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Tropical Storm Humberto Forecast Discussion Number 6
2019-09-14 05:01:29| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Fri Sep 13 2019 000 WTNT44 KNHC 140300 CCA TCDAT4 Tropical Storm Humberto Discussion Number 6...Corrected NWS National Hurricane Center Miami FL AL092019 1100 PM EDT Fri Sep 13 2019 Corrected to change depression to storm in the second paragraph Deep convection has been gradually increasing this evening, and it is currently most organized in a curved band to the east of the estimated center. In addition, data from the NOAA Hurricane Hunters indicate that the depression has strengthened. The maximum flight-level wind at 700 mb was 41 kt and reliable SFMR values were 35 kt. Based on that data, the initial intensity is increased to 35 kt, making the cyclone Tropical Storm Humberto. The data from the aircraft indicate that the cyclone is titled to the northeast with height, likely due to southwesterly wind shear. Humberto has been moving erratically during the past 12 to 18 hours as the cyclone has been trying to organize, but my best guess at the initial motion is 320/5. During the next few days, a ridge to the north of the system over the eastern United States and the western Atlantic is expected to slide southeastward, with a weakness in the ridge developing due to a mid- to upper-level trough over the northeastern U.S. This change in the steering pattern should cause the storm to slow down and turn northward off the east coast of Florida in 36 to 48 hours. The models show the trough over the northeastern U.S. amplifying early next week, which should cause Humberto to turn northeastward and then eastward away from the U.S. The NHC track forecast has been nudged south and east of the previous one to be in better agreement with the latest consensus models. Since there is increasing confidence that the storm will remain well offshore of the coast of Florida, the Tropical Storm Watch for that area has been discontinued. The storm is still feeling some effects of southwesterly shear and drier air, which is causing its lopsided appearance in satellite images and strong tilt in the aircraft data. The atmospheric conditions are expected to gradually become more conducive for strengthening while Humberto moves over the warm Gulf Stream waters. These environmental parameters support intensification, and the cyclone is expected to become a hurricane in 2 to 3 days. The NHC intensity forecast is largely an update of the previous one and in line with the HCCA and IVCN guidance. Key Messages: 1. Humberto will likely bring tropical-storm-force winds and heavy rainfall to portions of the northwestern Bahamas on Saturday. Significant storm surge is not expected in the northwest Bahamas from this system. Residents there should follow any advice given by local officials. 2. Heavy rainfall and scattered flash flooding is possible this weekend in coastal sections of eastern Florida, Georgia, and South Carolina. The chance of heavy rainfall affecting coastal North Carolina early next week continues to diminish. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 25.6N 75.2W 35 KT 40 MPH 12H 14/1200Z 26.5N 76.5W 35 KT 40 MPH 24H 15/0000Z 27.6N 77.6W 40 KT 45 MPH 36H 15/1200Z 28.8N 78.2W 50 KT 60 MPH 48H 16/0000Z 29.8N 78.1W 60 KT 70 MPH 72H 17/0000Z 31.0N 75.5W 70 KT 80 MPH 96H 18/0000Z 31.3N 72.0W 75 KT 85 MPH 120H 19/0000Z 32.3N 67.2W 75 KT 85 MPH $$ Forecaster Cangialosi
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