| Maybe we'll start a new post for each advisory to track the intensity better as it gets stronger over the next few days. Track: https://www.nhc.noaa.gov/refresh/graphics_at3+shtml/?cone#contents Tropical Storm Laura Discussion Number 21 NWS National Hurricane Center Miami FL AL132020 1100 PM EDT Mon Aug 24 2020 Tropical Storm Laura made landfall on the Pinar del Rio province in western Cuba around 0000 UTC with maximum winds of about 55 kt. Around that time, a wind gust of 56 kt was reported in Havana. Since then the storm has moved across western Cuba and is now coming off the island and over the extreme southeastern Gulf of Mexico. Radar data from Cuba and satellite images indicate that the storm has become better organized with deep convection beginning to wrap around the center with persistent thunderstorms on the south side. Data from the NOAA and Air Force Hurricane Hunters indicate that the pressure has fallen to 996 mb and that the winds are around 55 kt. Laura continues to move fairly steadily to the west-northwest with the latest initial motion estimated to be 290/17 kt. The track forecast reasoning is generally unchanged from previous discussions. Laura should continue to move west-northwestward at about the same forward speed through Tuesday as it remains in the flow on the southwest side of the Atlantic subtropical ridge. By early Wednesday, Laura will likely slow down and turn northwestward and then northward as it moves into a break in the ridge, caused by a weak trough over the south-central U.S. This motion should cause the system to make landfall in either southwestern Louisiana or the Upper Texas coast Wednesday night or early Thursday. After landfall, Laura is forecast to continue moving northward before turning eastward on Friday as it becomes embedded in the mid-latitude westerlies. Although the global models are in relatively good agreement, there remains some spread in the ensemble members, especially in the ECMWF. Therefore, confidence in the track forecast is still not high. The NHC track forecast is slightly to the left of the previous one, trending toward the latest consensus aids. The storm is starting to pull away from the western portion of Cuba, and it should be over the warm Gulf of Mexico waters for about 2 days. Since Laura will have a notable amount of time over waters with high oceanic heat while moving through a low wind shear and high moisture air mass, significant strengthening seems quite likely until the storm makes landfall. The intensity models all show Laura making landfall as a hurricane, but there are differences on exactly how strong it will be. The NHC intensity forecast continues to stay near the consensus aids, which usually perform best, and Laura could be near major hurricane strengthen when it reaches the coast. Users are again reminded not to focus on the exact details of the track or intensity forecasts as the average NHC track error at 48 h is around 80 miles and the average intensity error is close to 15 mph. In addition, wind, storm surge, and rainfall hazards will extend far from the center. Key Messages: 1. Laura is forecast to reach the northwestern Gulf Coast as a hurricane late Wednesday and early Thursday. Do not focus on the details of the official forecast given the typical uncertainty in NHC's 2 to 3 day track and intensity predictions. In addition, storm surge, wind, and rainfall hazards will extend well away from Laura's center along the Gulf Coast. 2. There is a risk of life-threatening storm surge from San Luis Pass, Texas, to Ocean Springs, Mississippi, within the next 48 hours, and a storm surge watch is in effect for these areas outside of the southeast Louisiana Hurricane and Storm Damage Risk Reduction System. Residents in these areas should follow any advice given by local officials. 3. Hurricane conditions are possible by late Wednesday from Port Bolivar, Texas, to west of Morgan City, Louisiana, with tropical storm conditions possible by Wednesday afternoon, and a hurricane watch is in effect. Additional hurricane watches may be needed farther south along the Texas coast if the track forecast shifts toward the south and west tonight and Tuesday. 4. Tropical storm conditions and heavy rainfall are expected across central and western Cuba for several more hours. These rains could cause mudslides and life-threatening flash and urban flooding. