Experts are now expecting fewer hurricanes than they predicted in late May.
“There are still more storms to come — the hurricane season is far from being over,” said Gerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center.
Nine to 13 named storms — including four to seven hurricanes and zero to two major hurricanes of Category 3 strength or higher — are predicted this season, which began June 1 and runs through November 30, the federal agency predicted.
The forecast number includes the four named storms that already have formed this year.
An average six-month Atlantic season typically produces 12 named storms, of which six become hurricanes. including three major hurricanes.
The latest forecast is well short of what the Atlantic experienced in 2017, when 17 named storms formed and three major hurricanes struck US soil. Last year’s season ended with 10 hurricanes and six major hurricanes.
NOAA added Thursday that there is a 60% chance that the 2018 season will see a below-normal number of storms in the Atlantic basin. That’s up from 25% in the original forecast in May, when it looked like the basin would experience an average to above-average season.
The likelihood of a near-normal season is now 30%, and the chance of an above-normal season has dropped from 35% to 10%.
As usual, the latest forecast cannot offer the bit of information most critical to residents living in hurricane-prone areas: precisely where this year’s storms might strike. The zone extends from the Gulf Coast of Texas around Florida to the Carolinas and, sometimes, as far north as Boston.
Hurricanes Harvey, Irma and Maria last year put a dramatic end to a 12-year period with no major hurricane landfalls in the United States and ranked among the top five costliest hurricanes in history. The top US official over NOAA this spring offered that experience as a cautionary tale.
“The devastating hurricane season of 2017 demonstrated the necessity for prompt and accurate hurricane forecasts,” US Commerce Secretary Wilbur Ross said.
El Niño pattern could make for fewer storms
Last year’s season was very active, in part, because of a weak La Niña that developed during the six-month hurricane period.
La Niña is a naturally occurring phenomenon characterized by cooler-than-normal water in the eastern Pacific equatorial region. While La Niña occurs in the Pacific Ocean, it has a widespread impact on the global climate. That includes decreased wind shear — the changing of wind speed and direction with height — across the tropical Atlantic, which creates favorable conditions for tropical development.
La Niña in 2017 made way for what became “ENSO-neutral conditions” — meaning neither La Niña nor its opposite, El Niño, is present — Bell said in May, noting that El Niño could develop later in the season.
Now, there is a nearly 70% likelihood of El Niño forming during this year’s hurricane season, the Climate Prediction Center said Thursday.
El Niño features warmer water in the eastern Pacific equatorial region, creating greater wind shear in the Atlantic, and thus, fewer tropical storms.
If El Niño does develop by October, “it could possibly shut down or weaken the latter part of the season,” Bell said.
But that is certainly no guarantee. And if El Niño fails to appear, Bell warned, “we could certainly see the seasonal activity near the higher-end of the predicted range.”
Sea surface temperatures also play a part
Sea surface temperatures across the tropical Atlantic Ocean and the Caribbean Sea also have continued to remain much cooler than average, NOAA said Thursday.
“Hurricanes use warm oceans as fuel to build in intensity and size. With cooler ocean temperatures, hurricane development should be below normal,” CNN meteorologist Chad Myers said.
Cooler temperatures, combined with a strong wind shear and drier air in the region where storms typically develop will further suppress hurricanes, NOAA stated.