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| #979409 (Received by flhurricane at: 5:09 PM 25.Aug.2019) TCDAT5 Tropical Storm Dorian Discussion Number 6 NWS National Hurricane Center Miami FL AL052019 500 PM AST Sun Aug 25 2019 While still looking a bit ragged, convection has continued to increase near the center of Dorian since the last advisory, and a just-received SSMI/S overpass shows a convective band wrapped about three-quarters of the way around the center. Various Dvorak-based objective and subjective satellite intensity estimates are in the 35-45 kt range, while recent microwave-based estimates are in the 45-60 kt range. Based on these data, the initial intensity is increased to 45 kt. The initial motion remains 280/12 kt. The subtropical ridge to the north of the cyclone should steer it generally westward to west-northwestward for the next 72 h or so, with a more northwestward motion possible thereafter as Dorian approaches an upper-level low pressure area forecast to be over the north-central Caribbean. The model guidance has not shifted much since the previous advisory. However, some of the normally reliable models are in disagreement. The ECMWF and GFS keep Dorian weaker and farther south, and they are on the left side of the guidance envelope. The HWRF and UKMET have more northerly tracks, and forecast Dorian to pass near Puerto Rico and then near or north of Hispaniola. The various consensus models are between these extremes, and the earlier forecast is now close to them. Thus, the new forecast track is little changed from the previous forecast, and it calls for Dorian to move through the Windward Islands between 36-48 h and cross Hispaniola between 96-120 h. Dorian still appears to be ingesting dry air based on the somewhat ragged convective pattern. This entrainment is expected to continue sporadically for the next 2-3 days, and this could slow intensification despite an environment of light to moderate shear. The intensity guidance is split on how much intensification could occur during this time. The statistical-dynamical SHIPS and LGEM models showing more intensification and forecast Dorian to become a hurricane. On the dynamical side, the latest HWRF run shows little development, and the GFS/ECMWF keep the system weak to the point where it degenerates into a tropical wave before reaching Hispaniola. The intensity forecast follows the general trend of the statistical-dynamical models, but shows less intensification out of respect for the dynamical models. The intensity forecast becomes even lower confidence after 72 h due to uncertainties in how much shear and land that Dorian will encounter. The new forecast calls for Dorian to weaken to a depression due to passage over Hispaniola. However, the large range of possibilities also includes both Dorian going north of Hispaniola and remaining a hurricane and the small cyclone dissipating completely over the island. Key Messages: 1. Dorian is expected to bring tropical storm conditions to portions of the Lesser Antilles, where tropical storm watches and warnings are in effect. Residents in these areas should refer to advice from local government officials and products from their local meteorological service for additional information. 2. Dorian is expected to produce 2 to 4 inches of rainfall across portions of the Lesser Antilles, with isolated amounts as high as 6 inches. 3. While it is too soon to determine the specific time or magnitude of possible direct impacts in Puerto Rico, the Virgin Islands, or Hispaniola interests in those areas should monitor the progress of Dorian. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 11.5N 54.2W 45 KT 50 MPH 12H 26/0600Z 11.8N 55.9W 50 KT 60 MPH 24H 26/1800Z 12.4N 58.2W 55 KT 65 MPH 36H 27/0600Z 13.1N 60.3W 55 KT 65 MPH 48H 27/1800Z 14.1N 62.3W 60 KT 70 MPH 72H 28/1800Z 16.4N 66.4W 65 KT 75 MPH 96H 29/1800Z 18.5N 70.0W 60 KT 70 MPH...INLAND 120H 30/1800Z 20.5N 73.0W 25 KT 30 MPH...OVER WATER $$ Forecaster Beven |
