1966 photo of the crew and personnel of Project Stormfury
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
The working hypothesis of Project Stormfury
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.[1] Schaefer found that when he dumped crushed dry ice into a cloud, precipitation in the form of snow resulted.[2]
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.[3] 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,[4] a slight lowering of wind speed would have a large reduction in destructiveness.[4]
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.[2] 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.[5]
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.[7] 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.[1] The crew reported "Pronounced modification of the cloud deck seeded".[5] 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.[6] Cirrus was canceled,[5] 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.[5] 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 Sept. 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."[8]
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.[5]
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.[9] 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".[10]
The objective of Project BATON was the analysis of the life history of thunderstorms. A Department of Defense research activity supported by the Advanced Research Project Agency, Project BATON sought to expand understanding of storm physics as an aid to weather forecasting, fire prevention, and, possibly, for artificially controlling the weather. Dr. Helmut Weickmann, as an employee of the U.S, Army Signal Research and Development Laboratory, and Dr. Paul MacCready of Meteorology Research, Inc., were joint leaders of the Project BATON team.[11]
During the 1962 July–August storm season in Flagstaff, Arizona, the scientists, selected "guinea pig" storms, and seeded them with chemicals. Effects were thoroughly analyzed from the ground and from the air with time-lapse motion picture cameras, stereo still cameras, storm radar, lightning detectors, and airborne heat sensors. Among the agents inserted in selected clouds were "condensation nuclei" which temporarily increased the number of water droplets in the cloud, and pulverized dry ice, which turns a portion of the cloud to fine snow crystals that remain aloft. The utilization of these agents facilitated study of a storm's characteristics.[11]
Project STORMFURY begins
Robert Simpson became its first director, serving in this capacity until 1965.[12] There were several guidelines used in selecting which storms to seed. The hurricane had to have a less than 10 percent chance of approaching inhabited land within a day;[13] it had to be within range of the seeding aircraft; and it had to be a fairly intense storm with a well-formed eye.[9] The primary effect of these criteria was to make possible seeding targets extremely rare.[14]
No suitable storms formed in the 1962 season. Next year, Stormfury began by conducting experiments on cumulus clouds. From August 17 to 20 of that year, experiments were conducted in 11 clouds, of which six were seeded and five were controls. In five of the six seeded clouds, changes consistent with the working hypothesis were observed.[15]
On August 23, 1963, Hurricane Beulah was the site of the next seeding attempt. It had an indistinct eyewall. In addition, mistakes were made, as the seedings of silver iodide were dropped in the wrong places. As a consequence, nothing happened.[10] The next day, another attempt was made, and the seeders hit their targets. The eyewall was observed to fall apart and be replaced by another eyewall with a larger radius.[15] The sustained winds also fell by twenty percent.[15] All in all, the results of the experiments on Beulah were "encouraging but inconclusive."[16]
In the six years after Beulah, no seedings were conducted for several different reasons. In 1964, measurement and observation equipment was not ready to be used.[15] The year after that, all flights were used for additional experimentation in non-hurricane clouds.[15]
Joanne Simpson became its director beginning in 1965.[12][17] While out to sea in August of the 1965 Atlantic hurricane season, Stormfury meteorologists decided that Hurricane Betsy was a good candidate for seeding.[13] However, the storm immediately swung towards land, and on September 1, the planned flights were canceled. For some reason, the press was not notified that there were no seedings, and several newspapers reported that it had begun.[13] As Betsy passed close to the Bahamas and smashed into southern Florida, the public and Congress thought that seeding was underway and blamed Stormfury.[13] It took two months for Stormfury officials to convince Congress that Betsy was not seeded, and the project was allowed to continue.[13] A second candidate, Hurricane Elena, stayed too far out to sea.[15]
After Betsy, two other hurricanes came close to being seeded. Hurricane Faith was considered a likely candidate, but it stayed out of range of the seeding planes.[15] That same year, recon flights were conducted into Hurricane Inez, but there were no seedings.[15] Both the 1967 and 1968 seasons were inactive. Because of that, there were no suitable seeding targets in either of those two seasons.[15]
Dr. R. Cecil Gentry became the director of Stormfury in 1968.[18] There were no more near-seedings until 1969. In the interim, equipment was improved. What once was the primitive method of hand-dumping dry ice was replaced with rocket canisters loaded with silver iodide, and then gun-like devices mounted on the wings of the airplanes that fired silver iodide into the clouds. Observation equipment was improved.[13] Additional reconnaissance data was utilized to modify the working hypothesis. The new theory took cumulus towers outside the eyewall into account. According to the revised theory, by seeding the towers, latent heat would be released. This would trigger the start of new convection, which would then cause a new eyewall. Since the new eyewall was outside the original one, the first eyewall would be choked of energy and fall apart. In addition, since the new eyewall was broader than the old one, the winds would be lower due to a less sharp pressure difference.[13]
Hurricane Debbie in 1969 provided the best opportunity to test the underpinnings of Project Stormfury. In many ways it was the perfect storm for seeding: it did not threaten any land; it passed within range of seeding aircraft; and was intense with a distinct eye.[19] On August 18 and again on August 20, thirteen planes flew out to the storm to monitor and seed it. On the first day, windspeeds fell by 31%.[15] On the second day, windspeeds fell by 18%.[15] Both changes were consistent with Stormfury's working hypothesis. Indeed, the results were so encouraging that "a greatly expanded research program was planned."[20] Among other conclusions was the need for frequent seeding at close to hourly intervals.[21]
The 1970 and 1971 seasons provided no suitable seeding candidates.[15] Despite this, flights were conducted into Hurricane Ginger. Ginger was not a suitable storm for seeding, due to its diffuse, indistinct nature. The seeding had no effect. Ginger was the last seeding done by Project Stormfury.[15]
Atlantic hurricanes meeting all of the criteria were extremely rare, which made duplication of the "success" reached with Hurricane Debbie extremely difficult. Meanwhile, developments outside of meteorology hindered the cause of hurricane modification.
