Aletta becomes first hurricane of eastern Pacific season

Postado Junho 08, 2018

Hurricanes and tropical storms, known as tropical cyclones, are moving slower around the planet, according to a new study from National Oceanic and Atmospheric Administration scientist James Kossin.

These slower speeds don't mean the winds circling the eye of the storm are slowing down. He found hurricanes in 2016 moved an average of 10 percent slower than hurricanes in 1949.

"Hurricane Harvey a year ago was a great example of what a slow storm can do".

Atlantic Basin storms have slowed down by 6 percent over water but by 20 percent over land.

"Long-duration or slower-moving storms, even when weaker, can have exacerbated impacts through prolonged wind exposure [in addition to] flooding", according to Colin Zarzycki, a project scientist with the National Center for Atmospheric Research who was not involved with the study.

Tropical cyclones have slowed more in the Northern Hemisphere, which is significant because that is where a majority of storms occur each year.

First, he noted that over the more than 60-year period of the study, there may be natural, decades-long cycles in the climate system that could affect the steering of storms and have little or nothing to do with global warming.

Although commending the study for its findings, she said it is not without its limitations.

Dr Christina Patricola, from the Climate and Ecosystems Sciences Division at University California, Davis, says the findings raise several questions, especially regarding "stalled" tropical cyclones.

Kossin acknowledged problems with pre-1970s data but said that most of it deals with how strong storms are.

Kossin would actually agree on that point. The fact that their results show quite similar trends should be a wake-up call.

In a warming world where atmospheric circulations are expected to change, the atmospheric circulation that drives tropical cyclone movement is expected to weaken. A slow storm increases the risk of damaging floods.

While the new research suggests hurricanes and typhoons are slowing down over time, more work needs to be done to improve prediction models for how hurricanes may behave in the future. "And, unfortunately, this signal would point to more freshwater flooding".