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Hurricane Ida Intermediate Advisory Number 11A
NWS National Hurricane Center Miami FL AL092021
100 AM CDT Sun Aug 29 2021
...AIR FORCE HURRICANE HUNTER AIRCRAFT FINDS IDA HAS STRENGTHENED
INTO A MAJOR HURRICANE...
...LIFE-THREATENING STORM SURGE, POTENTIALLY CATASTROPHIC WIND
DAMAGE, AND FLOODING RAINFALL EXPECTED TO IMPACT THE NORTHERN GULF
COAST BEGINNING THIS MORNING...
SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
ABOUT 105 MI...170 KM SSE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 185 MI...295 KM SE OF HOUMA LOUISIANA
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...955 MB...28.20 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Storm Surge Warning is in effect for...
* East of Rockefeller Wildlife Refuge Louisiana to the
* Vermilion Bay, Lake Borgne, Lake Pontchartrain, Lake Maurepas,
and Mobile Bay
A Hurricane Warning is in effect for...
* Intracoastal City Louisiana to the Mouth of the Pearl River
* Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans
A Tropical Storm Warning is in effect for...
* Cameron Louisiana to west of Intracoastal City Louisiana
* Mouth of the Pearl River to the Alabama/Florida border
A Storm Surge Warning means there is a danger of life-threatening
inundation, from rising water moving inland from the coastline,
during the next 36 hours in the indicated locations. For a depiction
of areas at risk, please see the National Weather Service Storm
Surge Watch/Warning Graphic, available at hurricanes.gov. This is a
life-threatening situation. Persons located within these areas
should take all necessary actions to protect life and property from
rising water and the potential for other dangerous conditions.
Promptly follow evacuation and other instructions from local
A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area within the next 6 to 12 hours.
Preparations to protect life and property should be rushed to
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within the
next 12 to 24 hours.
For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.
DISCUSSION AND OUTLOOK
At 100 AM CDT (0600 UTC), the center of the eye of Hurricane Ida was
located by an Air Force Reserve Hurricane Hunter aircraft and NOAA
Doppler weather radars near latitude 27.6 North, longitude 88.7
West. Ida is moving toward the northwest near 15 mph (24 km/h), and
this general motion should continue through tonight and early
Monday, followed by a slower northward motion on Monday afternoon.
A northeastward turn is forecast by Monday night. On the forecast
track, the center of Ida will continue moving across the
north-central Gulf of Mexico this morning, and make landfall along
the coast of Louisiana within the hurricane warning area this
afternoon or evening. Ida is then forecast to move well inland over
portions of Louisiana and western Mississippi on Monday and Monday
Maximum sustained winds are near 115 mph (185 km/h) with higher
gusts. Ida is now a category 3 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Rapid strengthening is forecast to continue
during the next 12 hours or so, and Ida is expected to be an
extremely dangerous major hurricane when it makes landfall along the
Louisiana coast this afternoon. Rapid weakening is expected after
Hurricane-force winds extend outward up to 40 miles (65 km) from
the center and tropical-storm-force winds extend outward up to 140
miles (220 km).
The minimum central pressure measured by an Air Force Hurricane
Hunter aircraft is 955 mb (28.20 inches).
HAZARDS AFFECTING LAND
Key messages for Ida can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC,
and on the web at hurricanes.gov/graphics_at4.shtml?key_messages.
STORM SURGE: The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline. The water could
reach the following heights above ground somewhere in the indicated
areas if the peak surge occurs at the time of high tide...
Morgan City, LA to Mouth of the Mississippi River...10-15 ft
Mouth of the Mississippi River to Ocean Springs, MS including Lake
Burns Point, LA to Morgan City, LA...6-9 ft
Lake Pontchartrain...5-8 ft
Ocean Springs, MS to MS/AL border...4-7 ft
Intracoastal City, LA to Burns Point, LA including Vermilion
Lake Maurepas...4-6 ft
Pecan Island, LA to Intracoastal City, LA...2-4 ft
MS/AL border to AL/FL border including Mobile Bay...2-4 ft
Sabine Pass to Pecan Island, LA...1-3 ft
Overtopping of local levees outside of the Hurricane and Storm
Damage Risk Reduction System is possible where local inundation
values may be higher than those shown above.
The deepest water will occur along the immediate coast near and to
the east of the landfall location, where the surge will be
accompanied by large and dangerous waves. Surge-related flooding
depends on the relative timing of the surge and the tidal cycle, and
can vary greatly over short distances. For information specific to
your area, please see products issued by your local National Weather
Service forecast office.
WIND: Hurricane conditions are expected in the Hurricane Warning
area along the Louisiana coast beginning by late morning with
tropical storm conditions expected to begin by early this morning.
These conditions will spread inland over portions of Louisiana and
Mississippi tonight and Monday.
RAINFALL: Heavy rainfall from Ida will begin to impact the
Louisiana later this morning, spreading northeast into the Lower
Mississippi Valley by later today into Monday. Total rainfall
accumulations of 8 to 16 inches with isolated maximum amounts of 20
inches are possible across southeast Louisiana into southern
Mississippi through Monday. This is likely to result in
life-threatening flash and urban flooding and significant riverine
Elsewhere across eastern Louisiana, Mississippi, far southwestern
Alabama and the Middle Tennessee Valley -- considerable flash and
riverine flooding impacts are likely on Monday and Tuesday, with
rainfall totals of 4 to 8 inches possible. Rainfall from Ida will
begin to affect the Ohio Valley by mid-week, resulting in flash and
riverine flooding impacts.
TORNADOES: Tornadoes will be possible today into Monday across
eastern Louisiana, Mississippi, central and southern Alabama, and
the Florida Panhandle.
SURF: Swells are beginning to reach the northern Gulf coast and
will continue to affect that area through Monday. These swells are
likely to cause life-threatening surf and rip current conditions.
Please consult products from your local weather office.
Next complete advisory at 400 AM CDT.
Hourly Tropical Cyclone Updates will begin at 200 AM CDT. These
can be found under WMO header WTNT64 KNHC and under AWIPS header