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 22.7N 84.0W 55 KT 65 MPH 12H 25/1200Z 23.7N 86.3W 65 KT 75 MPH 24H 26/0000Z 25.2N 89.1W 75 KT 85 MPH 36H 26/1200Z 26.8N 91.6W 85 KT 100 MPH 48H 27/0000Z 28.8N 93.0W 95 KT 110 MPH 60H 27/1200Z 31.3N 93.6W 65 KT 75 MPH...INLAND 72H 28/0000Z 33.8N 93.0W 40 KT 45 MPH...INLAND 96H 29/0000Z 36.7N 89.1W 25 KT 30 MPH...INLAND 120H 30/0000Z 36.9N 77.1W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi Tropical Storm Laura Advisory Number 21 NWS National Hurricane Center Miami FL AL132020 1100 PM EDT Mon Aug 24 2020 ...LAURA FORECAST TO BECOME A HURRICANE ON TUESDAY... ...HEAVY RAINS AND FLASH FLOODING CONTINUES OVER WESTERN CUBA... SUMMARY OF 1100 PM EDT...0300 UTC...INFORMATION ----------------------------------------------- LOCATION...22.7N 84.0W ABOUT 80 MI...130 KM NE OF THE WESTERN TIP OF CUBA ABOUT 765 MI...1230 KM SE OF LAKE CHARLES LOUISIANA MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H PRESENT MOVEMENT...WNW OR 290 DEGREES AT 20 MPH...31 KM/H MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The Tropical Storm Warning for the Middle Florida Keys has been discontinued. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Watch is in effect for... * San Luis Pass Texas to Ocean Springs Mississippi * Lake Pontchartrain, Lake Maurepas, and Lake Borgne A Hurricane Watch is in effect for... * Port Bolivar Texas to west of Morgan City Louisiana A Tropical Storm Warning is in effect for... * Cuban provinces of Villa Clara, Cienfuegos, Matanzas, Mayabeque, La Habana, Artemisa, Pinar del Rio, and the Isle of Youth * Florida Keys from the Seven Mile Bridge to Key West * Dry Tortugas A Tropical Storm Watch is in effect for... * South of Port Bolivar to San Luis Pass Texas * Morgan City Louisiana to the Mouth of the Mississippi River 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 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. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 1100 PM EDT (0300 UTC), the center of Tropical Storm Laura was located near latitude 22.7 North, longitude 84.0 West. Laura is moving toward the west-northwest near 20 mph (31 km/h) and this general motion with some decrease in forward speed is expected over the next day or so. 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 away from Cuba and over the southeastern Gulf of Mexico overnight. Laura is then forecast to move over the central and northwestern Gulf of Mexico Tuesday night and Wednesday, and approach the northwestern coast of the Gulf of Mexico Wednesday night. Maximum sustained winds are near 65 mph (105 km/h) with higher gusts. Strengthening is expected, and Laura is foreast to become a hurricane on Tuesday. Additional strengthening is forecast on Wednesday, and Laura could be near major hurricane strength when it approaches the coast. Tropical-storm-force winds extend outward up to 175 miles (280 km) from the center. The estimated minimum central pressure based on data from the NOAA and Air Force Hurricane Hunters is 996 mb (29.42 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... High Island TX to Morgan City LA including Sabine Lake, Calcasieu Lake, and Vermilion Bay...7-11 ft Port Bolivar TX to High Island TX...4-6 ft Morgan City LA to Mouth of the Mississippi River...4-6 ft Mouth of the Mississippi River to Ocean Springs MS including Lake Borgne...3-5 ft San Luis Pass TX to Port Bolivar TX...2-4 ft Galveston Bay...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. 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: Laura is expected to produce the following storm total rainfall accumulations into tonight: Western Cuba: 4 to 6 inches, with maximum amounts of 10 inches. This heavy rainfall could lead to life-threatening flash and urban flooding, and the potential for mudslides. From Wednesday afternoon into Saturday, Laura is expected to produce rainfall of 4 to 8 inches, with isolated maximum amounts of 12 inches across portions of the west-central U.S. Gulf Coast near the Texas and Louisiana border north into portions of the lower Mississippi Valley. This rainfall could cause widespread flash and urban flooding, small streams to overflow their banks, and minor to isolated moderate river flooding. WIND: Tropical storm conditions are expected to spread westward within the warning area in western Cuba during the next few hours. Tropical storm conditions are also expected within the warning area in the middle and lower Florida Keys and the Dry Tortugas tonight. Hurricane conditions are possible in the hurricane watch area along the Gulf Coast by late Wednesday, with tropical storm conditions possible by Wednesday afternoon. 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 on Tuesday and Tuesday night, 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 200 AM EDT. Next complete advisory at 500 AM EDT. $$ Forecaster Cangialosi |