1. Tropical storm conditions are expected across much of Cubatoday. Heavy rainfall is likely across Cuba and Jamaica today, and these rains could cause mudslides and life-threatening flash and urban flooding. Tropical storm conditions are expected in the Dry Tortugas, and the Middle and Lower Florida Keys later today.

2. While the details of the long-range track and intensity forecastsremain uncertain, Laura is forecast to strengthen over the Gulf ofMexico and there is an increasing risk of dangerous storm surge,wind, and rainfall impacts along portions of the U.S. Gulf Coast bythe middle of the week. This could result in a prolonged period ofhazardous weather for areas that are likely to be affected by Marco.Interests along the Gulf Coast should monitor the progress of Lauraand Marco and updates to the forecast during the next couple ofdays.

CHANGES WITH THIS ADVISORY:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
- Little Cayman and Cayman Brac
- Cuban provinces of Camaguey, Las Tunas, Holguin, Guantanamo, Santiago de Cuba, Granma, Ciego De Avila, Sancti Spiritus, Villa Clara, Cienfuegos, Matanzas, Mayabeque, La Habana, Artemisa, Pinar del Rio, and the Isle of Youth
- Florida Keys from Craig Key to Key West
- Dry Tortugas

The Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within the next 12 to 24 hours.

Hurricane and Storm Surge Watches will likely be required for portions of the U.S. northwest Gulf coast area by this evening.

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.

RAINFALL: Laura is expected to produce the following storm total rainfall accumulations through Tuesday:

Jamaica and Cuba: 4 to 8 inches, with maximum amounts of 12 inches.

Cayman Islands: 2 to 4 inches, maximum amounts of 6 inches.

Florida Keys, Turks and Caicos Islands, and the Northwest Bahamas: 1 to 2 inches.

Across the Greater Antilles this heavy rainfall could lead to lifethreatening flash and urban flooding, and the potential for mudslides.

From late Wednesday into Friday, Laura is expected to produce rainfall of 5 to 10 inches, with isolated maximum amounts of 15 inches across portions of the westcentral U.S. Gulf Coast near the Texas and Louisiana border north into portions of the lower Mississippi Valley. This rainfall could cause widespread flash and urban flooding, small streams to overflow their banks, and the possibility of some minor river flooding across this region.

WIND: Tropical storm conditions are expected to spread westward within the warning area in Cuba through today. Tropical storm conditions are expected in Little Cayman and Cayman Brac today. Tropical storm conditions are also expected within the warning area in the middle and lower Florida Keys and the Dry Tortugas this afternoon and tonight.

SURF: Swells generated by Laura are affecting portions of Hispaniola, eastern Cuba, the southeastern Bahamas and the Turks and Caicos Islands. These swells are expected to spread across central and western Cuba, the central and northwestern Bahamas, and the Florida Keys today. Please consult products from your local weather office.

TORNADOES: An isolated tornado will be possible later today into tonight across the Florida Keys.

At 800 AM EDT (1200 UTC), the center of Tropical Storm Laura was located near latitude 20.9 North, longitude 79.7 West. Laura is moving toward the westnorthwest near 21 mph (33 km/h), and this general motion with some decrease in forward speed is expected over the next couple of days. A turn toward the northwest is forecast by Wednesday. On the forecast track, the center of Laura will move over the Caribbean Sea just offshore the southern coast of Cuba today, and move into the southeastern Gulf of Mexico by early Tuesday morning. Laura is then forecast to move over the central and northwestern Gulf of Mexico Tuesday night and Wednesday.

Maximum sustained winds are near 65 mph (100 km/h) with higher gusts. Gradual strengthening is expected, and Laura is forecast to become a hurricane by early Tuesday.

Tropicalstormforce winds extend outward up to 175 miles (280 km) from the center.

The estimated minimum central pressure is 1000 mb (29.53 inches).

Satellite data indicate that Laura has moved back over the warm waters of the Caribbean Sea south of Cuba. Modest northerly vertical wind shear has kept the bulk of the deep convection displaced into the southern semicircle of Laura's circulation. Earlier ASCAT-B/-C scatterometer passes around 0210Z-0250Z revealed a small circulation just offshore southeastern Cuba. However, this feature is considered to be a leeside vortex, possibly having developed in response to the long-fetch southerly low-level flow passing over Jamaica, and not the primary low-level center associated with Laura. The initial intensity is being maintained at 55 kt based on 43-46 kt wind vectors located just offshore southeastern Cuba that were present in the aforementioned ASCAT data, and allowing for some undersampling by the scatterometer instrument.

The initial motion estimate is 290/18 kt. The deep-layer Bermuda-Azores ridge to the north of the cyclone is forecast by all of the models to build and expand westward across the Bahamas, Florida, and into the eastern and central Gulf of Mexico over the new few days. This dominant steering flow pattern is expected to keep Laura moving west-northwestward just offshore the southern coast of Cuba today, followed by the cyclone emerging over the southeastern Gulf of Mexico on Tuesday. By late Tuesday and early Wednesday, a mid- to upper-level trough located over the south-central U.S. is forecast to pinch off and dig southwestward and merge with the remnants of Tropical Storm Marco over the western Gulf of Mexico, eroding the western extent of the ridge in the process. This is expected to cause Laura to slow down and gradually turn northwestward and then northward toward the northwestern Gulf coast by late Wednesday and early Thursday. The latest NHC model guidance is in excellent agreement on this developing synoptic pattern, and the official forecast is similar to but slightly left or south of the previous advisory track to account for the expected northerly to northeasterly wind shear keeping the convection and low-level center displaced to the south for the next 24 hours or so. On the forecast track, Laura is expected to remain just offshore the southern Cuba today, move into the Gulf of Mexico by early Tuesday morning, and approach the U..S northwest Gulf coast area Wednesday night and early Thursday.Since Laura's center is expected to remain over water just south of Cuba, there is the possibility that some slight strengthening could occur today or tonight before the cyclone reaches the Gulf of Mexico in 24 hours. After that, Laura will be moving over the very warm and deep waters of Gulf Stream and Loop Current located over the southeastern Gulf, which could trigger a brief period of rapid intensification. The GFS and ECMWF models, along with the statistical and corrected-consensus models, only strengthen the cyclone to a peak intensity around 75 kt. In contrast, the HRWF and HMON models bring Laura to major hurricane strength by 60 hours. Given the very favorable environmental conditions of high SSTs near 31 deg C and low vertical shear values less than 10 kt after 24-36 hours, subsequent intensity forecasts might have to trend more toward the regional models. But for now, the official intensity forecast will continue to follow a blend of the regional and global model intensity forecasts, and lies at the high-end of the intensity guidance at 60 and 72 hours.

Users are again reminded to not to focus on the exact details ofthe track or intensity forecasts as the average NHC track error at72 h is around 100 miles and the average intensity error is around15 mph (13 kt). In addition, winds, storm surge, and rainfallhazards will extend far from the center.