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Abstract. This paper presents an observational study of the tornado outbreak that took place on the 7 September 2005 in the Llobregat delta river, affecting a densely populated and urbanised area and the Barcelona International airport (NE Spain). The site survey confirmed at least five short-lived tornadoes. Four of them were weak (F0, F1) and the other one was significant (F2 on the Fujita scale). They started mostly as waterspouts and moved later inland causing extensive damage estimated in 9 million Euros, three injured people but fortunately no fatalities. Large scale forcing was provided by upper level diffluence and low level warm air advection. Satellite and weather radar images revealed the development of the cells that spawned the waterspouts along a mesoscale convergence line in a highly sheared and relatively low buoyant environment. Further analysis indicated characteristics that could be attributed indistinctively to nonsupercell or to mini-supercell thunderstorms.

Abstract. 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.

in 1764 (almost 250 years ago), a group of educated citizen of Barcelona decided to organize a "Physico-Mathematical Conference" to follow the progress of science and technology. Several years earlier, in 1717, and as a consequence of the Catalonia's stance against king Philip V at the beginning of the 18 th century, the Catalan universities (including the University of Barcelona) were moved to Cervera, a town in the interior of Catalonia, where they remained until 1842.

Durante el miércoles 12 y el jueves 13 de octubre de 2016 tuvo lugar un episodio de precipitaciones intensas y generalizadas en toda la península ibérica. En la comarca del Maresme (Barcelona) se acumularon en diversas zonas más de 200 mm en menos de 4 horas, con cortes de tráfico, trenes y del suministro eléctrico, y el arrastre de coches en rieras, uno de los cuales provocó la desafortunada pérdida de una vida humana.Estos episodios altamente convectivos sobre el Mediterráneo occidental suelen tener corta duración, ocurriendo en verano-otoño y provocando a menudo el desbordamiento repentino de ríos provenientes de los Pirineos y de arroyos/torrentes costeros. El litoral catalán es una de las regiones más afectadas por estos episodios, y en particular el Maresme es el área de más impacto así como una de las más pobladas, y por tanto de mayor riesgo natural. Este estudio presenta un análisis meteorológico detallado, así como los impactos del evento, evaluando la predicción por contraste con los avisos de fenómenos adversos emitidos para ese día por AEMET.