Tropical Storm Dorian Strengthening. Hurricane Warnings In Effect.

At 11:00 AM, the center of Tropical Storm Dorian was located near latitude 17.5 North, longitude 64.5 West. Dorian is moving toward the northwest near 13 MPH (20 KM/H), and this motion is expected to continue for the next day or two. On this track, Dorian should move near the U.S. and the British Virgin Islands and then continue over the open Atlantic well east of the southeastern Bahamas.

Maximum sustained winds have increased to near 70 MPH (110 KM/H) with higher gusts to 150 KM/H. Dorian is forecast to become a hurricane later today and continue strengthening during the next few days over the Atlantic waters.

Tropical-storm-force winds extend outward up to 130 kilometers, primarily to the east of the center. An Air Force plane just estimated a minimum central pressure of 999 millibars.

Tropical Storm Dorian’s Key Messages

Hurricane conditions are expected in the U.S. and the British Virgin Islands, Culebra, and Vieques today. Tropical storm conditions are expected in Puerto Rico today with hurricane conditions possible.

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

The risk of dangerous storm surge and hurricane-force winds is increasing in the central and northwestern Bahamas and along the Florida east coast, although it is too soon to determine where these hazards will occur. Residents in these areas should ensure that they have their hurricane plan in place and not focus on the exact forecast track of Dorian’s center.

This system poses no further threat to the Windward Islands, including Trinidad and Tobago.

Watches & Warnings (11:00 AM Wednesday)

Hurricane Warning: Vieques and Culebra, the U.S. Virgin Islands and the British Virgin Islands.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area, in this case within the next 12 hours.

Hurricane Watch: Puerto Rico.

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.

Tropical Storm Warning: Puerto Rico.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. Note that this warning only considers tropical-storm-force winds and not associated rainfall, storm surge, and other hazards.

Tropical Storm Watch: The Dominican Republic from Isla Saona to Samana.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Note that this warning only considers tropical-storm-force winds and not associated rainfall, storm surge, and other hazards.

Tropical Storm Dorian’s Forecast Track

Fixes from the reconnaissance plane indicate that Tropical Storm Dorian has been moving toward the northwest or 315 degrees at 11 kt. The cyclone is heading toward a weakness in the Atlantic subtropical ridge, and this motion should continue for the next 2 to 3 days.

On its forecast path, after traversing the Greater Antilles over the next 12-24 hours, it will likely remain east and then north of the Turks and Caicos Islands, as well as much of the Bahamas until late Saturday.

However, after that time, all global models build a robust ridge over the western Atlantic, and this flow pattern should force Dorian to turn more to the west-northwest toward Florida and the southeast coast of the United States.

All indications are that by this Labor Day weekend, a powerful hurricane will be near the Florida or southeastern coast of the United States.

The new NHC track forecast is not significantly different from the previous one, and it very closely follows the multi-model consensus TVCA and the HCCA. Users are reminded not to focus on the exact forecast track, as the average 5-day track error is around 200 miles.

Forecast Intensity

Satellite and radar images indicate that the cloud pattern has become better organized during the past several hours. This was confirmed by data from an Air Force reconnaissance plane currently investigating Dorian, which reported a flight-level wind of 72 kt (133 KM/H) and a peak SFMR value of 60 kt (110 KM/H).

The estimated central pressure was 999 millibars in the last fix. On this basis, the initial intensity has been adjusted upward to 60 kt (110 KM/H). Only a slow strengthening is anticipated today while Dorian is moving through the U.S. and the British Virgin Islands.

However, once the cyclone reaches the western Atlantic well east of the Bahamas, it will encounter a favorable environment of low shear and warm waters, resulting in a more marked intensification.

The NHC forecast is more aggressive than the previous one and brings Tropical Storm Dorian to category 3 intensity by the end of the period. This forecast very closely follows the intensity consensus, the HCCA model, and the SHIPS guidance.

Hazards Affecting Land

Rainfall: Tropical Storm Dorian is expected to produce the following rainfall accumulations:

  • Northern Leeward Islands – 1 to 3 inches (25-75 mm)
  • Eastern Puerto Rico, the Virgin Islands, and the northwest
  • Bahamas – 4 to 6 inches (100-150 mm), isolated 10 inches (250 mm)
  • Western Puerto Rico and the central Bahamas – 2 to 4 inches (50-100 mm)
  • Coastal sections of the Southeast United States – 4 to 8 inches (100-200 mm), isolated 10 inches (250 mm)

This rainfall may cause life-threatening flash floods.

Wind: Hurricane conditions are expected over Vieques, Culebra, and the U.S. and the British Virgin Islands today. Tropical storm conditions are expected in Puerto Rico this afternoon and tonight. Tropical storm conditions are still possible in portions of the Dominican Republic tonight and Thursday but are becoming less likely to occur.

Wind speeds atop and on the windward sides of hills and mountains are often up to 30 percent stronger than the near-surface winds indicated in this advisory, and in some elevated locations could be even greater.

Seas: Swells are expected to increase later today across the U.S. and the 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.

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