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Hurricane Dorian Forecast Discussion Number 46
2019-09-04 22:57:12| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Wed Sep 04 2019 000 WTNT45 KNHC 042057 TCDAT5 Hurricane Dorian Discussion Number 46 NWS National Hurricane Center Miami FL AL052019 500 PM EDT Wed Sep 04 2019 Dorian has become a little better organized during the past several hours, with the eye becoming somewhat more distinct and the cold cloud tops in the eyewall becoming more symmetric. An Air Force Reserve Hurricane Hunter aircraft has twice reported 110-kt flight-level winds in the eastern eyewall, and the central pressure has fallen to 961 mb. Based on these data and that of eyewall dropsondes, the initial intensity is increased to 95 kt. The aircraft data show that hurricane-force winds are 50-60 n mi offshore of northeastern coast of Florida, while surface observations show that tropical-storm conditions are affecting portions of the coasts of Georgia and South Carolina. The initial motion is now 345/8. Dorian is moving around the western end of the subtropical ridge, and it should recurve northward and northeastward into the mid-latitude westerlies during the next 12-36 h. This motion should bring the center of Dorian near the coast of South Carolina in about 24 h and near or over the coast of North Carolina during the 36-48 h period. After that time, the cyclone is forecast to accelerate northeastward into the Atlantic toward the Canadian Maritimes, with a quick northeastward motion continuing through 120 h. The track guidance remains very tightly clustered, and the new forecast track is little changed from the previous forecast. It should be noted that the track is close to and almost parallel to the coast of the southeastern United State, and any deviation to the left of the track could bring the center onshore anywhere in the Carolinas. Dorian is expected to remain in an environment of light to moderate vertical wind shear and warm sea surface temperatures during the next 36 h or so. None of the guidance shows significant strengthening during this time, and the official forecast is similar to, but slightly stronger than, the previous forecast. However, based on current trends it is possible that Dorian could briefly regain major hurricane strength during the next 12-24 h. The hurricane is expected to maintain Category 2 intensity as it passes near the southeastern United States coast during the 24-48 h period, followed by a weakening trend due to increasing shear and dry air entrainment. Extratropical transition is now expected to begin between 48-72 h and be complete just after 72 h, with Dorian forecast to become a hurricane-force extratropical low as it moves towards Nova Scotia and Newfoundland. Since the NHC track prediction continues to take Dorian dangerously close to the southeast U.S. coast, all interests from northeast Florida to the Carolinas should remain vigilant to the possibility of experiencing destructive winds, flooding rains, and life- threatening storm surges from this hurricane. Key Messages: 1. Life-threatening storm surge and dangerous winds are expected along portions of the Florida east coast, the coasts of Georgia, South Carolina, and North Carolina, and portions of southeast Virginia and the southern Chesapeake Bay, regardless of the exact track of Dorian's center. Water levels could rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 2. Flash flooding will become increasingly likely across coastal Georgia into the eastern Carolinas tonight into Friday. There is a high risk of flash flooding over coastal sections of the Carolinas, where significant, life-threatening, flash flooding is expected. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 30.6N 79.8W 95 KT 110 MPH 12H 05/0600Z 31.4N 79.8W 95 KT 110 MPH 24H 05/1800Z 32.7N 79.0W 90 KT 105 MPH 36H 06/0600Z 34.0N 77.3W 85 KT 100 MPH 48H 06/1800Z 35.9N 74.4W 85 KT 100 MPH 72H 07/1800Z 42.1N 65.6W 75 KT 85 MPH 96H 08/1800Z 50.5N 56.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 09/1800Z 56.5N 42.5W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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