BULLETIN
Tropical Storm Ida Intermediate Advisory Number 4A
NWS National Hurricane Center Miami FL AL092021
800 AM EDT Fri Aug 27 2021
…AIR FORCE AND NOAA AIRCRAFT FIND IDA STRENGTHENING OVER THE
NORTHWEST CARIBBEAN SEA…
SUMMARY OF 800 AM EDT…1200 UTC…INFORMATION
———————————————-
LOCATION…20.3N 81.7W
ABOUT 75 MI…125 KM NNW OF GRAND CAYMAN
ABOUT 115 MI…185 KM SE OF THE ISLE OF YOUTH
MAXIMUM SUSTAINED WINDS…60 MPH…95 KM/H
PRESENT MOVEMENT…NW OR 320 DEGREES AT 15 MPH…24 KM/H
MINIMUM CENTRAL PRESSURE…996 MB…29.41 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:
The government of the Cayman Islands has discontinued the Tropical
Storm Warning for Grand Cayman. The Tropical Storm Warning remains
in effect for Little Cayman and Cayman Brac.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Storm Surge Watch is in effect for…
* Sabine Pass to Alabama/Florida border
* Vermilion Bay, Lake Borgne, Lake Pontchartrain, Lake Maurepas, and
Mobile Bay
A Hurricane Watch is in effect for…
* Cameron, Louisiana to the Mississippi/Alabama border
* Lake Pontchartrain, Lake Maurepas, and Metropolitan New Orleans
A Tropical Storm Warning is in effect for…
* Little Cayman and Cayman Brac
* Cuban provinces of Matanzas, Mayabeque, Havana, Artemisa, Pinar
del Rio, and the Isle of Youth
A Tropical Storm Watch is in effect for…
* Mississippi/Alabama border to the Alabama/Florida border.
A Storm Surge Watch means there is a possibility of life-
threatening inundation, from rising water moving inland from the
coastline, in the indicated locations during the next 48 hours.
For a depiction of areas at risk, please see the National Weather
Service Storm Surge Watch/Warning Graphic, available at
hurricanes.gov.
A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds, conditions that make outside preparations difficult or
dangerous.
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.
A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.
Interests elsewhere in central and western Cuba and elsewhere along
the northern U.S. Gulf coast should monitor the progress of this
system. Hurricane warnings will likely be required for portions of
the northern Gulf coast later today. Interests in the Dry Tortugas
should also monitor the progress of Ida.
For storm information specific to your area in the United States,
including possible inland watches and warnings, please monitor
products issued by your local National Weather Service forecast
office. For storm information specific to your area outside of the
United States, please monitor products issued by your national
meteorological service.
DISCUSSION AND OUTLOOK
———————-
At 800 AM EDT (1200 UTC), the center of Tropical Storm Ida was
located by reconnaissance aircraft and weather radar on Grand
Cayman near latitude 20.3 North, longitude 81.7 West. Ida is moving
toward the northwest near 15 mph (24 km/h) and this general motion
should continue over the next few days. On the forecast track, the
center of Ida will move away from the Cayman Islands this morning,
pass near or over the Isle of Youth and western Cuba later today,
and move over the southeastern and central Gulf of Mexico tonight
and Saturday. The system is forecast to approach the U.S. northern
Gulf coast on Sunday.
Data from Air Force Reserve and NOAA reconnaissance aircraft
indicate that the maximum sustained winds have increased to near 60
mph (95 km/h) with higher gusts, and additional steady to rapid
strengthening is expected during the next few days. Ida is forecast
to become a hurricane over the southeastern Gulf of Mexico, and to
be at or near major hurricane strength when it approaches the
northern Gulf coast.
Tropical-storm-force winds extend outward up to 80 miles (130 km)
from the center.
The estimated minimum central pressure from reconnaissance
aircraft data is 996 mb (29.41 inches).
HAZARDS AFFECTING LAND
———————-
Key messages for Tropical Storm 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: A dangerous storm surge will raise water levels by
as much as 2 to 4 feet above normal tide levels in areas of onshore
winds along the immediate coast of the Isle of Youth and near and to
the east of where the center crosses the coast of western Cuba.
Near the coast, the surge will be accompanied by large and
destructive waves.
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 Ocean Springs, MS including Lake Borgne…7-11 ft
Rockefeller Wildlife Refuge, LA to Morgan City, LA including
Vermilion Bay…4-7 ft
Ocean Springs, MS to MS/AL border…4-7 ft
MS/AL border to AL/FL border including Mobile Bay…3-5 ft
Lake Pontchartrain…4-6 ft
Lake Maurepas…3-5 ft
Sabine Pass to Rockefeller Wildlife Refuge, LA…2-4 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: Tropical storm conditions are expected on Little Cayman
and Cayman Brac this morning, and are expected to reach the Isle of
Youth and portions of western Cuba in the warning area later today.
Hurricane conditions are possible in the hurricane watch area along
the northern Gulf coast late Saturday night or Sunday and tropical
storm conditions are possible in the watch area late Saturday night
or Sunday.
RAINFALL: Ida is expected to produce total rainfall accumulations
of 6 to 10 inches with maximum totals of 15 inches across Jamaica.
Rainfall totals of 8 to 12 inches with isolated maximum amounts of
20 inches are expected across the Cayman Islands and western Cuba,
including the Isle of Youth. These rainfall amounts may produce
life-threatening flash floods and mudslides.
As Ida approaches the central Gulf Coast Sunday afternoon, total
rainfall accumulations of 8 to 16 inches with isolated maximum
amounts of 20 inches are possible from southeast Louisiana to
coastal Mississippi and Alabama through Monday morning. Ida is
forecast to turn northeast as it moves inland later Monday with
rainfall totals of 4 to 8 inches possible across southern and
central Mississippi. This is likely to result in considerable flash,
urban, small stream, and riverine flooding.
SURF: Swells generated by this system will affect Jamaica, the
Cayman Islands and Cuba tonight and Friday. Swells will begin
reaching portions of the northern Gulf coast Saturday night or
early Sunday. These swells are likely to cause life-threatening
surf and rip current conditions. Please consult products from your
local weather office.
