Extended Abstract (644K)P6.1
Investigating Preconvective Synoptic and Frontal Heavy Rainfall Atmospheric Settings Utilizing Proximity Soundings
Michael J. Paddock, NOAA/NWS, Phoenix, AZ; and C. E. Graves and J. T. Martinelli
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.
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. These events were located in the central United States. Observational soundings within six hours prior to the onset of rainfall and within 250 km of the region that received the greatest accumulation of precipitation were utilized to examine dynamic and thermodynamic parameters for the heavy rainfall preconvective environments. The 250 km threshold lies within the range of 80 km (Darkow 1969; Brooks et al. 1994) and 400 km (Rasmussen and Blanchard 1998). To improve spatial and temporal proximity, Rapid Update Cycle Version II model analysis soundings were examined and included, which improve the proximity criteria with typical temporal and spatial values of 30 minutes and 50 km, respectively.
Dynamic and thermodynamic parameters associated with these heavy rainfall environments are investigated and compared to the preconvective environments of lighter rainfall episodes, which follow the same aforementioned proximity criteria. Differences and similarities between atmospheric parameters associated with frontal and synoptic flood producing atmospheric settings (Maddox et al. 1979) are illustrated and examined against test cases from the years 2006 through 2007. In this manner, the statistical results obtained from the 2003 through 2005 datasets are examined to test their case-by-case predictability potential.
Poster Session 6, New Approaches to Hydrologic Prediction and Forecast Communication
Thursday, 15 January 2009, 9:45 AM-11:00 AM, Hall 5
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