...LIFE-THREATENING STORM SURGE AND HURRICANE-FORCE WINDS EXPECTED ALONG PORTIONS OF THE U.S. GULF COAST...
Tropical Storm Marco Advisory Number 13
NWS National Hurricane Center Miami FL AL142020
1000 AM CDT Sun Aug 23 2020
SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
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LOCATION...24.7N 87.3W
ABOUT 325 MI...520 KM SSE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 475 MI...765 KM SE OF LAFAYETTE LOUISIANA
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NNW OR 340 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...993 MB...29.33 INCHES
WATCHES AND WARNINGS
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CHANGES WITH THIS ADVISORY:
The Storm Surge Watch has been discontinued from the Mississippi/Alabama border to the Alabama/Florida border, including Mobile Bay.
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 Hurricane Warning is in effect for...
* Morgan City Louisiana to the Mouth of the Pearl River
A Storm Surge Watch is in effect for...
* Sabine Pass to Morgan City Louisiana
* Ocean Springs Mississippi to the Mississippi/Alabama border
* Lake Pontchartrain and Lake Maurepas
A Hurricane Watch is in effect for...
* Intracoastal City Louisiana to west of Morgan City
* Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans
A Tropical Storm Warning is in effect for...
* Mouth of the Pearl River to the Mississippi/Alabama border
* Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans
A Tropical Storm Watch is in effect for...
* Mississippi/Alabama border to the Alabama/Florida border
A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline, during the next 36 hours in the indicated locations. This is a life-threatening 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 Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.
DISCUSSION AND OUTLOOK
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At 1000 AM CDT (1500 UTC), the center of Tropical Storm Marco was located near latitude 24.7 North, longitude 87.3 West. Marco is moving toward the north-northwest near 14 mph (22 km/h), and this motion is expected to continue through tonight, followed by a turn to the northwest by Monday. On the forecast track, Marco will cross the central Gulf of Mexico today and will approach southeastern Louisiana on Monday. A gradual turn toward the west-northwest with a decrease in forward speed is expected after Marco moves inland.
Maximum sustained winds are near 70 mph (110 km/h) with higher gusts. Some strengthening is anticipated and Marco is forecast to become a hurricane later today and be at hurricane strength when it approaches the northern Gulf Coast on Monday. Rapid weakening is expected after Marco moves inland.
Tropical-storm-force winds extend outward up to 70 miles (110 km) from the center.
The estimated minimum central pressure is 993 mb (29.33 inches).
HAZARDS AFFECTING LAND
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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...4-6 ft
Sabine Pass to Morgan City LA...2-4 ft
Ocean Springs MS to the MS/AL Border...2-4 ft
Lake Pontchartrain and Lake Maurepas...2-4 ft
MS/AL Border to AL/FL Border including Mobile Bay...1-3 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. Surge-related 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 expected within the hurricane warning 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, and hurricane conditions are possible within the hurricane watch areas late Monday.
RAINFALL: Marco is expected to produce rainfall accumulations of 2 to 4 inches with isolated maximum amounts of 6 inches across the Central U.S. Gulf coast through Tuesday.
This rainfall may result in isolated areas of flash and urban flooding along the Central U.S. Gulf Coast.
SURF: Swells generated by Marco are likely to affect portions of the northern Gulf Coast later today. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office.
TORNADOES: An isolated tornado will be possible early Monday morning near the southeast Louisiana coast.
