Ten consecutive hurricanes, including six major storms, stained 2017 with devastating floods in Houston, evacuation horrors in Florida, and months of darkness in Puerto Rico.
It’s different this year.
Although statistics show near normal activity as the heady days of 2018’s peak season arrive — five named storms when the average is three, two hurricanes when one is typical — the creep of an El Niño and a balm of cool water may thwart an atmospheric escalation.
The hurricane season, which began June 1, is not dead.
But experts have characterized it so far as “classic junk” and “season of slop.”
“We’ve had five storms and nobody would probably guess that because none of them have been very significant,” said Chris Davis, a senior scientist and associate director at the National Center for Atmospheric Research. “The development’s been pushed to the margins and hasn’t had time to organize into anything intense.”
Beryl and Chris, the season’s two hurricanes, were short lived and steered clear of land. While Chris reached Category 2 strength briefly, Beryl maxed out at 80 mph and was a hurricane for just longer than a day.
Alberto, Debby and Ernesto all remained tropical or subtropical storms. Subtropical cyclones are spread out, with their strongest winds further from the center and slapdash thunderstorms that don’t always form a continuous doughnut of clouds.
“The storms that have formed are different than what we saw last year,” said Phil Klotzbach, a hurricane researcher at Colorado State University and lead author of the school’s hurricane forecasts. “They are pretty classic of what we see with junk seasons.”
Peak hurricane season runs mid-August through mid-October when an average of 95 percent of hurricanes form as tropical waves spin off the coast of Africa ripe for development into fearsome Cape Verde cyclones.
Last year, Hurricane Franklin started the marathon of monsters when it formed Aug. 9 and was followed by a streak that included six hurricanes of Category 3 or higher — Harvey, Irma, Jose, Lee, Maria and Ophelia.
Harvey, Irma and Maria made U.S. landfalls in Texas, Florida and Puerto Rico, respectively. Irma left the coast of Africa as a tropical wave on Aug. 27. Four days later it was a hurricane.
“What a difference a year makes,” said Eric Blake, a hurricane specialist with the National Hurricane Center, in a Tweet on Friday. “One year ago, Harvey was forming and NHC was monitoring three potential Atlantic systems.”
As of Friday, Tropical Storm Ernesto was fading as it headed toward Ireland and just one area of potential development was churning in the tropical Atlantic with a 10 percent chance of development.
“Amazing change,” Blake said.
Early hurricane forecasts for this season called for an average to above average season, but a spring flip-flop in ocean conditions is expected to keep 2018 more subdued.
A muscle-bound Bermuda High — a clockwise spin of winds that shifts toward Bermuda in the summer and the Azores in the winter — has strengthened trade winds in areas of the eastern tropical Atlantic. Robust trade winds increase upwelling in the ocean, continually replacing warmer water at the surface with cooler water from below.
Where 2017 saw Atlantic sea surface temperature running 2 to 3 degrees warmer than normal, this year’s temperatures have been some of the coldest since the 1990s, Klotzbach said.
Cool water is less conducive to storms.
One reason for Ernesto and Debby forming where they did in the far away Central Atlantic near 40 degrees latitude is because while the tropical waters are cooler, waters more to the north are warmer, said Dan Kottlowski, AccuWeather’s hurricane specialist.
“All of this comes together like a puzzle,” Kottlowski said. “You don’t have to be a brilliant sleuth to see what’s going on.”
Saharan dust wafted off African in above normal plumes this summer, reflecting solar energy back into the atmosphere in a way that can add to cooler waters. The dust also introduces dry air into the middle atmosphere that limits storm formation.
Blake said it’s not unusual to have a hyperactive storm season followed by a quiet one.
“It’s remarkable how different two years can be back to back,” Blake said.
Sometimes it’s an El Niño that can shut down a season. A forecast updated this month put the odds of an El Niño forming in the fall at 65 percent and up to 70 percent of a winter El Niño that could last into 2019.
Still, experts said quiet seasons can take radical turns when September arrives.
And Klotzbach is concerned if the Bermuda high remains strong, it could steer any storms that do form right into the U.S.
“A lot of things that have been holding storms back go away late August through September,” Klotzbach said. “Don’t let your guard down because the next 4 to 5 weeks are really important for Floridians.”
How the 2018 hurricane sesaon compares with normal (in parentheses) through Aug. 17:
Named storms, 5 (3.3)
Named storm days, 17.5 (10.8)
Hurricanes, 2 (1)
Hurricane days, 3.25 (2.5)
Accumulated cyclone energey, 17 (13.7)
Major hurricanes, 0 (0.3)
Major hurricane days, 0 (0.4)
Source: Colorado State University