Atlantic hurricane season begins 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 currentand it’s the 800-pound gorilla of Gulf hurricane hazard.
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 temperature charts from 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. .
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 as it draws energy from the current. ‘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 27 named storms that yearseven became major hurricanes. Wilma and Rita also crossed the loop current that year and became one of the most intense Atlantic hurricanes recorded.
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. An important forecast foresees 19 tropical storms – 32% above 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 make the most of their strength of the first 100 feet (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 whirlwind that fueled Hurricane Ida in 2021 was more than 86 F (30 C) at the surface and was warm 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.
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 recorded in the Atlantic, and Rita and Katherine were not far behind.
La Nina, wind shear and other drivers of a busy season
Forecasters have other clues about how the hurricane season could unfold. One is La Nina, the opposite climate to El Nino.
During La Nina, 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 the. 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 Nina, and more humidity in the atmosphere can mean more hurricanes.
La Nina was exceptionally strong in the spring of 2022, although it is possible that it could 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 reduce the likelihood of storms forming.
Climate change has a role
As global temperatures rise, ocean temperature increased. Much of the heat trapped by greenhouse gases that are released by human activities is stored in the oceanswhere it can provide supplemental fuel for hurricanes.
Studies suggest the Atlantic is likely to see more storms intensify into major hurricanes as these temperatures increase, although there are not necessarily more storms overall. A study looked at the 2020 hurricane season – which saw a record 30 named storms, 12 of which hit the US – and found the storms produces more rain they would have in a world without the effects of human-caused 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.