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Hurricane IDA

Hurricane Ida Discussion Number  16
NWS National Hurricane Center Miami FL       AL092021
1000 PM CDT Sun Aug 29 2021
Although Ida has been inland over southeastern Louisiana for several 
hours, it is still a very well organized hurricane. Doppler radar 
images indicate that the hurricane continues to have a well-defined 
eye, though the eyewall has become a bit ragged on the southwest 
side.  Beyond the inner core, rain bands remain well established, 
especially on the system's east side.  Earlier this evening, there 
were reports of extreme wind gusts over 120 kt along the coast of 
southeastern Louisiana.  Based on Doppler radar velocity data over 
the past hour or two, the initial intensity is estimated to be 90 
As Ida continues inland, rapid weakening is expected due to a 
combination of land interaction and an increase in wind shear. 
However, damaging winds, especially in gusts, are expected to spread 
further inland over southeastern Louisiana and southwestern 
Mississippi through Monday morning.  To account for this, the gust 
factor in the Forecast/Advisory has been adjusted accordingly.  Ida 
is likely to weaken to a tropical storm by Monday morning and a 
tropical depression by Monday night.  Some slight restrengthening as 
an extratropical storm is possible when Ida moves over the western 
Atlantic in 4 days or so.  In addition, heavy rains will spread 
northward and then northeastward along the forecast track.
Ida is expected to turn northward by early Monday as it moves in the 
flow on the western side of a subtropical ridge.  A faster motion to 
the northeast is expected by Tuesday as a mid- to upper-level trough 
approaches the system, with that motion continuing through much of 
the remainder of the week.  The NHC track forecast is a little to 
the south or right of the previous one to come into better agreement 
with the latest models.
Key Messages:
1. Life-threatening storm surge inundation will continue through 
tonight along portions of the coast between 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.
2. Wind damage will occur near the core of Ida as it continues  
inland over southeastern Louisiana during the next few hours. 
Damaging winds, especially in gusts, will spread inland near the 
track of Ida's center into southwestern Mississippi through early 
Monday. These winds will likely lead to widespread tree damage and 
power outages.
3. Ida will continue to produce heavy rainfall tonight through 
Monday across southeast Louisiana, coastal Mississippi, and 
southwestern Alabama, resulting in considerable to life-threatening 
flash and urban flooding and significant riverine flooding impacts. 
As Ida moves farther inland, considerable flooding impacts are 
possible across portions of the Lower Mississippi Valley, Tennessee 
Valley, Upper Ohio Valley, Central Appalachians, and Mid-Atlantic 
through Wednesday.
INIT  30/0300Z 30.3N  90.7W   90 KT 105 MPH...INLAND
 12H  30/1200Z 31.5N  90.8W   50 KT  60 MPH...INLAND
 24H  31/0000Z 33.0N  90.1W   30 KT  35 MPH...INLAND
 36H  31/1200Z 34.6N  88.5W   25 KT  30 MPH...INLAND
 48H  01/0000Z 36.1N  85.9W   25 KT  30 MPH...POST-TROP/INLAND
 60H  01/1200Z 37.5N  82.5W   25 KT  30 MPH...POST-TROP/INLAND
 72H  02/0000Z 38.9N  78.8W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  03/0000Z 40.0N  72.5W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  04/0000Z 40.7N  67.9W   35 KT  40 MPH...POST-TROP/EXTRATROP
Forecaster Cangialosi