Tropical Storm Aletta grows stronger in Pacific

Hurricanes Are Lingering Longer. That Makes Them More Dangerous.

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

In particular, a slowing of circulation as the polar regions warm up faster than equator ought to slow down storm tracks, as well.

The slower a cyclone moves over the ocean, the more moisture and intensity it gathers; the slower it moves over the land, the more time it spends drenching it.

The unusually slow-moving Hurricane Harvey was a recent example.

The western North Pacific basin, where the strongest systems are referred to as typhoons and super typhoons, sees the most storms annually and has seen the most slowing, at 20%.

A scientist at the National Oceanic and Atmospheric Administration has found a link between global warming and the speed of hurricanes.

The study published in Nature this week by USA weather experts shows the problem weather systems are taking longer to travel across the planet.

"Tropical cyclones are just carried along by the wind, so it makes sense", Kossin says.

Kossin said the findings were of great importance to society.

In addition to slower atmospheric circulations possibly causing the storms to move slower, the amount of rainfall that the storms are able to dump is increasing as global temperatures climb.

But Kossin can't say whether Harvey's rains are a model for the future. But here was a 10 percent slowdown in storm movement speed with only a half- degree Celsius (.9 degrees Fahrenheit) of warming globally over the period he studied. So it isn't clear just how much of the change that Kossin found is actually attributable to human-induced climate change.

Scientists expect climate change is going to make tropical cyclones - including hurricanes - more severe.

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