BULLETIN
Tropical Storm Sally Intermediate Advisory Number 9A
NWS National Hurricane Center Miami FL AL192020
700 PM CDT Sun Sep 13 2020
…SALLY FORECAST TO STRENGTHEN AND SLOW DOWN…
…LIFE-THREATENING STORM SURGE, HURRICANE-FORCE WINDS, AND HEAVY
RAINFALL EXPECTED ALONG PORTIONS OF THE NORTHERN GULF COAST
STARTING ON MONDAY…
SUMMARY OF 700 PM CDT…0000 UTC…INFORMATION
———————————————-
LOCATION…27.9N 86.2W
ABOUT 160 MI…260 KM S OF PANAMA CITY FLORIDA
ABOUT 195 MI…315 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
MAXIMUM SUSTAINED WINDS…60 MPH…95 KM/H
PRESENT MOVEMENT…WNW OR 295 DEGREES AT 9 MPH…15 KM/H
MINIMUM CENTRAL PRESSURE…996 MB…29.41 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:
None
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Storm Surge Warning is in effect for…
* Port Fourchon Louisiana to the Mississippi/Alabama Border
* Lake Pontchartrain, Lake Maurepas, and Lake Borgne
A Hurricane Warning is in effect for…
* Morgan City Louisiana to Ocean Springs Mississippi
* Lake Pontchartrain and Lake Maurepas including metropolitan New
Orleans
A Storm Surge Watch is in effect for…
* Mississippi/Alabama Border to the Alabama/Florida Border
A Hurricane Watch is in effect for…
* East of Ocean Springs to the Alabama/Florida Border
A Tropical Storm Warning is in effect for…
* East of Ocean Springs to Indian Pass
* Intracoastal City Louisiana to west of Morgan City
A Tropical Storm Watch is in effect for…
* Indian Pass to Ochlockonee River Florida
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. A warning is typically issued
36 hours before the anticipated first occurrence of
tropical-storm-force winds, conditions that make outside
preparations difficult or dangerous. 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.
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 Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, in this case within 12 to 24 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 Tropical Storm Sally was
located near latitude 27.9 North, longitude 86.2 West. Sally is
moving toward the west-northwest near 9 mph (15 km/h), and this
motion is expected to continue through tonight. A slower west-
northwestward motion is expected Monday and Monday night, followed
by a further decrease in forward speed and a turn to the northwest
Monday night and Tuesday. On the forecast track, the center of
Sally will move over the north-central Gulf of Mexico tonight and
Monday, and approach the north-central Gulf Coast within the
hurricane warning area Monday night. Sally is expected to move
slowly northward near the southeastern Louisiana or Mississippi
coasts through Tuesday.
Maximum sustained winds are near 60 mph (95 km/h) with higher
gusts. Strengthening is expected over the next day or so, and Sally
is forecast to become a hurricane on Monday, with some additional
strengthening possible before the center crosses the northern Gulf
Coast.
Tropical-storm-force winds extend outward up to 125 miles (205 km)
primarily to the east of the center.
The estimated minimum central pressure is 996 mb (29.41 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 Ocean Springs, MS including Lake
Borgne…7-11 ft
Port Fourchon, LA to Mouth of the Mississippi River…4-7 ft
Ocean Springs, MS to MS/AL Border…4-7 ft
Lake Pontchartrain and Lake Maurepas…4-6 ft
MS/AL Border to AL/FL Border including Mobile Bay…2-4 ft
AL/FL Border to Chassahowitzka, FL including Pensacola Bay,
Choctawhatchee Bay, and Saint Andrew Bay…1-3 ft
Burns Point, LA to Port Fourchon, LA…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 within the hurricane
warning area starting late Monday. Tropical storm conditions are
possible within the watch area tonight, and are expected within the
warning area beginning Monday.
RAINFALL: Sally is expected to be a slow moving system resulting
in significant flash flooding for the central Gulf Coast Monday
into Wednesday. Sally is expected to produce rainfall of 8 to 16
inches with isolated amounts of 24 inches over portions of the
central Gulf Coast from the western Florida Panhandle to southeast
Louisiana from Monday through the middle of the week. This rainfall
will likely result in new widespread minor to isolated major
flooding on area rivers.
Sally is forecast to move inland early Wednesday and track into the
Southeast with rainfall of 5 to 10 inches possible across much of
inland Mississippi and Alabama. Flash and urban flooding is
possible, as well as widespread minor to moderate flooding on some
rivers in Mississippi and Alabama.
Further heavy rain is then anticipated across portions of Tennessee,
northern Georgia and western North Carolina. Flash, urban, and
minor river flooding is possible across this region.
Outer bands of Sally are expected to produce additional rainfall of
1 to 3 inches across central and northern Florida through Monday.
This rainfall may produce flash and urban flooding and prolong high
flows and ongoing minor flooding on rivers across central Florida.
TORNADOES: The risk of isolated tornadoes will begin to increase
Monday afternoon and evening over parts of the western Florida
Panhandle, southern Alabama, southern Mississippi, and southeast
Louisiana.
SURF: Swells from Sally are affecting the west coast of the
Florida peninsula, the coast of the Florida Panhandle, and will
be spreading northwestward along the northern Gulf coast through
Monday. These swells are likely to cause life-threatening surf
and rip current conditions. Please consult products from your
local weather office.