In the early 1970s, the Navy withdrew from the project.[22] Stormfury began to refocus its efforts on understanding, rather than modifying, tropical cyclones.[23] At the same time, the Project's B-17s were nearing the end of their operational lifetimes. At the cost of $30million (year unknown)[22] two Lockheed P-3's were acquired. Due to the rarity of Atlantic hurricanes meeting the safety requirements, plans were made to move Stormfury to the Pacific and experiment on the large number of typhoons there.[14] This action required many of the same safety requirements as in the Atlantic, but had the advantage of a much higher number of potential subjects.[22]
The plan was to begin again in 1976, and seed typhoons by flying out of Guam. However, political issues blocked the plan. The People's Republic of China announced that it would not be happy if a seeded typhoon changed course and made landfall on its shores,[14] while Japan declared itself willing to put up with difficulties caused by typhoons because that country got more than half of its rainfall from tropical cyclones.[14]
Similar plans to operate Stormfury in the eastern north Pacific or in the Australian region also collapsed.[24]
Failure of the working hypothesis
Multiple eyewalls had been detected in very strong hurricanes before, including Typhoon Sarah[25] and Hurricane Donna.[26] Double eyewalls were usually only seen in very intense systems. They had also been observed post-seeding in some of the seeded storms. At the time, the only observations of rapid changes in eyewall diameter, other than during presumably successful seedings, occurred during rapid changes in storm intensity.[27] It remained unclear whether the seedings caused the secondary eyewalls or whether it was just part of a natural cycle[28] (because correlation does not imply causation). It was initially thought that eyewall changes similar to those observed in seeded but not unseeded systems provided the evidence that Project Stormfury was a success. But if it was later observed that such eyewall changes were common in unseeded systems as well, such observations would throw doubt on the hypothesis and assumptions driving Project Stormfury.[29]
Data and observations did in fact begin to accumulate that debunked Stormfury's working hypothesis. Beginning with Hurricanes Anita and David, flights by hurricane hunting aircraft encountered events similar to what happened in "successfully" seeded storms.[29] Anita itself had a weak example of a concentric eyewall cycle, and David a more dramatic one.[28] In August 1980, Hurricane Allen passed through the Atlantic, Caribbean, and Gulf of Mexico. It also underwent changes in the diameter of its eye and developed multiple eyewalls. All this was consistent with the behavior that would have been expected of Allen had it been seeded. Thus, what Stormfury thought to have accomplished by seeding was also happening on its own.[30]
Other observations in Hurricanes Anita, David, Frederic, and Allen[31] also discovered that tropical cyclones have very little supercooled water and a great deal of ice crystals.[32] The reason that tropical cyclones have little supercooled water is that the updrafts within such a system are too weak to prevent water from either falling as rain or freezing.[33] As cloud seeding needed supercooled water to function, the lack of supercooled water meant that seeding would have no effect.
