ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
 
Hurricane Ida Special Discussion Number  13
NWS National Hurricane Center Miami FL       AL092021
700 AM CDT Sun Aug 29 2021
 
Recent reports from both NOAA and Air Force Reserve Hurricane Hunter
aircraft indicate that Ida has continued to strengthen since the
0900 UTC advisory and the maximum winds are estimated to be 130
kt. This intensity is based on peak 700-mb flight-level winds of
146 kt that have been reported by both aircraft and believable SFMR
winds of around 130 kt. The NOAA aircraft very recently reported 
that the minimum pressure has fallen to around 933 mb.  This special 
advisory is issued to raise the 12-hour forecast intensity to 135 
kt, but it is possible that Ida could peak slightly above that 
before landfall occurs.
 
The initial motion estimate is 320/13 kt, slightly faster than 
the previous forecast.  Therefore, the 12-hour forecast point has
also been adjusted slightly.  No other changes were made to the 
track or intensity forecasts.
 
The initial and forecast 64-kt wind radii were adjusted outward in
the northeast and southeast quadrants based on aircraft data.
 
Note that this Special advisory replaces the regular 1200 UTC (700
AM CDT) intermediate public advisory.
 
Key Messages:
 
1. Extremely life-threatening storm surge inundation of 9 feet or 
greater above ground level is imminent somewhere within the area 
from Burns Point, Louisiana, to Ocean Springs, 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 Storm Surge Warning 
area should follow any advice given by local officials.

2. Catastrophic wind damage is likely where the core of Ida moves 
onshore along the southeast coast of Louisiana in the next few 
hours. Hurricane-force winds are expected today within the Hurricane 
Warning area along the Louisiana coast, including metropolitan New 
Orleans. 

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 today through early Monday. These winds 
will likely lead to widespread tree damage and power outages.

4. Ida will produce heavy rainfall today through Monday across the 
central Gulf Coast from southeastern Louisiana, coastal Mississippi, 
to 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  29/1200Z 28.5N  89.6W  130 KT 150 MPH
 12H  29/1800Z 29.2N  90.4W  135 KT 155 MPH
 24H  30/0600Z 30.6N  91.1W   70 KT  80 MPH...INLAND
 36H  30/1800Z 32.2N  91.0W   45 KT  50 MPH...INLAND
 48H  31/0600Z 33.8N  90.0W   30 KT  35 MPH...INLAND
 60H  31/1800Z 35.4N  87.9W   25 KT  30 MPH...INLAND
 72H  01/0600Z 36.7N  85.2W   20 KT  25 MPH...INLAND
 96H  02/0600Z 38.9N  78.9W   20 KT  25 MPH...POST-TROP/INLAND
120H  03/0600Z...DISSIPATED
 
$$
Forecaster Brown/Brennan
 
NNNN