Influences of the Palmer Divide on Convective Storm Initiation

The Palmer Divide, a region of higher terrain oriented west to east in central eastern Colorado, has long been known for its impacts on mesoscale and synoptic-scale processes that affect the Denver and Colorado Springs areas. While studies have been conducted to determine the Palmer Divide's effects on surrounding weather processes such as the Denver Cyclone and Denver Convergence Vorticity Zone, unexpected storm initiation and development above the Divide is not fully understood. This research attempts to address and identify what meteorological parameters cause convective thunderstorm development along and above the Divide. In order to better understand storm development along the Palmer Divide, students in the Metropolitan State University of Denver's meteorology program deployed a surface weather station on the Divide to augment the surrounding surface station data. This data as well as radar, satellite, numerical model output, and Rawinsonde data were used to analyze case studies of convective thunderstorm development that occurred during the summer of 2014. The data obtained illustrated that in eighty percent of the convective cases analyzed, surface dewpoint depressions were greater than eighteen degrees Celsius on the Divide and in the surrounding areas as initiation and development was occurring. The most significant source of moisture during these times was located at 750-650 millibars where dewpoints were between -2 and 3 degrees and dewpoint depressions were less than 11 degrees. When these conditions were present, the divide had thunderstorm development in advance of the surrounding areas in seventy percent of the cases. The data collected illustrated that low level moisture does not need to be present for thunderstorm development along the divide and that the 700 millibar dewpoint and dewpoint depression are valuable forecasting parameters to diagnosing convective development on the divide.