Four tropical horrors rippling with Category 5 fury have made landfall in the United States, killing hundreds of people and causing billions of dollars in damage.
All of them — the 1935 Labor Day hurricane, Camille in 1969, 1992’s Andrew and 2018’s Michael — were wispy tropical storms just three days ahead of reaching the coast, swirls of clouds and ocean froth with often underestimated intent.
The hurricanes are examples of some of the worst cases of rapid intensification on record, and why scientists have feverishly worked to improve forecasts for the scary spin up of winds defined as an increase of 35 mph or more in a 24-hour period.
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In the past few years slow gains have been made, giving National Hurricane Center meteorologists more confidence to forecast rapid intensification with recent successes seen in hurricanes Idalia and Lee last year.
The threat of rapid intensification with Idalia was noted while the storm was still a depression. It zoomed to a Cat 4 just 60 miles west of Cedar Key before slipping to a Cat 3 ahead of landfall.
Lee, which seethed in the far off Atlantic, was forecast to undergo the swift deepening in NHC’s second forecast. It rocketed from an 80-mph Category 1 hurricane to a 165 mph Cat 5 in one day.
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“That kind of nightmare scenario is important to be able to predict,” said Christopher Rozoff, a project scientist with the National Center for Atmospheric Research. “But it’s been a very difficult one to predict since the beginning of hurricane predictions.”
While track predictions have shown consistent improvement, intensity has floundered, stagnating through the '70s, '80s, '90s and early 2000s. Forecasting rapid intensification started making gains in about 2015.
An evaluation of forecasts following the 2020 season — the busiest on record with 30 named storms — found rapid intensification forecasts had improved by 20% to 25% compared to baseline errors from 2015 to 2017, according to a peer-reviewed paper published in May 2021 in the journal Atmosphere.
Research into cases of rapid intensification between 2015 and 2017 showed that NHC forecasts were too low in wind speed predictions by a mean of 22 mph.
That shrunk to 13 mph between 2021 and 2023, according to NHC senior hurricane specialist John Cangialosi, who calculates a seasonal report card on forecast accuracy.
“In 2010, we would have said we are getting better at track but not making progress with intensity,” Cangialosi said. “That doesn’t hold water anymore. Now, we are absolutely making progress.”
But the atmosphere is chaos, and out of that came Otis.
Man and the computer models failed to predict that the storm in the eastern Pacific Ocean would rapidly intensify, exploding from a 50-mph tropical storm to a 165 mph Category 5 hurricane the day ahead of making landfall in Acapulco, Mexico on Oct. 25.
Cangialosi said he was working the shift during Otis’ growth. He called for it to become a Category 1 hurricane, which he thought was a reach because nothing was hinting at rapid intensification.
“I thought I was being brave,” he said. “Well guess what? It wasn’t nearly good enough.”
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The 52 deaths reported by the government of Mexico is likely low “but still unknown” according to the NHC’s post storm report on Otis released in April. Damages are estimated to be as much as $16 billion.
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Predicting a storm's track is a matter of finding the winds that will steer it — big atmospheric highways that are conspicuous to forecasters.
Intensity is more of a puzzle of physical interactions. On the surface, it’s looking at whether there is water that is at least 80 degrees, low wind shear, lots of moisture in the air and a closed cyclonic center. But the riddle also includes small scale interactions between the ocean and atmosphere, and how water vapor turns to clouds, ice and rain.
Into the early 1990s intensity was based on climatology — what previous storms did when in a similar place at a similar time.
Then models started incorporating pieces of real-time information to make predictions for a specific hurricane. Increasingly refined information from satellites, ocean buoys, weather balloons, ships at sea, hurricane hunters and dropsondes (a reconnaissance device) is fed to the models, which are seeing more slices of the atmosphere at higher resolutions.
This July, a new weather model called the Hurricane Analysis and Forecast System, or HAFS, will launch operationally. It is expected to improve intensity forecasts by 2-3%. The average improvement has been 1%.
“Hence, 2-3% is quite significant,” said Vijay Tallapragada, senior scientist for NOAA’s Environmental Modeling Center.
A key component in HAFS is a new technology called “nest,” which allows computer models to track the hurricane as it moves. It has a resolution down to 1.2 miles.
HAFS also includes an improvement in understanding how the atmosphere and the ocean talk to each other by adding a model that examines the ocean’s surface. The winds on the ocean and the exchange in heat and evaporation from the sea to the sky are important elements in understanding intensity.
“For eons, hurricane models didn’t have that ability,” said Ben Kirtman, director of UM’s Cooperative Institute for Marine and Atmospheric Studies. “Rapid intensification, we think, critically depends on the processes associated with that coupling.”
While HAFS was the first model to predict 2022’s Hurricane Ian, which devasted Fort Myers Beach, would undergo a second period of rapid intensification, it didn’t do as well with Otis, Cangialosi said.
“If you are asking me what the state of the science is, we are getting there,” Cangialosi said at the National Hurricane Conference about forecasting rapid intensification. “But cases like Otis still happen and do happen.”
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The 2024 hurricane season is forecast to be one of the most active on record with most predictions calling for more than 20 named storms. To help our communities get prepared, The Palm Beach Post is hosting a forum on storm readiness Wednesday, June 5, from 6:15 to 8:30 p.m. at Palm Beach State College's Lake Worth Beach campus. To attend, please scan the QR Code to register or click this link.
Kimberly Miller is a journalist for The Palm Beach Post, part of the USA Today Network of Florida. She covers weather,real estate and how growth affects South Florida's environment. Subscribe to The Dirt for a weekly real estate roundup. If you have news tips, please send them to kmiller@pbpost.com.Help support our local journalism; subscribe today.
