Harvey, Irma, Jose: The science of ‘ mean season’
Less drought, wind, bad luck combined
First it was Harvey. Then Irma. Now Jose lurks.
The hurricane season has arrived with a deadly vengeance, and science can explain a few reasons why.
“Every year around this time, even in quiet years, we get some active systems,” AccuWeather meteorologist Evan Duffey said. “Hurricane season has a pretty defined peak of late September and early October.
“That’s just the way it is.”
These storms arrived a bit early, but not drastically so, Duffey said. He also provided some ideas to help explain this mean season, when two storms alone have killed dozens of Americans and caused more than a quarter- trillion dollars in damage.
“We don’t like to get into the political debate ( about climate change),” Duffey said. “This year we have had some events that may have contributed to the severity of the storms.”
Duffey said a drought in northwest Africa in recent years probably played a role in the relatively quiet seasons of the recent past. The dust from the drought is picked up by weather systems that roll west over the Atlantic. The dust tends to have a drying effect on developing storms — “that leads to weakening,” he said.
This year the drought was significant- ly reduced in Morocco and elsewhere, the dust waned earlier, and it wasn’t as heavy, Duffey said.
Another factor was El Niño, or the lack thereof. The weather phenomenon enhances vertical wind shear, which can suppress hurricane activity.
No dust from Africa to dry the storms, no winds from El Niño to chop them down. Nature and some bad luck did the rest. Hurricane Harvey smashed into the southeast coast of Texas and southwest Louisiana, stalling and churning out rain for days. Then came Irma, blasting straight up Florida and wreaking havoc on both its coasts.
Jose is next. It’s smaller, weaker and not likely to make landfall in the U. S. But its odd, looping track has meteorologists watching it closely. “If you live on the East Coast, don’t get too worried,” Duffey said. “But pay attention.”