Sally becomes hurricane, will unleash life-threatening storm surge along Gulf coast
By Courtney Spamer, AccuWeather meteorologist
Tropical Storm Sally will bring flooding rain and wind to the Central Gulf Coast early in the week, but first Paulette will pound Bermuda as a hurricane.
Gulf Coast residents were rushing preparations to completion on Monday as the region braced for another hit from a hurricane — a little over two weeks after Laura’s devastating blow to areas farther west. Sally strengthened over the north-central Gulf of Mexico, with maximum sustained winds increasing to 90 mph Monday midday, as outer rain bands began soaking parts of the Florida Panhandle and western Florida.
The hurricane is expected to strengthen further before it makes its first landfall Tuesday night to early Wednesday along the central Gulf coast. AccuWeather meteorologists are expecting the storm to reach Category 2 strength with winds of 96-110 mph. There is a chance the hurricane could reach major hurricane strength with winds of at least 111 mph, prior to weakening before making landfall.
“While some additional strengthening of Sally is likely into early Tuesday, it is believed that the hurricane will weaken a bit prior to making landfall due to slow movement of the storm causing Gulf waters to cool and increased friction from the land,” according to AccuWeather’s top hurricane expert Dan Kottlowski.
“We also expect wind shear to increase over the storm prior to making landfall, which would imply weakening of the intensity as well, but regardless this will still be a significant hurricane strike in the region.” Kottlowski said.
Sally was churning 160 miles southeast of Biloxi, Mississippi, during Monday afternoon. The hurricane was crawling slowly west-northwestward at 7 mph.
Because of the wind, coastal flooding and inland flooding impacts combined, however, AccuWeather meteorologists have rated Sally a 2 on the AccuWeather RealImpact™ Scale for Hurricanes.
The AccuWeather RealImpact™ Scale for Hurricanes is a 6-point scale with ratings of less than one and 1 to 5 that was introduced by AccuWeather in 2019 to rate tropical systems based on multiple impacts, rather than just wind, like the Saffir-Simpson Wind Scale does.
State of emergency declarations have been issued by Louisiana Gov. John Bel Edwards and Mississippi Gov. Tate Reeves prior to Sally closing in on the region. Mandatory evacuations have been ordered in low-lying areas of both states, including for areas outside of New Orleans levee system.
AccuWeather meteorologists expect Sally to take a northward turn that keeps the eye just east of the Mississippi Delta region of Louisiana with a landfall along the Mississippi or Alabama coast late Tuesday night to early Wednesday morning. With this more eastward track, concern is increasing for a significant storm surge on Mobile Bay, Alabama.
As the system moved from the waters off Florida’s southeast across the southern tip of the Sunshine State and over the Gulf, local officials along the Gulf Coast began taking action to prepare for Sally’s arrival. Edwards noted on Twitter that parts of Louisiana were ravaged by Hurricane Laura late last month.
“This when combined with the COVID-19 pandemic, can make us all weary,” Edwards said on Twitter. “I implore Louisianans to take their preparations seriously.”
Mississippi Gov. Tate Reeves also formally requested pre-landfall assistance from President Donald Trump.
Sally was the earliest named “S-Storm” to ever form in the Atlantic Ocean basin, beating out 2005’s Hurricane Stan which was named on Oct. 2.
In less than 24 hours, Sally went from being a mass of showers and thunderstorms east of the Bahamas on Friday afternoon and to a tropical depression on Friday evening, before becoming a tropical storm on Saturday afternoon.
This image, captured around 11 a.m. CDT Monday, Sept. 14, 2020, shows thunderstorms erupting near the center of Hurricane Sally. (CIRA at Colorado State/GOES-East)
Torrential rain fell across South Florida as the tropical disturbance passed through. Marathon and Key West, Florida, both set preliminary daily and monthly rainfall records, with 8.13 inches and 9.37 inches falling, respectively, on Saturday.
The National Hurricane Center (NHC) issued a hurricane warning for areas from Morgan City, Louisiana, to the Alabama/Florida border,
Lake Pontchartrain and Lake Maurepas, including metropolitan New
Orleans. A tropical storm warning is in effect from the Alabama/Florida border to Indian Pass, Florida and from Intracoastal City, Louisiana to west of Morgan City.
A storm surge warning was issued for Port Fourchon, Louisiana, to the Alabama/Florida Border, Lake Pontchartrain, Lake Maurepas, Lake Borgne and Mobile Bay.
Beachgoers and boaters should be prepared for rapidly changing conditions that include sudden squalls, downpours and rough seas and surf. Sally could produce a couple of isolated tornadoes and waterspouts as its outer bands sweep along the western coast of Florida Monday.https://playlist.megaphone.fm/?e=ACC5221366856
Strengthening is expected as Sally travels over the warm waters of the Gulf of Mexico into early Tuesday. Sea surface temperatures were in the 80s to near 90 F, plenty warm to support strengthening of a tropical system, forecasters said.
All residents along the eastern and central Gulf coast should finalize preparations and heed all evacuation orders. Impacts from Sally will range from strong winds to heavy, flooding rainfall and dangerous storm surge.
Widespread wind gusts of 40 to 60 mph are expected from the central Florida Panhandle to eastern Louisiana, with the strongest wind near or east of the anticipated landfall.
Damaging winds will also be a concern along the immediate coast.
An AccuWeather Local StormMax™ wind gust of 120 mph is possible near the track of the center of the storm.
Near the center of the storm, and to the east, is where coastal inundation is expected with Sally.
“The shape of the southeasterly Louisiana coast, combined with the circulation of the storm and the storm’s track will still push a significant amount of water into Lake Borgne and Lake Pontchartrain, even with a more eastward track,” according to AccuWeather Senior Meteorologist Alex Sosnowski. “However, with a more eastward track you have concerns for higher storm surge in areas such as Mobile Bay.”
Storm surge of 6-10 feet is anticipated in eastern Louisiana and along coastal portions of Mississippi with locally higher levels possible, while storm surge of 1-3 feet extends all the way through the Florida Panhandle.
After moving inland, the storm will lose wind intensity, but continue to pull moisture northward into the Deep South.
Downpours are expected to spread across the interior South into the end of the week with an AccuWeather Local StormMax™ rainfall of 24 inches near and just northeast of where the center of the storm moves in from the Gulf coast.
Significant, life-threatening flash flooding is possible due to such high rainfall amounts. Roads may become impassable and some communities may become cutoff from first responders and medical services for a time.
“Rivers will be on the rise in the region, especially in portions of Mississippi and Alabama, where torrential rainfall will spread slowly inland,” according to AccuWeather Senior Meteorologist Alex Sosnowski.
AccuWeather meteorologists said that natural gas and oil production is expected to be shut down for 1 to 2 days in the north-central Gulf as Sally moves through the region, but the majority of the rigs are located farther west, over the western Gulf of Mexico.
And Sally wasn’t the only system that meteorologists were busy monitoring on Monday. As Paulette slams Bermuda, Sally aims for the Gulf Coast and Rene harmlessly dissipates over the open Atlantic, forecasters are also keeping tabs on the latest additions to the basin — Tropical Storm Teddy and Tropical Storm Vicky. Sept. 14, 2020, marked the first time and the only other documented time since Sept. 10-12, 1971, that there have been five tropical cyclones swirling simultaneously in the basin.
Hurricane season does not officially end until the end of November, and forecasters say that named systems could emerge into December this year.https://playlist.megaphone.fm/?p=ACC5215102922
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