1. Tropical storm conditions are possible across portions of thenorthern Leeward Islands by Friday night, and Tropical Storm Watcheshave been issued for some of these islands. Heavy rainfall islikely across this area beginning late Friday.

2. There is a risk of tropical storm conditions in the VirginIslands and Puerto Rico Friday night and Saturday and TropicalStorm Watches could be required for these islands later today.Interests there should closely monitor the progress of this system.

3. 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 rainfall and wind impacts to portions of Hispaniola,Cuba, the Bahamas, and Florida this weekend and early next week.Interests there should monitor this system's progress and updates tothe 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...
- Saba and St. Eustatius

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 1 to 3 inches of rain with isolated maximum totals of 5 inches through Sunday over the northern Leeward Islands and Puerto Rico.

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

At 500 AM AST (0900 UTC), the center of Tropical Depression Thirteen was located near latitude 15.2 North, longitude 49.8 West. The depression is moving toward the westnorthwest near 21 mph (33 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 and near or north of the Virgin Islands and Puerto Rico on Saturday.

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

The estimated minimum central pressure is 1008 mb (29.77 inches).

There has been little change in the organization of Tropical Depression Thirteen during the past several hours. An area of ragged but persistent convection continues near the estimated center position, and there is some outer banding in the southern semicircle. Dvorak-based satellite intensity estimates have changed little since the last advisory, so the initial intensity remains 30 kt.The initial motion is a somewhat uncertain 295/18. The subtropical ridge to the north of the cyclone is expected to build westward to the north of the Greater Antilles during the next several days, and this should steer the cyclone generally west-northwestward through the forecast period. The track guidance remains in fairly good agreement with this scenario, but there remains a spread between the GFS/UKMET on the south side of the guidance and the Canadian/HMON on the north side. Overall, the envelope has shifted a little to the south since the previous advisory and the new forecast track, which lies just to the north of the consensus models, is also nudged southward. The new track calls for the cyclone to pass near the Leeward Islands in 36-48 h, near or north of Puerto Rico and the Virgin Islands in 48-60 h, and then near or over Hispaniola and the southeastern Bahamas by 72 h.Overall, the environment looks generally favorable for strengthening, with the cyclone expected to encounter light- to moderate shear during forecast period. However, the guidance responds to this environment with a wide range of solutions. The HWRF/HMON forecast the cyclone to intensify into a major hurricane by 120 h. On the other hand, the GFS and ECMWF show the system degenerating into an open wave by 120 h. The UKMET and Canadian models are between these extremes. The weak GFS solution appears to be due to forecast dry air entrainment, which is a possibility as satellite imagery suggests Saharan dust not far from the cyclone. Between these factors and the possibility of land interaction, the low-confidence intensity forecast is changed little from the previous advisory.