New study highlights growing threat looming over US cities: 'Consistent, unrelenting conditions'

Scientists say more tropical cyclones are stalling for days along vulnerable coastlines. These stubborn storms raise the risk of damage from the strong winds and heavy rains they bring for prolonged periods.

What's happening?

Louisiana State University professor Jill Trepanier led a study that was published in the Journal of Applied Meteorology and Climatology titled "Stalling North Atlantic Tropical Cyclones." Researchers for the study identified a growing risk, particularly in September and October, of tropical cyclones stalling for more than a day at a time along some U.S. coastlines. Many were clustered in the central Gulf Coast and near Florida and the Carolinas. 

"It doesn't have to be a Category 4 [storm] to do major damage," said Trepanier, per the Washington Post. "It's really about these consistent, unrelenting conditions, over and over, day after day." 

One of the most notorious stalling storms in recent history was Hurricane Harvey, which hit the Houston area hard in late August 2017. Harvey made landfall on San José Island, Texas, as a major Category 3 hurricane with maximum sustained winds of 130 miles per hour. The storm weakened quickly to a tropical storm but lingered for days in eastern Texas near Houston, producing prolific rainfall. The town of Friendswood received nearly five feet of rain, and parts of Houston saw more than 44" of rain.

Trepanier thinks officials must convey the risks of slow-moving storms when they approach because residents might not fully comprehend all the risks associated with lingering storms that can bring several days of driving rains and whipping winds. 

"They're not always thinking about, what if it sits in one spot?" Trepanier said, referring to authorities trying to protect people when these storms strike.

Why are stalling storms important?

The world is warming, but it is warming faster in some areas than others. Our planet's variable warming impacts weather patterns.

The study did not address the theory some scientists hold that Arctic Amplification — the phenomenon of the Arctic warming twice as fast as the Northern Hemisphere — can alter jet stream patterns to make conditions more conducive for storms to stall. Stalling tropical cyclones means people sometimes must endure several days of pounding wind and heavy rain. 

What's being done about the risk of stalling storms?

Vulnerable communities along the U.S. coastline need to be made aware of the potential hazards of stalling storms. Hurricanes Helene and Milton, while deadly and destructive, were well-warned for in advance, but they were fairly fast-moving storms. 

Slow-moving storms that linger for days sometimes don't get the advanced level of warning and attention needed to ensure people properly prepare for their risks. Trepanier wants emergency managers to encourage people to prepare for possibly several days of power outages and the need to shelter in place for the duration of the storm.

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