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| #979541 (Received by flhurricane at: 5:06 PM 26.Aug.2019) TCDAT5 Tropical Storm Dorian Discussion Number 10 NWS National Hurricane Center Miami FL AL052019 500 PM AST Mon Aug 26 2019 Dorian`s convective pattern has waxed and waned this afternoon due to intrusions of dry mid-level air while the upper-level outflow pattern has continued to expand and become more symmetrical. Although the inner-core convection has decreased recently, a recent burst of strong convection with cloud tops colder than -80C has redeveloped just north of the low-level center. The initial intensity remains at 50 kt based on a an average of satellite intensity estimates ranging from 45 kt to 61 kt from TAFB, SAB, and UW-CIMSS SATCON and ADT. An Air Force Reserve reconnaissance aircraft is scheduled to investigate Dorian by 0000 UTC this evening, and will provide a better estimate of the cyclone`s intensity. The initial motion is west-northwestward or 290/12 kt. There is no significant change to the previous forecast track or reasoning. The latest NHC model guidance remains in very agreement that Dorian will move west-northwestward across the central Lesser Antilles tonight and into the northeastern Caribbean Sea on Tuesday as the cyclone moves around the edge of the Bermuda-Azores ridge located well to the north. On Wednesday, Dorian should turn northwestward into a small weakness in the ridge, allowing the tropical cyclone to pass near or between western Puerto Rico and the eastern Dominican Republic. By late Thursday and Friday, the ridge is forecast to build back in as an upper-level trough lifts out to the north, causing Dorian to turn back toward the west-northwest in the vicinity of the central Bahamas. The new official forecast track is just an extension of the previous one since the latest model guidance, especially the consensus models, are tightly packed around the previous track forecast. The intensity forecast remains something of an enigma. The majority of the environmental conditions support at least steady strengthening, with the main hindrance being the very dry mid-level air surrounding the cyclone and occasionally being entrained into Dorian`s inner-core region. The small but robust circulation should continue mix out the brief dry air intrusions, but when an eyewall will form is still uncertain. Given that Dorian will be moving into the convective maximum period later tonight, the intensity forecast still calls for Dorian be near hurricane strength when it passes through the Windward Islands. Interaction with Hispaniola and possibly Puerto Rico should result in some weakening in 72-96 hours, followed by restrengthening on days 4 and 5 when Dorian will be moving over the very warm waters in the Bahamas in low shear conditions. Most of the global models along with the statistical- dynamical SHIPS and LGEM intensity models are now showing pronounced strengthening while Dorian is moving near or through the Bahamas, so the official forecast shows a significant change to the previous one at 96 and 120 hours. However, confidence in the intensity forecast at days 4 and 5 is very low given the uncertainty about how much of Dorian`s core will interact with Hispaniola. Key Messages: 1. Dorian is expected to bring tropical storm conditions to portions of the Lesser Antilles tonight and Tuesday, where tropical storm watches and warnings are in effect. Hurricane conditions are possible in St. Lucia, where a Hurricane Watch is in effect. Rainfall of 3 to 8 inches is expected from Martinique to St. Vincent, including Barbados, with isolated totals as high as 10 inches possible. 2. Tropical storm conditions are possible in Puerto Rico on Wednesday, where a tropical storm watch has been issued. Rainfall of 2 to 4 inches with maximum totals of 6 inches are possible across Puerto Rico and St. Croix. 3. Watches will likely be issued for portions of Hispaniola tonight or Tuesday, as the threat of wind and rain impacts continues to increase. 4. While uncertainty is high, wind and rain impacts are possible in the Bahamas and Florida later this week and this weekend. Residents in these areas should monitor the progress of Dorian and ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 12.7N 58.8W 50 KT 60 MPH 12H 27/0600Z 13.4N 60.5W 55 KT 65 MPH 24H 27/1800Z 14.5N 62.6W 60 KT 70 MPH 36H 28/0600Z 15.7N 64.6W 65 KT 75 MPH 48H 28/1800Z 17.1N 66.7W 70 KT 80 MPH 72H 29/1800Z 20.1N 70.2W 50 KT 60 MPH 96H 30/1800Z 23.0N 73.8W 55 KT 65 MPH 120H 31/1800Z 25.5N 78.0W 60 KT 70 MPH $$ Forecaster Stewart |
