1. Tropical storm conditions are expected in the U.S. Virgin Islands and Puerto Rico on Wednesday and in portions of the Dominican Republic Wednesday night and Thursday. Hurricane conditions are possible in Puerto Rico and portions of the Dominican Republic.

2. Heavy rainfall over portions of Puerto Rico and the Dominican Republic could produce flash flooding during the next few 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 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 later this week remains higher than usual due to the potential for Dorian's interaction with Puerto Rico and Hispaniola to weaken the storm.

WHAT'S NEW:

A Tropical Storm Warning has been issued for Vieques, Culebra, and the U.S. Virgin Islands. The Tropical Storm Watch has been discontinued for Saba and St. Eustatius.

SUMMARY OF ALERTS:

A Hurricane Watch is in effect for...
- Puerto Rico
- Dominican Republic from Isla Saona to Samana

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

A Tropical Storm Watch is in effect for...
- 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 tropicalstormforce 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. 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:

Martinique to Saint Vincent...3 to 6 inches, isolated 10 inches. Grenadines to Grenada...1 to 3 inches. Guadeloupe to Dominica...1 to 4 inches. Puerto Rico and Dominican Republic...4 to 6 inches, isolated 8 inches. Virgin Islands and Haiti...1 to 3 inches, isolated 4 inches. Bahamas...2 to 4 inches. Florida...3 to 5 inches, isolated 7 inches.

This rainfall may cause life-threatening flash floods.

WIND: [TOP] Tropical storm conditions are expected and hurricane conditions are possible in Puerto Rico on Wednesday and in portions of the Dominican Republic late Wednesday and Thursday. Tropical storm conditions are expected in the U.S. Virgin Islands on Wednesday.

SURF: [TOP] Swells generated by Dorian should gradually subside in the Lesser Antilles by this evening. 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.

At 500 PM AST (2100 UTC), data from the Guadeloupe radar indicate that the center of Tropical Storm Dorian was located near latitude 15.3 North, longitude 62.5 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 will move across the northeastern Caribbean Sea tonight, pass over or near western and central Puerto Rico on Wednesday, and move near or just east of eastern Hispaniola Wednesday night. On Thursday night and Friday, the center of Dorian is forecast to move near or to the east of the Turks and Caicos and the southeastern Bahamas.

Maximum sustained winds remain near 50 mph (85 km/h) with higher gusts. Slow strengthening is forecast during the next 24 hours, and Dorian is forecast to be near hurricane strength when it approaches Puerto Rico on Wednesday. Some weakening is expected after Dorian moves across the higher terrain of Puerto Rico Wednesday night. Dorian is expected to gradually re-strengthen on Thursday and Friday while passing near or to the east of the Turks and Caicos and southeastern Bahamas.

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).

Dorian's convective pattern has continued to fluctuate this afternoon due to some interaction with the Windward and Leeward Islands, but mainly due to intrusions of very dry mid-level air. A 10-mile wide eye feature developed in Martinique and Guadeloupe radar data between 1500-1600 UTC and again between 1700-1800 UTC. But this feature had been short-lived due to erosion of the inner-core convection caused by dry air entrainment, although a recent burst of deep convection has developed near and over the low-level center. Dorian's upper-level outflow has continued to expand and is very symmetrical. The initial intensity has been maintained at 45 kt based on earlier aircraft flight-level and SFMR surface wind data.

Despite the center redeveloping farther north, radar and recon fixes indicate that the motion remains west-northwestward or 300/11 kt. Due to the more northward initial position, the new forecast track was shifted 30-60 n mi northeast of the previous one track through 96 hours. The global models are in good agreement on Dorian moving west-northwestward tonight and then turning northwestward on Wednesday, bringing the cyclone's center near or over the central or western portions of Puerto Rico. After clearing the island by early Thursday, Dorian is forecast to move cyclonically around the eastern portion of a southwestward-moving mid/upper-level low on days 3-5. The evolution of the upper-low and how strong the mid-level ridge to the north builds in behind the low and across the southeastern U.S. will determine when and how sharp Dorian's turn back the west-northwest will occur. The new NHC track is close to a blend consensus models TVCN, HCCA, and FSSE, and brings Dorian near the east-central Florida coast in 120 hours. 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.

Dry air should continue to plague Dorian for the next 24 hours or so, resulting in only slow strengthening. Land interaction with Puerto Rico should significantly weaken the small cyclone, thus the intensities were lowered at 36 and 48 hours. On days 3-5, the models continue to indicate that the upper-level flow pattern and shear conditions should favor strengthening, especially since Dorian will be moving over SSTs greater than 29 deg C and into a moist mid-level environment. The dynamical models such as the GFS, UKMET, and ECMWF are now showing more strengthening than previous runs, but still remain well below the statistical SHIPS and LGEM intensity models, which bring Dorian to category 1 or 2 strength by day 5. The official intensity forecast remains a compromise between the these two extremes, and is close to the HCCA and FSSE consensus models. Given the large spread in the guidance, there remains lower-than- normal confidence in the intensity forecast, especially on days 4 and 5.