On the Use of Indices and Parameters in Forecasting Severe Storms

This paper discusses our concept of the proper (and improper) use of diagnostic variables in severe-storm forecasting. A framework for classification of diagnostic variables is developed, indicating the limitations of such variables and their suitability for operational diagnosis and forecasting. The utility of diagnostic indices and parameters as prognostic tools for forecasting is discussed, revealing the relevant issues in designing new diagnostic variables used for making weather forecasts. Finally, criteria required to claim that a new diagnostic variable represents an effective prognostic variable are proposed. We argue that few, if any, diagnostic variables have met these criteria for demonstrated utility at prognosis.