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| #873665 (Received by flhurricane at: 4:53 PM 01.Sep.2016) TCDAT4 HURRICANE HERMINE DISCUSSION NUMBER 18 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 400 PM CDT THU SEP 01 2016 Hermine was recently upgraded to a hurricane based on an SFMR-observed surface wind from an Air Force Hurricane Hunter aircraft. The initial intensity is set at 65 kt based on that observation. Satellite images show that the cloud pattern continues to gradually become better organized with more distinct curved bands of showers and thunderstorms, although the system currently lacks concentrated inner-core convection. Hermine has a little more time to strengthen, so the official forecast shows a slight additional increase in intensity before landfall. This is consistent with the latest LGEM guidance. Hermine is forecast to become extratropical at 48 hours when the global models forecast it to become embedded within a frontal zone. Later in the forecast period, vertical shear decreases and the cyclone could be situated over marginally warm waters. Therefore there is the possibility of the system regaining some tropical characteristics in 4-5 days, although this is speculative at this time. Aircraft center fixes indicate that the motion remains 030/12 kt. The flow on the eastern side of a mid-level trough over the southeastern United States should cause Hermine to move north-northeastward to northeastward with some increase in forward speed during the next day so. By 48 hours, the track guidance shows the system slowing down as it begins to interact with a mid-level cutoff vortex over the eastern United States. In 3 days or so, the post-tropical cyclone merges with the cutoff low and a further slowing down of the motion is expected. The official track forecast lies between the latest GFS and ECMWF predictions. KEY MESSAGES: 1. As landfall nears, it is important to not focus on the exact forecast track. Hermine is an extremely asymmetric storm, with a large extent of dangerous winds, life-threatening storm surge, and flooding rains well to the east and southeast of the path of the center. 2. 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 01/2100Z 28.5N 85.0W 65 KT 75 MPH 12H 02/0600Z 30.2N 83.9W 70 KT 80 MPH 24H 02/1800Z 32.4N 81.6W 50 KT 60 MPH...INLAND 36H 03/0600Z 34.5N 78.2W 45 KT 50 MPH...INLAND 48H 03/1800Z 36.3N 75.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 04/1800Z 38.0N 72.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 05/1800Z 38.5N 71.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 06/1800Z 39.5N 70.5W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch |
