| Track: https://www.nhc.noaa.gov/refresh/graphics_at1+shtml/?cone#contents Satellite: https://rammb-data.cira.colostate.edu/tc_realtime/storm.asp?storm_identifier=al262020 https://www.star.nesdis.noaa.gov/GOES/floater.php?stormid=AL262020 Hurricane Delta Discussion Number 14 NWS National Hurricane Center Miami FL AL262020 1000 PM CDT Wed Oct 07 2020 Observations from an Air Force Reserve Unit Hurricane Hunter aircraft indicate that Delta is gradually strengthening while it moves over the open waters of the south-central Gulf of Mexico. Based on a blend of adjusted flight-level and SFMR wind measurements from the plane, the current intensity is set at 80 kt. The cloud pattern of the hurricane continues to become better organized on satellite images, with a growing Central Dense Overcast, and convective banding features becoming better defined, particularly over the northern semicircle of the circulation. Additional intensification is likely while Delta moves through a favorable environment during the next day or so, and the official forecast is fairly close to the corrected consensus guidance, HCCA. When the system moves into the northern Gulf, a decrease in oceanic heat content, drier mid-tropospheric air, and increased vertical shear should cause at least slow weakening. The NHC intensity forecast is above the numerical guidance in 36-48 hours. It should be noted that 1-2 day tropical cyclone intensity forecasts are subject to errors of around 1 Saffir-Simpson category. The global models show a further increase in the size of the hurricane while it moves into the northern Gulf. The official wind radii forecasts are based on a consensus of these model predictions. The latest center fixes from the Hurricane Hunters show a west-northwestward motion, at about 300/15 kt. Delta should turn toward the north-northwest and north over the next 36 hours or so while moving around the western periphery of a subtropical high pressure system centered over Florida. When the hurricane moves into the northern Gulf of Mexico on Friday, Delta should turn toward the north-northeast on the southeastern side of a mid-tropospheric shortwave over the southern United States. The official track forecast is close to both the simple and corrected dynamical model consensus predictions, TVCA and HCCA, respectively. These objective aids are in close agreement with one another. Based on the official forecast, it is time to issue storm surge and hurricane warnings for a portion of the northern Gulf of Mexico coast. Key Messages: 1. Delta is expected to grow in size as it approaches the northern Gulf Coast, where life-threatening storm surge and dangerous hurricane-force winds are likely beginning Friday, particularly for portions of the Louisiana coast. Storm Surge and Hurricane Warnings are in effect, and residents in these areas should follow advice given by local officials and rush preparedness actions to completion. 2. Flash, urban, small stream and minor to isolated moderate river flooding is likely Friday and Saturday from portions of the central Gulf Coast into portions of the Lower to Middle Mississippi Valley. As Delta moves farther inland, additional heavy rainfall is expected in the Ohio Valley and Mid Atlantic this weekend. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 22.5N 90.9W 80 KT 90 MPH 12H 08/1200Z 23.7N 92.2W 95 KT 110 MPH 24H 09/0000Z 25.4N 93.4W 105 KT 120 MPH 36H 09/1200Z 27.5N 93.5W 100 KT 115 MPH 48H 10/0000Z 30.0N 92.7W 85 KT 100 MPH 60H 10/1200Z 32.4N 91.5W 35 KT 40 MPH...INLAND 72H 11/0000Z 34.2N 89.6W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 12/0000Z 37.5N 85.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 13/0000Z...DISSIPATED $$ Forecaster Pasch Hurricane Delta Advisory Number 14...Corrected NWS National Hurricane Center Miami FL AL262020 1000 PM CDT Wed Oct 07 2020 Corrected to remove Mobile Bay from the Storm Surge Warning area ...STORM SURGE AND HURRICANE WARNINGS ISSUED FOR A PORTION OF THE NORTHERN GULF COAST... SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION ----------------------------------------------- LOCATION...22.5N 90.9W ABOUT 525 MI...845 KM SSE OF CAMERON LOUISIANA MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...28 KM/H MINIMUM CENTRAL PRESSURE...972 MB...28.71 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: A Storm Surge Warning has been issued from Sabine Pass to Ocean Springs, Mississippi, including Calcasieu Lake, Vermilion Bay, Lake Pontchartrain, Lake Maurepas, and Lake Borgne. A Hurricane Warning has been issued for the northern Gulf of Mexico coast from east of Sabine Pass to Morgan City, Louisiana. A Tropical Storm Warning has also been issued for the northern Gulf of Mexico coast from San Luis Pass, Texas to Sabine Pass, and east of Morgan City, Louisiana to the mouth of the Pearl River, including New Orleans, Lake Pontchartrain and Lake Maurepas. The Storm Surge Watch has been discontinued from the Mississippi/Alabama border to the Alabama/Florida border, including Mobile Bay. The government of Mexico has discontinued the Tropical Storm Warning from Rio Lagartos to Dzilam, Mexico. