| Over the Mediterranean Pyrenees and near coastal region there is a high
frequency of convective storms during summertime. This fact determines a
local maximum of precipitation at this season unlike the normal and general
minimum over Mediterranean basin.
The common synoptic and mesoscale patterns associated to convective
phenomena are briefly analyzed and diagnosed with radar imagery, surface
pressure and isobaric level fields and surface data. They usually involves a
little distant through at medium levels, very weak pressure gradient at the
surface and not significant instability, but a preferred Planetary Boundary
Layer low-level convergence zones tied to the orography. As a result of this
analysis two different kinds of circulations associated to recurrent
convergence zones have been recognized: upvalley/upslope winds and sea
breezes.
High resolution simulations from a Numerical Weather Prediction model for a
case study have carried out to analyze the role of the main key components,
i.e. the orography, the sea and valley breeze and their influence to
generate local convergence zones. Furthermore, the skills of the model to
simulate the location and the intensity of the precipitation of these summer
Mediterranean storms have been discussed. |