A fuzzy expert system to assist in the prediction of hazardous wind conditions within the Mediterranean basin

Abstract

An expert system (MEDEX) for predicting the gale-force onset, continuation, and cessation of seven major wind types within the Mediterranean basin has been designed, developed, and tested. The six wind types consist of the bora (flowing through both the Adriatic and Aegean Seas), etesian, levante, mistral, sirocco and westerly (poniente and vendaval). Except for the sirocco, these winds result from synoptic situations that lead to topographical channelling. MEDEX is rule-based and incorporates fuzzy logic to handle both objective and subjective inputs, the latter being a unique application of fuzzy logic. MEDEX has approximately 330 fuzzy rules, covering the seven winds in both winter and summer seasons. While MEDEX has been designed as a nowcasting tool (0–12 h), it can be applied to any future time for which forecasting charts (consisting of surface pressure and 500 mb height fields) are available. Inputs consist of objective pressure gradients in addition to subjective interpretations of various synoptic features. These inputs, as well as the corresponding rules, were developed, tuned, and verified over a two-year period during which the weather conditions from 539 days were individually analysed. Ground truth verification was produced primarily from over-water Special Sensor Microwave/Imager (SSM/I) wind speed measurements but also included observations as available, model predictions, and official Navy wind warnings. Evaluations of MEDEX performance for both onset and cessation of winter and summer winds are presented. In addition, comparisons with forecast statistics for the Navy's regional weather centre in Rota, Spain show that MEDEX has comparable forecasting skill.