 Multiple eyewalls had been detected in very strong hurricanes before , including Typhoon Sarah and Hurricane Donna , although the double eyes were usually seen in very intense systems . Double eyewalls were also seen post @-@ seeding in some of the seeded storms . At the time however , the only known times that rapid changes in eyewall diameter , other than during presumably successful seedings , was during rapid changes in intensity . It remained controversial whether the seedings caused the secondary eyewalls or whether it was just a natural cycle . Basically , if eyewall changes similar to those observed in seeded hurricanes were rare in unseeded tropical cyclones , it would provide powerful evidence that Project Stormfury was successful . Conversely , if such changes were common in unseeded systems , it would throw doubt on the very hypothesis and assumptions driving Project Stormfury . 
