Microscale rainfall variations as measured by a local volunteer network

Following a devastating flash flood that killed 5 people, injured dozens of others and caused more than $250m in property damage in Fort Collins, Colorado, the Colorado Climate Center made the decision to organize a network of volunteer precipitation observers. The primary reason for the decision was that in the two-to-three months following the flood, several dozen residents were identified who had been operating reliable, reasonably well-sited gages the night of the event. The data from those sites provided an unexpectedly detailed mapping of the rainfall, and allowed an unprecedented analysis of the catastrophe. The results also showed remarkably large variations in rainfall total across the 30 sq. mi urban area.

This paper will describe the network and present some initial analyses based on the first two years of network operation. Data from the first 173 cases show a large variation in rainfall amounts for a number of different weather situations including, but not limited to, convective rainfall. Analyses are also presented which look at seasonal dependence. Finally, the authors address the question of whether or not the centrally-located Colorado State University campus observing station (the site upon which the 110 year record for the city is based) is typically representative of the city as a whole.