Those observations called the basis for Project Stormfury into question. In the middle of 1983, Stormfury was finally canceled after the hypothesis guiding its efforts was invalidated.[34]
Legacy
In the sense of weakening hurricanes to reduce their destructiveness, Project Stormfury was a complete failure because it did not distinguish between natural phenomena in tropical cyclones and the impact of human intervention.[32] Millions of dollars had been spent. In the end, "[Project] STORMFURY had two fatal flaws: it was neither microphysically nor statistically feasible."[34]
In addition, Stormfury had been a primary generator of funding for the Hurricane Research Division. While the project was operational, the HRD's budget had been around $4million (1975 USD; $16million 2008USD), with a staff of approximately 100people.[35] In 2000, the HRD employed 30people and has a budget of roughly $2.6million each year.[36]
However, Project Stormfury had positive results as well. Knowledge gained during flights proved invaluable in debunking its hypotheses.[36] Other science resulted in a greater understanding of tropical cyclones. In addition, the Lockheed P-3s were perfectly suitable for gathering data on tropical cyclones, allowing improved forecasting of these monstrous storms.[36] Those planes were still used by the NOAA as of 2005.[37]
Former Cuban president Fidel Castro alleged that Project Stormfury was an attempt to weaponize hurricanes.[38]
In meteorology, a cyclone is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above. Cyclones are characterized by inward-spiraling winds that rotate about a zone of low pressure. The largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as tropical cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes, and dust devils lie within the smaller mesoscale.
Weather modification is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rainfall or snowfall, usually for the purpose of increasing the local water supply. Weather modification can also have the goal of preventing damaging weather, such as hail or hurricanes, from occurring; or of provoking damaging weather against an enemy, as a tactic of military or economic warfare like Operation Popeye, where clouds were seeded to prolong the monsoon in Vietnam. Weather modification in warfare has been banned by the United Nations under the Environmental Modification Convention.
An Atlantic hurricane is a type of tropical cyclone that forms in the Atlantic Ocean primarily between June and November. The terms "hurricane", "typhoon", and "cyclone" can be used interchangeably to describe this weather phenomenon. These storms are continuously rotating around a low pressure center, which causes stormy weather across a large area, which is not limited to just the eye of the storm. They are organized systems of clouds and thunderstorms that originate over tropical or subtropical waters and have closed low-level circulation, and should not be confused with tornadoes, which are just another type of cyclone. They form over low pressure systems. In the North Atlantic and the Eastern Pacific, the term "hurricane" is used, whereas "typhoon" is used in the Western Pacific near Asia. The more general term "cyclone" is used in the rest of the ocean basins, namely the South Pacific and Indian Ocean.
Hurricane Esther was the first large tropical cyclone to be discovered by satellite imagery. The fifth tropical cyclone, named storm, and hurricane of the 1961 Atlantic hurricane season, Esther developed from an area of disturbed weather hundreds of miles west-southwest of the southernmost Cape Verde Islands on September 10. Moving northwestward, the depression strengthened into Tropical Storm Esther on September 11, before reaching hurricane intensity on the following day. Early on September 13, Esther curved westward and deepened into a major hurricane. The storm remained a Category 3 hurricane for about four days and gradually moved in a west-northwestward direction. Late on September 17, Esther strengthened into a Category 5 hurricane with sustained winds of 160 mph (260 km/h) on September 18. The storm curved north-northeastward on September 19, while offshore of North Carolina. Esther began to weaken while approaching New England and fell to Category 3 intensity on September 21. The storm turned eastward early on the following day, and rapidly weakened to a tropical storm.
The eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically 30–65 kilometers in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weather and highest winds of the cyclone occur. The cyclone's lowest barometric pressure occurs in the eye and can be as much as 15 percent lower than the pressure outside the storm.
Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact of arriving there.
The central dense overcast, or CDO, of a tropical cyclone or strong subtropical cyclone is the large central area of thunderstorms surrounding its circulation center, caused by the formation of its eyewall. It can be round, angular, oval, or irregular in shape. This feature shows up in tropical cyclones of tropical storm or hurricane strength. How far the center is embedded within the CDO, and the temperature difference between the cloud tops within the CDO and the cyclone's eye, can help determine a tropical cyclone's intensity with the Dvorak technique. Locating the center within the CDO can be a problem with strong tropical storms and minimal hurricanes as its location can be obscured by the CDO's high cloud canopy. This center location problem can be resolved through the use of microwave satellite imagery.
The Atlantic hurricane reanalysis project of the National Oceanic and Atmospheric Administration seeks to correct and add new information about past North Atlantic hurricanes. It was started around 2000 to update HURDAT, the official hurricane database for the Atlantic Basin, which has become outdated since its creation due to various systematic errors introduced into the database over time. This effort has involved reanalyses of ship observations from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) as well as reanalyses done by other researchers over the years. It has been ongoing as of 2024.
A tropical cyclone is a rapidly rotating storm system with a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is called a hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean. A typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean and South Pacific, comparable storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half of which develop hurricane-force winds of 65 kn or more.
