Aviation turbulence remains one of the leading causes of weather-related aviation accidents. Therefore, turbulence prediction is a major concern of aviation forecasters.
The performance of several turbulence diagnostics derived from ECMWF forecasts is evaluated over Portuguese Flight Information Regions (FIR) and surrounding areas, for the period February 2020 to April 2021, excluding May and June. In addition, the algorithm developed and used operationally by aviation meteorologists at IPMA to forecast moderate and severe turbulence over Portuguese FIRs is also discussed. The forecasts were compared with turbulence observations from special air reports and DEVG data from AMDARs received at the Portuguese MWO.
The objective verification approach in this paper uses not only the Relative Operating Characteristic curves but also novel measures such as the recently proposed Symmetric Extreme Dependence Index (SEDI) and Symmetric Extreme Dependence Index (SEDS). These measures are particularly suitable for assessing the forecasting skill of rare, such as moderate or greater turbulence, which accounts for 1.6% of the total data.
The vertical wind shear (VWS), DUTTON, Brown and Ellrod indices outperform the other turbulence diagnostics. In addition, VWS performs the best in terms of all verification measures. It has been found that adding a Richardson number function to these five turbulence diagnostics improves the performance of aviation turbulence forecasting. Consequently, the operational index combines these five diagnostics with the Richardson number.
Prediction of moderate and severe turbulence depends on the choice of the optimal threshold. However, this optimal threshold varies with the verification measure used. The results show that TSS and SEDI achieve a higher value for lower thresholds compared to SEDS. This is because when the contingency table becomes dominated by the correct predictions of non-events, both TSS and SEDI penalize under-prediction more than over-prediction.
Finally, the performance of the operational turbulence index and compared with the WAFS product is also illustrated for two turbulence episodes.
How to cite: Belo-Pereira, M.: Aviation Turbulence Forecasting over the Portuguese Flight Information Regions: Objective Verification and case study, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-482, https://doi.org/10.5194/ems2022-482, 2022.