Operational Forecasts of Maximum Hailstone Diameter in Mendoza, Argentina


  • Julian C Brimelow University of Alberta Edmonton, Canada
  • Terry W Krauss Weather Modification, Inc. Red Deer, Canada
  • Gerhard W Reuter University of Alberta Edmonton, Canada


A coupled one-dimensional cloud and hail growth model was used to simulate the growth of hailstones in Mendoza, Argentina. The model-derived maximum hail size forecasts were based on 118 representative soundings released during the 1999-2000 hail season. Model ensemble, persistence and subjective hail forecasts were also verified against daily observations of the maximum size. The model control and ensemble showed promising skill when forecasting the occurrence of hail as measured by the Heidke’s Skill Score (HSS=0.60). On days with severe hail (diameter of 2 cm or more), the model control forecasts showed the best skill (HSS=0.59). The model showed improved forecast skill when run using sounding and surface data from the Alberta Hail Project. This was likely attributable to the stringent criteria placed on the proximity soundings and the availability of real-time surface data in Alberta. Although certain cloud model parameters were useful for inferring the potential (and size) of hail in Mendoza, the best results were achieved using the coupled cloud and hail model. The data also suggest that the ensemble technique improves the accuracy and skill of the hail forecasts on some days.






Scientific Papers