Miami lab simulates hurricane mystery zone
University researchers provide clues for critical gap in forecasting.
There’s a critical gap in the science of hurricane forecasting, a thin slice of atmosphere between ocean and storm that researchers say could be key in improving predictions for major Atlantic basin cyclones.
But a unique lab at the University of Miami is now pro- viding clues to the turbulent interactions occurring in the mystery zone just above the waves so that surprises like the quick intensifification of 2005’s Hurricane Wilma before landfall can be avoided.
The lab, which began active experiments this year, includes a clear 75-foot-long tank with 38,000 gallons of seawater and a 1,700-horsepower fan that can simulate Category 5 hurricane force winds over water.
It is the only lab of its kind in the world, said Brian Haus, Follow Kimberly Miller’s updates on twitter
and at The Post’s WeatherPlus blog at professor in the Rosenstiel School of Marine and Atmospheric Science and director of the lab, dubbed Surge Struc- ture Atmosphere Interaction, or SUSTAIN. Category 5 winds on the Saffiffir-Simpson scale begin at 157 mph.
“All the hurricane forecast models have to put in some kind of estimate of what is happening in that area, but there has been very limited data or no data in intense storms,” Haus said. “In the lab we can re-create these intense conditions at the surface and try to provide data to help the models do better.”
Hurricanes feed on the warm waters of the ocean. How fast a storm grows depends on how much energy it can take out of the water as it evaporates into the swirling winds of an intensifying hurricane.
The faster the winds, the more evaporation. But how much energy is transferred from ocean to storm is still mostly a guess, said David Nolan, an atmospheric sciences professor at the Rosenstiel School.
The SUSTAIN tank can heat its 38,000 gallons to 90 degrees, simulating temperatures in the Atlantic Ocean during the six months of hurricane season.
“The interaction is some strange function we really don’t understand,” Nolan said. “We have a guess of how much energy is coming out of the ocean, but not a formula, and the only way to get it is to better understand this relationship.”
Hurricane Wilma, which hit the west coast of Florida a decade ago on Oct. 24, was forecast to be a Category 2 when it made landfall. But as it approached the shore, it ramped up to a 120 mph Category 3 hurricane.
In the final National Hurricane Center report on Wilma it’s noted that the storm fought through strong wind shear that forecasters believed would keep it from intensifying.
More recently, Hurricane Joaquin, which formed Sept. 27, wasn’t expected to be a very strong storm. But it quickly became a Category 4 hurricane before hitting the southern islands of the Bahamas, and later topped out at 155 mph winds.
“We had it moving west and north and staying pretty weak. Instead it moved west and south and got very strong,” said Dennis Franklin, National Hurricane Center specialist and unit branch chief. “It was definitely not one of our more accurate forecasts.”
While Franklin said the information from the SUSTAIN lab will likely be useful, he’s not sure it will solve all the mysteries of hurricane forecasting or could have fixed predictions about Joaquin.
He believes the problem with Joaquin was how the vortex held together in strong wind shear, allowing it to be steered in an unexpected direction.
“I think Joaquin was an issue of not having enough observations in and around the core,” Franklin said.
Still, learning about the sea surface interaction is important enough that researchers have flown their giant P-3 “hurricane hunter” airplanes precariously close to the ocean, and tens of thousands of dollars is being spent on drones that can be sent skimming above the surface before being sacrificed to the storm.
Haus said the SUSTAIN tank has already revealed discoveries just from visual observations, including how sea spray is generated. Instead of occurring at the foamy front of a wave, it’s happening at the crest, which could affect evaporation rates.
“We have a unique opportunity to have a window to the sea surface in a hurricane,” Haus said. “That’s pretty rare.”