SIMULATIONS OF THE 14-JULY-1987 SQUALL LINE USING A FULLY COMPRESSIBLE MODEL

Numerical simulations of the severe squall line of 14 July 1987 are di scussed within the context of semi-Lagrangian and semi-implicit integr ations. The fully compressible non-hydrostatic Euler set of equations constitutes the basic dynamical framework of the numerical model. With elementary precipitation physics and with a generalized treatment of lateral boundary conditions, nested integrations simulate the observed structure of the squall line. The numerical solution and observations show a well organized precipitation system including a mesoscale fast -propagating prefrontal squall line and a slow-propagating system movi ng with the synoptic wave. The prefrontal squall line is seen to be a manifestation of the organization of an inertia-gravity wave and has c haracteristics of a wave-CISK mechanism. Owing to the interaction betw een the upper jet stream dynamics and moisture, the prefrontal perturb ation is initiated locally and subsequently irradiates away from its p oint source. The high computational efficiency and the accuracy of the model emphasize its potential and demonstrate its value as an interes ting tool for mesoscale modelling.