Category 6 hurricanes? Computer model predicts increasingly extreme, frequent storms

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The 21st century is projected to see not only more hurricanes, but also ones so intense that scientists might need to create a new category to classify them, new research suggests.

By simulating interactions between meteorological forces like the atmosphere and oceans, a computer model created at the National Oceanic and Atmospheric Administration’s (NOAA) Geophysical Fluid Dynamics Laboratory is able to provide detailed forecasts of hurricanes, both in past and future environments.

Recently, a team led by NOAA researcher Kieran Bhatia used the technology to glimpse into the future to see how a warming climate might affect tropical storms across the globe. The sight was unsettling.

For 2016 to 2035, the projections showed an 11-percent increase hurricanes of categories 3, 4 and 5, compared to the late 20th century. That increase jumped to 20 percent by the end of the 21st century.

Alarmingly, the intensity of some storms is projected to be off the charts.

Scientists currently use the Saffir-Simpson scale to measure the intensity of tropical storms and tropical depressions. A storm registers on the lowest end of the scale when its winds reach 74 miles per hour. The most severe category, 5, begins at 157 mph and is left open-ended.

The new projections forecast some storms with maximum sustained winds of more than 190 mph. Only 9 such storms were observed in the 20th century. But from 2016 to 2035, the projections produced 32 of these extreme storms, and 72 from 2081 to 2100.

Some scientists argue adding a new category to the Saffir-Simpson scale would help the public grasp the changes climate change is bringing to the planet.

“Scientifically, [six] would be a better description of the strength of 200-mph storms, and it would also better communicate the well-established finding now that climate change is making the strongest storms even stronger,” Climatologist Michael Mann, director of the Earth System Science Center at Penn State University, said at a conference earlier this year.

“Since the scale is now used as much in a scientific context as it is a damage assessment context, it makes sense to introduce a category six to describe the unprecedented strength 200mph storms we’ve seen over the past few years both globally [Patricia] and here in the southern hemisphere [Winston].”

One primary driver of the planet’s increasingly extreme hurricanes is warming oceans.

“When the water in the oceans gets hotter, which is happening because of global warming, it’s like fuel for a hurricane’s engine that’s spinning up, gaining strength,” science reporter Rebecca Hersher told NPR’s Up Firstpodcast. “So you can think of it as a hot bath. The evaporating moisture feeds the storm. So here’s the really bad news when it comes out that: The oceans are warmer now than they’ve ever been.”

Hersher noted that the water feeding Hurricane Florence, which is a category 4 storm currently surging off the east coast of the U.S., is slightly warmer than normal.


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