Coastlines throughout Mississippi, Alabama and west Florida remain on hurricane warning as forecasters warned of “historic” and “life-threatening” flooding from Hurricane Sally, a slow-moving weather system that is winding its way to the US Gulf coast.
The 85mph weather system is predicted to reach land by late Tuesday or early Wednesday as forecasters revised the storm’s predicted pathway on Tuesday morning and cautioned it was still “too early” to determine where the eye of the storm would make landfall. The storm could unleash 30in of rain leading to dangerous flash flooding.
Warnings of life-threatening storm surge remained in place from south-east Louisiana to the Florida panhandle. Sally peaked as a category 2 hurricane on Monday evening but has since been downgraded to a category 1.
Stacy Stewart, a senior specialist with the National Hurricane Center (NHC), said people should continue to take the storm seriously since “devastating” rainfall is expected in large areas. People could drown in the flooding, he said.
“This is going to be historic flooding along with the historic rainfall,” Stewart said. “If people live near rivers, small streams and creeks, they need to evacuate and go somewhere else.”
The storm was moving at only 2mph before dawn on Tuesday, centered about 115 miles south-south-east of Biloxi, Mississippi, and 60 miles east-south-east of the mouth of the Mississippi river.
Florida’s governor, Ron DeSantis, declared an emergency in the Panhandle’s western-most counties, which were being pummeled by rain from Sally’s outer bands early on Tuesday. The threat of heavy rain and storm surge was exacerbated by the storm’s slow movement.
Donald Trump issued emergency declarations for parts of Louisiana, Mississippi and Alabama, and tweeted that residents should listen to state and local leaders.
Alabama’s governor, Kay Ivey, sought the presidential declaration after the National Weather Service (NWS) in Mobile, Alabama, warned of the increasing likelihood of “dangerous and potentially historic flooding”, with waters rising as much as 9ft above ground in parts of the Mobile metro area.
While the threat to Louisiana appeared to be easing, authorities remained on guard, closing gates along networks of waterways that could be pushed over their banks by the possible surge from the Gulf.
The south-western part of the state was pummeled by Hurricane Laura on 27 August and an estimated 2,000 evacuees from that storm were sheltered in New Orleans, mostly in hotels.
Monday marked only the second time on record, forecasters said, that five tropical cyclones swirled simultaneously in the Atlantic basin. The last time that happened was in 1971. None of the others were expected to threaten the US this week, if at all, and one was downgraded to a low pressure trough on Monday evening.
The US Gulf coast is still reeling from the aftermath of Hurricane Laura, which arrived on land as a devastating Category 4 storm in south central Louisiana last month.
The extraordinarily busy hurricane season – like the catastrophic wildfire season on the west coast – has focused attention on the role of climate change. Scientists say global warming is making the strongest of hurricanes, those with wind speeds of 110mph or more, even stronger. Also, warmer air holds more moisture, making storms rainier, and rising seas from global warming make storm surges higher and more damaging.
In addition, scientists have been seeing tropical storms and hurricanes slow down once they hit the US by about 17% since 1900, and that gives them the opportunity to unload more rain over one place, as 2017’s Hurricane Harvey did in Houston.