000 WTNT44 KNHC 281457 TCDAT4  Hurricane Ida Discussion Number   9 NWS National Hurricane Center Miami FL       AL092021 1000 AM CDT Sat Aug 28 2021  The satellite presentation of Ida has continued to improve this  morning with the center embedded within a fairly symmetric Central  Dense Overcast and hints of the eye in both visible in infrared  satellite imagery. Earlier microwave imagery revealed a well-  defined low- to mid-level eye and excellent spiral banding over the  northern semicircle.  Both NOAA and Air Force Reserve hurricane  hunter aircraft, somewhat surprisingly, have not found a  significantly deepening tropical cyclone yet, but given the very  recent increase in organization and structure, the winds are likely  to catch up to the satellite appearance very soon.  Using the latest  flight-level and SFMR wind data from the aircraft and satellite  intensity estimates the initial wind speed remains 75 kt for this  advisory.  The aircraft data does indicate that Ida's wind field has  expanded, and the NHC wind radii have been adjusted accordingly.  Given the improved inner-core structure Ida appears poised to  rapidly intensify during the next 12 to 24 hours as it remains  within a favorable environment of low vertical wind shear and over  warm water.  Although the interpolated intensity guidance has  lowered somewhat due to the fact that Ida has not significantly  strengthened yet, the explicit forecasts from the dynamical models  continue to support significant deepening, and the latest runs of  the HWRF and HMON models indicate Ida will reach Category 4 strength  before landfall.  The new NHC intensity forecast calls for rapid  intensification to Category 4 strength during the next 24 hours.   After that time, fluctuations in intensity are possible due to  eyewall replacement cycles as Ida approaches the northern Gulf  coast.  After landfall, rapid weakening is expected and Ida is  forecast to weaken to a tropical depression by Monday night, and  become a post-tropical cyclone as it moves over the Tennessee Valley  by mid-week.  Ida has been moving steadily northwestward or 315/14 kt.  A deep  layer ridge near the southeastern United States coast is forecast to  shift westward during the next day or so, and this should continue  to steer Ida northwestward through landfall on Sunday. The track  guidance remains in remarkably good agreement through 36 hours, and  the new NHC track forecast is essentially unchanged during that  time, and continues to indicate that Ida will reach the coast of  Louisiana on Sunday. After landfall, Ida will be near the western  extent of the ridge and should turn northward and then northeastward  as it recurves into the southern portion of the mid-latitude  westerlies.  The track guidance has shifted slightly westward beyond  48 hours, and the track forecast over the southern U.S. and the  Tennessee Valley has been adjusted accordingly.  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.  Wind and rainfall impacts will also penetrate inland  through early next week after Ida makes landfall.  Key Messages:  1. There is a danger of life-threatening storm surge inundation  Sunday along the coasts of Louisiana and Mississippi 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 today in the warning area.   3. Ida is likely to produce heavy rainfall Sunday and Monday across  the central Gulf Coast from southeast Louisiana to coastal  Mississippi, resulting in life-threatening flash and urban flooding  and significant river flooding impacts. As Ida moves inland,  significant flooding impacts are likely across portions of the Lower  Mississippi and Tennessee Valleys Monday and Tuesday.  FORECAST POSITIONS AND MAX WINDS  INIT  28/1500Z 24.8N  86.1W   75 KT  85 MPH  12H  29/0000Z 26.3N  87.9W  100 KT 115 MPH  24H  29/1200Z 28.0N  89.8W  115 KT 130 MPH  36H  30/0000Z 29.4N  91.0W  115 KT 130 MPH...INLAND  48H  30/1200Z 31.0N  91.5W   60 KT  70 MPH...INLAND  60H  31/0000Z 32.7N  91.0W   30 KT  35 MPH...INLAND  72H  31/1200Z 34.4N  89.8W   25 KT  30 MPH...INLAND  96H  01/1200Z 36.8N  85.3W   20 KT  25 MPH...POST-TROP/INLAND 120H  02/1200Z 37.9N  79.9W   20 KT  25 MPH...POST-TROP/INLAND  $$ Forecaster Brown