The point where the roiling ocean meets the fury of a hurricane’s winds may hold the key to improving storm intensity forecasts — but it’s nearly impossible for scientists to see.
That may change this summer, thanks to post-Hurricane Sandy federal funding and a handful of winged drones that can spend hours spiraling in a hurricane’s dark places, transmitting data that could help forecasters understand what makes some storms fizzle while others strengthen into monsters. Knowing that information while a storm is still far offshore could help emergency managers better plan for evacuations or storm surge risks.
A hurricane is like an engine, and warm ocean water is its fuel. One secret, scientists say, is getting a better understanding of how the warm water transfers energy to tropical storms.
“We really need to get a better idea of what’s going on down there before we even look to improve our intensity forecast,” said Joe Cione, who studies how storms interact with the ocean at the National Oceanic and Atmospheric Administration’s Hurricane Research Division in Miami.
Hurricane hunter aircraft typically don’t fly below 5,000 feet and can’t descend below 1,500 feet, and real-time radar doesn’t provide information about the thermodynamics at work inside a storm’s cloudy core. Canisters stuffed with electronics dropped from the planes transmit data about a storm’s pressure, temperature, winds and moisture as they fall to the ocean, but they remain airborne for only a few minutes.
The kind of drone that Cione plans to launch from the hurricane hunters will spend hours descending slowly, cruising on the air currents spinning through a storm, possibly even orbiting a hurricane’s eyewall. The amount of data the 3-foot, 7-pound drone — the Coyote, shaped like a thin missile with retractable wings — could collect in the lowest parts of a hurricane would give researchers a movie compared to the snapshots sent back by the canisters, Cione said.
The drones have a propeller and are controlled by someone in the hurricane hunter aircraft, but they are designed to float on air currents, not fly against strong winds. And the small drones are disposable — once they hit the water, they won’t be recovered.
Hurricane forecasters have gotten good at predicting where a storm is will hit, and the so-called “cone of uncertainty” that shows a storm’s likely path will shrink again this year. Improvements in predicting changes in the intensity of storms, though, have lagged.
Several factors can alter a storm’s intensity, such as cold water from the ocean’s depths mixing with warm water at the surface, wind shear, the cyclical rebuilding of the wall of clouds that ring a hurricane’s eye or a change in the energy a storm is pulling from the ocean. That last variable is what Cione calls a “data void region,” and it’s where the drones will aim.
“There’s a reason you don’t have hurricanes over land — they need the water, they need that evaporation and condensation, which is the source of their energy. So, how does that happen?” Cione said. “If we can’t sample this region very well, very accurately, all the time, we could have the potential to miss how much energy is coming out of the ocean by a third or a half.”
Cione plans to test five or six drones in the peak of hurricane season, and possibly next year, to see how well they communicate data in real time. The $1.25 million project is among a slew of other NOAA hurricane research funded by last year’s Sandy supplemental bill that authorized $60 billion for disaster relief agencies.
The potential for the data collected by the drones is priceless, Cione said.
“A lot of people talk about first responders, and I have the utmost respect for that, but we’re sort of like pre-first-responders,” Cione said. “Imagine these type of things out there 12 hours before landfall, and it’s a category higher than we think. Maybe that’s the difference between evacuating people and not evacuating people.”
It’s the kind of information forecasters would have liked to have had when Hurricane Charley suddenly strengthened to Category 4 as it sped into southwest Florida in 2004.
Forecasters knew where it was going, and they warned coastal residents to prepare for a possibly major hurricane. But they couldn’t see that it would intensify into a monster even as it approached land — forecasters still can’t explain what’s behind that rapid intensification process.
Charley cut a swath of destruction across Florida, killing nine people in the state.
“At the 11th hour, having the intensity information is good, yes. It helps me to tell people, ‘Stay where you are, don’t go outside because you’re now putting yourself at far greater risk of injury from flying debris,'” said Charlotte County Emergency Management Director Wayne Sallade, who is still chief almost a decade after Charley’s landfall.
However, it would be even more helpful to know more about whether a hurricane might continue strengthening when it’s 36 hours or more from landfall, Sallade said. That would help determine the risk of storm surge — the dangerous water rise created by tropical storms.
Good forecasts hinge on details, and intensity forecasts may just need a little tweaking, not a complete overhaul, to improve dramatically, said Florida International University hurricane expert Hugh Willoughby, who led NOAA’s Hurricane Research Division from 1995 until 2002.
“I think the problem is we’re not getting enough of the details right,” Willoughby said. “It’s not something where there’s going to be a huge breakthrough.”
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