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.

Hail cannon in 2007
Hail cannons in 1901
Hail cannon in Banská Štiavnica Old Castle (Slovakia). Probably designed by Julius Sokol