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| #1013395 (Received by flhurricane at: 1:50 AM 23.Aug.2020) TCPAT4 BULLETIN Tropical Storm Marco Intermediate Advisory Number 11A NWS National Hurricane Center Miami FL AL142020 100 AM CDT Sun Aug 23 2020 ...MARCO FORECAST TO BECOME A HURRICANE LATER TODAY... ...STORM SURGE AND HURRICANE WATCHES IN EFFECT FOR PORTIONS OF THE NORTHERN GULF COAST... SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION ---------------------------------------------- LOCATION...23.1N 86.6W ABOUT 135 MI...220 KM NW OF THE WESTERN TIP OF CUBA ABOUT 440 MI...705 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...994 MB...29.36 INCHES WATCHES AND WARNINGS -------------------- 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 tropical-storm-force 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. DISCUSSION AND OUTLOOK ---------------------- At 100 AM CDT (0600 UTC), the center of Tropical Storm Marco was located near latitude 23.1 North, longitude 86.6 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 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 have increased to near 70 mph (110 km/h) with higher gusts. Some strengthening is anticipated and Marco is forecast to become a hurricane today. 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. 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 Bay...3-5 ft 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 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 the next few hours. 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. NEXT ADVISORY ------------- Next complete advisory at 400 AM CDT. $$ Forecaster Blake |