NHC: http://www.nhc.noaa.gov/ Forecast for water levels above ground higher. Hurricane Harvey Special Advisory Number 17 NWS National Hurricane Center Miami FL AL092017 100 PM CDT Thu Aug 24 2017 ...HARVEY RAPIDLY INTENSIFYING... ...PREPARATIONS ALONG THE MIDDLE TEXAS COAST SHOULD BE RUSHED TO COMPLETION TODAY... SUMMARY OF 100 PM CDT...1800 UTC...INFORMATION ---------------------------------------------- LOCATION...24.4N 93.6W ABOUT 335 MI...540 KM SE OF CORPUS CHRISTI TEXAS ABOUT 325 MI...525 KM SSE OF PORT OCONNOR TEXAS MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H PRESENT MOVEMENT...NNW OR 335 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...979 MB...28.91 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Warning is in effect for... * Port Mansfield to San Luis Pass Texas A Storm Surge Watch is in effect for... * South of Port Mansfield Texas to the Mouth of the Rio Grande * North of San Luis Pass to High Island Texas A Hurricane Warning is in effect for... * Port Mansfield to Matagorda Texas A Tropical Storm Warning is in effect for... * North of Matagorda to High Island Texas * South of Port Mansfield Texas to the Mouth of the Rio Grande A Hurricane Watch is in effect for... * South of Port Mansfield Texas to the Mouth of the Rio Grande A Tropical Storm Watch is in effect for... * South of the Mouth of the Rio Grande to Boca de Catan Mexico 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 Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. 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 Tropical Storm Watch means that tropical storm conditions are possible within the watch area. In addition, interests in southwestern Louisiana should continue to monitor the progress of this system. 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 the United States, please monitor products issued by your national meteorological service. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 100 PM CDT (1800 UTC), the eye of Hurricane Harvey was located by reconnaissance aircraft near latitude 24.4 North, longitude 93.6 West. Harvey is moving toward the north-northwest near 10 mph (17 km/h). A turn toward the northwest is expected later today, and Harvey's forward speed is forecast to slow down during the next couple of days. On the forecast track, Harvey will approach the middle Texas coast on Friday and make landfall Friday night or early Saturday, and then stall near the middle Texas coast through the weekend. Data from Air Force Reserve and NOAA Hurricane Hunter aircraft indicate that maximum sustained winds have increased to near 85 mph (140 km/h) with higher gusts. Additional rapid strengthening is forecast, and Harvey is expected to become a major hurricane by Friday before it reaches the middle Texas coast. Hurricane-force winds extend outward up to 25 miles (35 km) from the center, and tropical-storm-force winds extend outward up to 90 miles (150 km). Data from the NOAA Hurricane Hunter plane indicate that the minimum central pressure is 979 mb (28.91 inches). HAZARDS AFFECTING LAND ---------------------- RAINFALL: Harvey is expected to produce total rain accumulations of 12 to 20 inches and isolated maximum amounts of 30 inches over the middle and upper Texas coast through next Wednesday. During the same time period Harvey is expected to produce total rain accumulations of 5 to 12 inches in far south Texas and the Texas Hill Country to central Louisiana, with accumulations of less than 5 inches extending into other parts of Texas and the lower Mississippi Valley. Rainfall from Harvey may cause life-threatening flooding. 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 is expected to reach the following heights above ground if the peak surge occurs at the time of high tide... N Entrance Padre Island Natl Seashore to Sargent...6 to 12 ft Sargent to Jamaica Beach...5 to 8 ft Port Mansfield to N Entrance Padre Island Natl Seashore...5 to 7 ft Jamaica Beach to High Island...2 to 4 ft Mouth of the Rio Grande to Port Mansfield...2 to 4 ft High Island to Morgan City...1 to 3 ft The deepest water will occur along the immediate coast near and to the northeast 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. WIND: Hurricane conditions are likely within the hurricane warning area late Friday or Friday night, with tropical storm conditions expected to first reach the coast in the hurricane warning area Friday. SURF: Swells generated by Harvey are likely to affect the Texas, Louisiana, and northeast Mexico coasts by Friday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next complete advisory at 400 PM CDT. $$ Forecaster Berg Hurricane Harvey Special Discussion Number 17 NWS National Hurricane Center Miami FL AL092017 100 PM CDT Thu Aug 24 2017 This special advisory is being issued to update Harvey's initial and forecast intensities through the 48-hour period. The storm surge values in the public advisory have also been updated based on the new intensity forecast. Recent data from Air Force Reserve and NOAA Hurricane Hunter aircraft indicate that Harvey's maximum sustained winds have increased to 75 kt. The Air Force plane measured maximum 850-mb flight-level winds of 88 kt and reliable SFMR winds around 75 kt. Based on the hurricane's current rate of intensification, the forecast intensities at 12 and 24 h have been raised by 15 kt, with a 10-kt increase at 36 h. There are no changes to the track or wind radii forecast with this special advisory. It is critical that users not focus on the exact forecast track of Harvey, since cycle-to-cycle adjustment are likely. All locations within the hurricane and storm surge warning areas should be preparing for the possibility of major hurricane-force winds and life-threatening storm surge. Note that this special advisory takes the place of the scheduled 100 PM CDT (1800 UTC) intermediate advisory. Key Messages: 1. Harvey has intensified rapidly, and is forecast to be a major hurricane at landfall, bringing life-threatening storm surge, rainfall, and wind hazards to portions of the Texas coast. Preparations to protect life and property should be completed by tonight, as tropical-storm-force winds will first arrive in the hurricane and storm surge warning areas on Friday. 2. A Storm Surge Warning is in effect for much of the Texas coast. Life-threatening storm surge flooding could reach heights of 6 to 12 feet above ground level at the coast between the north entrance of the Padre Island National Seashore and Sargent. For a depiction of areas at risk, see the Storm Surge Watch/Warning Graphic at hurricanes.gov. 3. Life-threatening flooding is expected across much of the Texas coast from heavy rainfall of 12 to 20 inches, with isolated amounts as high as 30 inches, from Friday through early next week. Please refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. 4. The Potential Storm Surge Flooding Map is available on the NHC website. This product depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded at each individual location. This map best represents the flooding potential in those locations within the watch and warning areas. FORECAST POSITIONS AND MAX WINDS INIT 24/1800Z 24.4N 93.6W 75 KT 85 MPH 12H 25/0000Z 24.9N 94.2W 85 KT 100 MPH 24H 25/1200Z 26.0N 95.3W 105 KT 120 MPH 36H 26/0000Z 27.3N 96.3W 110 KT 125 MPH 48H 26/1200Z 28.3N 97.0W 100 KT 115 MPH...INLAND 72H 27/1200Z 29.0N 97.7W 40 KT 45 MPH...INLAND 96H 28/1200Z 28.5N 97.5W 35 KT 40 MPH...INLAND 120H 29/1200Z 28.5N 96.5W 30 KT 35 MPH...INLAND $$ Forecaster Berg |