Hurricane Leslie Forecast Discussion Number 30
Issued at 500 PM AST Wed Oct 09 2024 199 WTNT43 KNHC 092033 TCDAT3 Hurricane Leslie Discussion Number 30 NWS National Hurricane Center Miami FL AL132024 500 PM AST Wed Oct 09 2024 Leslie continues to take advantage of the little time it has left under favorable environmental conditions. Although an eye is not currently seen on visible or infrared imagery, a 1611 UTC AMSR2 image shows that an eye exists on microwave imagery, and it is located underneath the middle of the central dense overcast. Subjective Dvorak numbers from TAFB and SAB are a unanimous T-4.5/77 kt, whereas recent objective intensity estimates from UW-CIMSS have been averaging in the 78-85 kt range for the past several hours. The initial intensity is bumped up to 80 kt, using a blend of the subjective and objective estimates. Leslie's initial motion estimate is northwestward, or 310/8 kt. There has been no change to the track forecast reasoning. Leslie is expected to turn northward in 24-36 h as it rounds the southwestern and western periphery of a subtropical ridge to the east. Afterward, Leslie should accelerate toward the northeast in response to a strong trough approaching the cyclone from the northwest. The guidance is a bit farther west this cycle, and the new NHC forecast has shifted west of the previous one. Saildrone data from the last several hours indicates that Leslie is over sea-surface temperatures approximately 1 to 2 degrees warmer than other data sources are indicating, and this could be the main reason why Leslie has strengthened a bit more than anticipated over the past 12 to 24 h. A bit more strengthening is forecast during the next 12 h while the vertical wind shear remains relatively low. In about 12 to 18 h, Leslie is expected to run into a wall of strong northerly shear caused by a strengthening upper-level anticyclone in between Milton and Leslie. The shear is expected to cause Leslie to rapidly weaken during the 24 to 48 h period. While it is possible that Leslie could lose most of its convection in 2 to 3 days, the latest GFS and ECMWF simulated satellite imagery now show several periodic bursts of convection continuing into Day 4. Leslie might also merge with a front and become extratropical in 3 to 4 days. Regardless, Leslie will be traveling over much colder water by that time, and the official forecast calls for Leslie to become post-tropical in 3 to 4 days. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 22.2N 49.0W 80 KT 90 MPH 12H 10/0600Z 22.9N 49.7W 85 KT 100 MPH 24H 10/1800Z 23.8N 50.4W 80 KT 90 MPH 36H 11/0600Z 25.3N 50.5W 60 KT 70 MPH 48H 11/1800Z 27.2N 49.4W 50 KT 60 MPH 60H 12/0600Z 29.7N 47.0W 45 KT 50 MPH 72H 12/1800Z 31.9N 43.2W 45 KT 50 MPH 96H 13/1800Z 35.4N 33.4W 45 KT 50 MPH...POST-TROPICAL 120H 14/1800Z 36.5N 25.2W 30 KT 35 MPH...POST-TROPICAL $$ Forecaster Hagen
Issued at 500 PM AST Wed Oct 09 2024
199 WTNT43 KNHC 092033 TCDAT3 Hurricane Leslie Discussion Number 30 NWS National Hurricane Center Miami FL AL132024 500 PM AST Wed Oct 09 2024 Leslie continues to take advantage of the little time it has left under favorable environmental conditions. Although an eye is not currently seen on visible or infrared imagery, a 1611 UTC AMSR2 image shows that an eye exists on microwave imagery, and it is located underneath the middle of the central dense overcast. Subjective Dvorak numbers from TAFB and SAB are a unanimous T-4.5/77 kt, whereas recent objective intensity estimates from UW-CIMSS have been averaging in the 78-85 kt range for the past several hours. The initial intensity is bumped up to 80 kt, using a blend of the subjective and objective estimates. Leslie's initial motion estimate is northwestward, or 310/8 kt. There has been no change to the track forecast reasoning. Leslie is expected to turn northward in 24-36 h as it rounds the southwestern and western periphery of a subtropical ridge to the east. Afterward, Leslie should accelerate toward the northeast in response to a strong trough approaching the cyclone from the northwest. The guidance is a bit farther west this cycle, and the new NHC forecast has shifted west of the previous one. Saildrone data from the last several hours indicates that Leslie is over sea-surface temperatures approximately 1 to 2 degrees warmer than other data sources are indicating, and this could be the main reason why Leslie has strengthened a bit more than anticipated over the past 12 to 24 h. A bit more strengthening is forecast during the next 12 h while the vertical wind shear remains relatively low. In about 12 to 18 h, Leslie is expected to run into a wall of strong northerly shear caused by a strengthening upper-level anticyclone in between Milton and Leslie. The shear is expected to cause Leslie to rapidly weaken during the 24 to 48 h period. While it is possible that Leslie could lose most of its convection in 2 to 3 days, the latest GFS and ECMWF simulated satellite imagery now show several periodic bursts of convection continuing into Day 4. Leslie might also merge with a front and become extratropical in 3 to 4 days. Regardless, Leslie will be traveling over much colder water by that time, and the official forecast calls for Leslie to become post-tropical in 3 to 4 days. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 22.2N 49.0W 80 KT 90 MPH 12H 10/0600Z 22.9N 49.7W 85 KT 100 MPH 24H 10/1800Z 23.8N 50.4W 80 KT 90 MPH 36H 11/0600Z 25.3N 50.5W 60 KT 70 MPH 48H 11/1800Z 27.2N 49.4W 50 KT 60 MPH 60H 12/0600Z 29.7N 47.0W 45 KT 50 MPH 72H 12/1800Z 31.9N 43.2W 45 KT 50 MPH 96H 13/1800Z 35.4N 33.4W 45 KT 50 MPH...POST-TROPICAL 120H 14/1800Z 36.5N 25.2W 30 KT 35 MPH...POST-TROPICAL $$ Forecaster Hagen
