| Track: https://www.nhc.noaa.gov/refresh/graphics_at3+shtml/?cone#contents Hurricane Laura Discussion Number 24 NWS National Hurricane Center Miami FL AL132020 400 PM CDT Tue Aug 25 2020 Satellite imagery shows some changes in the convective pattern of Laura since the last advisory. The ragged central dense overcast seen earlier has been replaced by a curved convective band that wraps almost all the way around a cloud-filled banding-type eve. One possible reason for this change is that the imagery also suggests a tongue of dry air is trying to entrain into the cyclone just west of the central convection. Aircraft data received after the last advisory did not show any fall in the central pressure, but did have high enough flight-level and SFMR winds to justify nudging the initial intensity up to 70 kt. The initial motion is now west-northwestward or 300/15 kt. There is no change in the forecast philosophy since the last advisory. The hurricane is currently on the south side of a large-deep layer ridge over the southeastern United States, and it is moving toward a break in the ridge caused by mid- to -upper-level troughing over Texas and the southern Great Plains. The current and forecast synoptic pattern should steer Laura west-northwestward this evening, followed by a turn toward the northwest tonight and toward the north by Wednesday night and Thursday. This will result in the hurricane making landfall in the area of southwestern Louisiana or the upper Texas coast late Wednesday night or Thursday morning. The new forecast track has a slight eastward nudge during the first 12-24 h, but the landfall position is almost unchanged from that of the previous forecast. It should the be noted that the current forecast track lies to the east of the ECMWF and UKMET models, so it is still possible that the forecast track could nudge westward in later advisories. After landfall, Laura is expected to recurve into the westerlies and move eastward through the Tennessee Valley and the mid-Atlantic States before reaching the Atlantic in about 120 h. All indications are that the hurricane should steadily to rapidly intensify during the next 24 h, with the only negative factor being the possibility of more dry air entrainment. The intensity forecast will go with the scenario that the dry air will not significantly hinder strengthening. The global models are in good agreement that Laura will encounter increasing southwesterly shear in the last 6-12 h before landfall, so the intensity forecast shows slower strengthening during that time. With all that said, the landfall intensity of 100 kt is unchanged from the previous advisory. After landfall, Laura should weaken through the 96 h point, followed by re-intensification through baroclinic energy as the cyclone becomes extratropical. Users are again reminded not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 36 h is around 60 miles and the average intensity error is close to 10 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. There is a danger of life-threatening storm surge with large and dangerous waves producing potentially catastrophic damage from San Luis Pass, Texas, to the Mouth of the Mississippi River, including areas inside the Port Arthur Hurricane Flood Protection system. This surge could penetrate up to 30 miles inland from the immediate coastline in southwestern Louisiana and far southeastern Texas. Actions to protect life and property should be rushed to completion this evening, as water levels will begin to rise on Wednesday. 2. Hurricane-force winds are expected Wednesday night in the warning area from San Luis Pass, Texas, to west of Morgan City, Louisiana, and the strongest winds associated with Laura's eyewall will occur somewhere within this area. Hurricane-force winds and widespread damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. 3. The threat of widespread flash and urban flooding along with small streams overflowing their banks will increase due to heavy rainfall Wednesday night into Thursday from far eastern Texas, across Louisiana, and Arkansas. This will also result in minor to isolated moderate river flooding. The heavy rainfall threat will spread northeastward into the middle-Mississippi, lower Ohio and Tennessee Valleys Friday night and Saturday. