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Hurricane Sally Intermediate Advisory Number 15A
NWS National Hurricane Center Miami FL AL192020
100 AM CDT Tue Sep 15 2020
...SALLY WEAKENS SLIGHTLY WHILE JOGGING WESTWARD...
...LIFE-THREATENING STORM SURGE, HURRICANE-FORCE WINDS, AND FLASH
FLOODING LIKELY ALONG PORTIONS OF THE NORTHERN GULF COAST LATER
SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
ABOUT 75 MI...120 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 115 MI...190 KM SSE OF BILOXI MISSISSIPPI
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...986 MB...29.12 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Storm Surge Warning is in effect for...
* Port Fourchon Louisiana to the Okaloosa/Walton County Line Florida
* Lake Pontchartrain, Lake Maurepas, and Lake Borgne
* Mobile Bay
A Hurricane Warning is in effect for...
* Grand Isle Louisiana to the Navarre Florida
* Lake Pontchartrain and Lake Maurepas including metropolitan New
A Tropical Storm Warning is in effect for...
* East of of Navarre Florida to Indian Pass Florida
* West of Grand Isle to Morgan City Louisiana
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. Preparations to protect life
and property should be rushed to completion.
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 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 Hurricane Sally was located
an Air Force Reserve reconnaissance aircraft and NOAA Doppler
weather radars near latitude 28.8 North, longitude 88.0 West. Sally
is moving slowly toward the west near 3 mph (6 km/h). A slow
west-northwestward motion is expected to resume later this morning.
A northward turn is expected this afternoon, followed by a slow
north-northeastward to northeastward motion tonight and continuing
through Wednesday night. On the forecast track, the center of Sally
will move near the coast of southeastern Louisiana later today, and
make landfall in the hurricane warning area tonight or Wednesday
Data from the reconnaissance aircraft indicate that maximum
sustained winds have decreased to near 90 mph (150 km/h) with higher
gusts. However, some re-strengthening is forecast early to occur
later today, and Sally is expected to be a dangerous hurricane when
it moves onshore along the north-central Gulf coast.
Hurricane-force winds extend outward up to 45 miles (75 km) from
the center and tropical-storm-force winds extend outward up to 125
miles (205 km). A NOAA C-MAN observing station on Dauphin Island,
Alabama, recently reported a wind gust of 51 mph (81 km/h), while a
buoy just south of Dauphin Island recently reported a wind gust to
59 mph (94 km/h).
The estimated minimum central pressure based on data from the Air
Force Hurricane Hunter aircraft is 986 mb (29.12 inches).
HAZARDS AFFECTING LAND
Key messages for Sally can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC,
and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml
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...
Mouth of the Mississippi River to Dauphin Island including Lake
Mobile Bay...6-9 ft
Lake Pontchartrain and Lake Maurepas...3-5 ft
Dauphin Island to AL/FL Border...4-7 ft
Port Fourchon to Mouth of the Mississippi River...2-4 ft
AL/FL Border to Okaloosa/Walton County Line including Pensacola Bay
an Choctawhatchee Bay...2-4 ft
Okaloosa/Walton County Line to Chassahowitzka including Saint Andrew
Burns Point to Port Fourchon...1-2 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 in areas of
onshore winds, where the surge will be accompanied by large and
damaging 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
WIND: Hurricane conditions are expected to begin within the
hurricane warning area later today. Tropical storm conditions are
occurring in portions of the warning area across Alabama, and these
conditions will gradually spread westward this morning.
RAINFALL: Sally is expected to be a slow moving system as it
approaches land, producing 8 to 16 inches of rainfall with isolated
amounts of 24 inches over portions of the central Gulf Coast from
the western Florida Panhandle to far southeastern Mississippi
through the middle of the week. Life-threatening flash flooding is
likely. In addition, this rainfall will likely lead to widespread
minor to isolated major flooding on area rivers.
Sally is forecast to turn inland early Wednesday and track across
the Southeast producing rainfall of 4 to 8 inches, with isolated
maximum amounts of 12 inches, across portions of eastern
Mississippi, central Alabama, northern Georgia, southeastern
Tennessee, and the western Carolinas. Significant flash and urban
flooding is likely, as well as widespread minor to moderate flooding
on some rivers.
Outer bands of Sally could produce additional rainfall of 1 to 3
inches across the Florida peninsula through tonight. This rainfall
may produce flash and urban flooding and prolong high flows and
ongoing minor flooding on rivers across central Florida.
TORNADOES: A tornado or two will be possible this morning in
coastal areas of the Florida Panhandle and Alabama. The threat for
tornadoes should increase and slowly spread inland during the day
SURF: Swells from Sally will continue to affect the coast from the
Florida Big Bend westward to southeastern Louisiana during the next
couple of days. 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.