Hail cannons?

My sister just emailed me from France to tell me that all the vineyards they were visiting talked about weather modification via "hail cannon."  I had never heard of this and did a quick search to see what it was and if there's any evidence that the technology works.

hail cannons in 1901
modern hail cannon installation
(from boingboing)
Apparently, it's a 100 year old technology with [perfect] properties that make it impossible for individuals on the ground to evaluate whether it works or not.  The manufacturer's claim is that directed explosions on the ground can generate shock waves that interfere with hail stone formation.  More "support" for this claim is here, but the latest scientific paper cited is a theory paper from 1966 (be sure to check out this entertaining "explanatory" animation).

It doesn't seem like anyone has seriously tried to evaluate whether this approach works. In 1981, a review of the evidence suggested that our understanding had changed little between 1902 and 1975:

From: History Repeated: The Forgotten Hail Cannons of Europe
Stanley A. Changnon Jr. and J. Loreena Ivens (BAMS, 1981)

A more recent review contains additional interesting history:
[H]ail cannons are the best known apparatus to fight hail by force.  They direct the sound of an acetylene explosion, more than 120 dB, upward by way of a conical vertical muzzle. Originally these cannons were developed in 1896 by Albert Stiger, an Austrian winegrower.  When in Stiger's valley no hail had fallen for two  years, employing these cannons became an immense craze in Austria and in northern Italy.  A cannon industry  developed, and over ten thousand cannons were employed in the region around 1900.  At a hail conference in Lyon in 1901, many different makes of cannon were offered for sale (Fig.5).  However, when regularly locations with plenty of cannons were heavily damaged by hail, public confidence decreased and the authorities organized a systematic experiment  of several years in some Austrian and Italian regions.  By the time that this experiment was concluded in 1906, most farmers already had sold their useless cannons as scrap iron (PERNTER, 1907; ODDIE, 1965; CHANGNON and IVENS, 1981)
RCT anyone?

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