Previous studies have investigated proximity soundings, which were mainly geared toward severe storm environments (e.g., tornadic supercells). Their findings have illustrated an immense value toward predicting supercell development. However, there is a noticeable void when it comes to investigating proximity soundings associated with heavy rainfall producing storms. The research presented here applies a similar statistical strategy as previous studies, but with an emphasis toward a different atmospheric phenomenon.

In this study, an observational proximity sounding is defined as a sounding that occurs within six hours prior to the onset of rainfall and within 250 km of the region that received the greatest accumulation of precipitation. The 250 km threshold lies within the range of 80 km (Darkow 1969; Brooks et al. 1994) and 400 km (Rasmussen and Blanchard 1998). Additionally, model analysis soundings improve the proximity criteria, with typical temporal and spatial values of 30 minutes and 50 km, respectively.

Flood and flash flood producing heavy rainfall events with maximum accumulations of four inches or greater in a 24 hour period from one rainfall producing system were collected from March through September for the years 2003 through 2005 that were located in the central United States. Observational and Rapid Update Cycle Version II model analysis soundings were utilized to examine dynamic and thermodynamic parameters for the heavy rainfall preconvective environments. The dynamic and thermodynamic parameters associated with these heavy rainfall environments are compared to two datasets: 1) rainfall events with lesser accumulations, and 2) days where no rainfall occurred at all. These two additional datasets are comprised from the same aforementioned time periods and spatial area. NOAA CSTAR supports this research under award number NA03-NWS4680019.