1. Gusty winds, dangerous storm surge, and heavy rainfall are expected from Marco along portions of the Gulf Coast beginninglater today. Interests in these areas should follow any advice givenby local government officials.

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

DISCONTINUED FOR MARCO BUT DANGEROUS STORM SURGE STILL ANTICIPATED...

SUMMARY OF 400 AM CDT...0900 UTC...INFORMATION LOCATION...27.6N 88.2W ABOUT 115 MI...190 KM SSE OF THE MOUTH OF THE MISSISSIPPI RIVER MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H PRESENT MOVEMENT...NW OR 325 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES

WATCHES AND WARNINGS CHANGES WITH THIS ADVISORY:

The Hurricane Warning from Morgan City Louisiana to the Mouth of the Pearl River has been changed to a Tropical Storm Warning.

The Hurricane Watch for Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans has been discontinued.

The Tropical Storm Watches west of Intracoastal City Louisiana and from the Mississippi/Alabama border to the Alabama/Florida border have been discontinued. All Storm Surge Watches have been discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Warning is in effect for....
- Morgan City Louisiana to Ocean Springs Mississippi
- Lake Borgne

A Tropical Storm Warning is in effect for...
- Intracoastal City to the Mississippi/Alabama border
- Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans

A Storm Surge Warning means there is a danger of lifethreatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. This is a lifethreatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

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

For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

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...

Morgan City LA to Ocean Springs MS, including Lake Borgne...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 dangerous 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: Tropical storm conditions are expected to start by this afternoon in portions of the warning area.

RAINFALL: Marco is expected to produce total rainfall accumulations of 3 to 5 inches with isolated maximum amounts of 10 inches across portions of the northeast and northcentral Gulf coast through Tuesday. This rainfall may result in areas of flash, urban and small stream flooding along the area.

SURF: Swells generated by Marco are likely to affect portions of the northern Gulf Coast for the next couple of days. These swells are likely to cause lifethreatening surf and rip current conditions. Please consult products from your local weather office.

TORNADOES: A couple of tornadoes will be possible today from southeast Louisiana to the western Florida Panhandle.

At 400 AM CDT (0900 UTC), the center of Tropical Storm Marco was located near latitude 27.6 North, longitude 88.2 West. Marco is moving toward the northwest near 10 mph (17 km/h). Marco is forecast to approach the coast of Louisiana this afternoon, and then turn westward and move very close to the coast of Louisiana through Tuesday night.

Data from the Hurricane Hunter plane indicate that maximum sustained winds have decreased to near 60 mph (95 km/h) with higher gusts. Further weakening is expected, and Marco is forecast to become a tropical depression late on Tuesday and dissipate on Wednesday.

Tropicalstormforce winds extend outward up to 105 miles (165 km), primarily northeast of the center.

The estimated minimum central pressure is 1003 mb (29.62 inches).

Marco is clearly weakening tonight. Data from an Air Force Reserve Hurricane Hunter mission showed that flight-level and SFMR had decreased along with a substantial rise in central pressure. In addition, GOES-16 1-min satellite data show the surface center well displaced from the deep convection, and it appears that Marco is decoupling from its mid-level circulation to the northeast. The initial wind speed is set to 50 kt, and that could be generous.

Some large changes have been required on this forecast. Considering the shear is only forecast to increase, there is no significant chance that Marco re-intensifies to a hurricane, and the hurricane warnings have been replaced with tropical storm warnings. Furthermore, now that the storm is losing vertical coherence, the intensity forecast has been decreased as well, and is fairly consistent with the model consensus and almost every model.Marco has turned northwestward this morning at about 9 kt. The storm should gradually turn westward as it approaches southeastern Louisiana due to the shallower cyclone feeling the low-level ridge. Marco will likely dissipate in a couple of days near the Texas/Louisiana border due to continued strong shear. Guidance has come into better agreement on the track going slightly inland or just brushing the Louisiana coast, and the track has been nudged southward on this advisory. It should be noted that the heaviest rain and strongest winds will likely be northeast of the center, so users should not focus on the exact track of the cyclone.