It's over: The six-month Atlantic hurricane season finally comes to an end Thursday.
"We don't foresee any more tropical development," NOAA's lead hurricane forecaster Matthew Rosencrans told USA TODAY this week. The 2023 Atlantic hurricane season is over, he said.
Overall, it was a season with lots of storms (20), but fortunately only three landfalls in the U.S.
Indeed, it was a very active season, but except for Harold, Idalia and Ophelia, the U.S. was repeatedly spared from disastrous storms supercharged by record heat in the ocean. Major, potentially calamitous storms such as Hurricane Lee – which was a Category 5 out in the open Atlantic – and Category 4 Hurricane Franklin both swerved away from U.S. shores.
Here's what to know about the end of the 2023 Atlantic hurricane season:
4th-most active season on record
"It was quite busy for named storms," Colorado State University hurricane researcher Phil Klotzbach told USA TODAY this week. "The 20 named storms is tied with 1933 for the 4th most on record, trailing only 2020 (30), 2005 (28) and 2021 (21)."
Seven storms were hurricanes and three intensified to major hurricanes, NOAA said.
An average season has 14 named storms, of which seven are typically hurricanes.
One measurement that scientists use to determine a season's strength is known as ACE (Accumulated Cyclonic Energy), which was somewhat above normal, and met NOAA's definition of an above-normal season, Klotzbach said.
El Niño vs the warm Atlantic
Before the season started, forecasters were confronted with two competing factors: A strong El Niño, which tends to reduce Atlantic hurricane activity due to the wind shear it produces, and record-warm water in the Atlantic Ocean, which would favor an increased number of storms.
Both factors ended up playing a role in the hurricane season:
“The Atlantic basin produced the most named storms of any El Niño influenced year in the modern record,” said Rosencrans. “The record-warm ocean temperatures in the Atlantic provided a strong counterbalance to the traditional El Niño impacts.”
Overall, El Niño acted to protect the U.S. from what could have been an even more active year due to the unusually warm waters of the Atlantic, which were caused in part by climate change.
So, which factor 'won' the season?
"Overall, I would say that the warm Atlantic won, in that we ended up with below-normal shear in a strong El Niño year," Klotzbach told USA TODAY. "Basically, we would have expected a lot more shear in the western Atlantic given the strength of El Niño"
Rosencrans told USA TODAY that although the warm Atlantic might have "won" overall, wind shear from El Niño did have an impact on the Gulf of Mexico, which had a quiet season (except for Idalia).
In the tropical Atlantic Ocean, sea-surface temperatures were at record warm levels during the peak of the 2023 hurricane season. These warm waters and associated low pressures in the tropical Atlantic were likely the reason why El Niño did not have its normal effect across the tropical Atlantic, Colorado State University forecasters said.
Hurricane season ends: See how 4th most active season produces just 3 landfalling storms
Meteorologist Jeff Masters of Yale Climate Connections told USA TODAY that the level of activity in the Atlantic was far higher than was typical for an El Niño year, so he said the record-warm waters “won” out over the usual suppressive factors (chiefly, higher wind shear) that El Niño usually brings. Wind shear over the tropical Atlantic in 2023 was much lower than usual for an El Niño year.
Fortunately, the steering pattern in 2023 was typical of that for an El Niño year, with a weaker and farther-east Bermuda-Azores high leading to most storms recurving out to sea without affecting the U.S., Masters said.
The high "helped to allow storms to turn north well before reaching the U.S. or even the Caribbean," said University of Miami meteorologist Brian McNoldy on his blog this week.
Was climate change a factor in the warm Atlantic waters?
Masters told USA TODAY that the record-warm waters in the Atlantic in 2023 were largely caused by an unusual atmospheric circulation pattern brought on by the rapid transition from a three-year La Niña event to strong El Niño conditions.
"While the El Niño/La Niña cycle is natural, there has been research published linking the unusual circulation patterns of 2023 to human-caused climate change," he said.
Climate change has also been causing a slow increase in Atlantic sea temperatures of about 1 degree Celsius (1.8 degrees F) in the tropical Atlantic’s main development region for hurricanes in the past century (during August-October).
Damage was lowest since 2015
According to global reinsurance broker Gallagher Re, the total damage from Atlantic named storms was the lowest since 2015. Three storms each caused over $100 million in damage:
Hurricane Idalia: $2.4 billion
Tropical Storm Ophelia: $375 million
Hurricane Lee: $150 million
Hurricane Idalia was the only U.S. landfalling hurricane in 2023. It made landfall as a category-3 hurricane on Aug. 30 near Keaton Beach, Florida, causing storm surge inundation of 7 to 12 feet and widespread rainfall flooding in Florida and throughout the Southeast, NOAA said.
Idalia led to seven direct and three indirect deaths in the U.S., Masters said.
Tropical Storm Ophelia made landfall as a strong tropical storm with 70-mph winds on Emerald Isle, North Carolina, on Sept. 23, causing widespread heavy rainfall, gusty winds and significant river and storm surge flooding in portions of eastern North Carolina, NOAA said.
Eastern Pacific storms also wreaked havoc
Several hurricanes from the eastern Pacific made news in 2023:
Tropical Storm Hilary brought widespread heavy rainfall and flooding to Southern California, with some areas receiving up to 600% of their normal August rainfall. According to NOAA, Hilary led to the first ever issuance of tropical storm watches and warnings for the Southern California coastline by National Hurricane Center.
Hurricane Otis made landfall near Acapulco, Mexico, on Oct. 25 as a category-5 hurricane with sustained winds of 165 mph. Otis holds the record as the strongest landfalling hurricane in the eastern Pacific after undergoing rapid intensification, in which wind speeds increased by 115 mph in 24 hours, according to NOAA. At least 50 people died in Mexico due to Otis.
Hurricane Dora, a category-4 storm that began in the eastern Pacific but then crossed into the central Pacific, passed south of Hawaii in early August, marking the first major hurricane in the central Pacific basin since 2020. The strong gradient between a high-pressure system to the north and Dora to the south was a contributing factor to the catastrophic, wind-whipped wildfires in Hawaii that killed more than 100 people, NOAA reported.
Contributing: Cheryl McCloud, USA TODAY NETWORK - Florida
This article originally appeared on USA TODAY: Atlantic hurricane season 2023 ends: How bad was it? How many storms?