A very powerful El Niño kept the lid on the 2015 Atlantic hurricane season, but simultaneously created a spawning ground for powerful hurricanes in the Pacific Ocean.
Only 11 named tropical storms formed in the Atlantic Basin, which includes the Atlantic Ocean, Gulf of Mexico and Caribbean Sea. Four of those storms became hurricanes with winds of at least 74 mph, and two intensified into major hurricanes with winds exceeding 110 mph.
“El Niño produces a see-saw effect, suppressing the Atlantic season while strengthening the eastern and central Pacific hurricane seasons,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at the National Oceanic and Atmospheric Administration’s Climate Prediction Center.
Bell said El Niño suppressed the Atlantic season by producing strong vertical wind shear combined with increased atmospheric stability, stronger sinking motion and drier air across the tropical Atlantic, all of which make it difficult for tropical storms and hurricanes to form and strengthen. But the weather phenomenon fueled the eastern and central Pacific seasons this year with the weakest vertical wind shear on record. That, coupled with very warm water, allowed record-setting activity, with 18 named storms forming in the eastern Pacific and 14 named storms in the central Pacific.
Two of the storms in the eastern Pacific—Hurricane Patricia and Hurricane Sandra—were among the most powerful on record. On October 23, Patricia became the most intense hurricane on record for the Western Hemisphere when its barometric pressure fell to 879 millibars and its strongest sustained winds reached 200 mph as it approached the Pacific coast of Mexico.
About a month later on November 23, Hurricane Sandra became the most powerful hurricane to form so late in the season when its winds reached 145 mph.
Researchers Phil Klotzbach and William Gray at Colorado State University noted that the El Niño—caused by warmer than usual water in the equatorial Pacific—suppresses tropical storm formation in the Atlantic because it increases upper level winds that make it more difficult for storms to form.
“Vertical wind shear in the Caribbean was the strongest on record since at least 1979 for June through October,” the researchers said in a prepared statement.
Still, one very powerful hurricane did form in the Atlantic, and that storm hammered the Bahamas in early October. Hurricane Joaquin’s 155 mph winds made it the strongest storm to strike the Bahamas since 1866.
The summer of 2015 marked the 10th consecutive year that no major hurricane made landfall in the U.S. The last time such a hurricane touched U.S. shores was 2005, when Hurricane Wilma struck the Florida Keys. Since Wilma, 27 major hurricanes have formed in the Atlantic Basin, but none of them have touched U.S. shores.
During the 20th century, about 30 percent of all major hurricanes that formed in the Atlantic Basin made landfall in the U.S.
North Carolina author Willie Drye will be discussing his new book, For Sale—American Paradise, on “Tropical Currents” on WLRN, Miami’s NPR affiliate, on Monday, December 7. He will also be taking calls from listeners. The show starts at 1 p.m.