Hurricane Ida looks eerily like a dangerous sequel to 2005 Hurricane Katrina, the costliest storm in American history. But there are a few more twists that could make Ida meaner in some ways, but not quite as terrible in others.
Ida is predicted to have overcharged hurricanes on the same calendar date, the 29th.
What matters, however, is what could be different: direction and size.
Katrina meets Louisiana from the south, while Ida comes to the same part of the state from the southeast. A day and a half before landing, Ida’s hurricane winds extended 21 kilometers from the center, compared to 170 kilometers for the much more massive Katrina at the same time prior to the incursion.
“This has the potential to become more of a natural disaster, while the major problem in Katrina was more man-made,” said Brian McNoldy, University of Miami hurricane researcher. Dike failures raised Katrina’s death toll to 1,833 and total damage to about $ 176 billion today, and experts don’t expect Ida to get anywhere near that figure.
Ida comes from a slightly different direction to the same general place. Several hurricane experts fear the angular difference could bring New Orleans more into the dangerous storm quadrant – the right front portion of a hurricane – than it did in Katrina, when the city was devastated more by levee failure than by storm surges. Katrina’s northeast quadrant has triggered 28 foot (8.5 meters) long storm surges in Mississippi, not New Orleans.
Ida’s “angle is possibly worse,” said McNoldy. Because it’s smaller, “it won’t easily create a huge storm surge … but the angle this comes in is, in my opinion, more conducive to pushing water into the lake (Pontchartrain).”
This northwest trail from Ida not only gets New Orleans more on the mark than Katrina, but also targets Baton Rouge and key industrial areas more, said meteorologist Jeff Masters, who flew hurricane missions for the government and founded Weather Underground. He said Ida is likely to be roaming “the absolute worst place for a hurricane” to be.
“It is predicted to cross the industrial corridor between Baton Rouge and New Orleans, one of the most important infrastructure regions in the US that is critical to the economy. There are hundreds of large industrial sites there, I mean petrochemical sites, three of the 15 largest ports in America, a nuclear power plant, ”said Masters. “You will probably close the Mississippi to shipping for several weeks. “
“It’s not just the coastal impact. It’s not just New Orleans, ”said meteorologist Steve Bowen, head of Global Catstrophe Insight at risk and advisory firm Aon. “We are certainly looking at potential losses in the billions.”
THE SIZE IS IMPORTANT
The difference is that in addition to being physically huge, the size is important to damage. Storms that are larger in width have larger storm surges due to the wider pressure of the water.
Ida “isn’t going to create the huge storm surge like Katrina did, but a more focused storm surge like (1969) Camille,” Masters said.
But bigger storms are often weaker, Bowen said. There is a tradeoff between doing intense damage in a smaller area and doing less damage, but still bad, in a larger area. Bowen and Gabriel Vecchi of Princeton University said they did not know which scenario would be worse in this case.
Ida is about to hit a vortex of the so-called loop current. The Loop Current is that deep spot with incredibly warm water. It takes warm water from the Yucatan Peninsula, makes a loop in the Gulf of Mexico, and hurls the eastern edge of Florida into the Gulf Stream. Water above 79 degrees (26 degrees Celsius) is hurricane fuel.
Typically, when a storm intensifies or halts, it absorbs all of the warm water in the area and then encounters colder water which weakens the storm, or at least prevents it from intensifying further. But these warm water stains keep stirring up a storm. Katrina turned on this way, and Ida is expected to do the same. The vortex that Ida will pass has the warm water it needs, which is more than 150 meters deep, “just a whirlpool,” McNoldy said. That means a lot of quick intensification.
“Walking over these loop currents (eddies) is a very big deal. It’s really dangerous, ”said climate and hurricane scientist Kossin of The Climate Service. “It could be explosive.”
Over the past 40 years, more and more hurricanes have intensified and climate change seems to be at least partially responsible, Kossin and Vecchi said. Hurricane Grace has already intensified rapidly this year and last year Hanna, Laura, Sally, Teddy, Gamma and Delta all intensified rapidly.
“It has a human fingerprint,” said Kossin, who was involved with Vecchi in a 2019 study of the recent rapid intensifications.
NEW EYE WALL
After a hurricane intensifies quickly, it becomes so strong and its eye so small that it often can’t quite keep going, causing it to form an outer eye wall and collapse the inner eye wall, Kossin said. This is called eyewall replacement.
When a new wall of eyes forms, a storm often gets bigger but a little weaker, Kossin said. So the key for Ida is when and if that happens. It happened for Katrina, who was steadily weakening in the 12 hours before she hit land.
However, many of the other forces like crosswinds that weakened Katrina at the last minute aren’t there for Ida, McNoldy said.
Follow Seth Borenstein on Twitter at @borenbears.
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