WEST PALM BEACH, Fla. —The atmosphere is leaving scant clues as to its plans for the 2020 hurricane season, but an early forecast is seeing little respite from the yearslong streak of tropical cyclone tumult.
Colorado State University’s first review of the global climate patterns that could influence the next hurricane season, which begins June 1, found only a 10% chance for below normal activity, lead author and storm researcher Phil Klotzbach said.
The probability for an above normal season was 45% with the same chances given for a normal season.
CSU’s December outlook does not predict a specific number of storms, but forecasts the amount of accumulated cyclone energy, or ACE, for the season. ACE is a measure of the strength and longevity of a tropical cyclone.
“All in all, I’d say conditions favor a near-to somewhat above-average season given the odds of El Nino appear to me to be fairly low,” Klotzbach said. “Of course, my ability to predict El Nino this far in advance for next year’s hurricane season is extremely low.”
El Nino is a periodic global climate pattern that forms when the waters in the equatorial Pacific warm. The resulting changes in where towering thunderstorms form and shifts in wind directions high in the atmosphere work against Atlantic basin hurricanes.
But predicting El Nino, even a few months in advance, can be difficult.
This year, scientists from the National Oceanic and Atmospheric Administration, believed El Nino would grow to moderate strength and live through August, September and October —peak hurricane months.
Instead, it abruptly died in August, and the 2019 hurricane season ended with 18 named storms, including six hurricanes and three major hurricanes of Category 3 or higher. A normal season has 12 named storms, including six hurricanes and three major hurricanes.
“Making successful seasonal hurricane forecasts requires that one make a successful El Nino forecast,” said Jeff Masters, co-founder of Weather Underground who writes the Eye of the Storm blog for Scientific American. “When there are neutral conditions in December, as is the case now, there is not much we can say about what the state of El Nino will be next hurricane season —it could be virtually anything.”
Klotzbach notes that three quiet hurricane seasons between 2013 through 2015 led CSU researchers to believe that the Earth may be entering into a decades-long period of relaxed hurricane activity.
Then came the past four years that were not only above average in number of storms, but also damaging, with Hurricane Matthew (2016), Harvey, Irma and Maria (2017), Michael (2018) and this year’s Cat 5 Hurricane Dorian.
The chances of a storm hitting the U.S. based on historic activity is also considered in this month’s report.
Florida has the highest chance of having a hurricane make landfall at 51%. There is a 21% chance a major hurricane could hit the Sunshine State.
“No one can completely understand the full complexity of the atmosphere-ocean system,” CSU’s report says. “But, it is still possible to develop a reliable statistical forecast scheme.”
Some scientists, however, are wary of seasonal forecasts.
“I’ve never felt that seasonal outlooks had any value for coastal residents, in the sense that they provide no information on which to base preparedness decisions,” said James Franklin, the former chief of forecast operations at the National Hurricane Center. “A quiet season, even if predicted accurately in advance, offers no assurance that you won’t be struck by a devastating hurricane. And an active season, even if predicted in advance, doesn’t mean you’ll be hit or even threatened.”
CSU considers several factors in its December climate review, including the Atlantic Multi-Decadal Oscillation, or AMO. A positive phase of the AMO, which the Earth has been in since 1995, leads to three to five times more hurricane activity, as warmer waters feed hurricanes.
The AMO also is associated with a stronger African monsoon season, which forms the tropical waves that travel into the Atlantic and can form hurricanes.
“There is a maze of changing physical linkages between the many variables,” CSU’s report says.
Franklin’s advice is the same each time the calendar approaches June 1.
“Preparations should be taken each and every year, regardless of what the tea leaves might be saying about the upcoming season,” he said.
CSU’s first detailed forecast is scheduled for release April 2.