What's the 'Loop Current' and how does it impact hurricanes? LSU professor answers our questions
With the hurricane season now upon us, experts are saying 2022 could see another above-average year of activity. NOAA is predicting the possibility of three to six major hurricanes. There’s a lot of factors that can speak to the severity of the season and intensity of these hurricanes, including and not limited to, the ongoing La Niña conditions, climate change and the Loop Current.
The latter of those three has especially received attention this year due to some reports saying it looks similar to how the Loop Current appeared the year that Hurricane Katrina hit in 2005. But does it typically play that big of a role in the intensification of major hurricanes forming in the Gulf?
WWNO talks with Nan Walker, LSU professor of Oceanography and Coastal Sciences and director of the Earth Scan Laboratory about the Loop Current.
What exactly is the Loop Current?
The Loop Current is a warm and deep ocean current located in the Gulf of Mexico. It is fed by equatorial waters that enter the Gulf from the Yucatan Channel between Mexico and Cuba. The water entering the Gulf extends 1,000 meters deep and the volume of the flow is enormous, seven Superdomes full of water every second and - about 639,360 Superdomes full of water every day.
In early June, the Gulf waters are warm, with sea surface temperatures in the Loop Current recorded at about 82 degrees Fahrenheit. And once the region enters the summer months, the water will likely be several degrees warmer.
Here’s the Loop Current route: first, it travels quickly north towards Louisiana and then about 100 miles southeast of the Mississippi River Delta it undergoes a sharp bend or loop back to the south and heads towards the Florida Straits. That’s where its name changes to the Florida Current. When the Loop Current is fully intruded into the Gulf of Mexico such as is shown on May 30, 2022, the warm water occupies much of the central and eastern Gulf.
The northern portion of the Loop Current occasionally separates every three to 17 months, creating a “warm core eddy,” most with dimensions of hundreds of miles in diameter. A warm core eddy is a spin-off of water from the main loop that can last up to a year.
“These newly-shed warm eddies have a similar impact as the Loop Current on hurricane intensification,” Walker said.
After a large eddy sheds, the Loop Current often retracts to the southern Gulf and flows directly from the Yucatan Channel to the Florida Straits, according to Walker.
Scientists track the Loop Current through satellite data, drifters and gliders due to its constantly changing nature.
Where is the Loop Current right now?
The Loop Current is about 100 miles southeast of the Mississippi River Delta on the central Gulf coast based on recent mapping, placing it a little closer to the Louisiana coast than the typical long-term position. Nonetheless, Walker said that the volume of Loop Current water in the central and eastern Gulf is still sufficient to provide energy to fuel rapid intensification to a hurricane that tracks over it.
According to Walker, Loop Current water was closer to the Louisiana coastline when Hurricane Ida and Hurricane Katrina crossed the Gulf. In both cases, a large warm core eddy was forming from the northern bulge of the Loop Current. This caused the area of warm water to be elongated west to east as a result. Therefore, an abnormally large expanse of warm water was available to fuel rapid intensification for both major hurricanes.
The Loop Current is currently in a position where a large warm core eddy could develop and separate within days to weeks. The current system is highly variable and unpredictable. However, there is no indication that the formation of a warm core eddy is currently underway.
How does the Loop Current intensify hurricanes?
During Hurricane Ida, the Loop Current temperature was over 86 degrees Fahrenheit, with the heat fueling energy for the hurricane. In the span of 24 hours, Hurricane Ida was able to travel the entire length of the Loop Current, causing it to intensify from a Category 1 to a Category 4 Hurricane, going from 80 mph to more than 132 mph winds while over the Loop Current and then finally making landfall with 150 mph winds.
“The Loop Current has an unlimited amount of heat within the top 150 meters that has the potential to greatly intensify hurricanes,” Walker said.
Has climate change affected the Loop Current?
Along with NOAA, other independent researchers have also pointed to another above-average season.
Colorado State University’s Tropical Meteorology Project predicts 19 named storms, and expects nine to become hurricanes and four to become major hurricanes.
AccuWeather anticipates 16 to 20 named storms, with six to eight becoming hurricanes and three to five becoming major hurricanes.
The four main things needed to create a hurricane are warm ocean water, lots of moisture in the air, low vertical wind shear and a pre-existing disturbance — for example, a cluster of thunderstorms. Ongoing La Niña conditions are conducive for hurricane formation in our region because there’s less wind shear to rip apart a developing hurricane or keep it from forming.
And WWNO is continuing coverage on what residents should do to get prepared before the next storm hits.
Some say the increasing intensity and frequency of tropical cyclones in successive hurricane seasons can be attributed to climate change. But as for the Loop Current and how it’s been impacted by the planet warming, Walker points to the need to expand on that research because there are a lot of factors in play that affect the Loop Current and how it intensifies a hurricane.
“The short answer is that I don't think anyone has studied that in enough detail yet. Updating the climatology may reveal an answer,” Walker said. “