Western Hemisphere: Heaviest Hailstone

References

Arndt, Deke, 2010: Official Documentation of the Verification of the Vivian, SD record setting hailstone of 2010, Memorrandum for the Record

Discussion

The stone fell at approx. 2300 UTC (6pm CDT).The stone fell from a storm that developed in a very favorable environment for supercell thunderstorms, which frequently produce large hail. Very warm, moist air at the surface, combined with conditions higher in the atmosphere established very large values of instability (an indicator of the potential strength of storm updraft). In particular, the estimated Convective Available Potential Energy approached 4,500 J/kg in the region (this value is quite extreme: 1,000?1,500 J/kg is often cited as a “rule of thumb” threshold for the potential to support severe weather). Strong wind shear(the turning of winds in the lower atmosphere, related to the potential for storms to tilt and rotate) was also evident in the region.(

A formal WMO investigation committee (specifically Derek (Deke) Ardnt (Chief, Climate Monitoring Branch, NOAA's National Climatic Data Center), Manola Brunet, University Rovira i Virgili, Tarragona Spain, WMO CCl president of OPACE 2) Randy Cerveny (Arizona State University, Tempe AZ), Fatima Driouech (Direction de la Météorologie Nationale Casablanca, co-president of WMO CCl OPACE 2), Pulak Guhathakurta (Hydrology Division, Office of ADGM(Research), India Meteorological Department), Charles Knight (NCAR Senior Scientist,Tom Peterson, NOAA’s National Climatic Data Center, president of the WMO CCl), and José Luis Stella (Departamento Climatología Servicio Meteorológico Nacional, co-Rapporteur, Argentina)accepted this event as the new western hemispheric record for the hailstone dimensions of diameter and weight. These value exceeded existing records of 7.0 inches (on 22 June 2003 in Aurora, NE) and 1.67 pounds (on 3 September 1970 in Coffeyville, KS), respectively.