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The Loop Current, source of monstrous storms, looks a lot like it did in 2005, the year of Katrina

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The Loop Current, source of monstrous storms, looks a lot like it did in 2005, the year of Katrina

 | Top storiesA satellite image of ocean heat shows the strong loop current and swirling eddies. Christopher Henze, NASA/Ames

Atlantic hurricane season begins on June 1, and the Gulf of Mexico is already warmer than average. Even more ominous is a current of warm tropical water that loops unusually far into the gulf at this time of year, with the power to turn tropical storms into monster hurricanes.

It’s called the Loop Current, and it’s the 800-pound gorilla of Gulf hurricane risk.

When the loop current hits this north so early in hurricane season — especially during what is expected to be a busy season — it can spell disaster for residents of the northern Gulf Coast, from Texas to Florida.

If you look at temperature maps of the Gulf of Mexico, you can easily spot the loop current. It meanders through the Yucatan Channel between Mexico and Cuba, into the Gulf of Mexico, then returns through the Florida Strait to southern Florida as the Florida Current, where it becomes the main contributor to the Gulf Stream. .

The Loop Current, source of monstrous storms, looks a lot like it did in 2005, the year of Katrina

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The loop current was about as far north as Tampa, Florida in mid-May 2022. The scale, in meters, indicates the maximum depth at which temperatures were 78 F (26 C) or higher . Nick Shay/University of MiamiCC BY-ND

When a tropical storm passes over the Loop Current or one of its giant whirlpools – large rotating pools of warm water that break away from the current – the storm can explode in force drawing its energy from the Hot water.

This year, the Loop Current looks remarkably like it did in 2005, the year Hurricane Katrina passed through the Loop Current before devastating New Orleans. Of the 27 named storms that year, seven became major hurricanes. Wilma and Rita also crossed the loop current that year and became two of the strongest Atlantic hurricanes on record.

The Loop Current, source of monstrous storms, looks a lot like it did in 2005, the year of Katrina

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The loop current in May 2005 looked surprisingly like May 2022. Nick Shay/University of MiamiCC BY-ND

I have been monitoring ocean heat content for over 30 years as a marine scientist. The conditions I see in the Gulf in May 2022 are concerning. A major forecast calls for 19 tropical storms – 32% more than average – and nine hurricanes. Loop current has the potential to supercharge some of these storms.

Why Loop Current Worries Forecasters

Warm ocean water does not necessarily mean more tropical storms. But once tropical storms reach waters around 26°C (78°F) or warmer, they can develop into hurricanes.

Hurricanes draw most of their strength from the upper 30 meters of the ocean. Normally, these upper ocean waters mix, allowing hot spots to cool quickly. But the subtropical loop current water is deeper and warmer, and also saltier, than common Gulf water. These effects inhibit ocean mixing and sea surface cooling, allowing the warm current and its eddies to trap heat at great depths.

In mid-May 2022, satellite data showed the loop current had water temperatures of 78°F or warmer out to about 330 feet (100 meters). In the summer, this heat could extend up to about 500 feet (about 150 meters).

The vortex that powered Hurricane Ida in 2021 was over 86 F (30 C) at the surface and had heat up to about 590 feet (180 meters). With favorable atmospheric conditions, this deep reservoir of heat helped the storm explode almost overnight into a very powerful and dangerous Category 4 hurricane.

The Loop Current, source of monstrous storms, looks a lot like it did in 2005, the year of Katrina

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Hurricane Ida’s pressure dropped rapidly as it crossed a warm, deep vortex boundary on August 29, 2021. Nick Shay/University of MiamiCC BY-ND

During a storm, warm ocean water can create towering plumes of warm, moist air, providing high-octane fuel for hurricanes. Think about what happens when you boil a large pot of spaghetti on the stove and how the steam rises as the water gets hotter. As the humidity and heat increase in a hurricane, the pressure drops. The difference in horizontal pressure from the center of the storm to its periphery then causes the wind to accelerate and the hurricane to become increasingly dangerous.

Since the loop current and its vortices are so hot, they do not cool significantly and the pressure will continue to drop. In 2005, Hurricane Wilma had the lowest central pressure on record in the Atlantic, and Rita and Katrina were not far behind.

La Niña, wind shear and other drivers of a busy season

Forecasters have other clues about how the hurricane season could unfold. One is La Niña, the opposite climate to El Niño.

During La Niña, stronger trade winds in the Pacific Ocean bring colder water to the surface, creating conditions that help push the jet stream further north. This tends to exacerbate drought in the southern United States and weaken wind shear there. Wind shear involves the change in wind speed and direction with height. Too much wind shear can tear apart tropical storms. But less wind shear, thanks to La Niña, and more humidity in the atmosphere can mean more hurricanes.

La Niña was exceptionally strong in the spring of 2022, although it may weaken later in the year, allowing more wind shear towards the end of the season. For now, the upper atmosphere does little to prevent a hurricane from intensifying.

It is too early to tell what will happen to the guiding winds that guide tropical storms and affect their direction. Even before that, conditions over West Africa are crucial in determining whether tropical storms form in the Atlantic. Sahara dust and low humidity can both reduce the likelihood of storms forming.

Climate change has a role

As global temperatures rise, the temperature of the ocean rises. Much of the heat trapped by greenhouse gases that are released by human activities is stored in the oceans, where it can provide additional fuel for hurricanes.

Studies suggest that the Atlantic is likely to see more storms intensifying into major hurricanes as these temperatures rise, although there may not necessarily be more storms overall. A study looked at the 2020 hurricane season – which recorded a record 30 named storms, 12 of which hit the United States – and found that the storms produced more rain than they would in a world without the effects of human-induced climate change.

Another trend we’ve noticed is that the warm loop current eddies are hotter than they were 10 to 15 years ago. Whether this is linked to global warming is not yet clear, but the impact of a warming trend could be devastating.

This article is republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Nick Shay, University of Miami.

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Professor Lynn K. (Nick) Shay receives funding from the National Science Foundation and the National Oceanic and Atmospheric Administration. I sit on the board of directors of the Regional Association of the Gulf of Mexico Integrated Ocean Observing System.

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