| Track: https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/?cone#contents Hurricane Sally Discussion Number 19 NWS National Hurricane Center Miami FL AL192020 1000 PM CDT Tue Sep 15 2020 Observations from an Air Force Hurricane Hunter aircraft and WSR-88D Doppler radar data indicate some strengthening. The eye has become a little better defined on the radar, and the central pressure has fallen to 972 mb. The eye has also become evident on recent IR imagery. Using a blend of flight-level and SFMR-observed surface winds, along with the Doppler velocities, gives a current intensity estimate of 75 kt. Given the recent trends, the official forecast allows for some more intensification before landfall, which is likely to occur in less than 12 hours. Rapid weakening will occur after the center moves inland, and the system should become a remnant low in a couple of days. This is consistent with the model guidance. Radar and aircraft center fixes indicate that the motion is now north-northeastward, or 020/2 kt. Sally should move north-northeastward, and then northeastward, with a gradual increase in forward speed, along the northwestern side of a weak mid-level high pressure area for the next couple of days. Then, as the system approaches the westerly flow at higher latitudes, the cyclone should turn toward the east-northeast with a slight further increase in forward speed until becoming a dissipating remnant low near the southeast U.S. coast in 2-3 days. The official forecast is close to the latest corrected dynamical model consensus, HCCA, prediction. KEY MESSAGES: 1. Historic, life-threatening flash flooding due to rainfall is likely through Wednesday along and just inland of the coast from the Florida Panhandle west of the Apalachicola River to the Alabama/Mississippi border. Widespread moderate to major river flooding is forecast across the Florida Panhandle and southern Alabama. Significant flash and urban flooding, as well as widespread minor to moderate river flooding, is likely across inland portions of Mississippi and Alabama, and into Georgia and the western Carolinas this week. 2. Life-threatening storm surge is expected along portions of the coastline from Alabama to the western Florida Panhandle, including Mobile Bay. 3. Hurricane conditions are expected this evening and overnight within portions of the Hurricane Warning area along the Mississippi and Alabama coastlines and the western Florida Panhandle. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 29.8N 87.8W 75 KT 85 MPH 12H 16/1200Z 30.3N 87.5W 80 KT 90 MPH...ON THE COAST 24H 17/0000Z 31.2N 86.8W 40 KT 45 MPH...INLAND 36H 17/1200Z 32.0N 85.7W 30 KT 35 MPH...INLAND 48H 18/0000Z 32.9N 83.9W 25 KT 30 MPH...INLAND 60H 18/1200Z 33.6N 81.5W 20 KT 25 MPH...INLAND 72H 19/0000Z 34.0N 79.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 20/0000Z...DISSIPATED $$ Forecaster Pasch Hurricane Sally Advisory Number 19 NWS National Hurricane Center Miami FL AL192020 1000 PM CDT Tue Sep 15 2020 ...HURRICANE CONDITIONS EXPECTED TO REACH PORTIONS OF THE NORTH-CENTRAL GULF COAST LATE TONIGHT AND EARLY WEDNESDAY... ...HISTORIC LIFE-THREATENING FLOODING LIKELY ALONG PORTIONS OF THE NORTHERN GULF COAST... SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION ----------------------------------------------- LOCATION...29.8N 87.8W ABOUT 65 MI...105 KM SSE OF MOBILE ALABAMA ABOUT 60 MI...95 KM SW OF PENSACOLA FLORIDA MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H PRESENT MOVEMENT...NNE OR 20 DEGREES AT 2 MPH...4 KM/H MINIMUM CENTRAL PRESSURE...972 MB...28.71 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Storm Surge Warning has been extended east of the Okaloosa/Walton County Line to the Walton/Bay County Line Florida. The Hurricane Warning has been extended east of Navarre Florida to the Okaloosa/Walton County line Florida. The Storm Surge Warning has been discontinued between the Mouth of the Pearl River and the Mississippi/Alabama border. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * Mississippi/Alabama border to the Walton/Bay County Line Florida * Mobile Bay * Mouth of the Mississippi River to the Mouth of the Pearl River A Hurricane Warning is in effect for... * East of Bay St. Louis Mississippi to the Okaloosa/Walton County line Florida A Tropical Storm Warning is in effect for... * East of the Okaloosa/Walton County line Florida to Indian Pass Florida * Bay St. Louis Mississippi westward to Grand Isle 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 1000 PM CDT (0300 UTC), the center of Hurricane Sally was located near latitude 29.8 North, longitude 87.8 West. Sally is moving toward the north-northeast near 2 mph (4 km/h). A north-northeastward to northeastward motion at a slightly faster forward speed is expected on Wednesday and Wednesday night, followed by a faster northeastward motion on Thursday. On the forecast track, the center of Sally will approach the northern Gulf Coast tonight, and make landfall in the hurricane warning area early Wednesday. Sally is expected to move inland across southeastern Alabama Wednesday night and Thursday. Maximum sustained winds are near 85 mph (140 km/h) with higher gusts. Some strengthening is possible before landfall, 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 40 miles (65 km) from the center and tropical-storm-force winds extend outward up to 125 miles (205 km). The minimum central pressure reported by the Hurricane Hunters is 972 mb (28.71 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 RAINFALL: Sally is forecast to produce 10 to 20 inches of rainfall with isolated amounts of 30 inches along and just inland of the central Gulf Coast from the Florida Panhandle west of the Apalachicola River to the Alabama/Mississippi border. Historic, life-threatening flash flooding is likely. In addition, this rainfall will lead to widespread moderate to major flooding on area rivers. Sally is forecast to turn inland Wednesday and track across the Southeast producing rainfall of 4 to 8 inches, with isolated maximum amounts of 12 inches, across portions of southeastern Mississippi, southern and central Alabama, central and northern Georgia, and the western Carolinas. Significant flash and urban flooding is likely, as well as widespread minor to moderate flooding on some rivers. 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... Dauphin Island AL to Okaloosa/Walton County FL Line...4-6 ft Pensacola Bay and Choctawhatchee Bay FL...4-6 ft Mobile Bay...3-5 ft Okaloosa/Walton County Line to Walton/Bay County line FL...2-4 ft Mouth of the Mississippi River to Mouth of the Pearl River including Lakes Pontchartrain, Maurepas and Borgne...2-4 ft MS/AL Border to Dauphin Island AL...2-4 ft Walton/Bay County line to Chassahowitzka FL including Saint Andrew Bay...1-3 ft Mouth of the Pearl River to MS/AL Border...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 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 tonight. Tropical storm conditions are already occurring in portions of the warning areas, and will continue through Wednesday night. TORNADOES: A few tornadoes may occur through Wednesday across portions of the Florida Panhandle and southern Alabama. 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 intermediate advisory at 100 AM CDT. Next complete advisory at 400 AM CDT. $$ Forecaster Pasch |