Hail cannon

These devices frequently engender conflict between farmers and neighbors when used,[1] because they are loudly and repeatedly fired every 1 to 10 seconds while a storm is approaching and until it has passed through the area, yet there is no scientific evidence for their effectiveness.

[2] In the French wine-growing regions, church-bells were traditionally rung in the face of oncoming storms[3] and later replaced by firing rockets or cannons.

This shock wave then travels through the cloud formations above, a disturbance which manufacturers claim disrupts the growth phase of hailstones.

A 2006 review by Jon Wieringa and Iwan Holleman in the journal Meteorologische Zeitschrift summarized a variety of negative and inconclusive scientific measurements, concluding "the use of cannons or explosive rockets is a waste of money and effort".

Charles Knight, a cloud physicist at the National Center for Atmospheric Research in Boulder, Colorado, said in a July 10, 2008, newspaper article that "I don't find anyone in the scientific community who would validate hail cannons, but there are believers in all sorts of things.