Previous researchers have found that thunderstorms in the Rocky Mountains have favored intitiation locations and that these locations vary with changes in the mid-tropospheric wind direction. This problem is a significant one not only because of the precipitation generated by the mountain thunderstorms themselves but also because these storms may generate longer lived multicellular storms on the adjacent plains. We are investigating the physical causes of these patterns with the Clark-Hall numerical model. Our test cases are initialized from a simgle sounding and thus contain no horizontal gradients.

We find that the previously observed patterns can be reproduced with no synoptic forcing indicating that they are primarily caused by the interaction of the local flow with the heated terrain. The amounts, but not generally the locations, of precipitation are sensitive to the magnitude of CAPE in the sounding and the amount of evaporation of falling rain. There is more sensitivity to the wind direction than previous authors have indicated. We anticipate evaluating the role of wind speed in controlling these convective initiation spots as well.