| Track: https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/024545.shtml?cone#contents Tropical Storm Dorian Discussion Number 12 NWS National Hurricane Center Miami FL AL052019 500 AM AST Tue Aug 27 2019 Dorian passed over Barbados a few hours ago and it is now very near the Windward Islands. Data from the Air Force Hurricane Hunters earlier this morning suggest that the storm has held steady in intensity with a blend of the flight level and SFMR winds supporting a wind speed of 45 kt. The Caribbean composite radar data show that Dorian remains a very compact system and that it still lacks a well-defined inner core. Dry air in the mid-levels of the atmosphere around Dorian has been causing the storm to remain in a fairly steady state during the past day or so despite relatively low wind shear conditions and warm SSTs. The models show this dry air persisting in the vicinity of the system while it tracks across the Caribbean during the next day or two, so it seems likely that Dorian will continue to only gradually intensify during that time. When Dorian nears Hispaniola in 36 to 48 hours, there will likely be some increase in wind shear and those less favorable winds aloft and the interaction with the landmasses of Puerto Rico and Hispaniola should cause considerable weakening. Once the system moves north of the Greater Antilles, the environmental conditions become more favorable for intensification, and most of the intensity guidance responds by showing an increase in winds. However, there remains considerable uncertainty for this part of the forecast because the future intensity of Dorian will be quite dependent on how much land interaction there is with the mountainous island of Hispaniola. The NHC intensity forecast lies near the upper end of the guidance in the short term, while the system is over the Caribbean Sea, but near the middle of the guidance envelope after that. The storm is moving west-northwestward at 11 kt steered by a subtropical ridge to the north. This general motion should continue for another 12 to 24 hours taking Dorian across the eastern Caribbean Sea. After that time, a slight turn to the northwest is likely when the cyclone nears the eastern portion of a cut off mid- to upper-level low and moves toward a weakness in the ridge. This should take Dorian across the Dominican Republic and the Mona Passage and over the Bahamas in the 3 to 4 day time period. A ridge is likely to rebuild to the north of Dorian when it is forecast to be over the Bahamas and that could cause it to turn slightly to the left by the end of the forecast period. The new NHC track forecast is largely unchanged while Dorian is in the Caribbean, but it has been shifted slightly to the north thereafter. Users are reminded not to focus on the details of the extended track forecast as the average 5-day track error is around 200 miles. Key Messages: 1. Dorian is expected to bring tropical storm conditions to portions of the Lesser Antilles during the next several hours, where tropical storm watches and warnings are in effect. Rainfall of 3 to 6 inches is expected from Martinique to St. Vincent with isolated totals as high as 10 inches possible. 2. Tropical storm conditions are expected and hurricane conditions are possible in Puerto Rico on Wednesday, where a tropical storm warning and hurricane watch have been issued. Rainfall of 2 to 4 inches with maximum totals of 6 inches are possible across Puerto Rico and St. Croix. 3. Hurricane and Tropical Storm Watches have been issued for portions of the Dominican Republic. 4. While uncertainty remains 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 27/0900Z 13.5N 60.7W 45 KT 50 MPH 12H 27/1800Z 14.4N 62.3W 50 KT 60 MPH 24H 28/0600Z 15.7N 64.5W 55 KT 65 MPH 36H 28/1800Z 17.0N 66.5W 60 KT 70 MPH 48H 29/0600Z 18.5N 68.2W 60 KT 70 MPH 72H 30/0600Z 21.7N 71.4W 50 KT 60 MPH 96H 31/0600Z 24.7N 75.1W 60 KT 70 MPH 120H 01/0600Z 27.1N 79.6W 60 KT 70 MPH $$ Forecaster Cangialosi Tropical Storm Dorian Advisory Number 12 NWS National Hurricane Center Miami FL AL052019 500 AM AST Tue Aug 27 2019 ...DORIAN MOVING THROUGH THE WINDWARD ISLANDS WITH TROPICAL STORM FORCE WINDS... ...NEW WATCHES AND WARNINGS ISSUED FOR PUERTO RICO