Topography and vertical velocity of air in relation to severe storms near the Southern Andes Mountains

DE LA TORRE, A.; PESSANO, H.; HIERRO, R.; SANTOS, J.R.; LLAMEDO, P.; ALEXANDER, P.

Congreso; 8th European Conference on Severe Storms; 2015

On the basis of 180storms which took place between 2004 and 2011 over the province of Mendoza (Argentina) near to the Andes Range atsouthern mid-latitudes, we consider those registeredin the northern and central crop areas (oases). The regions affected by thesestorms are currently protected by anoperational hail mitigation project. Differences with previously reported storms detected in the southern oasis arehighlighted. Mendoza is a semiarid region situatedroughly between 32S and 37S at the east of the highest Andes top. It forms anatural laboratory where different sources ofgravity waves, mainly mountain waves, occur. In this work,we analyze the effects of flow over topography generating mountain waves andfavoring deep convection. The joint occurrenceof storms with hail production and mountain waves is determinedfrom mesoscale numerical simulations, radar and radiosounding data. In particular, two case studies that properlyrepresent diverse structures observed in the region areconsidered in detail. A continuous wavelet transform is applied to eachvariable and profile to detect the mainoscillation modes present. Simulated temperature profiles are validated and compared with radiosounding data. Each first radarecho, time and location are determined. Thenecessary energy to lift a parcel to its level of free convection is testedfrom the Convective Available Potential Energyand Convection Inhibition. This last parameter is comparedagainst the mountain waves´ vertical kinetic energy. The time evolution andvertical structure of vertical velocity andequivalent potential temperature suggest in both cases that the detected mountain wave amplitudes are able toprovide the necessary energy to lift the air parceland trigger convection. A simple conceptual scheme linking the dynamicalfactors taking place before and during stormdevelopment is proposed.