When The U.S. Tried To Control Hurricanes
From the 1940s to the 1970s, Project Stormfury and other government efforts tested the limits of the power of science. When The U.S. Tried To Control Hurricanes
As the end of the 2019 Atlantic hurricane season approaches on Nov. 30, the tally of destruction left by storms this year has been enormous. In August, Hurricane Dorian lingered over much of the Bahamas for three devastating days, leaving the country with over 65 people dead. In September, Tropical Storm Imelda dropped 40 inches of rain on coastal Texas. Repairing the damage caused by both storms will cost many billions of dollars.
Given the destruction and loss of life caused by such storms, the idea of diverting them is tempting. This summer, President Trump reportedly asked senior officials to explore using nuclear weapons to divert hurricanes from the U.S. This notion is so popular that the website of the National Oceanic and Atmospheric Administration (NOAA) includes a helpful explainer on the many reasons it is not a good idea (think radioactive fallout).
Trying to direct the course of a massive hurricane may sound foolhardy, but the idea was once pursued with serious intent. In the wake of World War II, many believed that control of the weather was imminently possible and would be a boon, making it possible to divert damaging storms and deliver rainfall to drought-stricken communities.
Cloud seeding, the basic tool for modifying clouds and therefore hurricanes, was first developed in 1946 by researchers at General Electric, who noticed that dry ice caused the clouds created by their own breath to produce snow inside the company’s new domestic freezers. The dry ice acted as an artificial nucleus, encouraging super-cooled water to form crystals of snow and in the process release latent heat.
That technique—modified to use tinier and more effective crystals of silver iodide—was soon put to use in real clouds to see if rain could be produced. Results were mixed, but projects in small-scale weather control nevertheless continued, with enthusiasm high in arid Western states.
Almost immediately interest ran from individual clouds to entire hurricanes. By October 1947, scientists working on the government-funded Project Cirrus made the first attempt to modify a hurricane. The results were both alarming and inconclusive. After seeding, the hurricane, east of Jacksonville, Fla., abruptly altered its course, reversing track and heading west before making landfall on the coast of Georgia and South Carolina and causing a public outcry. It was impossible to know for sure whether the seeding had caused the change in direction, but the episode nevertheless cast a pall over the prospects of weather control.
Despite the risks, the allure of controlling one of the most destructive natural forces on earth remained strong. Following a series of devastating hurricanes in 1954 and 1955, Congress allocated funding for a National Hurricane Research Project tasked with both basic research and investigating storm modification. Promising results from a test made on Hurricane Esther in 1961 paved the way for a joint effort of the Navy and the U.S. Weather Bureau called Project Stormfury.
Researchers working on the project believed that the eyewall of a hurricane contained abundant supercooled water. Dropping enough silver iodide into this precise location in a storm, they theorized, could cause the eyewall to release enough latent heat that it would become unstable and move outward. Due to the conservation of angular momentum, this movement would cause the storm to slow and weaken, just as the widely outstretched arms of a spinning ice skater slow her down.
“This was absolutely mainstream science at the time,” says Hugh Willoughby, a professor of atmospheric science at Florida International University and a former director of NOAA’s Hurricane Research Division. It was based, Dr. Willoughby says, on the prevailing assumption that hurricanes were inherently unstable, “like something that’s balanced on the edge of a counter and if a cat bumps against it, it falls and breaks.” Given the right trigger, even a small amount of energy could be enough to perturb the storm into a weaker state.
It was decided to attempt to modify hurricanes only in a safe zone far enough from coastal regions that inadvertent landfall would be avoided. In 1963, the Stormfury team decided to carry out two modification attempts on Hurricane Beulah, even though the storm was relatively weak and had an indistinct eye. On the first attempt, the seeding material missed the giant clouds, and the storm remained unchanged. On the second, the seeding was on target and maximum winds declined by 20%.
A lack of suitable hurricanes for seeding frustrated further attempts to refine or ratify the hypothesis until 1969, by which time researchers had revised their understanding of the storms. Rather than trying to cause instability in the inner eyewall, they focused on injecting a massive amount of silver iodide to stimulate the formation of a second, outer rainwall that would weaken the original eyewall by cutting off its supply of heat and moisture.
They tested this hypothesis on Hurricane Debbie in 1969, dropping more than 1,000 silver iodide capsules into the storm. The hurricane seemed to respond, with a reduction of wind speed in line with that predicted by the hypothesis. The only other hurricane to be seeded under the program was Ginger in 1971, but the storm lacked a strong center, and the results were considered inconclusive.
As it turned out, Hurricane Debbie was to be the high point of Project Stormfury. The program stalled during the 1970s thanks to a combination of factors including a dearth of hurricanes in the target area. Following the revelation in 1972 that the U.S. military had been using cloud seeding to trigger rainfall in North Vietnam, weather control took on a newly sinister aspect. Research into hurricanes continued, however, and scientists made two important observations: Supercooled water was not as abundant in the storms as had been thought, and concentric eyewalls frequently occur naturally.
These two observations undermined the hypothesis on which modification attempts had been made. Since “Mother Nature has her own eyewall replacement cycle,” explains Ed Zipser, a professor of atmospheric science at the University of Utah, there’s not much point in trying to create an artificial one. The apparent successes of the past might have been a result of mere chance rather than seeding. When Project Stormfury was eventually cancelled in 1983, it was deemed a failure.
Today, no one is seriously pursuing the once-irresistible idea of modifying hurricanes. In addition to other problems with the Stormfury hypothesis, it is no longer assumed that reducing the intensity, or wind speed, of a hurricane would be beneficial. Since rainfall or storm surge and not winds cause the most damage, it’s unclear, says Dr. Zipser, “how much good you are doing by turning a small compact intense storm into a larger but weaker storm.” Hurricane Maria in Puerto Rico is a good example, says Dr. Zipser. “It wasn’t only the eyewall that destroyed the infrastructure of that island.”
It’s possible that new ideas for modifying storms will be developed in the future. What’s needed, says Dr. Willoughby, is a deeper understanding of the small-scale dynamics of cloud physics. As important as computer models are for pushing understanding forward, there’s no substitute for observations of real clouds. There is still much to learn from the terrifying fury of hurricanes.
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