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Data and observations began to accumulate that debunked Stormfury's working hypothesis. Beginning with Hurricanes Anita
, flights by Hurricane Hunter
aircraft encountered events similar to what happened in "successfully" seeded storms.
Anita itself had a weak example of a concentric eyewall cycle, and David a more dramatic one.
In August 1980, Hurricane Allen passed through the Atlantic
, 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 was accomplishing by seeding was also happening on its own.
Other observations in Hurricanes Anita, David, Frederic
, and Allen
also discovered that tropical cyclones have very little supercooled water and a great deal of ice crystals.
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.
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.