Colorado State University’s first review of global climate patterns that could influence the 2019 hurricane season found a 65 percent chance that a less active hurricane season will unfold, giving an above-average season a 35 percent chance of occurring.
The December outlook does not predict the 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.
An average hurricane season has an ACE of 92. In comparison, the 2018 season had an ACE of 129, with 2017′s record-breaking season ending with an ACE of 226.
CSU outlines five scenarios that could occur for the 2019 season that begins June 1 based on two key indicators: the Atlantic Multi-Decadal Oscillation and El Nino.
Three of the five scenarios show below average activity with an ACE between 50 and 80. Two scenarios show a season with an ACE between 130 and 170.
“There is always considerable uncertainty as to how much activity an Atlantic hurricane season is going to generate as such a long forecast lead time,” authors Phil Klotzbach and Michael Bell wrote in a report released this month.
The first CSU forecast to predict storm numbers will be issued April 4, typically followed by a May forecast from the National Oceanic and Atmospheric Administration.
Both CSU and NOAA had predicted higher activity in their early-season forecasts last year, but reduced the numbers as the chances of a storm-killing El Niño increased.
But El Niño was a no-show, the winds quieted and nature turned to the periphery of the tropics, cooking up storms farther north in the Atlantic basin where water temperatures were record warm.
Many hurricane experts caution against giving too much credence to predictions made before the seasonal transition from winter to summer, which can shake up the atmosphere and lead to significantly different outcomes than forecasts made six months before.
“The things that will end up affecting the season overall are really hard to predict very far in advance,” said James Franklin, the National Hurricane Center’s former chief of the hurricane specialist unit in a 2017 interview. “There are frequently going to be big errors in these forecasts, even when they come out in April.”
The federal Climate Prediction Center said this month there is a 90 percent chance of at least a moderate El Nino forming this winter. There is a 60 percent chance of it continuing through spring.
But will it continue through the 2019 hurricane season?