1. Tropical storm conditions are expected in the U.S. and British Virgin Islands and Puerto Rico today, and are possible in portions of the Dominican Republic tonight and Thursday. Hurricane conditions are possible in Puerto Rico and the U.S. Virgin Islands today.

2. Heavy rainfall over portions of Puerto Rico and the U.S. and British Virgin Islands could produce flash flooding during the next couple of days. Heavy rains are expected to occur over portions of the Bahamas and Florida later this week and into early next week.

3. The threat of tropical storm or hurricane conditions, along with storm surge, in the northwestern Bahamas and along portions of the Florida east coast have increased. Residents in these areas should monitor the progress of Dorian and ensure that they have their hurricane plan in place.

4. Uncertainty in the intensity forecast late this week remains higher than usual due to a large spread in the model guidance.

WHAT'S NEW:

A Hurricane Watch has been issued for Vieques, Culebra, and the U.S. Virgin Islands.

SUMMARY OF ALERTS:

A Hurricane Watch is in effect for...
- Puerto Rico
- Vieques
- Culebra
- U.S. Virgin Islands

A Tropical Storm Warning is in effect for...
- Puerto Rico
- Vieques
- Culebra
- U.S. Virgin Islands
- British Virgin Islands
- Dominican Republic from Isla Saona to Samana

A Tropical Storm Watch is in effect for...
- Dominican Republic from Isla Saona to Puerto Plata

A Hurricane Watch means that hurricane conditions are possible within the watch area, in this case within 24 hours.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within 24 hours.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, in this case within 24 hours. 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.

RAINFALL: Dorian is expected to produce the following rainfall accumulations:

Western Leeward Islands from Guadeloupe to St. Kitts to Anguilla...1 to 4 inches. Southern and Eastern Puerto Rico and the U.S. and British Virgin Islands...4 to 6 inches, isolated 10 inches. Northwestern Puerto Rico...1 to 4 inches. Haiti and Dominican Republic...1 to 3 inches Southern Bahamas...1 to 4 inches. Northern Bahamas...3 to 6 inches. Florida Peninsula...4 to 8 inches, isolated 10 inches.

This rainfall may cause life-threatening flash floods.

WIND: [TOP] Tropical storm conditions are expected and hurricane conditions are possible in Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands today. Tropical storm conditions are expected in the British Virgin Islands today. Tropical storm conditions are possible in portions of the Dominican Republic tonight and Thursday.

SURF: [TOP] Swells generated by Dorian are gradually subsiding in the Lesser Antilles. Swells are expected to increase later this morning across the U.S. and British Virgin Islands and along the southern coasts of Puerto Rico and Hispaniola, and they could cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

At 500 AM AST (0900 UTC), the center of Tropical Storm Dorian was located near latitude 16.8 North, longitude 63.9 West. Dorian is moving toward the northwest near 13 mph (20 km/h), and this general motion is expected to continue during the next few days. On the forecast track, the center of Dorian will pass over or near the U.S. and British Virgin Islands and Puerto Rico later today. Dorian is then forecast to move to the east of the Turks and Caicos and the southeastern Bahamas on Thursday, and near or to the east of the central and northwestern Bahamas on Friday and Saturday.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts. Some strengthening is expected today, and Dorian is forecast to be near hurricane strength when it approaches the Virgin Islands and Puerto Rico. Although weakening is possible after Dorian moves across Puerto Rico and the Virgin Islands, the storm is forecast to strengthen late this week and this weekend while passing near or to the east of the Turks and Caicos and the Bahamas.

Tropical-storm-force winds extend outward up to 60 miles (95 km) from the center.

The estimated minimum central pressure is 1003 mb (29.62 inches).

Satellite images and Doppler radar data from Puerto Rico indicate that Dorian is becoming better organized with banding features now more established on the north side of the circulation. The flight-level and SFMR winds from the Air Force Hurricane Hunters were a little higher in the most recent passes through the storm, and a blend of that data supports an initial intensity of about 50 kt. The Hurricane Hunters also reported that Dorian has developed a partial eyewall and that the minimum pressure has dropped to 1003 mb. A combination of the reconnaissance data and recent ASCAT passes were used to modify the initial wind radii, and it confirms that Dorian remains a compact and asymmetric tropical storm.

Dorian is moving northwestward at 11 kt toward a weakness in the ridge caused by a cut off mid- to upper-level low to the north of Hispaniola. This motion should continue for the next few days, taking Dorian across the Virgin Islands or the eastern portion of Puerto Rico later today and to the east of the Bahamas on Thursday and Friday. By late in the week, the steering pattern is expected to change as the models show a ridge building over the western Atlantic. The flow between the ridge and the aforementioned mid- to upper-level low should cause Dorian to turn west-northwestward and approach the southeast U.S. coast this weekend. The new NHC track forecast is adjusted a little to the right at most forecast times trending toward the latest consensus aids. However, there has been considerable run-to-run variability among the models so confidence in the long term track remains low. In addition, users are reminded not to focus on the exact forecast points as the average 5-day track error is around 200 miles.

Some additional slow strengthening seems likely today before Dorian reaches Puerto Rico and the Virgin Islands. The land interaction could end the strengthening trend or even cause some temporary weakening, however, environmental conditions favor intensification after the storm pulls northward into the southwestern Atlantic. Nearly all of the intensity models show Dorian becoming a hurricane in about 2 days, with additional strengthening beyond that time. The NHC intensity forecast is increased from the previous one, especially at the longer forecast times, to be in better agreement with the latest models. This forecast, however, is still on the lower end of the guidance envelope, so additional upward adjustments could be needed if the guidance trends persists. It is also worth noting that the global models show Dorian increasing in size by the time it nears the southeast U.S.