Maryland’s National Oceanic and Atmospheric Administration predicts an above-average hurricane season this year – starting June 1 – with between 11 and 17 named storms, five to nine hurricanes and two to four major hurricanes.
In a formal statement, lead seasonal forecaster Gerry Bell said “the outlook reflects our expectation of a weak or non-existent El Niño, near- or above-average sea-surface temperatures across the Atlantic, and average or weaker-than-average vertical wind shear.”
Thursday’s NOAA report contrasted with an April 6 Colorado State University forecast of “slightly below-average activity,” pegging storm action at the lower end of Maryland’s predictions, calling for 11 named storms, four hurricanes and two major hurricanes.
“We anticipate a below-average probability for major hurricanes making landfall along the United States coastline and in the Caribbean,” CSU authors Philip Klotzbach and Michael Bell wrote in their 41-page statement.
In an average season, the Atlantic spins off 12 storm systems. In 2016, U.S. weather services predicted 10 to 16 would form, and the season eventually saw 15 storms.
CSU will release fresh predictions on June 1.
“As is the case with all hurricane seasons, coastal residents are reminded that it only takes one hurricane making landfall to make it an active season for them. They should prepare the same for every season,” the authors wrote in April.
Hazard Management Cayman Islands Awareness and Communications Officer Simon Boxall echoed the CSU authors’ warnings that it takes only one storm to create massive disruption. HMCI, he said, did not underwrite any particular prediction, but tended to place greater weight on “government-type forecasting” such as the NOAA and the Cayman Islands National Weather Service.
John Tibbetts, director general and chief meteorologist at the CINWS, said the NOAA and CSU predicted different North Atlantic temperatures and El Nino strengths, “and there is a degree of subjectivity to it as well.”
The NWS, he said, “comes down somewhere in the middle.”
El Nino, the “little boy,” refers to complex climate changes every few years, often in late December, producing warmer-than-normal water near northern Peru and Ecuador.
Notoriously difficult to predict, El Nino generally suppresses hurricane development, causing increased wind shear in the tropical Atlantic.
Wind shear, normally the scourge of airline pilots and airports, reduces storms because it “blows the top off hurricanes,” Mr. Boxall said, and “makes us less likely to be affected.”
The CSU team has forecast a “weak to moderate” El Niño in 2017 and a 42 percent chance of a major hurricane making landfall in the U.S. The average risk is 52 percent.
The last hurricane to make landfall in the U.S. was 2005’s Hurricane Wilma, Mr. Klotzbach said. “The odds of going 11 years without a major hurricane landfall in the U.S. is around 1 in 2,000. We have had 31 major hurricanes since Wilma … The odds of having 31 major hurricanes form in the Atlantic with zero landfalls would be around 1 in 7,500.”
The CSU-affiliated Barcelona Computing Centre, which aggregates nearly 20 major Atlantic forecasts, acknowledged “significant uncertainty” about El Nino as the mid-August peak approaches in 2017’s storm season, saying “significant alterations in seasonal forecasts are possible.”
The center launched its www.seasonalhurricanepredictions.org website last year. CSU has issued annual forecasts since 1984, however.
Thursday reports quoted acting NOAA administrator Ben Friedman predicting “a potential for a lot of Atlantic storm activity this year.”
He said between five and nine of the 2017 storms would reach hurricane strength – winds of at least 74 miles per hour. Two to four may reach Category 3 or more.
The 21 names selected for 2017 storms are Arlene, Bret, Cindy, Don, Emily, Franklin, Gert, Harvey, Irma, Jose, Katia, Lee, Maria, Nate, Ophelia, Philippe, Rina, Sean, Tammy, Vince and Whitney.
The first was applied to a late-April North Atlantic post-tropical cyclone.