Overlooked Atlantic cooling among reasons 2013 hurricane estimates missed so badly, no named hurricanes made US landfall in 2013

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11/25/13, "Why experts blew the 2013 hurricane forecasts," Orlando Sentinel, Ken Kaye

"Why did all the experts get the hurricane season outlook so wrong?

Twelve forecast teams predicted an average of 16 named storms, including eight hurricanes, four major. Yet this season, which ends Saturday, saw only 13 named storms, including two mediocre Category 1 hurricanes.

"Pretty much everyone who tried to forecast the number of hurricanes bombed," said Jeff Masters, chief meteorologist of Weather Underground, an online weather site.

Forecasters say they didn't foresee that a large-scale atmospheric wind pattern would blanket the tropical Atlantic with dry, sinking air. And they didn't anticipate that Saharan dust would further dry out the atmosphere.

Finally, they failed to anticipate that cooler waters would infiltrate the Atlantic in the spring. That helped stymie storm formation and keep those that did emerge relatively weak and short-lived.

"I think the magnitude of the cooling that occurred in the Atlantic was somewhat overlooked by ourselves and others," said Phil Klotzbach, who along with William Gray initially forecast 18 named storms, including nine hurricanes. "It was one of the largest busts for our research team in the 30 years we've been issuing this report."

The National Oceanic and Atmospheric Administration said it, too, was fooled by the arrival of so much dry air. It made this year the sixth-least-active Atlantic hurricane season since 1950, in terms of the collective strength and duration of named storms. The agency in May predicted up to 20 named storms, including up to 11 hurricanes.

"A combination of conditions acted to offset several climate patterns that historically have produced active hurricane seasons," said Gerry Bell, NOAA's lead hurricane forecaster. "As a result, we did not see the large numbers of hurricanes that typically accompany these climate patterns."

Before the season started in June, forecast teams thought a highly active season was brewing because wind shear was expected to be relatively low, tropical waters were projected to be abnormally warm and west African rainfall, which acts to energize tropical waves, was predicted to be heavy. 

Additionally, El Niño, the atmospheric force that suppresses storm formation, wasn't expected to develop.

Even in early August, NOAA predicted up to nine hurricanes, five major. Klotzbach and Gray forecast eight hurricanes, three major.

The forecast agency that came closest was Tropical Storm Risk, a British weather firm, which in early August called for 14.8 named storms, including 6.9 hurricanes, three major.

Tropical storm Andrea, the first of the season, was the only named storm to hit the U.S. coastline this year. It initially hit Northwest Florida in June and then generated tornadoes, heavy rain and flooding to portions of Florida, Georgia and South Carolina, causing one fatality.

Otherwise, most of this year's systems remained at sea and didn't last long. Of the 13 named storms, nine existed for three days or less, with the last one being Tropical Storm Melissa, which died in the Central Atlantic last week.

Because so many forecast teams misread the atmospheric signals, Klotzbach said, "people will probably not put as much stock in seasonal forecasts next year. You're only as good as your latest forecast."

Some of the early seasonal outlooks:

NOAA: 13 to 20 named storms, including seven to 11 hurricanes, three to six major;

WSI, a part of The Weather Channel: 16 named storms, including nine hurricanes, five intense;

AccuWeather.com: 16 named storms, including eight hurricanes, four intense;

Carolina Coastal University: 15 named storms, including eight hurricanes."


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