| Track: https://www.nhc.noaa.gov/refresh/graphics_at3+shtml/?cone#contents Hurricane Laura Discussion Number 28 NWS National Hurricane Center Miami FL AL132020 400 PM CDT Wed Aug 26 2020 Laura has continued to rapidly strengthen today with recent visible satellite imagery revealing a very distinct 25 nautical- mile-wide eye embedded in a symmetric central dense overcast. The upper-level outflow has also become well established in all quadrants. An Air Force Reserve hurricane hunter aircraft that is still investigating the hurricane has reported peak 700-mb flight-level winds of 136 kt and SFMR winds of 121 kt in the northeast eyewall. These data support an initial intensity of 125 kt, which is an increase of 55 kt over the past 24 hours. The minimum pressure has fallen to around 947 mb. The well-defined eye is now within range of the NWS Lake Charles WSR-88D radar, and hourly Tropical Cyclone Updates began at 1900 UTC (2 PM CDT) and will continue through landfall and beyond overnight. Laura still has about 12 hours remaining over the warm waters of the northwest Gulf of Mexico waters, but increasing southwesterly shear around the time of landfall and the possibility of an eyewall replacement could result in some fluctuations in intensity this evening, but Laura is expected to remain an extremely dangerous category 4 hurricane through landfall tonight. Although rapid weakening is expected on Thursday as Laura moves inland, the hurricane is expected to bring a swath of damaging winds well inland over western Louisiana and extreme eastern Texas. The cyclone or its remnants are forecast to move off Mid-Atlantic coast over the weekend and there remains some possibility that Laura will re-intensify as a tropical cyclone offshore of the United States east before it merges with a frontal boundary later in the forecast period. Recent satellite and aircraft fixes show that Laura is moving northwestward at about 13 kt. Laura is nearing the western extent of a mid-level ridge that is located over the southeastern United States. The hurricane should turn north-northwestward this evening and northward on Thursday between the ridge and a weak trough over the south-central United States. By Friday the cyclone should turn northeastward and then east-northeastward as it becomes embedded in the mid-latitude westerlies. The track model guidance continues to be in good agreement through 72, but there are some forward speed differences thereafter. The new NHC track is very close to the previous advisory and is near the middle of the guidance envelope. Laura is a large hurricane and users are reminded to not focus on the precise track forecast since wind, storm surge, and rainfall hazards extend far from the center. Key Messages: 1. Unsurvivable storm surge with large and destructive waves will cause catastrophic damage from Sea Rim State Park, Texas, to Intracoastal City, Louisiana, including Calcasieu and Sabine Lakes. This surge could penetrate up to 40 miles inland from the immediate coastline, and flood waters will not fully recede for several days after the storm. 2. Hurricane-force winds are expected tonight in portions of the hurricane warning area, with catastrophic wind damage expected where Laura's eyewall moves onshore. Hurricane-force winds and widespread damaging wind gusts will spread well inland into portions of extreme eastern Texas and western Louisiana early Thursday. 3. Widespread flash flooding along small streams, urban areas, and roadways is expected to begin this afternoon into Thursday from far eastern Texas into Louisiana and Arkansas. This will also lead to minor to moderate freshwater river flooding. The heavy rainfall threat and flash and urban flooding potential will spread northeastward into the middle-Mississippi, lower Ohio, and Tennessee Valleys Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 27.9N 92.8W 125 KT 145 MPH 12H 27/0600Z 29.7N 93.6W 130 KT 150 MPH 24H 27/1800Z 32.5N 93.5W 60 KT 70 MPH...INLAND 36H 28/0600Z 34.8N 92.7W 35 KT 40 MPH...INLAND 48H 28/1800Z 36.5N 90.1W 25 KT 30 MPH...INLAND 60H 29/0600Z 37.3N 85.6W 25 KT 30 MPH...INLAND 72H 29/1800Z 38.0N 79.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 30/1800Z 43.2N 64.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 31/1800Z 51.0N 49.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown Hurricane Laura Advisory Number 28 NWS National Hurricane Center Miami FL AL132020 400 PM CDT Wed Aug 26 2020 ...WIND AND WATER LEVELS INCREASING AS EXTREMELY DANGEROUS HURRICANE LAURA TAKES AIM AT THE NORTHWEST GULF COAST... ...CATASTROPHIC STORM SURGE, EXTREME WINDS, AND FLASH FLOODING EXPECTED ALONG THE NORTHWEST GULF COAST TONIGHT... SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...27.9N 92.8W ABOUT 155 MI...250 KM S OF LAKE CHARLES LOUISIANA ABOUT 155 MI...250 KM SSE OF PORT ARTHUR TEXAS MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H PRESENT MOVEMENT...NW OR 320 DEGREES AT 15 MPH...24 KM/H MINIMUM CENTRAL PRESSURE...947 MB...27.97 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Storm Surge Watch has been discontinued east of the Mouth of the Mississippi River, including Lake Pontchartrain, Lake Maurepas, and Lake Borgne. