A busy Atlantic hurricane season came to a close Wednesday, producing the Atlantic’s strongest storm in nine years, devastating western Haiti and throwing a scare into South Florida.
Hurricane Matthew, the first Category 5 storm in the Atlantic since 2007, was the most fearsome product of a hurricane season that generated seven hurricanes, of which three were major hurricanes, the most since 2010. Matthew achieved maximum sustained winds of 160 miles per hour, in a rapid intensification in the Caribbean that caught forecasters by surprise.
Although Matthew never made landfall in Florida, its run up the coast led to emergency declarations, an evacuation order for coastal Palm Beach County and power outages for tens of thousands of customers.
Unusually warm ocean temperatures contributed to the season’s crop of hurricanes, aided by an absence of the high-level winds that can prevent the formation of storms or tear them up when they arrive, said Gerry Bell, lead seasonal hurricane forecaster for the National Oceanic and Atmospheric Administration’s Climate Prediction Center.
A major factor in creating these conditions was the strong African monsoon, which weakens wind shear and trade winds. Weak trade winds reduce the quantity of water flowing into the central Atlantic from the north, leading to warmer ocean water.
It’s too soon to tell whether these factors will arise again next hurricane season, which officially begins June 1, he said. Forecasters will begin studying climate conditions in March to assess the coming season. Among the factors they will look at will be the persistence of La Nina, a cooling of the eastern Pacific Ocean that can lead to a more active hurricane season.
Bell said there were no real surprises about the season.
“A bigger surprise is what we’ve had the last several years, with a lack of major hurricanes making landfall,” he said.
The season that ended Wednesday saw three major hurricanes, storms of at least Category 3 strength, which means winds of 111 miles per hour or greater, the most such storms since 2010.
For Florida, which hadn’t experienced a landfall since Hurricane Wilma buzzed across the state in 2005, the season brought the long-anticipated end to that run of luck. Hurricane Hermine struck the Panhandle as a Category 1 storm on Sept. 2, killing one person and damaging many houses.
Although there’s much research into the potential impact of global warming on the frequency and intensity of hurricanes, Bell said it is a minor factor in season-to-season changes, which he said is more the result of natural variation in climate.