THE WEST-COAST PICKET FENCE EXPERIMENT DURING STORM-FEST

Mesoscale weather systems that develop in the central United States ar e often forced by environmental features that have formed far upstream over the conventional data-sparse Pacific Ocean. Although remotely se nsed observations, such as satellite retrievals, are becoming more num erous and accurate, they still may not have the resolution necessary t o enhance global model-based analyses. and forecasts over this region. These global model products are the primary source of lateral boundar y conditions that have been found to have large impacts on the downstr eam forecast skill of regional mesoscale models over the United States . In addition, the temporal and spatial resolution of the current rawi nsonde network along the West Coast may not be sufficient to detect an d measure mesoscale flow features as they move inland. During the STOR M-FEST experiment in February-March 1992, a ''Picket Fence'' of seven special rawinsonde stations were interspersed among the seven regular rawinsonde sites from Port Hardy, British Columbia, to San Diego, Cali fornia. All sites obtained observations every 3 h rather than the norm al 12 h. The objective of the Picket Fence was to examine the feasibil ity of using extra observations in time and space to improve upstream boundary conditions for forecasts of mesoscale weather events in the c entral United States. As a first step in examining the potential bound ary condition impact of the Picket Fence, fluxes of mass, heat, moment um, potential energy, kinetic energy, and moisture across the West Coa st resolved with various spatial and temporal combinations of Picket F ence data are compared with the 12-h regular upper-air sites as the st andard. When a wave system crossed the middle of the Picket Fence, sig nificantly different fluxes were calculated with the full spatial and 3-h Picket Fence observations. For other systems that crossed near the margins of the Picket Fence, only small changes were detected by the additional observations.