1. Tropical storm conditions will continue over portions of extremewestern Cuba for a few more hours. Heavy rainfall is also expectedovernight in the eastern portions of the Mexican states of QuintanaRoo and Yucatan, and across far western Cuba, which could result inflash flooding.

2. Marco is expected to be at or near hurricane strength when itapproaches the central Gulf Coast as a hurricane on Monday.Hurricane conditions, life-threatening storm surge, and heavyrainfall are possible along portions of the Gulf Coast beginning onMonday, and Hurricane and Storm Surge watches have been issued.Interests in these areas should follow any advice given by localgovernment officials.

3. Tropical Storm Laura could bring additional storm surge,rainfall, and wind impacts to portions of the U.S. Gulf Coast by themiddle of next week. This could result in a prolonged period ofhazardous weather for areas that may also be affected by Marco.Interests there should monitor the progress of Marco and Laura andupdates 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 Tuesday:

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

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 1000 PM CDT (0300 UTC), the center of Tropical Storm Marco was located near latitude 22.8 North, longitude 86.3 West. Marco is moving toward the northnorthwest near 13 mph (20 km/h). Marco is forecast to continue moving northnorthwestward across the central Gulf of Mexico on Sunday and will approach the northern Gulf Coast on Monday. A gradual turn toward the west with a decrease in forward speed is expected after Marco moves inland on Monday and on Tuesday.

Data from an Air Force Reserve Hurricane Hunter aircraft indicate that the maximum sustained winds remain near 65 mph (100 km/h) with higher gusts. Some strengthening is anticipated and Marco is forecast to become a hurricane on Sunday. Marco is expected to be at or near hurricane strength when it approaches the northern Gulf Coast on Monday. Rapid weakening is expected after Marco moves inland.

Tropicalstormforce winds extend outward up to 70 miles (110 km) from the center.

The estimated minimum central pressure based on data from the Air Force reconnaissance plane is 994 mb (29.36 inches).

Marco has taken on distinctly sheared appearance. Reports from an Air Force Reserve Hurricane Hunter plane, microwave imagery, and radar imagery from Cuba all indicate that deep convection is limited to the east side of the tropical storm and that it no longer has a nearly closed eyewall. The degradation of Marco's structure appears to be primarily due to strong upper-level southwesterly flow. Despite the shear, the plane still measured SFMR winds near 55 kt and the intensity is held at that value.

Marco is a small tropical storm and will be susceptible to rapid changes in structure and intensity until it reaches the northern Gulf Coast. Such systems are often not very resilient in a high-shear environment, however even a brief relaxation of the shear could result in quick strengthening. It would not be surprising if Marco's intensity evolves in step-wise fashion consisting of periods of arrested development followed by fast strengthening if/when the shear relaxes. While the statistical models still show Marco becoming a hurricane within 24 h, the run-to-run consistency of the dynamical guidance remains poor. The latest HWRF, HMON and GFS forecasts show Marco weakening as it approaches the northern Gulf Coast, and this remains a distinct possibility if the shear remains consistently high. The NHC intensity forecast has not been changed substantially, in large part due to the low confidence of the forecast, and is consequently above all of the guidance at 36 and 48 h when Marco is forecast to be near the northern Gulf Coast. Additional adjustments to the forecast are likely on Sunday.

In sharp contrast to earlier today, no large changes were made to the track forecast, though that should not be interpreted as an increase in forecast confidence. Marco is forecast to move north-northwestward and approach the northern Gulf Coast on Monday. As it moves inland and weakens, a turn toward the west at a slower forward speed is anticipated. This turn could occur before or after Marco moves inland, and will be tied in part to exactly when Marco begins to weaken since a stronger, deeper storm should continue to feel the affects of the upper-level southwesterly flow and move farther north while a weaker system will be steered westward by a low- to mid-level ridge extending over the southeastern US. The NHC forecast is nearly on top of the multi-model consensus, but the spread in the guidance is still higher than normal.