USA - Atlantic hurricane season 2023 was filled with monster storms: How bad was it?

"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 two landfalls in the U.S.

Indeed, it was a very active season, but except for 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 Franklinboth 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.

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.