Numerical study of the October 2000 torrential precipitation event over eastern Spain: analysis of the synoptic-scale stationarity

Numerical study of the October 2000 torrential precipitation event over eastern Spain: analysis of the synoptic-scale stationarity

Blog Article

A torrential precipitation event affected eastern Spain during 21 to 24 October 2000.Total accumulated rainfall higher than 500 mm was registered at some locations, with values up to 300 mm in a 24-h period.The synoptic-scale charts for these days show the presence of a cold cutoff low aloft, south of the Iberian Peninsula, as a part of an W-blocking structure over Europe.At low levels, persistent easterly winds, established between a dominant anticyclone over eastern Europe and a cyclone over Morocco, are found over the western Mediterranean throughout the entire period.

Satellite images show the advance and breaking away of a trough, with an associated cold front, over the Iberian Peninsula, which resulted in the cutoff low formation.Later, scattered convective cells are detected along the eastern Spanish coast during more than 3 days.Numerical simulations reveal that the convective environment was developed by the low-level advection of warm and moist Nursing air from central Mediterranean, being charged of moisture by evaporation from the sea.Sensitivity runs confirm that the synoptic-scale persistent low-level easterly flow, and specifically, the presence of a low level jet, was crucial for the subsynoptic processes leading to the long lasting torrential rainfall over the exposed terrains of eastern Spain.

The stagnancy of the low-level flow is attributed to the quasi-stationary characteristics of the upper level cutoff low located south of the Iberian Peninsula.Experiments with modified upper-level potential vorticity distributions reveal that slight deviations from the observed configuration result in enhanced mobility of the low-level flow pattern, and thereby a reduction of the precipitation persistence.This suggests the major importance of a correct representation in the model initial conditions of the intensity and location of the upper level features, in order to obtain valuable Trim / Bezel / Surrounds numerical forecasts of these heavy rainfall events.Key words.

Meteorology and atmospheric dynamics (convective processes; mesoscale meteorology; precipitation).