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * Sabine Pass to Ocean Springs, Mississippi including Calcasieu Lake, Vermilion Bay, Lake Pontchartrain, Lake Maurepas, and Lake Borgne A Storm Surge Watch is in effect for... * High Island, TX to Sabine Pass * East of Ocean Springs, Mississippi to the Mississippi/Alabama border A Hurricane Warning is in effect for... * East of Sabine Pass to Morgan City, Louisiana A Tropical Storm Warning is in effect for... * San Luis Pass, Texas to Sabine Pass * East of Morgan City, Louisiana to the mouth of the Pearl River, including New Orleans * Lake Pontchartrain and Lake Maurepas A Tropical Storm Watch is in effect for... * East of the mouth of the Pearl River to Bay St. Louis Mississippi 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 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 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 Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area. 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 Hurricane Delta was located near latitude 22.5 North, longitude 90.9 West. Delta is moving toward the west-northwest near 17 mph (28 km/h). A generally northwestward motion with a reduction in forward speed is expected through early Thursday. A north-northwestward motion is expected by late Thursday, and a faster northward to north-northeastward motion is forecast on Friday and Friday night. On the forecast track, the center of Delta will move over the southern and central Gulf of Mexico through Thursday, and approach the northern Gulf coast within the hurricane warning area on Friday. Delta is forecast to move inland within the hurricane warning area by late Friday or Friday night. Maximum sustained winds are near 90 mph (150 km/h) with higher gusts. Strengthening is forecast while the hurricane moves over the southern and central Gulf of Mexico through Thursday, and Delta is expected to become a major hurricane again. Some weakening is forecast as Delta approaches the northern Gulf coast on Friday. Hurricane-force winds extend outward up to 35 miles (55 km) from the center and tropical-storm-force winds extend outward up to 140 miles (220 km). The estimated minimum central pressure is 972 mb (28.71 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Delta can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT1, WMO header WTNT41 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT1.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... Pecan Island to Port Fourchon, LA including Vermilion Bay...7-11 ft Cameron, LA to Pecan Island, LA...4-7 ft Port Fourchon, LA to the Mouth of the Mississippi River...4-6 ft Mouth of the Mississippi River to Ocean Springs, MS...3-5 ft Lake Borgne, Lake Pontchartrain, and Lake Maurepas...3-5 ft Ocean Springs, MS to MS/AL border...2-4 ft High Island, TX to Cameron, LA including Calcasieu Lake...2-4 ft MS/AL border to the AL/FL border including Mobile Bay...1-3 ft Sabine Lake...1-3 ft Port O'Connor, TX to High Island, TX including Galveston Bay...1-3 ft The deepest water will occur along the immediate coast near and to the east of the landfall location, where the surge will be accompanied by large and dangerous 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 Friday evening, with tropical storm conditions expected within this area earlier on Friday. Tropical storm conditions are expected within the tropical storm warning areas on Friday. RAINFALL: Delta is expected to produce an additional 1 to 3 inches of rain over the far northwestern Yucatan Peninsula through early Thursday. The additional rainfall may still result in areas of significant flash flooding. Friday through Saturday, Delta is expected to produce 4 to 8 inches of rain, with isolated maximum totals of 12 inches across portions of the central Gulf Coast north into portions of the Lower to Middle Mississippi Valley. These rainfall amounts will lead to flash, urban, small stream and minor to isolated moderate river flooding. As Delta moves farther inland, 1 to 3 inches of rain, with locally higher amounts, is expected in the Ohio Valley and Mid Atlantic this weekend. TORNADOES: The risk of a few tornadoes will increase late Thursday night into Friday over portions of southern Louisiana, southern Mississippi, and southwest Alabama. SURF: Swells from Delta will begin to affect portions of the northern and western Gulf coast on Thursday. 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/Berg |