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Tropical Storm Marco Advisory Number 11
NWS National Hurricane Center Miami FL AL142020
1000 PM CDT Sat Aug 22 2020
...MARCO MOVING NORTH-NORTHWESTWARD ACROSS THE SOUTHERN GULF OF
...STORM SURGE AND HURRICANE WATCHES IN EFFECT FOR PORTIONS OF
THE NORTHERN GULF COAST...
SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
ABOUT 110 MI...175 KM NW OF THE WESTERN TIP OF CUBA
ABOUT 470 MI...755 KM SSE OF THE MOUTH OF THE MISSISSIPPI RIVER
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NNW OR 335 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.36 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
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
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 tropical-storm-force
winds, conditions that make outside preparations difficult or
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.
DISCUSSION AND OUTLOOK
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 north-northwest near 13 mph (20 km/h). Marco is
forecast to continue moving north-northwestward 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
Tropical-storm-force 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).
HAZARDS AFFECTING LAND
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
Lake Pontchartrain and Lake Maurepas...2-4 ft
Sabine Pass to Grand Isle LA...2-4 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. 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
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
This rainfall may result in areas of flash and urban flooding along
the Central U.S. Gulf Coast.
Next intermediate advisory at 100 AM CDT.
Next complete advisory at 400 AM CDT.