Debby is another example of a tropical storm or hurricane that slowed down or stalled after landfall. Three other notable storms that did the same were hurricanes Harvey in 2017, Florence in 2018, and Dorian in 2019.
Of course, many across southeast Texas remember Harvey. The hurricane spun over Texas for five days and dumped rounds of heavy rains that led to record flooding in Houston. Similarly, Florence slowed ahead of and after making landfall, which brought flooding rains to the Carolinas. The same area could also see historic flooding again from Debby this week. However, hurricane Dorian in 2019 stands out because it wasn't just the rain. This Category 5 hurricane stalled over the Abaco Islands in the Bahamas, pummeling the islands with hurricane-force gusts for over 24 hours. The damage was extensive and catastrophic.
Seeing tropical storms or hurricanes "slow down" is not a new phenomenon. In fact, a hurricane back in 1950 took a similar loop to that of Harvey but over the Gulf Coast of Florida instead. So, while there's a history of this happening with tropical systems, especially in the Caribbean and Gulf of Mexico, there has been a noticeable shift in the prevalence of storms slowing down or stalling since the turn of the century.
James Kossin is a professor and researcher with the University of Wisconsin Madison and found that rainfall rates associated with slow-moving hurricanes could double as the climate warms.
"Just a 10% slowdown in hurricane translational speed can more than double rainfall totals caused by a one-degree Celsius increase of global warming," Kossin said. Arguably, the most common impact when hurricanes slow down or stall is flooding from how much rain can fall.
Because tropical storms and hurricanes are large weather systems, it takes longer for them to fizzle out finally. And that's typically after a storm makes landfall. Here in the United States, what happens to the storm after it makes landfall depends on steering currents and other weather systems across the country.
With Debby, the storm was steered into Florida thanks to high-pressure systems out west, like the one over southeast Texas this week. But Debby will slow down and stay put because of other systems, like a clipper system over the Great Lakes and other areas of high pressure. Those will block Debby from moving farther north, allowing it to linger and spin over the same area. Typically, you'd like to see a trough or dip in the jet stream as a hurricane makes landfall to help sweep the system up and out, like what happened with Beryl last month.
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