1. Isaias will produce heavy rains and potentially life-threatening flash flooding and mudslides across Puerto Rico, the Dominican Republic, northern Haiti, the Turks and Caicos, and the Bahamas. Heavy rains associated with Isaias may begin to affect South Florida Saturday morning, potentially resulting in isolated flash and urban flooding.

2. Tropical storm conditions will continue across portions of the Virgin Islands and Puerto Rico through early afternoon and will spread across portions of the Dominican Republic, Haiti, the Turks and Caicos and the Bahamas later today through Friday, and Tropical Storm Warnings are in effect for these areas. Do not focus on the details of the track forecast, as rainfall and wind hazards will extend far from the center of the system.

3. There is a risk of impacts from winds, heavy rainfall, and storm surge along portions of the U.S. east coast beginning this weekend in Florida and spreading northward to the Carolinas and southern mid-Atlantic states early next week. Due to Isaias interacting with Hispaniola, the details of the track and intensity forecast remain uncertain and it is too soon to determine the magnitude and location of these potential impacts. Interests in these areas should monitor the progress of Isaias and updates to the forecast. Tropical storm or hurricane watches could be issued for portions of South Florida later today.

CHANGES WITH THIS ADVISORY:

The Tropical Storm Warning for Puerto Rico, Vieques, Culebra, and the U.S. Virgin Islands has been discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
- Dominican Republic entire southern and northern coastlines
- North coast of Haiti from Le Mole St Nicholas eastward to the northern border with the Dominican Republic
- Turks and Caicos Islands
- Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, and the Ragged Islands
- Central Bahamas, including Cat Island, the Exumas, Long Island, Rum Cay, and San Salvador

A Tropical Storm Watch is in effect for...
- Northwestern Bahamas including Andros Island, New Providence, Eleuthera, Abacos Islands, Berry Islands, Grand Bahamas Island, and Bimini

Interests in Cuba and the Florida peninsula should monitor the progress of this system. Watches may be required for a portion of the Florida peninsula later today.

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.

Key messages for Isaias can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml.

WIND: Tropical storm conditions will continue to spread across portions of the Dominican Republic and Haiti within the warning area, and are expected to spread over the southeastern Bahamas and Turks and Caicos later today. Tropical storm conditions are expected in the Central Bahamas beginning Friday morning and are possible in the northwestern Bahamas beginning late Friday.

RAINFALL: Isaias is expected to produce the following rain accumulations:

Puerto Rico, Dominican Republic and northern Haiti: 4 to 8 inches, with isolated maximum totals of 10 inches.

Bahamas, Turks and Caicos: 4 to 8 inches.

Cuba: 1 to 2 inches, with isolated maximum totals of 4 inches.

These rainfall amounts will lead to lifethreatening flash flooding and mudslides, as well as river flooding. Urban and small stream flooding is expected for the U.S. Virgin Islands, eastern and southwestern Puerto Rico, and Hispaniola.

Heavy rains associated with Isaias may begin to affect South Florida Saturday morning. This rain could result in isolated flash and urban flooding, especially in lowlying and poorly drained areas.

SURF: Swells generated by Isaias are affecting portions of the Leeward Islands, the Virgin Islands, Puerto Rico, the Dominican Republic, the Turks and Caicos Islands and the southeastern Bahamas. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 200 PM AST (1800 UTC), the center of Tropical Storm Isaias was located near latitude 18.9 North, longitude 69.8 West. Isaias is moving toward the northwest near 20 mph (31 km/h), and a west northwestward to northwestward motion with some decrease in forward speed is expected over the next couple of days. On the forecast track, the center of Isaias will continue to move over Hispaniola through this evening, and be near the Southeastern Bahamas by late tonight or early Friday. Isaias is forecast to be near the Central Bahamas Friday night and move near or over the Northwest Bahamas or South Florida on Saturday.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts. Some slight weakening is possible as Isaias continues to move over Hispaniola today. Restrengthening is forecast on Friday and Friday night.

Tropicalstormforce winds extend outward up to 310 miles (500 km) primarily to the north of the center. A weather station at Punta Cana near the eastern tip of the Dominican Republic reported sustained winds of 39 mph (63 km/h) with a gust to 52 mph (83 km/h) within the past couple of hours.

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

The satellite presentation of Isaias has improved over the past 24 hours with a concentrated area of deep convection occurring near and to the northeast of the low-level center. Radar imagery from Puerto Rico has shown a mid-level circulation that moved over the Mona passage and is now along the northern coast of Hispaniola. Surface observations and data from an Air Force Reserve reconnaissance aircraft, however, continue to place the center near the southeastern coast of Hispaniola. It is possible that a new center will re-form along the northern coast of Hispaniola as the system interacts with high terrain of that island later today or tonight. The initial intensity remains 50 kt, and is based on the earlier Doppler radar data and observations along the southern coast of Puerto Rico.

Isaias is moving northwestward or 310/16 kt. A high pressure ridge over the western Atlantic should steer Isaias on a west- northwestward to northwestward heading over the next couple of days, but the likelihood of a center re-formation during the next 12-18 hours means that some adjustments to the track and motion are possible. By late Friday, a mid-latitude trough moving into the east-central United States is expected to weaken the western portion of the ridge. This pattern should cause the cyclone to turn northwestward to north-northwestward on Saturday when it is near the northwestern Bahamas and South Florida. As the trough slides eastward over the United States, this should steer Isaias northward and northeastward early next week. Although the bulk of the track guidance agrees on this overall scenario, the confidence in the track forecast remains lower than usual due to the expected land interaction and possible center reformation in the short term. The new NHC track forecast is a blend of the HFIP corrected consensus and the TCVA multi-model consensus, and is similar to the previous advisory.

The intensity forecast remains challenging. The structure of the storm is likely to be disrupted by its passage near or over Hispaniola today, and some weakening is likely. Once the system moves away from the Greater Antilles gradual strengthening is anticipated. The global models and the SHIPS guidance suggest that Isaias will encounter an area of moderate southwesterly shear over the weekend, and the NHC intensity forecast is again leveled off at that time. There are models that continue to suggest Isaias could become a hurricane when it is near the U.S., but given the continued uncertainty, the NHC intensity forecast remains near the intensity conse