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 24.7N 88.3W 70 KT 80 MPH 12H 26/0600Z 25.7N 90.3W 85 KT 100 MPH 24H 26/1800Z 27.5N 92.4W 95 KT 110 MPH 36H 27/0600Z 29.7N 93.8W 100 KT 115 MPH...ON COAST 48H 27/1800Z 32.2N 93.9W 65 KT 75 MPH...INLAND 60H 28/0600Z 34.7N 93.3W 40 KT 45 MPH...INLAND 72H 28/1800Z 36.5N 90.9W 30 KT 35 MPH...INLAND 96H 29/1800Z 38.5N 80.5W 25 KT 30 MPH...INLAND 120H 30/1800Z 42.0N 66.5W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven Hurricane Laura Advisory Number 24 NWS National Hurricane Center Miami FL AL132020 400 PM CDT Tue Aug 25 2020 ...LAURA MOVING WEST-NORTHWESTWARD ACROSS THE CENTRAL GULF OF MEXICO... ...EXPECTED TO STRENGTHEN INTO A MAJOR HURRICANE BEFORE LANDFALL WEDNESDAY NIGHT OR THURSDAY MORNING... SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...24.7N 88.3W ABOUT 480 MI...770 KM SE OF LAKE CHARLES LOUISIANA ABOUT 510 MI...820 KM SE OF GALVESTON TEXAS MAXIMUM SUSTAINED WINDS...80 MPH...130 KM/H PRESENT MOVEMENT...WNW OR 300 DEGREES AT 17 MPH...28 KM/H MINIMUM CENTRAL PRESSURE...990 MB...29.24 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * San Luis Pass 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 Storm Surge Watch is in effect for... * Freeport Texas to San Luis Pass * Mouth of the Mississippi River to Ocean Springs Mississippi * Lake Pontchartrain, Lake Maurepas, and Lake Borgne 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, 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. 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 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. 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 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 center of Hurricane Laura was located near latitude 24.7 North, longitude 88.3 West. Laura is moving toward the west-northwest near 17 mph (28 km/h), and this general motion should continue tonight. A turn toward the northwest is forecast by Wednesday, and a northwestward to north-northwestward motion should continue through Wednesday night. On the forecast track, the center of Laura will move across the central Gulf of Mexico tonight and the northwestern Gulf of Mexico on Wednesday. The hurricane should approach the Upper Texas and Southwest Louisiana coasts on Wednesday night and move inland near those areas late Wednesday night or Thursday morning. Maximum sustained winds are near 80 mph (130 km/h) with higher gusts. Significant strengthening is forecast during the next 36 hours, and Laura is expected to be a major hurricane at landfall. Rapid weakening is expected after Laura makes landfall. Hurricane-force winds extend outward up to 45 miles (75 km) from the center and tropical-storm-force winds extend outward up to 175 miles (280 km). The estimated minimum central pressure is 990 mb (29.24 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: 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... Sea Rim State Park TX to Intracoastal City LA including Sabine Lake and Calcasieu Lake...9-13 ft Intracoastal City to Morgan City including Vermilion Bay...7-11 ft Port Bolivar TX to Sea Rim State Park...6-9 ft Morgan City LA to Mouth of the Mississippi River...4-6 ft San Luis Pass TX to Port Bolivar...3-5 ft Galveston Bay...3-5 ft Freeport TX to San Luis Pass...2-4 ft Mouth of the Mississippi River to Ocean Springs MS including Lake Borgne...2-4 ft Lake Pontchartrain and Lake Maurepas...2-4 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. This storm surge could penetrate up to 30 miles inland from the immediate coastline in southwestern Louisiana and far southeastern Texas. 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. RAINFALL: From Wednesday afternoon through Friday, Laura is expected to produce rainfall totals of 5 to 10 inches, with isolated maximum amounts of 15 inches across portions of the northwestern Gulf Coast from western Louisiana to far eastern Texas, and northward into much of Arkansas. Over the Lower to Middle Mississippi Valley from central Louisiana into western Tennessee and Kentucky, and southeastern Missouri, 2 to 4 inches of rainfall with isolated totals of 6 inches are expected. This rainfall will cause widespread flash and urban flooding, small streams to overflow their banks, and minor to isolated moderate river flooding. By late Friday into Saturday, portions of the Tennessee and Ohio Valley could see 2 to 4 inches with locally higher amounts as tropical moisture from Laura moves through the region. WIND: Hurricane conditions are expected in the hurricane warning area Wednesday night and Thursday. Tropical storm conditions are expected to reach the coast in the hurricane warning area late Wednesday or Wednesday night, and are expected in the tropical storm warning area Wednesday night and Thursday. Hurricane-force winds and damaging wind gusts are also expected to spread well inland into portions of eastern Texas and western Louisiana early Thursday. TORNADOES: A few tornadoes are expected Wednesday and Wednesday night over Louisiana, southeast Texas, and southwestern Mississippi. SURF: Swells generated by Laura are affecting portions of Cuba, the central Bahamas, and the Florida Keys. Swells are expected to spread northward along portions of the west coast of Florida peninsula and the coast of the Florida panhandle later today and tonight, and reach the northern and northwest Gulf coast by Wednesday. 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. $$ Forecaster Beven |