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * Freeport Texas to the Mouth of the Mississippi River A Hurricane Warning is in effect for... * San Luis Pass Texas to Intracoastal City Louisiana A Tropical Storm Warning is in effect for... * Sargent Texas to San Luis Pass * East of Intracoastal City Louisiana to the Mouth of the Mississippi River A Hurricane Watch is in effect for... * East of Intracoastal City to west of Morgan City Louisiana A Storm Surge Warning means there is a danger of life-threatening inundation, from rising water moving inland from the coastline 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 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. 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 400 PM CDT (2100 UTC), the eye of Hurricane Laura was located near latitude 27.9 North, longitude 92.8 West. Laura is moving toward the northwest near 15 mph (24 km/h). A turn toward the north-northwest and north is expected tonight, and a northward motion should continue on Thursday. A northeastward to east- northeastward motion is expected Thursday night and Friday. On the forecast track, Laura will approach the Upper Texas and southwest Louisiana coasts this evening and move inland within that area tonight. The center of Laura is forecast to move over northwestern Louisiana tomorrow, across Arkansas Thursday night, and over the mid-Mississippi Valley on Friday. Reports from an Air Force Reserve hurricane hunter aircraft indicate that the maximum sustained winds have increased to near 145 mph (230 km/h) with higher gusts. Laura is an extremely dangerous category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some additional strengthening is possible this evening before Laura reaches the northwest Gulf coast overnight. Rapid weakening is expected after Laura moves inland. Hurricane-force winds extend outward up to 60 miles (95 km) from the center and tropical-storm-force winds extend outward up to 205 miles (335 km). The latest minimum central pressure reported by an Air Force Reserve reconnaissance aircraft is 947 mb (27.97 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Laura can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC. Storm surge and tropical-storm-force winds will arrive within the warning areas well in advance of Laura's center. All preparations to protect life and property should be rushed to completion in the next few hours. 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... Johnson Bayou LA to Rockefeller Wildlife Refuge including Calcasieu Lake...15-20 ft Sea Rim State Park TX to Johnson Bayou LA including Sabine Lake...10-15 ft Rockefeller Wildlife Refuge to Intracoastal City LA...10-15 ft Intracoastal City LA to Morgan City including Vermilion Bay...8-12 ft Port Bolivar TX to Sea Rim State Park...6-9 ft Morgan City LA to Mouth of the Mississippi River...4-7 ft Freeport TX to Port Bolivar including Galveston Bay...2-4 ft Mouth of the Mississippi River to Ocean Springs MS including Lake Borgne...1-3 ft Lake Pontchartrain and Lake Maurepas...1-3 ft The deepest water will occur along the immediate coast near and to the right of the landfall location, where the surge will be accompanied by large and destructive waves. Unsurvivable storm surge with large and destructive waves will cause catastrophic damage from Sea Rim State Park, Texas, to Intracoastal City, Louisiana, including Calcasieu and Sabine Lakes. This surge could penetrate up to 40 miles inland from the immediate coastline, and flood waters will not fully recede for several days after the storm. 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 in the hurricane warning area tonight and Thursday, with catastrophic wind damage expected where Laura's eyewall moves onshore tonight. Tropical storm conditions are moving onshore along the coast of Louisiana within the tropical storm warning area and are expected to spread northwestward within the warning areas this evening. Hurricane-force winds and damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. RAINFALL: From this afternoon through Friday, Laura is expected to produce the following rainfall totals: Across the northwestern Gulf Coast from far southwest Louisiana and the Golden Triangle of Southeast Texas: 8 to 12 inches with isolated totals of 18 inches. Across central and the rest of western Louisiana into far eastern Texas: 5 to 10 inches with isolated totals of 15 inches. Across much of Arkansas: 3 to 7 inches with isolated totals of 10 inches. This rainfall will cause widespread flash and urban flooding, small streams and creeks to overflow their banks, and minor to moderate freshwater river flooding. By Friday into Saturday, Laura is expected to produce the following rainfall totals: Across the mid-Mississippi and portions of the Tennessee Valley, Lower Ohio Valley, and central Appalachians: 2 to 4 inches with isolated maximum amounts of 6 inches. This rainfall may lead to flash and urban flooding and rapid rises on small streams. Across the Mid-Atlantic Region: 1 to 3 inches. TORNADOES: Several tornadoes are expected late this afternoon through tonight over Louisiana, far southeast Texas, and southwestern Mississippi. The risk for a few tornadoes will continue into Thursday across Louisiana, Arkansas, and western Mississippi. SURF: Swells produced by Laura are affecting the U.S. Gulf coast from the west coast of Florida to Texas and northeastern Mexico. 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 700 PM CDT. Next complete advisory at 1000 PM CDT. Hourly Tropical Cyclone Updates will be issued between Public advisories. These can be found under WMO header WTNT63 KNHC and under AWIPS header MIATCUAT3. $$ Forecaster Brown |