1Instituto Nacional de Meteorología, Centro Meteorológico en Illes Balears, Palma de Mallorca - Spain
2Laboratorio de Física de la Atmósfera, Instituto de Medio Ambiente. Universidad de León, León - Spain
3Meteorology Group, Departament de Física, Universitat de les Illes Balears, Palma de Mallorca - Spain
During the afternoon of 14 July 2001, a hail event occurred over northeastern Spain affecting the Zaragoza, Huesca and Lérida provinces. Hail attained sizes of 3-4 cm diameter, producing strong damage on crops and fruit trees. Meteosat images as well as radar information show that several thunderstorms developed to the west of Zaragoza province and moved towards the east. The triggering of convection took place over an area initially free of clouds, with a very quick development of the convective clouds.
The analysis of the meteorological situation reveals that at low levels there was a thermal low over the Iberian peninsula, but displaced northeastwards with respect to its climatological position. The air over the peninsula was dry but the same thermal low favoured the entrance of humid air from the Mediterranean. On the other hand, a cold front arrived to the area of interest from the northwest.
At mid and high levels a trough with associated weak vorticity field was located over the northern atlantic spanish coast. A very weak secondary trough embedded within the westerly flow appears to had reached the area of interest at the time of convection development.
Quasigeostrophic diagnosis using ECMWF data does not provide clear guidance for the identification of an environment potentially favorable for convection development. The radiosounding data from Zaragoza allows us to perform a more detailed study of the environment in which the hailstorm developed.