The 2023 Atlantic Hurricane Season: Hot Water Fuels More Monsters

With the 2023 Atlantic hurricane season coming to an official close, our experts share some disturbing weather trends from the past few years. Though tropical weather events are not going away, there are ways businesses from coast to coast and offshore can better prepare their operations.

Following an exhausting, seven-year stretch of destructive and deadly hurricanes, there was considerable anticipation and uncertainty around the start of the 2023 Atlantic hurricane season.

Historically, at least one or two hurricanes make landfall in the United States each year, but over the last seven-year period, the numbers have been staggering:

• Seven hurricanes were Category 3 or higher at landfall.
• Twenty-three storms were billion-dollar disasters.
• More than 5,000 fatalities in the United States.
• Over $600 billion in damages.
• Fifteen storm names were retired by the World Meteorological Organization due to their devastating impacts.

 

The exceptional frequency of intense hurricanes over the last seven years can be attributed to warmer-than-normal ocean waters in the tropical Atlantic and to a long stretch of neutral to La Niña conditions in the equatorial Pacific.

Warm Atlantic waters serve as an energy source to fuel the development and intensification of tropical cyclones. The wind pulls moisture from the ocean surface, which rises and condenses into towering rain clouds. The updrafts within these clouds intensify low pressure and convergence at the surface, which strengthens the winds and furthers this feedback loop. The warmer the water, the easier it is for moisture to be swept up to fuel the storm and the stronger this feedback process becomes. Atlantic sea surface temperatures have been on an upward trend for the last 40 years; however, the Gulf of Mexico and western Atlantic adjacent to the U.S. East Coast have become particularly toasty over the past seven years.

The exceptional frequency of intense hurricanes can be attributed to warmer-than-normal ocean waters in the tropical Atlantic and a long stretch of neutral to La Niña conditions in the equatorial Pacific.

The result of the warmer waters is extra fuel that allows hurricanes to intensify, sometimes rapidly, up until landfall. Rapid intensification has become a bit of an attention-grabbing phrase, but it is simply defined as a strengthening of the winds by at least 35 mph in 24 hours. About one-third of all tropical cyclones undergo rapid intensification at some point in their lifespan, and that ratio has not changed over the years. However, the warmer ocean has changed the maximum potential intensity, which is a theoretical ceiling of the strength of a hurricane. The higher ceiling allows already strong storms to intensify even more rapidly, often close to land. There are huge ramifications that come with this increasingly common behavior: stronger hurricanes at landfall, of course, but also increased challenges for emergency management organizations who must deal with these quickly worsening situations.

Now let’s talk about Pacific Ocean temperatures. That might sound strange when we’re interested in Atlantic hurricanes, but the Pacific can have a significant influence through the cycle of El Niño and La Niña. El Niño conditions are characterized by a warmer Pacific Ocean generating more showers and thunderstorms, whose outflow in the upper levels of the atmosphere pushes eastward across the Atlantic. This outflow results in vertical wind shear or winds changing speed and direction with height. Wind shear can tear apart hurricanes by pushing deep rain clouds away from the center of circulation. La Niña, on the other hand, reduces wind shear and is typically more favorable for Atlantic hurricanes.

The last seven years have featured a long stretch of neutral to La Niña conditions, coming on the heels of a record-strong El Niño in the winter of 2015-2016. The one exception was 2018, with a brief warming in the Pacific, and sure enough, it featured the fewest major hurricanes during this time. The two that did develop were Florence and Michael — both names that were retired for their impacts in the United States. Otherwise, La Niña has reigned strong, and the effect of the reduced wind shear combined with the hot Atlantic water has produced devastating results.

And then came 2023.

After three consecutive years with moderate La Niña conditions, the likelihood of a fourth was very low, and the expectation was for El Niño to come charging forward like an excited dog, finally called to come get a treat. By summer, the dog had surged forth from its hind legs, and a moderate to strong El Niño was underway in the Pacific. With this change came an increase in wind shear across the Atlantic, which was anticipated for the 2023 hurricane season.

