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Hurricane Sally Public Advisory Number 15A
2020-09-15 07:56:52| National Hurricane Center (Atlantic)
Issued at 100 AM CDT Tue Sep 15 2020 000 WTNT34 KNHC 150556 TCPAT4 BULLETIN Hurricane Sally Intermediate Advisory Number 15A NWS National Hurricane Center Miami FL AL192020 100 AM CDT Tue Sep 15 2020 ...SALLY WEAKENS SLIGHTLY WHILE JOGGING WESTWARD... ...LIFE-THREATENING STORM SURGE, HURRICANE-FORCE WINDS, AND FLASH FLOODING LIKELY ALONG PORTIONS OF THE NORTHERN GULF COAST LATER TODAY... SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION ---------------------------------------------- LOCATION...28.8N 88.0W ABOUT 75 MI...120 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER ABOUT 115 MI...190 KM SSE OF BILOXI MISSISSIPPI MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H PRESENT MOVEMENT...W OR 270 DEGREES AT 3 MPH...6 KM/H MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * Port Fourchon Louisiana to the Okaloosa/Walton County Line Florida * Lake Pontchartrain, Lake Maurepas, and Lake Borgne * Mobile Bay A Hurricane Warning is in effect for... * Grand Isle Louisiana to the Navarre Florida * Lake Pontchartrain and Lake Maurepas including metropolitan New Orleans A Tropical Storm Warning is in effect for... * East of of Navarre Florida to Indian Pass Florida * West of Grand Isle to Morgan City Louisiana 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. Preparations to protect life and property should be rushed to completion. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 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. DISCUSSION AND OUTLOOK ---------------------- At 100 AM CDT (0600 UTC), the center of Hurricane Sally was located an Air Force Reserve reconnaissance aircraft and NOAA Doppler weather radars near latitude 28.8 North, longitude 88.0 West. Sally is moving slowly toward the west near 3 mph (6 km/h). A slow west-northwestward motion is expected to resume later this morning. A northward turn is expected this afternoon, followed by a slow north-northeastward to northeastward motion tonight and continuing through Wednesday night. On the forecast track, the center of Sally will move near the coast of southeastern Louisiana later today, and make landfall in the hurricane warning area tonight or Wednesday morning. Data from the reconnaissance aircraft indicate that maximum sustained winds have decreased to near 90 mph (150 km/h) with higher gusts. However, some re-strengthening is forecast early to occur later today, and Sally is expected to be a dangerous hurricane when it moves onshore along the north-central Gulf coast. Hurricane-force winds extend outward up to 45 miles (75 km) from the center and tropical-storm-force winds extend outward up to 125 miles (205 km). A NOAA C-MAN observing station on Dauphin Island, Alabama, recently reported a wind gust of 51 mph (81 km/h), while a buoy just south of Dauphin Island recently reported a wind gust to 59 mph (94 km/h). The estimated minimum central pressure based on data from the Air Force Hurricane Hunter aircraft is 986 mb (29.12 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Sally can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml 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... Mouth of the Mississippi River to Dauphin Island including Lake Borgne...6-9 ft Mobile Bay...6-9 ft Lake Pontchartrain and Lake Maurepas...3-5 ft Dauphin Island to AL/FL Border...4-7 ft Port Fourchon to Mouth of the Mississippi River...2-4 ft AL/FL Border to Okaloosa/Walton County Line including Pensacola Bay an Choctawhatchee Bay...2-4 ft Okaloosa/Walton County Line to Chassahowitzka including Saint Andrew Bay...1-3 ft Burns Point to Port Fourchon...1-2 ft Overtopping of local levees outside of the Hurricane and Storm Damage Risk Reduction System is possible where local inundation values may be higher than those shown above. The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and damaging 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 to begin within the hurricane warning area later today. Tropical storm conditions are occurring in portions of the warning area across Alabama, and these conditions will gradually spread westward this morning. RAINFALL: Sally is expected to be a slow moving system as it approaches land, producing 8 to 16 inches of rainfall with isolated amounts of 24 inches over portions of the central Gulf Coast from the western Florida Panhandle to far southeastern Mississippi through the middle of the week. Life-threatening flash flooding is likely. In addition, this rainfall will likely lead to widespread minor to isolated major flooding on area rivers. Sally is forecast to turn inland early Wednesday and track across the Southeast producing rainfall of 4 to 8 inches, with isolated maximum amounts of 12 inches, across portions of eastern Mississippi, central Alabama, northern Georgia, southeastern Tennessee, and the western Carolinas. Significant flash and urban flooding is likely, as well as widespread minor to moderate flooding on some rivers. Outer bands of Sally could produce additional rainfall of 1 to 3 inches across the Florida peninsula through tonight. This rainfall may produce flash and urban flooding and prolong high flows and ongoing minor flooding on rivers across central Florida. TORNADOES: A tornado or two will be possible this morning in coastal areas of the Florida Panhandle and Alabama. The threat for tornadoes should increase and slowly spread inland during the day today. SURF: Swells from Sally will continue to affect the coast from the Florida Big Bend westward to southeastern Louisiana during the next couple of days. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next complete advisory at 400 AM CDT. $$ Forecaster Stewart
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