1. Tropical storm conditions are possible across portions of thenorthern Leeward Islands, the Virgin Islands, and Puerto RicoFriday night and Saturday, and Tropical Storm Watches have beenissued for some of these islands. Heavy rainfall is likely acrossthis area beginning late Friday and could cause mudslides and flashand urban flooding through Sunday.

2. The details of the long-range track and intensity forecasts aremore uncertain than usual since the system could move over portionsof the Greater Antilles this weekend. However, this system couldbring some storm surge, rainfall and wind impacts to portions ofHispaniola, Cuba, the Bahamas, and Florida this weekend and earlynext week. Interests there should monitor this system's progressand updates to the forecast over the next few days.

CHANGES WITH THIS ADVISORY:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
- Puerto Rico, Vieques and Culebra
- U.S. Virgin Islands
- British Virgin Islands
- Saba and St. Eustatius
- St. Maarten
- St. Martin and St. Barthelemy
- Antigua, Barbuda, St. Kitts, Nevis, and Anguilla

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.

Interests elsewhere in the northern Leeward Islands, the Virgin Islands, and Puerto Rico should monitor the progress of this system, as additional tropical storm watches or warnings will be required for portions of those areas later today.

For storm information specific to your area, please monitor products issued by your national meteorological service.

RAINFALL: The depression is expected to produce 3 to 6 inches of rainfall over Puerto Rico and the Virgin Islands through Sunday. Heavy rainfall associated with the depression may cause mudslides on sensitive slopes and flash and urban flooding through Sunday. Over the northern Leeward Islands, the Dominican Republic, and Haiti, 1 to 3 inches of rain with isolated maximum totals of 5 inches are expected.

WIND: Tropical storm conditions are possible within the watch area late Friday and Saturday.

At 1100 PM AST (0300 UTC), the center of Tropical Depression Thirteen was located near latitude 17.3 North, longitude 56.4 West. The depression is moving toward the westnorthwest near 22 mph (35 km/h), and this motion is expected to continue for the next few days. On the forecast track, the depression is expected to move near or north of the northern Leeward Islands by late Friday, near or north of the Virgin Islands and Puerto Rico on Saturday, and near or north of Hispaniola Saturday night.

Maximum sustained winds remain near 35 mph (55 km/h) with higher gusts. Gradual strengthening is forecast, and the depression is likely to become a tropical storm by the weekend.

The estimated minimum central pressure based on NOAA Hurricane Hunter data is 1008 mb (29.77 inches).

A NOAA Hurricane Hunter aircraft has been flying all around the circulation of the depression this evening, providing valuable information on the low-level structure. The strongest winds are primarily northeast of the center, with an elongated surface circulation and a mid-level swirl near the southern end. While the plane couldn't locate a definite center, there's enough uncertainty and curvature in the plane's wind field data to hold onto the system as 30-kt tropical depression for now. Another mission should be in the area around 1200 UTC. A late-arriving scatterometer pass confirms both the disorganization of the cyclone and the maximum winds.The initial motion continues about the same as before, 290/19. A strong subtropical ridge over the western Atlantic should remain north of the depression during the next few days, steering the cyclone at a fast pace to the west-northwest. After the weekend, the ridge weakens some over the eastern Gulf of Mexico, leading todepression probably turning more to the northwest. The guidance has trended to the south and west after 24 hours tonight, led by the GFS and HWRF models. I'm not inclined to make significant changes since the models are about to ingest the information from the reconnaissance mission, plus the initial disorganization of the center, but the new track is still adjusted slightly to the south and west, north of much of the guidance.The depression should be moving through mixed conditions over the next few days. While the water is very warm, GFS forecasts show that there is significant mid-level shear that could continue to mix in nearby dry air toward the center. This shear will probably relax late this weekend or early next week, but there is very poor agreement on how much shear remains and the timing of this event. In addition, a track any farther south would result in potentially mountainous land interaction, which also increases the intensity forecast uncertainty. No significant changes were made to the previous wind speed forecast, and the overall confidence in both the track and intensity forecasts remain lower than normal.