BULLETIN
Hurricane Sally Advisory Number 17
NWS National Hurricane Center Miami FL AL192020
1000 AM CDT Tue Sep 15 2020
…SALLY CRAWLING NORTHWESTWARD TOWARD THE NORTHERN GULF COAST…
…HISTORIC FLOODING IS POSSIBLE FROM SALLY WITH EXTREME LIFE-THREATENING FLASH FLOODING LIKELY THROUGH WEDNESDAY ALONG PORTIONS OF THE NORTHERN GULF COAST…
SUMMARY OF 1000 AM CDT…1500 UTC…INFORMATION
———————————————–
LOCATION…29.1N 88.2W
ABOUT 55 MI…85 KM E OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 110 MI…180 KM S OF MOBILE ALABAMA
MAXIMUM SUSTAINED WINDS…85 MPH…140 KM/H
PRESENT MOVEMENT…NW OR 315 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 from the Mouth of the Pearl River to Bay St.
Louis Mississippi has been changed to a Tropical Storm Warning.
The Tropical Storm Warning for Lake Pontchartrain, Lake Maurepas,
and metropolitan New Orleans 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 Bay St. Louis to Navarre Florida
A Tropical Storm Warning is in effect for…
* East of Navarre Florida to Indian Pass Florida
* Bay St. Louis westward to Grand Isle 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
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 1000 AM CDT (1500 UTC), the center of Hurricane Sally was located
near latitude 29.1 North, longitude 88.2 West. Sally is moving
toward the northwest near 2 mph (4 km/h). A slow north-
northwestward to northward motion is expected this afternoon,
followed by a slow northward to north-northeastward motion tonight
through Wednesday night. On the forecast track, the center of Sally
will pass near the coast of southeastern Louisiana today, and make
landfall in the hurricane warning area late tonight or Wednesday.
Maximum sustained winds are 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 latest minimum central pressure reported by a NOAA 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…
MS/AL Border to AL/FL Border including Mobile Bay…4-7 ft
Mouth of the Mississippi River to Mouth of the Pearl River including
Lake Borgne…4-6 ft
Mouth of the Pearl River to MS/AL Border…3-5 ft
AL/FL Border to Okaloosa/Walton County Line, FL including Pensacola
Bay and Choctawhatchee Bay…3-5 ft
Lake Pontchartrain and Lake Maurepas…2-4 ft
Okaloosa/Walton County Line,FL to Chassahowitzka, FL including Saint
Andrews Bay…1-3 ft
Grand Isle, LA to Mouth of the Mississippi River…1-3 ft
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 later today or tonight. Tropical
storm conditions are already occurring in portions of the warning
areas, and these conditions will continue through Wednesday night.
RAINFALL: Sally is forecast to produce 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 likely 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 move inland Wednesday and track 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: Isolated tornadoes may occur today through Wednesday
across portions of the Florida Panhandle and southern Alabama.
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.