12a.3 a High-resolution Modeling Study of Convective Initiation on 19 June 2002 during Ihop

Accurate prediction of warm-season convective rainfall has remained a challenging problem in the United States. At present, the quantitative precipitation forecasting (QPF) skill associated with these warmseason systems is still very low (Fritsch and Carbone 2004). It is an essential step to improve the QPF skill by improving the knowledge of the timing, location and intensity of convective initiation (hereafter, CI) (Weckwerth et al. 2004; Weckwerth and Parsons 2006). While the prediction of CI is partly related to the accurate representation of important smaller-scale physical processes in mesoscale numerical models, and can also be highly dependent on very accurate estimates of water vapor within the boundary layer (Crook 1996; Weckwerth et al. 2004). It is because the water vapor is in high temporal and spatial variability within the boundary layer, and can evidently influence the vertical profile of buoyancy, which the CI sensitively dependent on. To understand the CI processes and QPF questions using more accurate observations of water vapor, the International H2O Project (IHOP_2002; Weckwerth et al. 2004) field experiment was carried out in the spring of 2002.