BULLETIN
Tropical Storm Marco Intermediate Advisory Number 12A
NWS National Hurricane Center Miami FL AL142020
700 AM CDT Sun Aug 23 2020
…MARCO NEARING HURRICANE STRENGTH AS IT CROSSES THE SOUTHEASTERN
GULF OF MEXICO…
SUMMARY OF 700 AM CDT…1200 UTC…INFORMATION
———————————————-
LOCATION…24.2N 87.1W
ABOUT 210 MI…340 KM NW OF THE WESTERN TIP OF CUBA
ABOUT 360 MI…580 KM SSE OF THE MOUTH OF THE MISSISSIPPI RIVER
MAXIMUM SUSTAINED WINDS…70 MPH…110 KM/H
PRESENT MOVEMENT…NNW OR 335 DEGREES AT 13 MPH…20 KM/H
MINIMUM CENTRAL PRESSURE…993 MB…29.32 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:
None.
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 to the Alabama/Florida border
* Lake Pontchartrain, Lake Maurepas, and Mobile Bay
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. 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 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.
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 Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.
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 in the United
States, including possible inland watches and warnings, please
monitor products issued by your local National Weather Service
forecast office. For storm information specific to your area
outside of the United States, please monitor products issued by
your national meteorological service.
DISCUSSION AND OUTLOOK
———————-
At 700 AM CDT (1200 UTC), the center of Tropical Storm Marco was
located near latitude 24.2 North, longitude 87.1 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 today and will approach southeastern Louisiana 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.
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 60 miles (95 km)
from the center.
The estimated minimum central pressure based on data from the Air
Force Reserve Hurricane Hunter aircraft 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…
Sabine Pass to Morgan City LA…2-4 ft
Morgan City LA to Ocean Springs MS including Lake Borgne…4-6 ft
Ocean Springs MS to the AL/FL Border including Mobile Bay…2-4 ft
Lake Pontchartrain and Lake Maurepas…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
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.