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Tropical Storm Leslie Forecast Discussion Number 45
2018-10-07 16:50:09| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sun Oct 07 2018 000 WTNT43 KNHC 071449 TCDAT3 Tropical Storm Leslie Discussion Number 45 NWS National Hurricane Center Miami FL AL132018 1100 AM AST Sun Oct 07 2018 Despite marginal SSTs near 24 deg C, Leslie has persisted with little change in its structure. An average of the UW-CIMSS SATCON and current intensity estimates from TAFB and SAB still supports an initial intensity of 50 kt. Although Leslie is currently located in a low-shear environment, GFS and ECMWF SHIPS diagnostics suggests that mid-level humidities are fairly low, and the cyclone should remain over marginal SSTs for the foreseeable future. All of the intensity guidance forecasts little to no intensity change during the next day or so. However, by 36 h, nearly all of the dynamical models, both global and regional, forecast that Leslie will begin to restrengthen. On the other hand, the statistical-dynamical models do not forecast much change through day 5. The NHC forecast has been adjusted a little higher to keep it close to the intensity consensus, and I can't rule out that Leslie could become a hurricane again at some point during the coming week. No large changes were made to the NHC track forecast, but this should not be interpreted as a sign of confidence in the forecast. Leslie is currently moving with an initial motion of east-southeast, or 115/9 kt. The track model spread is high from the very beginning of the forecast, with the GFS and its associated regional models indicating that Leslie will continue on a similar heading for the next several days, while the ECMWF and UKMET forecast that Leslie will slow down and turn soon turn toward the southeast or south-southeast. The track forecast variance stems from differences in how quickly the models show Leslie separating from a mid-level trough to its north, if at all, and by day 5, the GFS and ECMWF solutions vary by about 750 n mi. At this point, I don't have a good reason to pick one solution over another, and it should be noted that based on the ECMWF ensemble tracks, there is a whole spectrum of possible solutions between these extremes. The NHC track forecast therefore remains near the TVCN and GFEX aids as a course of least regret, but significant changes could be required to future advisories if the track of Leslie becomes more clear. Large swells generated by Leslie are expected to continue through tonight across the northeastern coast of the United States, Bermuda, the Greater and Lesser Antilles, and Atlantic Canada. 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 07/1500Z 36.6N 51.4W 50 KT 60 MPH 12H 08/0000Z 36.2N 49.7W 50 KT 60 MPH 24H 08/1200Z 35.4N 47.3W 50 KT 60 MPH 36H 09/0000Z 34.2N 44.5W 55 KT 65 MPH 48H 09/1200Z 32.6N 41.7W 55 KT 65 MPH 72H 10/1200Z 29.1N 36.6W 60 KT 70 MPH 96H 11/1200Z 28.5N 31.9W 60 KT 70 MPH 120H 12/1200Z 30.0N 28.0W 55 KT 65 MPH $$ Forecaster Zelinsky
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