NCAR Real-time Modeling Support for the Wyoming Weather Modification Pilot Project

The Wyoming Weather Modification Pilot Program (WWMPP) has the goal to evaluate the effectiveness of ground based AgI seeding to enhance winter orographic precipitation. The evaluation methodology is based on a Randomized Cross-over design using two mountain ranges with highly correlated snowfall on a four hour basis. Cases are chosen in which meteorological conditions are favorable for enhancement snow formation due to seeding in both ranges simultaneously. These conditions include cloud temperatures less than -8 C, wind direction from upstream of the generators, and the likely presence of super cooled liquid water. In order to assist forecasters in making this decision, NCAR has run the Real Time Four Dimensional Data Assimilation (RTFDDA) WRF model during each year of the field project. This paper will describe the performance of this modeling system compared to observations such as a radiometer to measure cloud liquid water and upstream sounding as well as other similar model simulations, such as the Colorado Headwaters simulations.