Diurnal moist convection in Majorca under sea breeze conditions: idealized numerical experiments

Abstract

Majorca has the adequate size to develop substantial sea breezes during the warm season, mainly along its long bays, that converge in the interior of the island. This low-level convergence acts as an effective triggering mechanism for thunderstorm development in situations of a convectively unstable air mass. The dependence of this triggering mechanism (intensity and location) on the large-scale flow and the possible role of the prominent orography of the island are two issues of scientific relevance and also of great practical interest for local forecasters. With the aim of analyzing how the synoptic wind interacts with the sea breeze, thirty-two different atmospheric scenarios (plus the non-orographic counterparts) were simulated with the MM5 model at 1 km grid resolution. Results confirm a great sensitivity of the early afternoon breeze convergence and associated convection on the direction of the large-scale flow. The position and extent of the convective area are also strongly conditioned by the orography. The convection is basically modulated by the sea breeze characteristics for the cases with weak synoptic wind intensity, while it is largely activated by the orographic forcing for the cases with higher wind intensity.