Twenty Seasons of Airborne Hail Suppression In Alberta, Canada

Abstract

After a catastrophic late-season hailstorm hit the Calgary, Alberta, metropolitan area in September 1991, causing about half a billion dollars (Canadian) in damage, the property and casualty insurance industry began actively seeking ways to actively mitigate hail damage. After nearly four years of intensive study and intra-industry negotiation, the Alberta Severe Weather Management Society (ASWMS) was born. The ASWMS was and is comprised of representatives of all the insurance companies making up >90% market share in southern Alberta, and through levies based on their market share, annually fund an airborne cloud seeding program having the exclusive purpose of reducing damaging hailfalls in metropolitan areas, the Alberta Hail Suppression Project (AHSP). Beginning in 1996, this program has become an annual endeavor conducted from June through mid-September. This paper summarizes the current structure and operations of the AHSP, and through radar data compares seeded and unseeded storms that occurred on 21 July 2015, one of the most active days of the 2015 storm season.