What Hurricane Went Out Into the Sea and Spinned Back Around Come Back Again
As Hurricane Ida headed into the Gulf of Mexico, a team of scientists was closely watching a giant, slowly swirling pool of warm water direct ahead in its path.
That warm puddle, an eddy, was a warning sign. It was around 125 miles (200 kilometers) across. And it was about to requite Ida the power boost that in the span of less than 24 hours would turn information technology from a weak hurricane into the dangerous Category 4 storm that slammed into Louisiana just exterior New Orleans on Aug. 29, 2021.
Nick Shay, an oceanographer at the University of Miami's Rosenstiel Schoolhouse of Marine and Atmospheric Scientific discipline, was one of those scientists. He explains how these eddies, part of what's known equally the Loop Current, help storms apace intensify into monster hurricanes.
How do these eddies form?
The Loop Current is a key component of a big gyre, or circular current, rotating clockwise in the Northward Atlantic Ocean. Its forcefulness is related to the flow of warm water from the tropics and Caribbean Sea into the Gulf of Mexico and out over again through the Florida Straits, between Florida and Cuba. From there, information technology forms the core of the Gulf Stream, which flows n along the Eastern Seaboard.
In the Gulf, this electric current tin can start to shed large warm eddies when it gets north of about the latitude of Fort Myers, Florida. At any given fourth dimension, there tin exist every bit many as iii warm eddies in the Gulf, slowly moving westward. When these eddies class during hurricane season, their heat can spell disaster for coastal communities around the Gulf.
Subtropical water has a different temperature and salinity than Gulf mutual water, so its eddies are easy to identify. They take warm h2o at the surface and temperatures of 78 degrees Fahrenheit (26 C) or more in water layers extending well-nigh 400 or 500 feet deep (about 120 to 150 meters). Since the potent salinity difference inhibits mixing and cooling of these layers, the warm eddies retain a considerable amount of heat.
When heat at the ocean surface is over about 78 F (26 C), hurricanes can grade and intensify. The eddy that Ida passed over had surface temperatures over 86 F (30 C).
How did you know this eddy was going to exist a trouble?
Nosotros monitor ocean heat content from infinite each twenty-four hours and keep an middle on the ocean dynamics, particularly during the summertime months. Keep in mind that warm eddies in the wintertime can also energize atmospheric frontal systems, such as the "tempest of the century" that caused snowstorms across the Deep South in 1993.
To estimate the risk this heat pool posed for Hurricane Ida, nosotros flew aircraft over the eddy and dropped measuring devices, including what are known every bit expendables. An expendable parachutes down to the surface and releases a probe that descends near 1,300 to 5,000 feet (400 to 1,500 meters) below the surface. It then sends back data about the temperature and salinity.
This eddy had oestrus downwardly to about 480 feet (effectually 150 meters) below the surface. Fifty-fifty if the storm's wind caused some mixing with cooler water at the surface, that deeper water wasn't going to mix all the manner down. The eddy was going to stay warm and continue to provide heat and moisture.
That meant Ida was about to get an enormous supply of fuel.
When warm water extends deep similar that, we get-go to see the atmospheric force per unit area drop. The moisture transfers, or latent rut, from the body of water to atmosphere are sustained over the warm eddies since the eddies are non significantly cooling. Every bit this release of latent heat continues, the central pressures continue to decrease. Somewhen the surface winds volition feel the larger horizontal pressure changes across the tempest and brainstorm to speed upwards.
That'south what we saw the day before Hurricane Ida fabricated landfall. The tempest was start to sense that actually warm water in the eddy. As the pressure level keeps going down, storms get stronger and more than well defined.
When I went to bed at midnight that nighttime, the air current speeds were about 105 miles per hour. When I woke up a few hours afterward and checked the National Hurricane Centre's update, it was 145 miles per hour, and Ida had become a major hurricane.
Is rapid intensification a new development?
We've known virtually this effect on hurricanes for years, just it's taken quite a while for meteorologists to pay more attention to the upper ocean heat content and its touch on the rapid intensification of hurricanes.
In 1995, Hurricane Opal was a minimal tropical tempest meandering in the Gulf. Unknown to forecasters at the time, a big warm eddy was in the center of the Gulf, moving about equally fast as Miami traffic in rush hr, with warm h2o down to about 150 meters. All the meteorologists saw in the satellite data was the surface temperature, and so when Opal apace intensified on its way to somewhen hitting the Florida Panhandle, it caught a lot of people by surprise.
Today, meteorologists keep a closer center on where the pools of oestrus are. Not every storm has all the right conditions. Also much wind shear tin can tear autonomously a tempest, but when the atmospheric weather and body of water temperatures are extremely favorable, you can get this large change.
Hurricanes Katrina and Rita, both in 2005, had pretty much the aforementioned signature as Ida. They went over a warm eddy that was just getting gear up to exist shed form the Loop Current.
Hurricane Michael in 2018 didn't go over an boil, but it went over the eddy'southward filament – like a tail – as it was separating from the Loop Current. Each of these storms intensified quickly earlier hit land.
Of class, these warm eddies are about common correct during hurricane season. You'll occasionally run into this happen along the Atlantic Declension, too, simply the Gulf of Mexico and the Northwest Caribbean are more contained, so when a tempest intensifies there, someone is going to get hit. When it intensifies close to the coast, like Ida did, it tin can be disastrous for coastal inhabitants.
What does climatic change have to practise with rapid intensification?
We know global warming is occurring, and we know that surface temperatures are warming in the Gulf of Mexico and elsewhere. When it comes to rapid intensification, however, my view is that a lot of these thermodynamics are local. How great a role global warming plays remains unclear.
This is an surface area of fertile research. Nosotros have been monitoring the Gulf'southward ocean oestrus content for more than 2 decades. By comparing the temperature measurements we took during Ida and other hurricanes with satellite and other atmospheric data, scientists can better understand the office the oceans play in the rapid intensification of storms.
Once we have these profiles, scientists can fine-tune the estimator model simulations used in forecasts to provide more than detailed and authentic warnings in the futures.
[Over 100,000 readers rely on The Conversation'southward newsletter. Sign up today.]
Source: https://theconversation.com/hurricane-ida-turned-into-a-monster-thanks-to-a-giant-warm-patch-in-the-gulf-of-mexico-heres-what-happened-167029
0 Response to "What Hurricane Went Out Into the Sea and Spinned Back Around Come Back Again"
Post a Comment