Jansa, A. (Instituto Nacional de Meteorologia, Palma de Mallorca, Spain)
Genoves, A. (same affiliation)
Garcia-Moya, J.A. (Instituto Nacional de Meteorologia, Madrid, Spain)
We have exposed in other places our conceptual model about the role of the shallow cyclones -organising the low level inflow- in locating and feeding the typical West Mediterranean heavy rain events. We have checked this conceptual model through a statistical approach, resulting that almost 90% of all the heavy rain events in several areas of the West Mediterranean are simultaneous to "well situated" weak or moderate cyclones. We have also shown, from a statistical point of view, that most of the shallow-weak/moderate Mediterranean cyclones have an orographic origin. We have performed in the past some numerical experiments that permited to stress the role of a moderate shallow Algerian low on the heaviest rain episode never registered in Spain and to establish the orographic origin of this Algerian low.
The present paper analyses, through numerical experimentation, using the HIRLAM model, the possible role of a weak Lyon- Ligurian low in organising the feeding flow in the Piedmont event. Also the orographic contribution to the low formation is considered. The present analysis is performed by comparing a quite succesful control simulation with a simulation without the Pyrenees and the other Iberian mountains.