The cyclonic formation of IOP 15 of MAP (6-7 Nov. 1999) is examined with respect to mesoscale features in the geopotential, temperature, wind and precipitation fields. The effect of orography at different scales is evaluated using a mesoscale meteorological model (BOLAM). Model errors are determined by comparing standard and special MAP-SOP observations with model output.

A reanalysis of the initial condition is applied, resulting in an overall reduction of the forecast error, including position of local scale precipitation maximum in the Lago Maggiore target area south of the Alps. The effects of different orographic representations has also an impact on the error patterns, since it is shown that the Alpine orography largely controls the cyclone growth over the Mediterranean. Particular attention is devoted to the model verification of different fields in the vicinity of the Alps, where special observations allow for a fine scale analysis.