Benech, Brigitte (Service Central d'Exploitation de la Meteorologie, Meteo-France)
Forecasting of severe meteorological mediterranean events has always been a big challenge for the french forecasters. The first reason of such an interest is of course due to the fact that such events are the major cause of serious natural damages (overall floodings) on the french territory.
The second one is that the meteorlogical patterns leading to those phenomena are among the most difficult to grasp. Indeed, many parameters have to be considered at the same time, and the different combinations (sometimes only slightly different) of those parameters are likely to give quite different types of severe weather conditions on the french mediterranean areas. So, as one type of situation can differ from another one only according to the changeable perception of a few parameters by the model (for instance low level temperature advection, or potential vorticity advection), it is often very difficult to determine precisely the threatened areas and the intensity of phenomena. However, we try to integrate more and more parameters (forecasted and observed ones) before giving our final forecasts, and to choose among the possible scenarii. A few years ago, because the forecasters had only a few parameters at their disposal, such a process was impossible.
So, within two year, since the first work stations appeared, forecasting methods have quite changed: it is now possible to investigate more easely through the models fields, to compare some forecasts with satellite or radar pictures, and to apply, when possible, parts of conceptual models.
In this lecture, we shall try to demonstrate, through examples, how french forecasters now manage with severe meteorological mediterranean events, and to underline some of the remaining limitations of those methods.