1. The system is forecast to become a tropical storm as it moves over the northeastern Caribbean Sea tonight. Tropical storm conditions are expected in portions of the U.S. Virgin Islands and Puerto Rico tonight, and are expected to begin in the Dominican Republic by Wednesday. Tropical storm conditions are possible in northern Haiti and the southeastern Bahamas by late Wednesday.

2. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and the potential for mudslides across the U.S. Virgin Islands, Puerto Rico, and the Dominican Republic. The greatest threat for flooding impacts will be across the eastern and southern portions of Puerto Rico.

3. There is a risk of wind and rainfall impacts elsewhere in portions of Hispaniola, the Bahamas, and Cuba during the next several days, although the forecast is more uncertain than usual since the system is still in its formative stage. Interests in these areas should monitor the system's progress and updates to the forecast.

4. There is a risk of wind and rainfall impacts in portions of Florida beginning Friday through the weekend. However, given the uncertainty in the long-range forecast it is too soon to determine the timing, location, and magnitude of any potential impacts. Interests in Florida should monitor updates to the forecast.

CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
- Puerto Rico, including Culebra and Vieques
- U.S. Virgin Islands
- Dominican Republic on the south coast from Punta Palenque eastward and on the north coast from Cabo Frances Viejo eastward

A Tropical Storm Watch is in effect for...
- Dominican Republic on the north coast from Cabo Frances Viejo to the Dominican Republic/Haiti border
- Haiti from the northern border with the Dominican Republic to Gonaives
- Turks and Caicos Islands
- Southeastern Bahamas

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.

Interests elsewhere in Haiti and the Bahamas, as well as in eastern and central Cuba, should monitor the progress of this system.

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 Potential Tropical Cyclone Six can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT1, WMO header WTNT41 KNHC and on the web at www.hurricanes.gov/graphics_at1.shtml?key_messages.

RAINFALL: The system is expected to produce the following rainfall amounts:

Over the Leeward Islands, Virgin Islands, Puerto Rico, and the Dominican Republic...2 to 4 inches, with isolated maximum totals of 6 inches. Heavy rainfall could lead to flash, urban, and small stream flooding, along with possible rapid river rises and the potential for mudslides across the U.S. Virgin Islands, Puerto Rico, and the Dominican Republic.

Over Haiti, the Turks and Caicos, eastern Bahamas, and eastern Cuba...1 to 3 inches with isolated maximum totals of 5 inches.

WIND: Tropical storm conditions are expected in the warning areas in the U.S. Virgin Islands and Puerto Rico during the next several hours, and in the warning area in the Dominican Republic by early Wednesday. Tropical storm conditions are possible elsewhere along the northern coasts of the Dominican Republic, northern Haiti, the Turks and Caicos, and the southeastern Bahamas beginning late Wednesday.

SURF: Swells generated by the disturbance are affecting portions of the Leeward Islands. These swells are expected to spread across the U.S. Virgin Islands and Puerto Rico today and reach portions of Hispaniola on Wednesday, where they could cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 800 PM AST (0000 UTC), the disturbance was located by an Air Force Reserve reconnaissance aircraft and Doppler radar data from San Juan near latitude 17.6 North, longitude 66.1 West. The system is moving toward the west near 17 mph (28 km/h) and this general motion is expected to continue tonight. A turn back toward the westnorthwest is forecast to occur early Wednesday, with a westnorthwestward motion continuing during the next few days. On the forecast track, the disturbance is expected to pass near the southern coast of Puerto Rico tonight and early Wednesday, be near or over Hispaniola on Wednesday, and be near the southeastern Bahamas and the Turks and Caicos Islands on Thursday.

Data from the aircraft and surface observations indicate that maximum sustained winds have increased to near 40 mph (65 km/h) with higher gusts. Gradual strengthening is forecast during the next day or so and the disturbance is expected to become a tropical storm later tonight. Some weakening is likely while the system interacts with Hispaniola on Wednesday. * Formation chance through 48 hours...high...90 percent. * Formation chance through 5 days...high...90 percent. The estimated minimum central pressure based on data from the aircraft and earlier surface observations is 1009 mb (29.80 inches). Tropicalstormforce winds extend outward up to 40 miles (65 km), mainly northeast of the center. During the past few hours, a sustained wind of 38 mph (61 km/h) and a gust to 49 mph (79 km/h) were measured by a Weatherflow observing station at Sandy Point on the western end of St. Croix. A wind gust to 47 mph (76 km/h) was reported near Yabucoa in southeastern Puerto Rico.

Satellite imagery this afternoon continues to show that the disturbance has an organized convective pattern, with satellite intensity estimates of tropical-storm strength from SAB and TAFB. However, the circulation still appears to not be well defined, with the San Juan WSR-88D Doppler radar showing multiple mid-level centers and several convective cells with small-scale rotation. Based on this, the system will not be upgraded to a tropical cyclone at this time. The initial intensity remains 30 kt based on mainly on continuity from earlier data. It should be noted that squalls with short-lived winds to tropical-storm force have been reported in bands over the northern Leeward Islands.

The initial motion remains west-northwestward or 295/17 kt. A strong low- to mid-level ridge to the north should steer the system generally west-northwestward for the next 72 h with some decrease in forward speed after 24 h. Beyond that time, a turn toward the northwest with an further decrease in forward speed is likely while the system moves near the western periphery of the ridge. There has been some increase in the spread of the track guidance from 72-120 h, with the GFS shifting to the right and the other models not changing very much. The new NHC forecast track has only minor changes from the previous one and lies near the various consensus models.

Conditions continue to appear favorable for strengthening before the system reaches Hispaniola in about 18 h, although there may be dry air entraining into the system in the southeastern quadrant. The intensity forecast will follow the previous prediction in calling for the disturbance to become a tropical storm before landfall, followed by weakening to a depression. From 24-60 h, the models have come into better agreement that the system will encounter westerly vertical wind shear, and based on that and the possibility of land interaction the intensity forecast shows little re-intensification during that time. After 60 h, the models still disagree on the evolution of the upper-level winds near the system, but they are in better agreement that conditions over the eastern Gulf will become more conducive for development. Thus, the intensity forecast calls for intensification during that time. The new intensity forecast is almost the same as the previous one.