Sigh of relief: A look back at the 2023 hurricane season that could have been horrible

It’s almost a wrap: With just a few days left in the 2023 hurricane season, South Florida got away clean — not a single hurricane made direct landfall in the tricounty region.

But by myriad measures, it was a robust hurricane season that ominously broke several climate records.

Hurricane season officially runs from June 1 to Nov. 30, but for many in South Florida, it felt like the season started on April 12, when 26 inches of rain fell in just 10 hours near Fort Lauderdale, closing the Fort Lauderdale/Hollywood International Airport for two days, flooding the streets, stranding motorists, and prompting President Biden to issue a major disaster declaration to free up federal aid.

That storm was not considered “tropical,” said University of Miami climatologist Brian McNoldy, because it did not derive most of its energy from warm ocean waters and did not form a cyclone motion, but it certainly focused our attention on the pending storm season.

Initially the National Hurricane Center predicted a “near-normal” season, but in August upgraded that forecast to “above normal.”

“Going into the season, we saw the two giant competing factors, being the record-warm ocean temperatures in the Atlantic and El Niño, and they work against each other,” McNoldy said. “But El Niño didn’t kick in as much as expected, so the very warm ocean temperatures absolutely won the race. So that’s what provided an above-average hurricane season, even though it was an El Niño year.”

The adjustment was on target. “By any measure, this has been an above-average year — the number of storms, the accumulated cyclone energy, how long storms lasted, the number of named-storm days,” McNoldy said.

The accumulated cyclone energy (ACE) that McNoldy mentioned was 120% of a normal year. It’s essentially a wind energy tally that combines named storms’ intensities and durations.

There were so many storms, 19, that we almost ran through the alphabet to name them. Going beyond one round of the alphabet has only happened twice, in 2005 and 2020. This year, only Vince and Whitney are the only names left. The average year sees 14 named storms.

Despite the high number of storms, Hurricane Idalia was the only Atlantic hurricane to make landfall (Lee made landfall in Canada, but it was technically an extratropical low with hurricane-force winds). Idalia came ashore as a Category 3 storm in the Big Bend region, one of the least populated areas of Florida.

The landfall location may have made the storm less costly. According to News Service Florida, early projections put losses from Idalia at between $3 billion and $5 billion, including $500 million related to the National Flood Insurance Program.

By comparison, 2022’s Hurricane Ian, which made landfall in more densely populated Southwest Florida with 150 mph sustained winds and a storm surge reaching 15 feet, has projected overall losses of $112 billion, according to the National Oceanic and Atmospheric Administration.

Idalia killed four people in Florida. Ian killed 150.

Three crucial factors

There were three major factors this year that combined to both boost the number of storms and diminish their deadliness, said meteorologist and hurricane preparedness expert Craig Setzer: Warm sea-surface temperatures gave us a higher number of storms; the Bermuda High was weak, which steered most storms north before they reached the U.S.; and wind shear from El Niño inhibited systems from developing in the Caribbean.

The Bermuda High is a pressure system that sits over the Atlantic in the summer. It acts as a barrier to hurricanes, and can shift in size and location. Once storms clear the high, they head north.

“Franklin kind of chewed up the Bermuda High, and it never really built back because storm after storm came in and recurved (north) and kept eroding it,” Setzer said.

The weak Bermuda High was a double-edged sword. It kept us safe by steering storms north to peter out over the Atlantic, but a weak high means weaker trade winds, calmer oceans, and therefore hotter sea-surface temperatures and potentially more storms.

McNoldy noted that the weak Bermuda High prompts hot-water temperatures in other ways.

“We also didn’t have Saharan dust blowing off of Africa as much, because the high was weaker. And the winds didn’t kick up sands from Africa as much,” he said. That dust filters sunlight and thus heat, and is carried by dry desert air, which kills hurricanes. Without it there’s more heat and moisture, and thus more fuel for storms.

Though weak trade winds may have helped heat up the oceans, the summer of 2023 was also globally the hottest on record, according to NASA. June, July and August were 0.41 degrees warmer than any summer on record, and 2.1 degrees warmer than the average summer between 1951 and 1980.

A report by the European Union’s Copernicus Climate Change Service showed that average sea-surface temperatures globally were the warmest on record for the month of September, and the second warmest for any month, only behind August 2023.

The hot September fits a larger trend. According to NOAA, the 10 warmest years in the historical record have all occurred since 2010.

That kind of heat both bakes oceans, and carries more moisture in the atmosphere, both of which cause storms to intensify.

Looking to next year

Though the National Weather Service has called for a strong El Niño this winter, which will likely bring more rain and storminess than usual to South Florida, McNoldy said forecast models show it weakening rapidly before next hurricane season.

That means less wind shear to topple tropical systems. “But that’s with all other things being equal, which we know from this past year, they aren’t,” McNoldy said.

The Bermuda High is also a concern. “It’s not real easy to predict,” Setzer said. “In the hurricane community there is some uneasiness,” he said. “We’ve loaded the dice somewhat with the warm water. If we don’t have a weak Bermuda Ridge, all those storms that turned (away from us) out there, they’re coming our way.”

Information from the News Service of Florida was used to supplement this news article.