Unhurried hurricanes: Study says tropical cyclones slowing

Hurricanes Are Lingering Longer. That Makes Them More Dangerous.

Hurricanes Are Slowing Down and Leaving More Damage When They Hit Land

The globe's hurricanes have seen a striking slowdown in their speed of movement across landscapes and seascapes over the past 65 years, a finding that suggests rising rainfall and storm-surge risks, according to research reported Wednesday. "Not quite like a cork in a stream, but similar", he said.

Scientists expect climate change is going to make tropical cyclones - including hurricanes - more severe. Instead, it means the tracks of the storms have slowed, allowing them to hover in one location for longer periods of time.

According to the study by Dr Jim Kossin from the National Centers for Environmental Information, tropical cyclones have slowed in both hemispheres and in every ocean basin except the Northern Indian Ocean. But when Atlantic storms hit land - like Harvey - the study said the slowdown is a significant 20 percent.

Therefore, it would make sense that if the flow around the hurricanes and typhoons is moving slowly, the storms will also be moving slower, which Kossin believes is what he is observing in the data.

The overall magnitude of the change in storm speed - a 10-degree reduction - was also striking in light of other changes expected in hurricanes under the amount of global warming that we have seen.

"Still, it's entirely plausible that local rainfall increases could actually be dominated by this slowdown rather than the expected rain-rate increases due to global warming".




In an editorial accompanying Kossin's work, she points out that it raises several new questions.

"My study is pretty far from an attribution study", he said. "At least not yet".

That means that storms farther from land in the earlier part of the study may not have had their speeds included in the study.

But there are probably more variables at play than a warmer climate putting the brakes on tropical cyclones.

"These trends are nearly certainly increasing local rainfall totals and freshwater flooding, which is associated with very high mortality risk", he said. "And when you start getting more and more lines of evidence that all point in the same direction, you get more confident in the answers". Follow him on Facebook, Twitter and Instagram.

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