Coalescence Activity in Texas Clouds: The Index of Coalescence Activity and First-echo Tops


  • Aldis Strautins West Texas Weather Modification Association San Angelo, Texas
  • Todd Flanagan South Texas Weather Modification Association Pleasanton, Texas
  • William L Woodley Woodley Weather Consultants Littleton, Colorado


This paper explores the use of the Index of Coalescence Activity (ICA) as a tool for operations and evaluation in Texas rain enhancement programs. Radar cross-sections through the first echoes were used to find the heights using the TITAN display software package from two WSR-74C radars located in San Angelo and Pleasanton, respectively. Index of Coalescence 5-cm Activity values were derived using the morning sounding data from three upper air stations. The ICA vs. the average height of First-echo Tops (FET) for a particular day was then plotted with calculated correlation coefficients of 0.62, 0.51, and 0.38 for the Del Rio, Corpus Christi, and Midland stations, respectively. The results show generally good agreement between the observed first-echo height and the Index of Coalescence Activity predicted First-echo Top except in one case, which is addressed in the text. The results of this study warrent continued research and preliminary use of the Index of Coalescence Activity as a forecasting and an evaluation tool in the cloud seeding operations of Texas.




Scientific Papers