In a change from its earlier outlook, the government said Thursday that conditions now are “more favorable” for an above-normal hurricane season in the Atlantic Basin.
And all indications are that the basin remains in a period of high tropical-storm activity that began in 1995, said Gerry Bell, hurricane specialist at the Climate Prediction Center.
In what could be an ominous development for the East and Gulf Coasts, the government also announced Thursday that the El Niño event — an anomalous warming of sea-surface temperatures across a broad expanse of the tropical Pacific — was dead.
El Niño tends to generate upper-level winds from the west that can snuff out incipient tropical storms in the Atlantic Basin, which includes the Caribbean Sea and the Gulf of Mexico.
“It looks like El Niño is pretty much faded in July,” Bell said after a media briefing. That was somewhat unexpected, and predicting the course of El Niños “is an ongoing scientific challenge,” he said.
El Niño was a factor when NOAA issued its May hurricane outlook, calling for 9 to 15 named storms, those with winds of at least 39 mph; four to eight hurricanes, winds of 74 mph or higher; and two to four “major” hurricanes, with winds of 111 mph or more.
The updated outlook sees 10 to 17 named storms, five to nine hurricanes, and two to four majors; the normals are 12, 6, and 3, according to the National Hurricane Center.
In addition to the fading El Niño, Bell said, the other factors favoring hurricanes include a stronger West African monsoon season and weakened shearing winds.
The stronger hurricanes tend to develop from waves bounding off the African coast near Cape Verde, typically starting in mid-August.
Those waves gain strength as they feed off the warm waters of the subtropical Atlantic over several days. Atlantic sea-surface temperatures are slightly above normal, Bell said, but weren’t a factor in the forecast update.
So far, two named storms have formed, in line with long-term averages. One of them, Barry, became a weak hurricane and doused the Gulf Coast, and eventually affected the Philadelphia region.
But activity tends to pick up as August progresses, and peaks in early September.
Looking further ahead, Bell said that it appears that an active hurricane period shows no signs of waning. It is in its 25th season, and historically they have lasted from 25 to 40 years, alternating with “lull” periods.