Hurricane Laura rapidly intensified from a Category 1 hurricane to a Category 4 monster storm — going from generating sustained winds of up to 95 mph to winds as powerful as 156 mph — in just 24 hours.
By Wednesday afternoon, it was forecast to lash Louisiana and Texas with “catastrophic” wind damage and “unsurvivable” storm surge as it makes landfall overnight, according to the National Hurricane Center.
How did Laura grow last week from a disorganized tropical storm into the most powerful storm of the year?
The Gulf of Mexico is abnormally warm, said National Oceanic and Atmospheric Administration hurricane scientist Jason Dunion said, and that has created conditions that are conducive for growing monster storms.
The high sea-surface temperatures in the Gulf are the energy that feeds storms, Dunion said. The longer those water temperatures remain above average, the higher the chance a tropical system that reaches the Gulf will strengthen into a potentially catastrophic storm.
And the margins are thin, he said, with a temperature raised by just one degree enough to significantly impact storms.
“Small numbers can be important for sea-surface temperature and to see an anomaly of a degree or so is pretty significant,” he said.
Colorado State University hurricane forecaster and research scientist Philip Klotzbach said everything came together to fuel Laura’s growth Tuesday through Wednesday. In that time frame, the storm intensified from 75 to 140 mph while moving over the “bath-like waters” of the Gulf of Mexico.
The last storm to intensify so quickly in a 24-hour span was Hurricane Maria in 2017, which brought mass destruction to Puerto Rico and Dominica.
Sea-surface temperatures need to be near 90 degrees for rapid intensification, Klotzbach said, while the water needs to be near 80 for any sort of intensification. The oceanic and atmospheric administration lists 35 locations on its water temperature table for the Gulf of Mexico, and five are at 90 degrees or above. Only one of the temperatures were below 84.
The absence of the same wind shear that “shredded” Hurricane Marco just days ago in the Gulf is another factor in Laura’s growth, Klotzbach said. Laura was left alone in the Gulf to grow with warm water, no land to weaken it and no wind shear to keep it from growing.
“We know the Gulf of Mexico is a bathtub every year,” Klotzbach said. “If the conditions were right, we could get rapid intensification in the Gulf every year. But we also need a low level of vertical wind shear, which doesn’t always happen, but certainly happened with Laura.”
Dunion says that the peak for sea-surface temperature in the Gulf is mid-September. Not coincidentally, that’s also close to the climatological peak of hurricane season: Sept. 10.
Last week, several models showed Laura wouldn’t strengthen above a Category 1 strength. Puerto Rico, Hispaniola and Cuba were in its projected path as of Aug. 19, and some forecasters didn’t think the storm could survive after spending so much time over land.
Laura did survive, however, thanks to its massive size. Once it made it out of the Caribbean Sea, the Gulf of Mexico took over.
“As Laura started to pull away from Cuba, the winds got very favorable and it got into this area of water that was warm at the surface and deep below it, giving it a lot of fuel to strengthen,” Dunion said.
The hurricane center warned that parts of Louisiana could see storm surge as high as 20 feet.
“In my five years as governor I don’t think I’ve ever had a press conference where I’m trying to convey the sense of urgency I’m trying to convey right now,” Louisiana Gov. John Bel Edwards said at a Wednesday news conference.
Klotzbach said the overheard satellite images of Laura show how dangerous a storm it is.
“It looks very beautiful on satellite, but, unfortunately, when hurricanes look really good on satellite that means they’re very deadly,” he said. “This is a really serious situation unfolding for extreme-east Texas and Louisiana ... The storm surge in that area is going to be mind-blowing.”
Forecasters have predicted that 2020 could be a historically active storm season, and Laura is helping prove that. The same conditions that helped produce and fuel Laura will be in play throughout the rest of this season.
After a quiet couple of days to end this week, Klotzbach said to expect to see more systems from in the Tropical Atlantic.
“We don’t know when a storm will form,” Klotzbach said, “but the conditions will be there.”
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2020 Tampa Bay Times Hurricane Guide
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