AND THE DOMINICAN REPUBLIC... SUMMARY OF 500 AM AST...0900 UTC...INFORMATION ---------------------------------------------- LOCATION...13.5N 60.7W ABOUT 30 MI...45 KM SE OF ST. LUCIA MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...WNW OR 290 DEGREES AT 13 MPH...20 KM/H MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: A Tropical Storm Warning and Hurricane Watch has been issued for Puerto Rico. The government of the Dominican Republic has issued a Hurricane Watch from Isla Saona to Samana. The government of the Dominican Republic has also issued a Tropical Storm Watch on the south coast of the island from Isla Saona to Punta Palenque and on the north coast from Samana to Puerto Plata. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Watch is in effect for... Puerto Rico Dominican Republic from Isla Saona to Samana A Tropical Storm Warning is in effect for... Martinique St. Lucia St. Vincent and the Grenadines Puerto Rico A Tropical Storm Watch is in effect for... Dominica Grenada and its dependencies Saba and St. Eustatius Dominican Republic from Isla Saona to Punta Palenque Dominican Republic from Samana to Puerto Plata A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Interests in the Virgin Islands should monitor the progress of Dorian. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 500 AM AST (0900 UTC), the center of Tropical Storm Dorian was located near latitude 13.5 North, longitude 60.7 West. Dorian is moving toward the west-northwest near 13 mph (20 km/h) and this motion is expected to continue through tonight, followed by a turn toward the northwest on Wednesday. On the forecast track, the center of Dorian is expected to move across the Windward Islands and into the eastern Caribbean Sea during the next several hours. Dorian is forecast to pass near or south of Puerto Rico on Wednesday, move near or over eastern Hispaniola Wednesday night, and move north of Hispaniola on Thursday. Maximum sustained winds remain near 50 mph (85 km/h) with higher gusts. Slow strengthening is forecast during the next 48 hours, and Dorian is forecast to be near hurricane strength when it moves close to Puerto Rico and eastern Hispaniola. Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center. The estimated minimum central pressure is 1005 mb (29.68 inches). HAZARDS AFFECTING LAND ---------------------- Rainfall: Dorian is expected to produce the following rain accumulations through Thursday: Barbados...Additional rainfall up to 1 inch, storm total around 6 inches. Windward Islands from Martinique to Saint Vincent...3 to 6 inches, isolated 10 inches. Grenadines to Grenada...1 to 3 inches. Leeward Islands from Guadeloupe to Dominica...1 to 4 inches. Puerto Rico and Saint Croix...2 to 4 inches, isolated 6 inches. Dominican Republic...2 to 4 inches, isolated 6 inches. This rainfall may cause life-threatening flash floods, especially where totals exceed 4 inches. WIND: Tropical storm conditions are occurring in portions of the tropical storm warning area in the Lesser Antilles and these conditions are expected to continue during the next several hours. Tropical storm conditions are expected and hurricane conditions are possible in Puerto Rico on Wednesday. Hurricane conditions are possible in the hurricane watch area in the Dominican Republic by late Wednesday and tropical storm conditions are possible in the tropical storm watch area beginning late Wednesday. Tropical storm conditions are possible within the tropical storm watch area in the Lesser Antilles today. SURF: Swells generated by Dorian are affecting portions of the Lesser Antilles and they should continue during the next several hours. Swells are expected to increase along the southern coasts of Puerto Rico and Hispaniola on Wednesday and they could cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 800 AM AST. Next complete advisory at 1100 AM AST. $$ Forecaster Cangialosi GFS: https://www.tropicaltidbits.com/analysis/models/?model=gfs®ion=watl&pkg=mslp_uv850 Euro: https://www.tropicaltidbits.com/analysis/models/?model=ecmwf®ion=watl&pkg=mslp_uv850 Storm specific models: http://hurricanecity.com/models/models.cgi?basin=al&year=2019&storm=05&display=google_map&latestrun=1 |