24th Conference on IIPS


Convective Hazards Assessment Process: Revised Ricks Index

Robert J. Ricks Jr., NOAA/NWS, Slidell, LA; and T. Erickson

A technique initially developed in 1986 to objectively and comprehensively estimate convective threats based on observed and forecast upper air soundings has been refined and tested in an operational setting since 1992. This technique scales expected convective weather outcomes based on the pressure difference between the freezing level and the midpoint of a parcel's Convectively Available Positive Energy. The output has been empirically scaled from 0 to 215, with values exceeding 150 indicating severe thunderstorms are likely. Routine application of this method has shown it to be successful, primarily by increasing situational awareness of potential hazardous weather situations. Computer software has been developed to facilitate the computation of the likelihood of other severe weather parameters, including convective wind gusts, heavy rainfall potential, expected hail size, and tornado intensity.

Since 2004, the software has been configured to analyze forecast soundings from the National Centers for Environmental Prediction's (NCEP's) North American Mesoscale Model. The output is a variety of weather parameters, similar to the operational model output statistics, but also includes the convective hazards parameters. The software has been recently modified to also analyze forecast soundings from the NCEP's Global Forecast System. Evaluation of the performance of the process has revealed some benefits, but also some obstacles in automating the computations. The computation and interpretation of the Ricks Index will be demonstrated, and some applications and verification data will be shown. Examples of the output statistics, operational strategies and plans for future development will also be presented to demonstrate a total convective hazards assessment process.

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Session 4A, Applications in Meteorology, Oceanography, Hydrology and Climatology - Part I
Tuesday, 22 January 2008, 11:00 AM-12:00 PM, 206

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