The rapid evolution of Hurricane Ida from category 1 status in the Gulf of Mexico to category 4 classification at landfall was a frightening element of the storm, which devastated Louisiana on Sunday.
The storm’s sustained winds accelerated from 85 miles per hour on Saturday to 150 miles per hour the next day as it approached the coast.
The storm’s strength grew so quickly and dramatically that the National Hurricane Center (NHC) of the National Oceanic and Atmospheric Administration labeled Ida a fast strengthening storm.
The National Hurricane Center (NHC) now uses one criterion to categorize such storms: sustained winds of at least 30 knots (approximately 35 mph) within 24 hours.
In the past, a tropical storm was labeled as “fast deepening” if its central pressure dropped by at least 42 millibars (about 0.61 pounds per square inch, or psi) in 24 hours.
Ida’s pressure plummeted by 56 millibars (approximately 0.81 psi) in just 24 hours, making it a “very fast increasing storm,” according to Jennifer Francis of the Woodwell Climate Research Center in Falmouth, Massachusetts.
And Ida dropped in pressure farther north than any previous storm in the Atlantic’s history, according to Sam Lillo, an NOAA meteorology expert.
Francis has a lot of expertise researching rapid changes in the Arctic climate system, such as air influences on sea ice and heat and moisture transfers from lower latitudes induced by climate change, among other things.
As a result of her research, she decided to look into their impact on weather patterns further south, including extreme weather events like winter storms and hurricanes.
Francis was asked by Scientific American to explain what provoked Ida’s forceful outburst.
[The following is an edited transcript of the interview.]
What variables contribute to a storm’s quick intensification?
First, it requires a large reservoir of energy in the form of a deep layer of additional warm water in the ocean. If that layer is too thin, there isn’t enough energy to support rapid intensification.
As a result, the storm will drain it quickly and will not intensify, especially if it is a rapid one.
The second requirement is for water vapor, which has been rising in recent decades as the atmosphere and oceans have warmed. Warmer water vaporizes more quickly, while warmer air can hold more vapor. Since the mid-1990s, we’ve seen an overall global average increase of around 4% in the amount of water vapor in the atmosphere.
The fuel for the storm’s intensification is contained in that water vapor. When that invisible water vapor condenses into clouds, as it happens in a storm, a lot of heat is released.
This amplifies the upward motions in the atmosphere that cause the tropical storm’s large thunderstorms.
Wind shear tends to pull apart those hot air updrafts that form as a result of water vapor condensation. And when those get skewed or ripped apart, the massive thunderstorms that feed into the development of a tropical cyclone do not emerge.
According to meteorologists, Ida’s rapid development was aided by an eddy in the Gulf of Mexico.
There was a blob of very warm, deep water in the Gulf of Mexico, which was coupled with a Caribbean current called the Loop Current, where both Hurricane Katrina and Hurricane Ida rapidly intensified.
It’s like an ocean river that flows into the Gulf from the warm Caribbean, then eastward toward southern Florida and up the East Coast, where it’s known as the Gulf Stream. In the Gulf of Mexico, the Loop Current occasionally makes a northward bend, creating an eddy or pool of abnormally warm, deep water. It’s not an uncommon event, but when it does, and a tropical storm passes by, it’s like giving the storm a shot of energy. From that pool of very heated water, energy pours into the storm.
In both Katrina and Ida, this was the case.
Are storms that strengthen quickly becoming more common as a result of climate change?
Yes, and this is one of the most obvious signs of how climate change is hurting tropical hurricanes. With the use of fossil fuels, we are warming the atmosphere and the oceans.
Because of these two processes, there is now more moisture in the atmosphere, as it can evaporate more easily from the oceans into a warmer atmosphere that can receive more water vapor.
All of this adds to the gasoline that tropical storms require to intensify.
Can you explain how climate change is contributing to an increase in the number of storms that are rapidly intensifying?
The ocean absorbs around 90% of the heat trapped in the atmosphere as a result of the extra greenhouse gases we’ve released.
So just having that heated saltwater, like a supercharged battery for storms, created by human-caused climate change, provides most of the elements needed for rapid intensification.
However, when a storm suddenly intensifies and becomes very strong, as we witnessed with Ida, it also produces stronger winds, resulting in more wind damage, as we’ve seen.
Another direct result of climate change is a larger storm surge, which, of course, comes on top of rising sea levels.
The stronger winds are generating waves, which are riding on top of a bigger storm surge and sea-level rise.
Climate change has exacerbated all of these concerns. And, whether it’s a tropical storm, a thunderstorm, or a nor’easter, the increased amount of water vapor in the atmosphere is creating more frequent and heavier downpours—an increasing frequency of heavy precipitation events.
Is it possible for forecasters to predict if a storm will strengthen quickly?
Satellites can only measure the temperature of the ocean’s surface.
They have no idea how deep that warm water layer is. That is currently one of the most significant impediments: we just do not have those data in most sections of the ocean.
In most cases, we just don’t know how deep that layer is. Right now, some research is focusing on figuring out how to collect better data on how much energy is stored in, like, the upper 500 feet of the ocean, because that’s where the energy that feeds the storms is held.
Autonomous ocean gliders that swim beneath the ocean surface and measure temperature, salinity, and other properties are one method of acquiring these data.
Satellites that measure the height of the sea surface can also be useful, as a warmer body of water takes up more space. So, if there’s a lot of warm water sitting in one place, you’ll notice a hump on the ocean surface, which can be seen from space.
What can be done to prevent and lessen the effects of tropical storms that are rapidly intensifying?
For more than 50 years, we have been exploiting the atmosphere as a trash can.
We’ve been dumping all of these waste gases into the atmosphere, largely from the combustion of fossil fuels. And we’ve known for a long time that these gases trap heat that otherwise would be lost to the ocean, driving storms and warming the atmosphere.
That is, in a sense, the underlying ailment that we must address. Stopping the emission of these heat-trapping gases is one strategy to do so. All levels of society, from national governments to businesses and individuals, have a role to play in this.
We already know that solar, wind, and other renewable energy sources can completely replace our electricity. All we have to do now is get on with it.
What are the options for individuals?
We can make a lot of decisions in our personal lives, in our communities, and at the state level, such as incentives to encourage people to buy more fuel-efficient cars, appliances, or better insulate their homes. We must use all of our resources.
We must also prepare ourselves. Our current behaviors will have an impact on how [future] warming occurs.
There will be more extremes; there will be more rapidly escalating storms; there will be more heat waves and fires. As a result, we must prepare for them.
Is it reasonable to use tax monies to help someone rebuild their home in the same location after it has been flooded for the third time in a decade? No, it doesn’t. People don’t aware that a large portion of our tax dollars goes to items like this.
“Oh, emergency money is going to help residents rebuild on this low island off the coast of South Carolina,” we hear.
The public should be incensed. I believe they are not connecting the links between the money they are donating and what it is being used for in some areas where infrastructure should not be rebuilt.
the author is : Journalist Robin Lloyd, a contributing editor at Scientific American, publishes the “Smart, Useful, Science Stuff about COVID-19” newsletter. She is an adjunct professor at New York University’s Science, Health and Environmental Reporting Program.