Project Stormfury (or stylized as Project STORMFURY) was an attempt to weaken tropical cyclones by flying aircraft into them and seeding them with silver iodide. The project was run by the United States Government from 1962 to 1983. The hypothesis was that the silver iodide would cause supercooled water in the storm to freeze, disrupting the inner structure of the hurricane, and this led to seeding several Atlantic hurricanes. However, it was later shown that this hypothesis was incorrect. It was determined that most hurricanes do not contain enough supercooled water for cloud seeding to be effective. Additionally, researchers found that unseeded hurricanes often undergo the same structural changes that were expected from seeded hurricanes. This finding called Stormfury's successes into question, as the changes reported now had a natural explanation. The last experimental flight was flown in 1971, due to a lack of candidate storms and a changeover in NOAA's fleet. Project Stormfury was officially canceled more than a decade after the last modification experiment. Although the project failed to achieve its goal of reducing the destructiveness of hurricanes, its observational data and storm lifecycle research helped improve meteorologists' ability to forecast the movement and intensity of hurricanes.
Hypothesis
Cloud seeding was first attempted by Vincent Schaefer and Irving Langmuir. After witnessing the artificial creation of ice crystals, Langmuir became an enthusiastic proponent of weather modification. Schaefer found that when he dumped crushed dry ice into a cloud, precipitation in the form of snow resulted. With regard to hurricanes, it was hypothesized that by seeding the area around the eyewall with silver iodide, latent heat would be released. This would promote the formation of a new eyewall. As this new eyewall was larger than the old eyewall, the winds of the tropical cyclone would be weaker due to a reduced pressure gradient. Even a small reduction in the speed of a hurricane's winds would be beneficial: since the damage potential of a hurricane increased as the square of the wind speed, a slight lowering of wind speed would have a large reduction in destructiveness. Due to Langmuir's efforts, and the research of Schaefer at General Electric, the concept of using cloud seeding to weaken hurricanes gathered momentum. Indeed, Schaefer had caused a major snowstorm on December 20, 1946 by seeding a cloud. This caused GE to drop out for legal reasons. Schaefer and Langmuir assisted the U.S. military as advisors for Project Cirrus, the first large study of cloud physics and weather modification. Its most important goal was to try to weaken hurricanes.
Project Cirrus
Project Cirrus was the first attempt to modify a hurricane. It was a collaboration of the General Electric Corporation, the US Army Signal Corps, the Office of Naval Research, and the US Air Force. After several preparations and initial skepticism by government scientists, the first attempt to modify a hurricane began on October 13, 1947 on Hurricane Cape Sable that was heading west to east and out to sea. The project's two B-17s and a B-29 of the 53rd Weather Reconnaissance group were dispatched from MacDill Field, Florida, to intercept the hurricane. The seeding B-17 flew along the rainbands of the hurricane, and dropped nearly 180 pounds (82 kilograms) of crushed dry ice into the clouds. The crew reported "Pronounced modification of the cloud deck seeded". It is not known if that was due to the seeding. Next, the hurricane changed direction and made landfall near Savannah, Georgia. The public blamed the seeding, and Irving Langmuir claimed that the reversal had been caused by human intervention. Cirrus was canceled, and lawsuits were threatened. Only the fact that a system in 1906 had taken a similar path, as well as evidence showing that the storm had already begun to turn when seeding began, ended the litigation. This disaster set back the cause of seeding hurricanes for eleven years. At first the seeding was officially denied and it took years before the government admitted it. According to the September 12, 1965 edition of the Fort Lauderdale News and Sun-Sentinel, in 1947 a hurricane "went whacky" and "Twelve years later it was admitted the storm had in fact been seeded."
Between the projects
The United States Weather Bureau's National Hurricane Research Project, founded in 1955, had as one of its objectives to investigate the scientific validity of hurricane modification methods. To this end, silver iodide dispensers were tested in Hurricane Daisy in August 1958. The flares were deployed outside of the hurricane eyewall, so this was an equipment test rather than a modification experiment. The equipment malfunctioned in all but one of the flights, and no conclusive data was acquired. The first seeding experiment since the Cirrus disaster was attempted on September 16, 1961, into Hurricane Esther by NHRP and the United States Navy aircraft. Eight cylinders of silver iodide were dropped into Esther's eyewall, and winds were recorded as weakening by 10 percent. The next day, more seeding flights were made. This time, the silver iodide did not fall into the eyewall, and no reduction in windspeed was observed. These two results were interpreted as making the experiment a "success". The seedings into Hurricane Esther led to the establishment of Project Stormfury in 1962. Project Stormfury was a joint venture of the United States Department of Commerce and the United States Navy.
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