FIRST COMPARE WORKSHOP - 3-5 OCTOBER 1994, MONTREAL, QUEBEC, CANADA

The first COMPARE (Comparison of Mesoscale Prediction and Research Exp eriments) workshop was held in Montreal, Quebec, Canada, from 3 to 5 O ctober 1994 and was cosponsored by Environment Canada and the World Me teorological Organization. The COMPARE project is an international mes oscale modeling intercomparison effort that aims to propose and perfor m mesoscale model and data assimilation intercomparison experiments, t o identify important issues of mesoscale research and prediction that may be addressed by numerical experimentation, and to gradually establ ish a test bed of interesting and challenging mesoscale cases. The wor kshop objectives were to discuss the results of the first case, to com plete the planning for the second case, and to discuss possible future cases and activities. The first case is a typical explosive marine cy clogenesis event drawn from the concurrent Canadian Atlantic Storms Pr ogram and the Genesis of Atlantic Lows Experiment. Twelve groups from seven countries performed a controlled set of horizontal and vertical resolution experiments using the provided reanalyses. The resulting fo recasts were objectively verified, and an evaluation study was underta ken. Each participating group summarized its results, and preliminary conclusions from the evaluation study were presented and discussed. Mo st models tended to underestimate the deepening of the secondary low a nd to position it too far westward. Forecasts generally improved with horizontal resolution but were relatively insensitive to higher vertic al resolution. The upper-level dynamics are important at the initiatio n of the storm, whereas surface fluxes contribute significantly to its later intensification. Follow-up work on the first case includes furt her experimentation and publication of an in-depth evaluation paper. T he second case is drawn from the Pyrenees Experiment, a field experime nt to better understand, model, and predict mountain wave phenomena. A ''straw man'' experimental design was proposed and refined, and a det ailed document is now available. A workshop will be held in Toulouse, France, to discuss the results of participating groups. Several other possible cases and activities were also presented and discussed. A cas e drawn from Tropical Cyclone Motion 1990, a field experiment to impro ve the basic understanding of tropical cyclone motion in the western N orth Pacific, is the most promising candidate for the third case. The envisaged time frame would lead to a workshop in 1997. A proposal was also made for a large-scale westerly wind burst case drawn from the Tr opical Ocean Global Atmosphere-Coupled Ocean Atmosphere Response Exper iment, but a sponsoring center remains to be identified. A FASTEX (Fro nts and Atlantic Storm Tracks Experiment) case would be a prime candid ate for a future mesoscale data assimilation and forecast intercompari son. FASTEX is a planned field experiment to understand end-of-storm-t rack cyclogenesis, the role of midlatitude stormtrack cloud systems wi thin the climate system, and stratosphere-troposphere exchange in trop opause folds. A further possible activity would be a short-range mesos cale ensemble forecast intercomparison.