On the Atlantic side, the streak of hot ocean waters continued and even challenged record highs. The entire ocean was much above normal heading into summer, and sea surface temperatures reached well into the 90s across the Gulf of Mexico. A storm over those waters could easily rapidly intensify into a major hurricane, with potential for even more explosive strengthening. Forecasters were very wary of this potential moving into the 2023 season. Even with the outlook for stronger wind shear, all it would take is a small window of opportunity for a little swirl to turn into a monster overnight.

One saving grace for the United States was an often-ignored component of seasonal hurricane outlooks — mostly because it’s a little trickier to predict — and that’s the expected path of storms. The normal path for any given storm in the northern hemisphere starts out westward with a clockwise turn toward the north and northeast, called recurving. El Niño tends to cause storms to recurve further east, over the open ocean and away from the United States. It is something that the DTN^® Long Range Team captured in their outlooks, showing less risk along the East Coast while still highlighting the potential for a headline-making hurricane or two in the Gulf. Sure enough, that’s what 2023 delivered.

Hurricane Idalia was the big headline-maker for the United States, undergoing the long-foreshadowed rapid intensification in the Gulf of Mexico right before landfall. Idalia became yet another deadly hurricane and billion-dollar disaster, continuing what has felt like a new normal in the country for the last several years.

In addition to Idalia, two other storms made U.S. landfall: Harold in Texas and Ophelia in North Carolina. Neither of these storms achieved hurricane intensity (maximum winds of at least 74 mph) during their lifespans and generally had much more modest impacts.

While these storms garnered most of the attention, the vast majority of this season’s tropical cyclone activity stayed over the open Atlantic, with paths recurving north and northeastward away from land. We can visualize how these tracks compare to normal by creating a map of storm density. The result for 2023 is overall below-normal activity across the Gulf of Mexico and up the East Coast, while further east, the central Atlantic saw an exceptional number of storms compared to normal.

The same type of analysis can be performed with a metric called Accumulated Cyclone Energy, or ACE for short. It was developed as an easy way to estimate the amount of energy released by a tropical cyclone and is simply a function of the maximum winds. Using this metric allows us to not only look at where there were storms but also where the storms were strongest. Two major hurricanes, Franklin and Lee, together light up the map in the western Atlantic. This show of much-above-normal strength is a reflection of the very warm ocean waters that occupied not only the Gulf of Mexico but the entire Atlantic this year. Hurricane Lee, in particular, demonstrated what a storm could do with the potential energy lurking in these waters, and its rapid intensification to Category 5 strength was forecasted well in advance by DTN.

Hurricane Lee, in particular, demonstrated what a storm could do with the potential energy lurking in these waters, and its rapid intensification to Category 5 strength was forecasted well in advance by DTN.

The Gulf of Mexico, meanwhile, sits under shades of blue on this map. Despite Idalia’s presence, the gulf typically spins up a few more hurricanes during the season, and this is an excellent depiction of the challenge of modern hurricane seasonal outlooks. Someone could draw this exact map as a forecast, and it would have verified perfectly. Except that, given no other information, this map makes it look like the Gulf Coast was safe from hurricanes. DTN forecasters strive to add value beyond these numbers — like communicating the risk of one high-impact hurricane in the gulf despite overall below-normal activity.

One of the most iconic examples of this type of situation was in 1992 — a very calm and quiet year featuring only seven tropical storms, but one was Hurricane Andrew.

All it takes is one.

And it seems like recently, every year has had at least one of those “ones.”

Stay ahead of today’s more intense storms with actionable insights from DTN that predict the weather’s severity and operational impacts on your business.

 

About the author

Sam Lillo is a software engineer on the DTN Forecast Team. He has a Ph.D. in meteorology from the University of Oklahoma and specializes in numerical weather prediction, tropical cyclones, and data visualization.