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The 'Montserrat-2000' severe flash flood event which occurred over Catalonia on 9 and 10 June 2000 is analyzed. Strong precipitation was generated by a mesoscale convective system associated with the development of a cyclone. The location of heavy precipitation depends on the position of the cyclone, which, in turn, is found to be very sensitive to various model characteristics and initial conditions. <P style='line-height: 20px;'> Numerical simulations of this case study using the hydrostatic BOLAM and the non-hydrostatic MOLOCH models are performed in order to test the effects of different formulations of the boundary layer parameterization: a modified version of the Louis (order 1) model and a custom version of the <i>E</i>-&#x2113; (order 1.5) model. Both of them require a diagnostic formulation of the mixing length, but the use of the turbulent kinetic energy equation in the <i>E</i>-&#x2113; model allows to represent turbulence history and non-locality effects and to formulate a more physically based mixing length. <P style='line-height: 20px;'> The impact of the two schemes is different in the two models. The hydrostatic model, run at 1/5 degree resolution, is less sensitive, but the quantitative precipitation forecast is in any case unsatisfactory in terms of localization and amount. Conversely, the non-hydrostatic model, run at 1/50 degree resolution, is capable of realistically simulate timing, position and amount of precipitation, with the apparently superior results obtained with the <i>E</i>-&#x2113; parameterization model.