Cool Atlantic could mean a weaker hurricane season

A National Oceanic and Atmospheric Administration satellite captured this image of Hurricane Irma near the Bahamas in September 2017. [NASA/NOAA GOES Project]
A National Oceanic and Atmospheric Administration satellite captured this image of Hurricane Irma near the Bahamas in September 2017. [NASA/NOAA GOES Project]
Published August 2 2018
Updated August 2 2018

Can you tell the difference between one degree Celsius?

Hurricanes can. At least thatís what Colorado State University researcher Phil Klotzbach is banking on.

His team released its last hurricane forecast of the 2018 season on Thursday, and Klotzbach offered encouraging news for those who live in the path of Atlantic storms:

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He predicted the season will bring a slightly below-average number of storms. Klotzbach anticipates the rest of the Atlantic storm season will see nine named storms, including three hurricanes and one major hurricane ó a Category 3 storm or above with winds speeds of at least 111 mph.

This season has already seen three named storms and two hurricanes, including Subtropical Storm Alberto in May. An average season delivers 12 named storms, 6.5 hurricanes and two major hurricanes.

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This latest forecast reverses the position scientists took before hurricane season, when Klotzbach and researchers at the National Oceanic and Atmospheric Administration all forecast above-average seasons.

That pivot, Klotzbach said, hangs on that one single degree.

The tropical Atlantic Ocean, from the west coast of Africa to the Lesser Antilles, is on average 26 degrees Celsius. Itís normally 27 (for those who only use Fahrenheit thatís 78.8 and 80.6 degrees, respectively.)

But even 1 degree Celsius or 1.8 degrees Fahrenheit, makes all the difference.

"Right now itís the coldest on record in late July, in the tropical Atlantic," Klotzbach said. The record goes back to 1982.

Hurricanes feed off warm surface water, so that tiny discrepancy could result in a significant reduction in the number, and severity, of storms.

Atlantic surface temperatures were average this spring. Unlike last year, when those waters rapidly warmed and produced one of the strongest, destructive and costly hurricane seasons on record, the summer warming has been slower than expected. And since the season is already approaching its peak ó normally late August through early October ó thereís little time for the ocean temperatures to catch up.

"Given how cold the Atlantic is, as Yogi Berra would say, itís getting late early," said Klotzbach, invoking the great and quotable New York Yankees legend.

The likelihood of storm landfall was also reduced. Klotzbach estimated Florida and the U.S. east coast have a 63 percent chance of being struck by a named storm, down from the usual 81 percent.

So whatís keeping the Atlantic temperature down? Klotzbach said itís likely a combination of two factors. There have been strong winds across the Atlantic, and winds tend to churn deeper, cooler water to the surface. Also, the air over the water has been dusty. The particles tend to reflect sunlight before it warms the ocean.

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Another factor in the weaker forecast is that a weak El NiŮo could develop, Klotzbach said. El NiŮo is the presence of warmer-than-normal water in the tropical Pacific that creates strong winds over the tropical Atlantic. Those winds can tear apart storms before they can coalesce into dangerous cyclones, dampening hurricane development and growth.

A weaker season would add another wrinkle to the debate hurricane scientists are having about whether the Atlantic Ocean is in a period of relatively high activity, as scientists agree it was from 1995 to 2012, or if it switched to a period of relative quiet. The 2013-16 seasons were slower seasons, and some scientists wondered if the ocean had transitioned to a slow cycle. A slow 2018 season could lend more credence to the theory that the Atlantic switched back to an inactive period in 2013, and last yearís historically hyperactive season was an anomaly.

The cool ocean temperatures, while welcome, were surprising, Klotzbach said.

"In this day in age, you expect everything to be hot, record high," he said. "So when you see record cold, that makes you pay attention."

Contact Josh Solomon at (813) 909-4613 or [email protected] Follow @ByJoshSolomon.

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