‘No evidence’ hail cannons effective

A Queensland Government report into the use of hail cannons has found no evidence the devices are effective. A group of Gayndah producers has been lobbying the North Burnett Regional Council to ban the use of the sonar-emitting devices due to concerns they were preventing rainfall in the area. The Queensland Climate Change Centre for Excellence’s Lynne Turner says a scientific review has found no proof the hail cannons suppress rain or hail.

A Hail cannon is a shock wave generator intended to disrupt the formation of hailstones in the atmosphere in their growing phase. An explosive charge of acetylene gas and air is fired in the lower chamber of the machine. As the resulting energy passes through the neck and into the cone it develops into a force that becomes a shockwave. This shockwave then travels at the speed of sound through the cloud formations above, a disturbance which manufacturers claim disrupts the growth phase of the hailstones.

The device is repeatedly fired every 4 seconds over the period when the storm is approaching and until it has passed through the area. The manufacturer’s claim is that what would otherwise have fallen as hail stones then falls as slush or rain. It is said to be critical that the machine is running during the approach of the storm in order to affect the developing hail stone. These machines can not alter the form of an already developed solidified hailstone