Record-shattering hurricane season has officially ended
After six months and 30 storms from Arthur to Iota, the record-shattering 2020 Atlantic hurricane season has ended.
“I didn’t think I would live to see that, but it’s happened,” said Penn State University meteorologist Michael Mann, referring to the record number of named storms in a single season.
A typical season sees only 12 storms.
All preseason forecasts said an active season was likely, but none came close to the actual number. “Our group here at Penn State predicted an unusually active season, as many as 24 named storms — the most of any of the preseason predictions,” he said. “But even THIS wasn’t aggressive enough a forecast.”
Of those 30 storms, 12 hit U.S. shores, also a record. The previous high was nine, set in 1916.
It was also the fifth consecutive season with above-normal activity, the National Oceanic and Atmospheric Administration said. This includes 18 above-normal seasons out of the past 26.
For Colorado State University hurricane researcher Phil Klotzbach, the season will be most remembered for the unusual late-season activity.
“I think really what stood out to me about 2020 was the extremely active late season,” he said. “October and November were extremely active with seven storms and a whopping four major hurricanes (Delta, Epsilon, Eta and Iota).”
Prior to this year, Klotzbach said, no other OctoberNovember had more than two major hurricane formations.
Although the official end of the hurricane season is Monday, storms sometimes can form in December. Meteorologists at the National Hurricane Center were monitoring an area of disturbed weather several hundred miles southeast of Bermuda for possible development. If the area becomes a named storm, it would be called Kappa, the 31st named storm of the season.
December tropical storms and hurricanes are exceedingly rare. “Only one season on record has had more than one named storm form in December, and that was all the way back in 1887,” Klotzbach said.
A major hurricane has wind speeds of at least 111 mph and is a storm that’s a Category 3, 4 or 5 on the Saffir-Simpson Scale of Hurricane Intensity.
Both Eta and Iota smashed into Central America as Category 4 storms in November, leaving hundreds dead and widespread misery and destruction. Iota was briefly a Category 5 before weakening and reaching land as a Cat 4.
Another calling card of the 2020 season was that many of the storms rapidly intensified as they approached land.
“One of the most notable features of 2020 was all of the intensifying (and often rapidly intensifying) hurricanes we had up until the point of landfall,” Klotzbach said. “Most notably for the United States, Hanna, Laura and Zeta all rapidly intensified in the 24
hours prior to landfall.”
Rapid intensification is typically defined to be a strengthening of 35-plus mph in 24 hours. And this season, several storms saw winds increase by as much as 50 mph or more in 24 hours.
Forecasting intensification, especially rapid intensification, is still a challenge and a nightmare for meteorologists who are trying to counsel emergency managers on evacuation decisions.
The 2020 season began early when Arthur formed on May 16. The extremely active season quickly went through the predetermined list of 21 names, ending with Wilfred on Sept. 18. Then for only the second time in history, the Greek alphabet was used for the remainder of the season, with Alpha forming the same day. Nine Greek alphabet letters have been used so far, up to Iota.
Laura was the U.S.’s deadliest hurricane of the season. The storm killed at least 40 people after roaring into Louisiana on Aug. 27 with winds of 150 mph. It was also the most destructive, causing at least $14 billion in damages in the U.S.
The causes of the active year, according to NOAA’s lead seasonal hurricane forecaster Gerry Bell, included warmer-than-average Atlantic sea-surface temperatures and a stronger west African monsoon, along with wind patterns coming off of Africa that were more favorable for storm development.
La Niña, a natural cooling of ocean water in the Pacific that appeared this fall, is more hurricane-friendly because it reduces wind shear in the Atlantic, which works to crush budding tropical cyclones.
And did climate change play a role in the active year? Penn State’s Mann said yes: “The main ingredient in our forecast was the unusual warmth of the tropical Atlantic Ocean, and the warmth of the oceans cannot be explained without taking into account the warming effect of increasing carbon dioxide concentrations in the atmosphere from fossil fuel burning.