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| #873559 (Received by flhurricane at: 10:59 PM 31.Aug.2016) TCDAT4 TROPICAL STORM HERMINE DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 1000 PM CDT WED AUG 31 2016 Data from NOAA and Air Force Reserve Hurricane Hunter aircraft this afternoon and evening indicate that Hermine has continued to strengthen, based on maximum 850-mb flight-level winds of 57 kt and peak SFMR surface winds of 52 kt. A recent dropsonde in the center of Hermine measured a pressure of about 998 mb, which is a decrease of 6 mb from the previous advisory. Recon fixes over the past 4 hours indicate that the estimated motion is north-northeastward or 025/09 kt. An approaching mid-tropospheric trough located over the southeastern United States and extending southward into the north-central Gulf of Mexico is expected to gradually lift out Hermine to the north-northeast tonight and Thursday, and then northeastward after 24 hours. The NHC model is in very good agreement on this developing steering flow pattern. Later in the forecast period, significant uncertainty in the track forecast remains, depending on how much the post-tropical cyclone interacts with a mid-latitude cutoff low that develops over the northeastern United States. The new NHC forecast track has been shifted slightly to the east of the previous advisory track, primarily due to the more eastward initial position determined from recent recon fixes, and lies just to the left of the consensus model TVCN. The vertical wind shear is forecast by the GFS and the ECMWF models to shift from the current west-northwesterly direction to southwesterly by 18-24 hours at about 5 to 10 kt. SSTs are expected to be near 30C. The intensity consensus IVCN again brings Hermine to hurricane strength prior to landfall and the offical forecast follows this guidance, forcing the issuance of a hurricane warning with this advisory. The predicted extratropical transition of the system is based on the global model guidance, which show the cyclone becoming embedded within a frontal zone over the eastern United States by 72 hours. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 25.8N 87.0W 50 KT 60 MPH 12H 01/1200Z 26.9N 86.4W 55 KT 65 MPH 24H 02/0000Z 28.7N 85.4W 65 KT 75 MPH 36H 02/1200Z 30.7N 83.8W 60 KT 70 MPH...INLAND 48H 03/0000Z 32.8N 81.4W 45 KT 50 MPH...INLAND 72H 04/0000Z 37.0N 76.3W 40 KT 45 MPH...POST-TROP/INLAND 96H 05/0000Z 39.0N 74.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 06/0000Z 39.0N 71.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart |
