000 WTNT43 KNHC 111444 TCDAT3 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