1. Potential Tropical Cyclone Nine will produce heavy rains and potentially life-threatening flash flooding and mudslides across the northern Leeward Islands, the Virgin Islands, Puerto Rico, and the Dominican Republic.

2. Tropical storm conditions are likely across portions of the Leeward Islands, the Virgin Islands, Puerto Rico, and portions of the Dominican Republic beginning Wednesday and spreading westward through Thursday. 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. The details of the long-range track and intensity forecasts are more uncertain than usual since the system does not have a well-defined center and it could move over portions of the Greater Antilles later this week. However, this system could bring some rainfall and wind impacts to portions of Hispaniola, Cuba, the Bahamas, and Florida by the end of the week. Interests there should monitor its progress and updates to the forecast over the next few days.

CHANGES WITH THIS ADVISORY:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
- Puerto Rico, Vieques, Culebra
- U.S. Virgin Islands
- British Virgin Islands
- Antigua, Barbuda, Montserrat, St. Kitts, Nevis, and Anguilla
- Guadeloupe, Martinique, St. Martin, and St. Barthelemy
- Saba and St. Eustatius
- St. Maarten
- Dominica
- Dominican Republic from Cabo Caucedo eastward to Cabo Engano and then westward along the northern coast to the Dominican Republic/Haiti border

A Tropical Storm Watch is in effect for...
- Dominican Republic from the southern Haiti border eastward to Cabo Caucedo
- Turks and Caicos Islands

Interests elsewhere in the southeast and central Bahamas should monitor the progress of this system.

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 Potential Tropical Cyclone Nine 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 are expected to reach the Leeward Islands during the next few hours, and spread across the U.S. and British Virgin Islands and Puerto Rico this afternoon through Thursday morning. These conditions are forecast to reach portions of the Dominican Republic within the warning area early Thursday. Tropical storm conditions are possible in the watch areas on Thursday.

RAINFALL: The potential tropical cyclone is expected to produce the following rain accumulations:

Across the northern Leeward Islands, British and U.S. Virgin Islands: 3 to 6 inches.

Across Puerto Rico: 3 to 6 inches, with isolated maximum totals of 10 inches.

Across the Dominican Republic: 3 to 6 inches, with isolated maximum totals of 8 inches.

These rainfall amounts could lead to life threatening flash flooding and mudslides, as well as potential riverine flooding.

Rainfall is also expected in the following locations:

Across the Windward Islands: 1 to 3 inches.

SURF: Swells generated by Potential Tropical Cyclone Nine will be affecting portions of the Leeward Islands, the Virgin Islands and Puerto Rico during the next day or two. These dangerous conditions are forecast to reach the north coast of the Dominican Republic and the Turks and Caicos Islands and the southeastern Bahamas on Thursday. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

At 200 AM AST (0600 UTC), the disturbance was centered near latitude 14.9 North, longitude 60.3 West. The system is moving toward the westnorthwest near 25 mph (41 km/h), and this general motion with some slight reduction in forward speed is expected over the next few days. On the forecast track, the center will move through the southern Leeward Islands during the next few hours, near or over the Virgin Islands and Puerto Rico Wednesday night, and near or over Hispaniola on Thursday.

Maximum sustained winds are near 45 mph (75 km/h) with higher gusts. Some strengthening is expected during the next 48 hours, and the system is forecast to become a tropical storm today.

Environmental conditions are expected to be conducive for additional development, and a tropical storm is forecast to form later today. * Formation chance through 48 hours...high...90 percent * Formation chance through 5 days...high...90 percent Tropicalstormforce winds extend outward up to 230 miles (370 km), north of the center.

The estimated minimum central pressure based on Air Force Reserve Hurricane data is 1006 mb (29.71 inches).

Earlier wind data from an Air Force reconnaissance aircraft and a recent 0038Z ASCAT-A overpass indicate that the disturbance has not become any better organized since the previous advisory. There were indications of a circulation center located near the position estimate used in this advisory. However, there was a sharp cusp noted in the ASCAT wind field, and that was used for positioning the disturbance since it lies closest to the strong convective band and best upper-level divergence. The initial intensity of 35 kt is based on several ASCAT wind vectors of 35-36 kt located well north of the center. The 35-kt intensity is also consistent with a 0000Z TAFB Dvorak satellite intensity estimate of T2.5/35 kt.

The initial motion estimate is an uncertain 295/22 kt. The ridge to the north of the disturbance is forecast to remain strong for the next 36-48 h, which keeps the system moving in a general west-northwestward direction across the Lesser Antilles tonight and Wednesday, and near or over the Greater Antilles Wednesday night and Thursday. For such a loosely organized system at this time, the models are in fairly good agreement on the large disturbance slowing down significantly after 48 h, reaching forward speeds of only 10-12 kt when it reaches the very warm waters of the Straits of Florida in 72-96 h. On days 4 and 5, the system is expected to slow even further and turn northward into a break in the subtropical ridge that is expected to develop across Florida and the Bahamas. The new NHC track forecast is similar to but a little south of the previous advisory track, mainly due to the more westward initial position, and lies along the southern portion of the guidance envelope near the middle of the consensus models. Regardless of the exact track, the system is expected to bring locally heavy rainfall to much of the Lesser Antilles, and tropical-storm-force winds to portions of the Leeward Islands, the Virgin Islands, and Puerto Rico during the next 24 hours.

The intensity forecast remains problematic for primarily two reasons: 1) the lack of a well-defined center and inner-core wind field and 2) likely land interaction to some degree. In the short-term, a bonafide center could develop tonight in response to the expected development of intense convection caused by orographic forcing by the mountainous islands of the central and northern Leeward Islands. Once a center closes off, which has likely been inhibited from doing so due to the disturbance's fast forward speed in excess of 20 kt, the low-level convergence will improve and convection will become more organized and symmetrical, allowing for strengthening to occur. The main question is how much land interaction with Puerto Rico and Hispaniola will disrupt the circulation in the 36-48-hour period. Assuming the system remains intact after emerging off the coast of Hispaniola, the slow track over the very warm waters of the Straits of Florida would result in more strengthening, assuming the system doesn't interact with the Cuban landmass. Although the GFS-and ECMWF-based SHIPS intensity guidance shows considerable southwesterly vertical wind shear of 20-30 kt in the 72-96 h period when the disturbance is over the Straits, the global model fields show that this is self-induced shear caused by the SHIPS model incorporating the system's impressive upper-level outflow winds in its shear calculations. As a result, this is not being considered a negative intensity factor compared to land interaction. Due to aforementioned uncertainties, the new NHC intensity forecast remains on the conservative side, and lies between the slightly weaker IVCN and stronger NOAA-HCCA consensus models. Interests in Hispaniola, the Bahamas, Cuba, and Florida should continue to monitor forecasts as changes to both the track and intensity are likely.