1. Tropical storm conditions will continue over portions of extremewestern Cuba through this evening. Heavy rainfall is also expected in the eastern portions of the Mexican states of Quintana Roo andYucatan, and across far western Cuba, which could result in flashflooding.

2. Marco is expected to approach the central Gulf Coast as a hurricane on Monday. Hurricane conditions, life-threatening storm surge, and heavy rainfall are possible along portions of the Gulf Coast beginning on Monday, and Hurricane and Storm Surge watches have been issued. Interests in these areas should follow any advice given by local government officials.

3. Tropical Storm Laura could bring additional storm surge, rainfall, and wind impacts to portions of the U.S. Gulf Coast by the middle of next week. This could result in a prolonged period of hazardous weather for areas that could be affected by Marco. Interests there should monitor the progress of Marco and Laura and updates to the forecast during the next few days.

CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Watch is in effect for...
- Sabine Pass to the Alabama/Florida border
- Lake Pontchartrain, Lake Maurepas, Lake Borgne, and Mobile Bay

A Hurricane Watch is in effect for...
- Intracoastal City Louisiana to the Mississippi/Alabama border
- Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans

A Tropical Storm Warning is in effect for...
- Province of Pinar del Rio Cuba

A Tropical Storm Watch is in effect for...
- Mississippi/Alabama border to the Alabama/Florida border

A Storm Surge Watch means there is a possibility of life threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropicalstormforce winds, conditions that make outside preparations difficult or dangerous.

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, please monitor products issued by your national meteorological service.

STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide...

Grand Isle LA to the AL/FL Border including Lake Borgne and Mobile Bay...35 ft Lake Pontchartrain and Lake Maurepas...24 ft Sabine Pass to Grand Isle LA...24 ft

The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surgerelated flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local National Weather Service forecast office.

WIND: Hurricane conditions are possible within the hurricane watch area by midday Monday, with tropical storm conditions possible by early Monday. Tropical storm conditions are possible within the tropical storm watch area on Monday.

Tropical storm conditions are expected to continue within the warning area in Cuba through this evening.

RAINFALL: Marco is expected to produce the following rainfall accumulations through Monday:

Far western Cuba: 2 to 4 inches of rain, with isolated maximum amounts of 6 inches possible

Eastern portions of the Mexican states of Quintana Roo and Yucatan: 1 to 3 inches.

Central U.S. Gulf Coast: 1 to 3 inches, isolated maximum amounts of 5 inches.

This rainfall may result in areas of flash and urban flooding along the Central U.S. Gulf Coast.

At 700 PM CDT (0000 UTC), the center of Tropical Storm Marco was located by an Air Force Reserve Hurricane Hunter Aircraft near latitude 22.3 North, longitude 86.0 West. Marco is moving toward the northnorthwest near 13 mph (20 km/h). Marco is expected to continue moving toward the northnorthwest across the central Gulf of Mexico on Sunday and is forecast to reach the northern Gulf coast on Monday. After moving inland, Marco is expected to slow down and turn toward the northwest and westnorthwest Monday night and Tuesday, moving across southern Louisiana and east Texas.

Maximum sustained winds based on preliminary data from the reconnaissance aircraft are near 65 mph (100 km/h) with higher gusts. Strengthening is forecast during the next day or two, and Marco is expected to become a hurricane later tonight or on Sunday. Marco is likely to still be at or near hurricane strength when it reaches the northern Gulf coast on Monday. Weakening is forecast to occur while the center moves farther inland Monday night and Tuesday.

Tropicalstormforce winds extend outward up to 90 miles (150 km) from the center.

The latest minimum central pressure reported by the hurricane hunter plane was 994 mb (29.35 inches).

Cutting to the chase, there have been some big changes among themodel guidance, and subsequently the NHC forecast, for Marco thisafternoon. While at this point it's a little speculative, the datacollected by this morning's NOAA G-IV flight in the environmentaround Marco and across the Gulf of Mexico may have played a keyrole in the significant eastward shift seen in nearly all the 12z models. This isn't to say that the uncertainty in the eventual track has diminished. In fact, various ensemble members from some of the global models still show a potential risk to the coast anywhere from Texas to Alabama, and it's entirely possible that the volatile shifts seen in the models could continue. That being said, the new NHC track forecast has been shifted significantly eastward and now shows the center of Marco reaching southeastern Louisiana in about 2 days, which is the scenario currently shown by the GFS, ECMWF, HCCA, Florida State Superensemble, and the TVCN multi-model consensus. After Marco reaches the coast, the western Atlantic ridge is expected to build westward and should cause the cyclone to move more slowly toward the west-northwest across southern portions of Louisiana.As far as the intensity is concerned, the last fix made by this morning's reconnaissance flight indicated that the pressure had leveled off, and no higher winds had been observed from what was measured earlier in the flight. The radar presentation from Cuban radar has also degraded a bit, so Marco's initial intensity is held at 55 kt. Marco is beginning to move into a zone of moderate southwesterly shear, but otherwise favorable conditions of warm ocean water and some upper-level divergence are expected to foster strengthening during the next day or so. With the exception of the HWRF, the other intensity models show Marco reaching hurricane strength, and the NHC foreast continues to show that possibility while Marco moves over the central Gulf. The shear is still expected to strengthen in 36-48 hours when the system is approaching the northern Gulf Coast, but with the shift in the forecast track, now there may not be enough time for Marco to weaken below hurricane intensity before it reaches land. The new NHC intensity forecast is near or just above the HCCA and Florida State Superensemble models and holds Marco as a hurricane until it reaches the coast.

The forecast track changes now bring tropical storm force winds to the coast in 36-48 hours, which necessitates the issuance of Hurricane and Storm Surge Watches for a portion of the northern Gulf Coast. These watches will likely need to be upgraded to warnings later tonight.