BULLETIN
Hurricane Sally Intermediate Advisory Number 18A
NWS National Hurricane Center Miami FL AL192020
700 PM CDT Tue Sep 15 2020
…TROPICAL-STORM-FORCE WINDS CONTINUE TO SPREAD ONSHORE ALONG
THE NORTH-CENTRAL GULF COAST…
…HISTORIC LIFE-THREATENING FLOODING LIKELY ALONG PORTIONS
OF THE NORTHERN GULF COAST…
SUMMARY OF 700 PM CDT…0000 UTC…INFORMATION
———————————————-
LOCATION…29.6N 88.0W
ABOUT 75 MI…125 KM S OF MOBILE ALABAMA
ABOUT 75 MI…125 KM SW OF PENSACOLA FLORIDA
MAXIMUM SUSTAINED WINDS…80 MPH…130 KM/H
PRESENT MOVEMENT…N OR 350 DEGREES AT 2 MPH…4 KM/H
MINIMUM CENTRAL PRESSURE…975 MB…28.79 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:
None
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 Mississippi to Navarre Florida
A Tropical Storm Warning is in effect for…
* East of Navarre Florida to Indian Pass Florida
* Bay St. Louis Mississippi 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 700 PM CDT (0000 UTC), the center of Hurricane Sally was located
by an Air Force Reserve Hurricane Hunter aircraft and NOAA Doppler
radar near latitude 29.6 North, longitude 88.0 West. Sally is
moving toward the north near 2 mph (4 km/h). A slow northward
motion is expected tonight, followed by a slow north-northeastward
to northeastward motion on Wednesday and Wednesday night. A
slightly faster northeastward motion is expected on Thursday. On
the forecast track, the center of Sally will approach the northern
Gulf Coast tonight, and make landfall in the hurricane warning area
late tonight or Wednesday. Sally is expected to move inland across
southeastern Alabama Wednesday night and Thursday.
Maximum sustained winds are near 80 mph (130 km/h) with higher
gusts. Little change in strength is forecast until landfall occurs,
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 40 miles (65 km) from
the center and tropical-storm-force winds extend outward up to 125
miles (205 km). A sustained wind of 55 mph (89 km/h) and a gust to
70 mph (113 km/h) were recently reported at Petit Bois Island,
Mississippi. A sustained wind of 54 mph (87 km/h) and a gust to 66
mph (106 km/h) were recently reported on Dauphin Island, Alabama.
The minimum central pressure estimated from Air Force Hurricane
Hunter aircraft observations is 975 mb (28.79 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
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 Florida Panhandle west of the
Apalachicola River to far southeastern Mississippi. Historic
life-threatening flash flooding is likely. In addition, this
rainfall will lead to widespread moderate to major flooding on area
rivers.
Sally is forecast to turn 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, central and northern Georgia, and the
western Carolinas. Significant flash and urban flooding is likely,
as well as widespread minor to moderate flooding on some rivers.
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…
Dauphin Island, AL to AL/FL Border including Mobile Bay…4-6 ft
Mouth of the Mississippi River to Mouth of the Pearl River including
Lake Borgne…3-5 ft
MS/AL Border to Dauphin Island, AL…3-5 ft
AL/FL Border to Okaloosa/Walton County Line, FL including Pensacola
Bay and Choctawhatchee Bay…3-5 ft
Mouth of the Pearl River to MS/AL Border…2-4 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 this evening. Tropical storm
conditions are already occurring in portions of the warning areas,
and will continue through Wednesday night.
TORNADOES: A few tornadoes may occur 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.