Tropical Cyclones Are Moving Slower, And That's Not Good News

James Marshall
June 8, 2018

Slow-moving tropical storms and hurricanes also lead to strong winds blowing for a longer duration over the same place and possibly more storm surge, Kossin told the AP.

That's the real risk of a slower storm.

Is Hurricane Harvey a preview?

According to Kossin's study, combining the additional water vapor available in the atmosphere from 1 degree Celsius of warming -essentially where we are now - with a 10% slowdown from tropical cyclones that he observed would double the local rainfall and flooding impacts.

Climate change is tinkering with and slowing down atmospheric circulation patterns - the wind currents that move weather along, Kossin said. That means a storm that may already hold more moisture will have time to drop more of it in each spot.

In 2017, Hurricane Harvey stalled for 4 days over southern Texas, dropping more than a meter of rain and causing $125 billion in damage (above).

Why are storms slowing down?

The U.S. National Hurricane Center said Aletta, which had become a tropical storm late Wednesday, was centered about 455 miles west-southwest of Manzanillo, Mexico, and had maximum sustained winds of 75 mph.

Worldwide weather research has revealed Australia has some of the slackest tropical cyclones.

Gutmann and Kossin took entirely different approaches-one looking at historical data; the other using modeling to see how storms would behave under predicted warming scenarios.

In a warming world where atmospheric circulations are expected to change, the atmospheric circulation that drives tropical cyclone movement is expected to weaken.

"It is far from clear that global climate change has anything to do with the changes being identified", said Kevin Trenberth, a senior climate scientist with the National Center for Atmospheric Research.

The result is more rainfall and more damage to buildings as hurricanes hover over population centers for longer periods of time.

Kossin concluded that the trend has all the signs of human-induced climate change. "We'll need more formal attribution studies to disentangle these factors".

Other reports by Click Lancashire

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