A method has been developed to calculate the lifetime precipitation efficiency (PE) of mesoscale convective systems (MCS) using gauge-calibrated radar reflectivity measurements of precipitation (for eliminated moisture) and hourly precipitable water fields from the Rapid Update Cycle (RUC) model (for ingested moisture). PE values have been calculated for 25 individual MCSs over Missouri during July-September 2000 and June-September 2001.

Concurrent with the collection of data on eliminated/ingested moisture, profiles from the GOES sounder were archived and analyzed to determine the thermodynamic and stability characteristics of each sounding in the pre-MCS environment. Individual variables that correlated best to precipitation efficiency include the mean relative humidity between the surface and the lifting condensation level (positive correlation), the convective inhibition of parcels lifted from the lowest 100 mb layer (negative), and the wind shear (derived from RUC initial fields) over the depth of the warm cloud (negative).

The precipitation efficiency of each MCS and the variables from the pre-cursor GOES sounding from the summer of 2000 were subjected to a stepwise forward regression procedure to determine a predictive expression for the PE. Using this expression, differences between calculated and predicted MCS PE for summer 2001 cases averaged less than 10%; the root mean square error between the calculated and predicted PE values was 5.6%.