SIMULATION OF A LONG-LIVED MESO-BETA SCALE CONVECTIVE SYSTEM OVER THE MEDITERRANEAN COAST OF SPAIN .1. NUMERICAL PREDICTABILITY

An unusually long-lived (33 hours), devastating (local maximum rainfall rate over 800 mm/24 hr) meso-beta-scale (diameter smaller than 200 km) convective system that occurred over the Mediterranean coast of Spain has been simulated reasonably well by means of a regional numerical model. Several runs of the model including parameterized convection and boundary conditions of varying degrees of complexity have been performed. In most of these experiments, the main characteristics of the event, namely its stationarity and duration, are captured. The direct relationship between the Lagrangian lifetime of a meteorological system and its degree of deterministic predictability seems to be corroborated by the results: It appears that the meso-alpha-scale forcing that preceded and favoured the MCS was especially well predictable, and once initiated, the simulated MCS seems to have several feedback mechanisms helping to extend its life. Results are encouraging, because they reveal that it might be possible to predict very severe episodes of small MCSs such as the one shown here sufficiently in advance.