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Hurricane Dorian Forecast Discussion Number 22
2019-08-29 22:47:17| National Hurricane Center (Atlantic)
Issued at 500 PM AST Thu Aug 29 2019 000 WTNT45 KNHC 292047 TCDAT5 Hurricane Dorian Discussion Number 22 NWS National Hurricane Center Miami FL AL052019 500 PM AST Thu Aug 29 2019 There has been little overall change in the structure of Dorian today. The hurricane has several well-defined bands of convection wrapping into the center and a small central dense overcast. The small eye has not been as apparent in geostationary satellite imagery this afternoon, but the NOAA Hurricane Hunter aircraft reported concentric eyewall diameters of 4 and 22 n mi several hours ago. The latest satellite intensity estimates still support an initial intensity of 75 kt, which is also in line with the earlier SFMR data from the aircraft. The next reconnaissance aircraft is scheduled to investigate the hurricane this evening. Dorian is moving northwestward or 325 at 11 kt. The hurricane should continue moving northwestward tonight between an upper-level low just to the west of Dorian and a mid-level ridge near Bermuda. On Friday, the ridge is forecast to begin building westward to the north of the cyclone, and this pattern is expected to cause the hurricane to turn west-northwestward. A west-northwestward to westward motion should then continue into the weekend with Dorian moving near or over the northwestern Bahamas and toward the Florida peninsula. The guidance envelope has nudged southward this cycle, with the ECMWF and HMON along the southern side, and the GFS bracketing the northern side. There has also been an increase in along-track spread or speed differences with day 5 positions among the dynamical models ranging from near the northwestern Bahamas to the northeastern Gulf of Mexico. This appears to be the result of differences in the models' depiction of the strength or lack thereof of the western portion of the ridge by day 5. The new NHC track forecast is essentially unchanged through the first 2 to 3 days, but has been adjusted southward and somewhat slower than the previous advisory at 96 and 120 hours. Users are reminded to not focus on the exact forecast track, as typical forecast errors at days 4 and 5 are around 155 and 205 miles, respectively. The new intensity forecast is unchanged from the previous one. Dorian will be moving through a favorable environment of low vertical wind shear and warm sea surface temperatures. This should allow for at least steady intensification, and Dorian is forecast to become major hurricane on Friday. Dorian is predicted to remain a dangerous hurricane throughout the remainder of the forecast period. The NHC intensity forecast is again near the upper end of the guidance in best agreement with the HWRF and FSSE models. The National Weather Service has begun 6-hourly upper-air soundings across portions of the mid-Atlantic and southeastern United States. Six-hourly balloons are also being launched in Bermuda and Nassau in the Bahamas. A NOAA G-IV synoptic surveillance mission is ongoing, and the data from this flight will be assimilated into the 0000 UTC model cycle. Key Messages: 1. The risk of life-threatening storm surge and hurricane-force winds this weekend continues to increase in the northwestern Bahamas, and hurricane watches could be issued there tonight or Friday. Residents should have their hurricane plan in place and listen to advice given by local emergency officials. 2. There is an increasing likelihood of life-threatening storm surge along portions of the Florida east coast late this weekend or early next week, although it is too soon to determine where the highest storm surge will occur. Residents should have their hurricane plan in place, know if they are in a hurricane evacuation zone, and listen to advice given by local emergency officials. 3. The risk of devastating hurricane-force winds along the Florida east coast and peninsula late this weekend and early next week continues to increase, although it is too soon to determine where the strongest winds will occur. 4. Regardless of the exact track of Dorian, heavy rains are expected to occur over portions of the Bahamas, Florida, and elsewhere in the southeastern United States this weekend and into the middle of next week. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 22.5N 67.7W 75 KT 85 MPH 12H 30/0600Z 23.8N 68.7W 90 KT 105 MPH 24H 30/1800Z 25.2N 70.4W 100 KT 115 MPH 36H 31/0600Z 26.0N 72.3W 105 KT 120 MPH 48H 31/1800Z 26.5N 74.2W 110 KT 125 MPH 72H 01/1800Z 27.0N 77.7W 115 KT 130 MPH 96H 02/1800Z 27.5N 80.0W 115 KT 130 MPH 120H 03/1800Z 28.1N 81.4W 65 KT 75 MPH...INLAND $$ Forecaster Brown
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