A study on the forecast quality of the mediterranean cyclones

Abstract

The main general objective of MEDEX is stated to be the improvement of knowledge and forecasting of cyclones that produce high impact weather in the Mediterranean area. So, for this scope one of the intermediate goals of the project concerns the development of an objective method to evaluate the quality of the forecast of the cyclones. The topic of the present study is to investigate the cyclone's forecast errors in that area and to propose an objective methodology to quantify them. An investigation on the performance of the HIRLAM(INM)-0.5 model in the forecast of cyclonic centres has been done. Databases of analysed and forecasted cyclones for the Western Mediterranean have been used in this study. The "distance" between the analysed and forecasted cyclone has been measured calculating the differences in the value of the parameters chosen to describe them at the sea level surface. Results on the characteristics of the errors are shown. An index constructed by means of these differences has been introduced to evaluate the ability of the model forecasting cyclones, and to quantify it. From this index, two others indexes have been derived in order to discriminate if the forecast has overestimated or underestimated some magnitudes in the description of the cyclone. Three different time forecast ranges, H+12,H+24 and H+48, have been considered to investigate temporal trend in their quality. Finally, to check this methodology, it has been applied to some MEDEX cases.