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Hurricane IDA

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.
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