800Z 33.1N  53.0W   50 KT  60 MPH
36H  01/0600Z 32.8N  53.5W   50 KT  60 MPH
48H  01/1800Z 32.5N  53.9W   55 KT  65 MPH
72H  02/1800Z 31.5N  54.7W   55 KT  65 MPH
96H  03/1800Z 31.5N  54.5W   60 KT  70 MPH
120H  04/1800Z 34.0N  54.0W   65 KT  75 MPH

Forecaster Zelinsky