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Tropical Storm HERMINE Forecast Discussion Number 20
2016-09-02 10:43:29| National Hurricane Center (Atlantic)
Issued at 500 AM EDT FRI SEP 02 2016 000 WTNT44 KNHC 020843 TCDAT4 TROPICAL STORM HERMINE DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 500 AM EDT FRI SEP 02 2016 Hermine made landfall near St. Marks, Florida, around 0530 UTC with 70-kt winds. Since that time radar data and surface observations indicate that the center has continued to move inland. The radar presentation has deteriorated, and it is estimated that Hermine has weakened to tropical storm status with 60-kt winds. Additional weakening is anticipated while the cyclone moves farther inland, but it could reinvigorate as an extratropical cyclone when it moves over water and interacts with a baroclinic trough in about 48 hours. The best estimate of the initial motion 025/12 kt. Hermine is embedded within the southwesterly flow ahead of a mid-latitude trough, and this flow pattern should steer the cyclone toward the northeast with an increase in forward speed during the next day or two. Track models are in very good agreement during this period. After that time, when Hermine begins to interact with a baroclinic trough, the cyclone should slow down significantly and begin to meander. On days 3-5, the track guidance becomes rather divergent, decreasing confidence in the forecast. The NHC prediction keeps an extratropical cyclone moving little or drifting northward a few hundred miles off the northeastern U.S coast during that time. There is a possibility that the system could regain some tropical characteristics in 4-5 days, but this remains uncertain as indicated in the previous NHC forecast. KEY MESSAGE: 1. Hermine is expected to become a post-tropical cyclone while still producing hazardous winds and storm surge over land. NWS policy allows NHC to write advisories on and issue tropical storm watches and warnings for post-tropical cyclones, when the system continues to pose a significant threat to life and property. NHC and the NWS Eastern Region have decided that this option will be invoked for Hermine. After Hermine becomes a post-tropical cyclone, NHC will continue to issue its full suite of advisory and warning products for as long as the system remains a significant threat to land. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 30.8N 83.6W 60 KT 70 MPH 12H 02/1800Z 32.5N 81.4W 45 KT 50 MPH...INLAND 24H 03/0600Z 34.5N 77.9W 40 KT 45 MPH...INLAND 36H 03/1800Z 36.0N 74.5W 40 KT 45 MPH...OVER WATER 48H 04/0600Z 37.0N 72.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 05/0600Z 38.0N 72.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 06/0600Z 38.5N 72.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 07/0600Z 39.0N 72.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Avila
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