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Potential Tropical Cyclone Sixteen Forecast Discussion Number 1
2019-10-17 17:03:16| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Thu Oct 17 2019 000 WTNT41 KNHC 171503 TCDAT1 Potential Tropical Cyclone Sixteen Discussion Number 1 NWS National Hurricane Center Miami FL AL162019 1000 AM CDT Thu Oct 17 2019 A complicated weather situation is evolving in the Gulf of Mexico. The circulation associated with the tropical disturbance over the southwestern Gulf of Mexico is getting better defined, and the associated convection is getting better organized. However, a strong mid- to upper-level trough is moving eastward across southern Texas and northern Mexico, and a frontal system is present over the northern and northwestern Gulf of Mexico. The ECMWF and GFS models suggest that the trough will spawn a low along the front, with the tropical disturbance merging with that low. On the other hand, the UKMET suggests the tropical disturbance will become the primary low pressure system. Either way, it is likely that a low pressure area with gale-force winds and at least some tropical cyclone characteristics will move northeastward and affect portions of the northern Gulf coast during the next 36-48 h. Based on this, advisories are initiated on Potential Tropical cyclone Sixteen, and coastal tropical cyclone and storm surge watches/warnings are being issued. The system should track generally northeastward in the southern portion of the mid-latitude westerlies, and the track model guidance is in reasonably good agreement through 96 h. The forecast track lies a little to the south of the model consensus, as the UKMET has a somewhat more southerly track. The forecast track brings the system across the southeastern United States between 48-72 h, and then has it moving into the Atlantic east of the mid-Atlantic States. Gradual strengthening is expected as strong upper-level divergence caused by the trough partly prevails over strong vertical shear. Thus, the intensity forecast calls for gradual strengthening along the lines of that in the global models. It is unlikely, though, that the system will develop into a classical tropical cyclone. The system is expected to be fully extratropical by 48 h, with gradual weakening expected after that time. Regardless of the exact evolution of this weather system, portions of the northern coast of the Gulf of Mexico will experience strong winds, locally heavy rains, and storm surge Friday and Saturday. Similar impacts are expected across portions of the Atlantic coast of the southeastern United States Saturday and Sunday. KEY MESSAGES: 1. Dangerous storm surge inundation of up to 5 feet above ground level is possible along the Florida Gulf Coast from Indian Pass to Clearwater, where a Storm Surge Watch is in effect. Residents in these areas should follow advice given by local officials. 2. Tropical storm force winds are likely along portions of the north-central and northeastern Gulf Coast where tropical storm watches and warnings are in effect. Regardless of the exact track and intensity of the system, these winds will cover a large area, especially east of the center, and begin well in advance of the arrival of the center. 3. Wind and coastal flooding hazards along the U.S. East Coast will be covered by non-tropical watches and warnings issued by local NWS offices, since the system is expected to lose any tropical characteristics after it moves inland along the Gulf Coast. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 22.4N 95.7W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 18/0000Z 23.7N 94.2W 35 KT 40 MPH...TROPICAL STORM 24H 18/1200Z 25.8N 91.0W 40 KT 45 MPH 36H 19/0000Z 28.5N 88.0W 45 KT 50 MPH 48H 19/1200Z 30.9N 85.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 20/1200Z 35.5N 77.2W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 21/1200Z 37.5N 70.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 22/1200Z 38.0N 66.5W 25 KT 30 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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