The National Hurricane Research Laboratory (NHRL) is the hurricane research arm of the National Oceanic and Atmospheric Administration. It was formed in December 1964 out of the National Hurricane Research Project, the U. S. Weather Bureau's effort to scientifically examine tropical cyclones in order to make better predictions. Laboratory status signified that this effort was now a permanent part of the Weather Bureau's activities.
The maximum sustained wind associated with a tropical cyclone is a common indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unlike gusts, the value of these winds are determined via their sampling and averaging the sampled results over a period of time. Wind measuring has been standardized globally to reflect the winds at 10 metres (33 ft) above mean sea level, and the maximum sustained wind represents the highest average wind over either a one-minute (US) or ten-minute time span, anywhere within the tropical cyclone. Surface winds are highly variable due to friction between the atmosphere and the Earth's surface, as well as near hills and mountains over land.
The 1947 Florida–Georgia hurricane(Air Weather Service designation: King) was a moderate hurricane that caused catastrophic flooding in South Florida and the Everglades in mid-October 1947. The ninth tropical storm and fourth hurricane of the 1947 Atlantic hurricane season, it first developed on October 9 in the southern Caribbean Sea and hence moved north by west until a few days later it struck western Cuba. The cyclone then turned sharply to the northeast, accelerated, and strengthened to a hurricane, within 30 hours crossing the southern Florida peninsula. Across South Florida, the storm produced widespread rainfall of up to 15 inches (380 mm) and severe flooding, among the worst ever recorded in the area, that led to efforts by the United States Congress to improve drainage in the region.
Hurricane Debbie was an intense and long-lived hurricane that formed during August 1969. The fifth tropical cyclone, fourth named storm, third hurricane and second major hurricane of the 1969 Atlantic hurricane season, Debbie formed on August 14 in the southern Atlantic Ocean and took a general northwesterly path until turning northward into the central Atlantic. The storm was characterized by numerous fluctuations in intensity, but it still reached winds corresponding to Category 3 status on the Saffir–Simpson scale. The hurricane bypassed the island of Bermuda to the southeast on August 22, before ultimately brushing southeastern Newfoundland with strong winds. It dissipated over the cold waters east of Greenland. Although Debbie had little effect on land, it was extensively researched and was subject to a weather modification experiment by Project Stormfury, in which it was seeded with silver iodide.
In meteorology, eyewall replacement cycles, also called concentric eyewall cycles, naturally occur in intense tropical cyclones with maximum sustained winds greater than 33 m/s, or hurricane-force, and particularly in major hurricanes of Saffir–Simpson category 3 to 5. In such storms, some of the outer rainbands may strengthen and organize into a ring of thunderstorms—a new, outer eyewall—that slowly moves inward and robs the original, inner eyewall of its needed moisture and angular momentum. Since the strongest winds are in a tropical cyclone's eyewall, the storm usually weakens during this phase, as the inner wall is "choked" by the outer wall. Eventually the outer eyewall replaces the inner one completely, and the storm may re-intensify.
Tropical convective clouds play an important part in the Earth's climate system. Convection and release of latent heat transports energy from the surface into the upper atmosphere. Clouds have a higher albedo than the underlying ocean, which causes more incoming solar radiation to be reflected back to space. Since the tops of tropical systems are much cooler than the surface of the Earth, the presence of high convective clouds cools the climate system.
The following is a glossary of tropical cyclone terms.
The history of Atlantic tropical cyclone warnings details the progress of tropical cyclone warnings in the North Atlantic Ocean. The first service was set up in the 1870s from Cuba with the work of Father Benito Viñes. After his death, hurricane warning services were assumed by the US Army Signal Corps and United States Weather Bureau over the next few decades, first based in Jamaica and Cuba before shifting to Washington, D.C. The central office in Washington, which would evolve into the National Meteorological Center and the Weather Prediction Center, assumed the responsibilities by the early 20th century. This responsibility passed to regional hurricane offices in 1935, and the concept of the Atlantic hurricane season was established to keep a vigilant lookout for tropical cyclones during certain times of the year. Hurricane advisories issued every 12 hours by the regional hurricane offices began at this time.
The Hurricane Rainband and Intensity Change Experiment (RAINEX) is a project to improve hurricane intensity forecasting via measuring interactions between rainbands and the eyewalls of tropical cyclones. The experiment was planned for the 2005 Atlantic hurricane season. This coincidence of RAINEX with the 2005 Atlantic hurricane season led to the study and exploration of infamous hurricanes Katrina, Ophelia, and Rita. Where Hurricane Katrina and Hurricane Rita would go on to cause major damage to the US Gulf coast, Hurricane Ophelia provided an interesting contrast to these powerful cyclones as it never developed greater than a Category 1.
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