In Search of Improved Severe Weather Composite Parameters (28)

John Hart, NOAA/NWS Storm Prediction Center, Norman, OK



Composite parameters have commonly been used for the past two decades to help predict severe thunderstorms. These parameters typically combine multiple measures of instability and shear to simplify the visualization of risks for the forecaster. Through years of use and study, a few of them have become widely relied upon to help quantify the risk of various severe weather events [e.g., significant tornado parameter (STP) and significant hail parameter (SHIP)].

This study uses the Statistical Severe Convective Risk Assessment Model (SSCRAM) database in an attempt to develop and/or improve upon a set of composite parameters for predicting tornadoes, severe wind, and severe hail, that maximize multiple statistical measures. These new computations are then compared to the more commonly used composite parameters (e.g., STP, SHIP, etc.) to determine whether improvements have been made. Finally, some of the complexities and limitations of composite parameters will be examined.