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 TODAY
BULLETIN
Hurricane Sally Advisory Number 16
NWS National Hurricane Center Miami FL AL192020
400 AM CDT Tue Sep 15 2020
…HISTORIC FLOODING IS POSSIBLE FROM SALLY WITH EXTREME LIFE-
THREATENING FLASH FLOODING LIKELY THROUGH WEDNESDAY ALONG PORTIONS
OF THE NORTHERN GULF COAST…
SUMMARY OF 400 AM CDT…0900 UTC…INFORMATION
———————————————-
LOCATION…28.9N 88.1W
ABOUT 60 MI…100 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 115 MI…185 KM SSE OF BILOXI MISSISSIPPI
MAXIMUM SUSTAINED WINDS…85 MPH…140 KM/H
PRESENT MOVEMENT…WNW OR 300 DEGREES AT 2 MPH…4 KM/H
MINIMUM CENTRAL PRESSURE…983 MB…29.03 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:
The Hurricane Warning has been replaced by a Tropical Storm Warning
from the Mouth of the Pearl River westward to Grand Isle Louisiana,
including Lake Pontchartrain, Lake Maurepas, and metropolitan
New Orleans.
The Tropical Storm Warning has been discontinued west of Grand Isle.
The Storm Surge Warning between Port Fourchon and the Mouth of the
Mississippi River has been discontinued.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Storm Surge Warning is in effect for…
* Mouth of the Mississippi River to the Okaloosa/Walton County Line
Florida
* Mobile Bay
A Hurricane Warning is in effect for…
* East of the Mouth of the Pearl River to the Navarre Florida
A Tropical Storm Warning is in effect for…
* East of Navarre Florida to Indian Pass Florida
* Mouth of the Pearl River westward to Grand Isle Louisiana,
including Lake Pontchartrain and Lake Maurepas and metropolitan
New Orleans
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
officials.
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 400 AM CDT (0900 UTC), the center of Hurricane Sally was located
an Air Force Reserve reconnaissance aircraft and NOAA Doppler
weather radars near latitude 28.9 North, longitude 88.1 West. Sally
is moving toward the west-northwest near 2 mph (4 km/h), and this
general motion is expected to continue 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
morning.
Data from the reconnaissance aircraft indicate that maximum
sustained winds have decreased to near 85 mph (140 km/h) with higher
gusts. Although little change in strength is forecast until
landfall occurs, Sally is still 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).
The estimated minimum central pressure based on data from the Air
Force Hurricane Hunter aircraft is 983 mb (29.03 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
Borgne…6-9 ft
Mobile Bay…6-9 ft
Dauphin Island to AL/FL Border…4-7 ft
AL/FL Border to Okaloosa/Walton County Line including Pensacola Bay
and Choctawhatchee Bay…2-4 ft
Lake Pontchartrain and Lake Maurepas…2-4 ft
Port Fourchon to Mouth of the Mississippi River…1-3 ft
Okaloosa/Walton County Line to Chassahowitzka including Saint Andrew
Bay…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 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
office.
WIND: Hurricane conditions are expected to begin within the
hurricane warning area this late afternoon or tonight. Tropical
storm conditions are occurring in portions of the warning area
across the western Florida Panhandle and Alabama, and these
conditions will gradually spread westward this morning and continue
into Wednesday.
RAINFALL: Sally is expected to be a slow moving system as it
approaches land producing 10 to 20 inches of rainfall with isolated
amounts of 30 inches along and just inland of the central Gulf Coast
from the western Florida Panhandle to far southeastern Mississippi.
Historic flooding is possible with extreme life-threatening flash
flooding likely through Wednesday. In addition, this rainfall will
lead to widespread moderate to major flooding on area rivers.
Sally is forecast to turn inland early Wednesday and move across
the Southeast producing rainfall of 4 to 8 inches, with isolated
maximum amounts of 12 inches, across portions of southeastern
Mississippi, southern and central Alabama, northern Georgia, and the
western Carolinas. Significant flash and urban flooding is likely,
as well as widespread minor to moderate flooding on some rivers.
TORNADOES: A tornado or two will be possible this morning in
coastal areas of the Florida Panhandle and Alabama. The tornado
threat should increase and slowly spread inland the rest of today
into Wednesday.
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.
