The slow-moving storm dumped 20 to 30 inches of rain, while piling up ocean water along the shore, inundating coastal communities.
While the storm is still dumping rain on the Carolinas, we can examine some of its key figures:
123 mph: The peak gust observed during the storm in Orange Beach, Ala. Most of the strongest gusts on land were seen in coastal Alabama. Several locations clocked gusts over 100 mph, with a few gusts over 120 mph.
These readings almost all have caveats, and it is typically difficult to get the strongest winds of a hurricane to hit a calibrated weather station. The damage, and there’s lots of it, leaves little doubt as to the storm’s severity, however. Numerous structures were damaged, and trees were mowed down — some uprooted, others splintered in half.
The Center for Severe Weather Research mobile radar unit, known as Doppler on Wheels, detected a 123-mph gust in Orange Beach, Ala., which is probably reliable.
965 millibars: The storm’s minimum central pressure when it made landfall. Sally was a strengthening Category 2 when it came ashore. Its pressure had cratered 18 millibars in the previous 24 hours, an indication of speedy strengthening.
2-mph forward speed: Sally was an extremely slow-moving hurricane. In the hours leading up to and after landfall, it crawled along.
On Monday, while over the eastern Gulf of Mexico, the storm traveled an average of 6 mph. By Tuesday, as it sat menacingly just offshore, it slowed to a mere 2 mph, a near-record-slow pace in the region. Sally made landfall moving at 3 mph before mercifully speeding up, if slowly, thereafter.
Its slow forward progress enabled it to unload tremendous rainfall along the coast while prolonging the storm surge. It finally started to gain some speed Wednesday afternoon as it passed through interior eastern Alabama.
Six feet: The approximate peak surge, or storm-driven rise in ocean water above normally dry land. This surge resulted in serious coastal flooding in Pensacola, Fla., where heights reached 5.6 feet, the third-highest level on record, trailing Hurricane Ivan in 2004 and the Great Miami Hurricane of 1926.
In addition to the storm surge pushing into the coast, there was the somewhat rare phenomenon of “reverse surge,” where water sloshed out of Mobile Bay and into the Gulf of Mexico as the center passed and winds pushed water off the bay.
30 inches: The maximum amount of rain observed in Bellview, Fla. When Sally slowed to a crawl, its eyewall — the zone of extreme winds and torrential rain surrounding the storm center — relentlessly hammered the Alabama coast and Florida Panhandle.
The National Weather Service declared a relatively unusual “high risk” for flooding rains in this zone, and 20 to 30 inches of rain descended.
In the predawn hours Wednesday, the Weather Service declared several flash-flood emergencies, the most urgent and severe flash-flood alert. Beyond that, flood watches and warnings have extended from the Gulf Coast to the lower Mid-Atlantic with the storm lifting northeastward.
By warming ocean waters, climate change is thought to be intensifying rainfall in tropical storms and hurricanes and increasing the amount of water they generate.
500,000 in the dark: As of Thursday morning, more than half a million customers in Alabama and Florida remained without power. In southwest Louisiana, an additional 55,000 customers remained without power as repairs continued in the aftermath of Hurricane Laura three weeks ago.
16 years: The number of years since Alabama’s previous direct hurricane strike — Hurricane Ivan in 2004. Coincidentally, Ivan hit at the exact same location as Sally — Gulf Shores, Ala. — on the same date, Sept. 16.
Eight landfalls: Sally is the eighth tropical cyclone to come ashore in the United States this year. The term tropical cyclone broadly refers to tropical depressions, storms and hurricanes. According to Colorado State University hurricane researcher Phil Klotzbach, that number is a record season-to-date, surpassing seven to date in 1916. The most in one year is nine, which certainly seems as if it could be threatened in 2020.
Four hurricanes: With Sally in the books, there have been four hurricane strikes in the United States in 2020. Hanna hit Texas, Isaias ran into North Carolina, Laura blasted Louisiana and Sally struck Alabama. Sally is also one of six hurricanes to have made landfall this year in the Atlantic Ocean basin, all while strengthening.
Eight storms left? With Sally one of 20 named storms in 2020, just eight more are needed to tie the most on record: 28 in 2005. Sally was the 18th named storm of the year, and there have been two more since. Assuming Tropical Storm Wilfred forms, forecasters will need to draw from the Greek alphabet for referencing storms.
10 weeks: The amount of time left in hurricane season, which runs through Nov. 30. We’re barely past peak.