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Hurricane Ida Forecast Discussion Number 11
2021-08-29 04:50:24| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Sat Aug 28 2021 000 WTNT44 KNHC 290250 TCDAT4 Hurricane Ida Discussion Number 11 NWS National Hurricane Center Miami FL AL092021 1000 PM CDT Sat Aug 28 2021 The NOAA Hurricane Hunters investigated Ida earlier this evening and found that the maximum winds were still around 90 kt. Although the peak winds appear to have leveled off for now, the minimum pressure has continued to fall and was down to 966 mb at the last pass through the center an hour or two ago. In fact, the pressure has been dropping by about 2 mb per hour based on the aircraft data. In addition, tail Doppler Radar data from the aircraft indicate that the vortex has become more symmetric and that the inner core has contracted from the mission earlier today. These are signals that Ida is poised to strengthen further, and based on recent satellite images it appears that strengthening is imminent. Flight-level and SFMR observations also indicate that Ida's wind field has expanded and there is some indication of a double-wind maximum. The tropical-storm-force winds now extend outward up to 120 n mi from the center and hurricane-force winds up to 35 n mi from the eye. Ida continues to move steadily to the northwest at about 14 kt. There has been little change to the track forecast rationale. A subtropical ridge situated near the southeast U.S. coast is expected to shift westward during the next day or two. This feature should continue to steer Ida northwestward toward the Louisiana coast. The latest runs of the numerical models bring the center of Ida to southeast or south-central Louisiana Sunday afternoon. Although landfall is not expected for about 18 hours, impacts will begin well before that time. Tropical-storm-force winds are likely to begin overnight, therefore, all preparations to protect life and property must be rushed to completion. The new track forecast is just a little to the east of the previous one through landfall. After Ida moves inland, a turn to the north and then the northeast is expected as the storm moves in the flow on the northwest and north sides of the ridge. Ida remains over waters with high oceanic heat content, and in an atmospheric environment of low wind shear and abundant moisture. These conditions, combined with the improved structure of the hurricane, should allow Ida to rapidly intensify until it makes landfall. The models remain in fairly good agreement, and the NHC forecast holds steady and brings Ida to a dangerous major hurricane prior to landfall. After the storm moves inland on Sunday, rapid weakening is forecast due to a combination of land interaction, drier air and some increase in wind shear. Users are again reminded to not focus on the exact details of the track forecast as storm surge, wind, and rainfall impacts will extend far from the center. Rainfall impacts will also spread inland across the Lower Mississippi and Tennessee Valleys through early next week. Key Messages: 1. There is a danger of life-threatening storm surge inundation Sunday along the coasts of Louisiana, Mississippi, and Alabama within the Storm Surge Warning area. Extremely life-threatening inundation of 9 feet or greater above ground level is possible somewhere within the area from Morgan City, Louisiana, to the coast of Mississippi. Overtopping of local levees outside of the Hurricane and Storm Damage Risk Reduction System is possible where local inundation values may be higher. Interests throughout the warning area should follow any advice given by local officials. 2. Ida is expected to be an extremely dangerous major hurricane when it reaches the coast of Louisiana. Hurricane-force winds are expected Sunday in portions of the Hurricane Warning area along the Louisiana coast, including metropolitan New Orleans, with potentially catastrophic wind damage possible where the core of Ida moves onshore. Actions to protect life and property should be rushed to completion in the warning area. 3. Damaging winds, especially in gusts, will spread inland near the track of the center of Ida across portions of southeastern Louisiana and southwestern Mississippi Sunday night and early Monday. These winds will likely lead to widespread tree damage and power outages. 4. Ida is likely to produce heavy rainfall Sunday into Monday across the central Gulf Coast from southeast Louisiana, coastal Mississippi, and far southwestern Alabama, resulting in considerable to life-threatening flash and urban flooding and significant river flooding impacts. As Ida moves inland, significant flooding impacts are possible across portions of the Lower Mississippi, Tennessee, and Ohio Valleys through Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 27.2N 88.0W 90 KT 105 MPH 12H 29/1200Z 28.4N 89.4W 115 KT 130 MPH 24H 30/0000Z 29.9N 90.7W 85 KT 100 MPH...INLAND 36H 30/1200Z 31.4N 91.2W 45 KT 50 MPH...INLAND 48H 31/0000Z 33.1N 90.6W 30 KT 35 MPH...INLAND 60H 31/1200Z 34.8N 89.1W 25 KT 30 MPH...INLAND 72H 01/0000Z 36.3N 86.7W 20 KT 25 MPH...INLAND 96H 02/0000Z 38.6N 80.6W 20 KT 25 MPH...POST-TROP/INLAND 120H 03/0000Z...DISSIPATED $$ Forecaster Cangialosi
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