Colorado Hail Accumulation from Thunderstorms (CHAT) project

In recent years, deep hail accumulations from thunderstorms have occurred frequently enough to raise the attention of the National Weather Service, the general public, and news agencies to this elusive phenomenon. Despite the extreme nature of these thunderstorms, no mechanism to obtain comprehensive reports, measurements, or forecasts of accumulated hail depth is currently in place. To better identify and forecast hail accumulations, the Colorado Hail Accumulation from Thunderstorms (CHAT) project has been initiated with the goal of collecting improved and more frequent hail depth reports on the ground as well as studying characteristics of storms that produce hail accumulations. A desired outcome of this research is to identify robust predictors that might be used as operational products in the future, from which informed decisions can be made to protect lives and property.

Currently, local storm reports collected by the NWS and then published in Storm Data focus only on maximum hail size and do not require information on hail depth. Thus, we asking amateur meteorologists and storm spotters to send general information, photos, videos, and drone footage of hail depth, hail size, and hail swath extent using Facebook, Twitter, telephone, and email (see flyer; click to enlarge).

How to report hail depth <click here>

Real-time radar-based hail accumulation maps <clicke here>

By the end of the 2016 thunderstorm season, we had received over 44 reports in Colorado alone with the detailed information requested. Can you find your report? We added 26 more reports from years 2012 through 2015 that were obtained from the Community Collaborative Rain, Hail and Snow (CoCoRaHS) network, the NWS, newspapers, and television stations. Most of the 70 total storms occurred along the Colorado Front Range between 2012–2016, and all data from them are archived.

Kalina, E. A., K. Friedrich, B. C. Motta, W. Deierling, G. T. Stano, N. N. Rydell, 2016: Colorado plowable hail storms: Synoptic weather, radar and lighting characteristics. Weather and Forecasting, 31, 663-693.