An extreme Koshava episode (EKE) from 30 January to 4 February 2014 has been studied. Koshava is a local windstorm in Southeast Europe. EKE was characterized by wind gusts above 45 m s −1 and deep snowdrifts. Strong Eurasian anticyclone in combination with large temperature gradient between the anticyclone region and the Mediterranean caused the EKE. The anticyclone had the probability of occurrence of 0.1%. Koshava layer was either statically stable or adiabatic. The event was numerically modelled using two mesoscale models: WRF-NMM and NMMB. Wind directions were forecasted more accurately than the mean speed and gusts.

Abstract:The aim of this work is to assess damage to the City of Belgrade caused by the unfavorable weather condition of hail due to the absence of anti-hail defense of the city, and to argumentatively point out the necessity of introducing new technical-technological systems for preventing the effects of adverse weather conditions. The results are based on the direct correlation-analyses of two real unfavorable weather events and the estimated financial damage caused by these events. The overall calculation also takes into account financial investments (new financial model) necessary to establish two essentially different systems for anti-hail protection. The damage caused by the hail on the territory of the City of Belgrade and the financial investment in anti-hail protection to reduce it are empirically established for the first time. It is shown how the damage could be transformed to profit, as the financial investment in anti-hail protection is lower than the damage that hail can cause.

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This study examines the simulation of the catastrophic precipitating event that occurred on 14–16 May 2014 over the western Balkans, using two regional models, the Eta model and the Weather Research and Forecasting Non‐hydrostatic Mesoscale Model (WRF‐NMM). This case was an extreme precipitation event with very large precipitation totals exceeding 200 mm in 72 h. The Eta model was run in two variants, switched to use the eta co‐ordinate with sloping steps and switched to use the sigma co‐ordinate. The aim of this study was to analyse the ability of the regional model to forecast heavy precipitation successfully as well as the impact of the vertical co‐ordinate on the forecasting of extreme precipitation events based on realistic model simulation. Experiments show the ability of regional models to reproduce extreme accumulations for 2 days of heavy precipitation with bias adjusted equitable threat score ranging from 0.3 to 0.5 for precipitation greater than the analysed threshold values (25–55 mm day−1), whereby the Eta model exhibits a slight advantage over the WRF‐NMM and the run of the Eta model switched to the eta co‐ordinate has the smallest frequency bias. For larger observed accumulations exceeding 50 mm day−1 all forecasts tend to be more biased. The root mean square precipitation difference varies insignificantly between the three forecasts. The results of the experiment indicate that, in the case of the extreme precipitation considered in this study, scores of the forecasts of the Eta model for 10 m wind speed and 2 m temperature show a small dependence on the vertical co‐ordinate and in favour of the run with the eta co‐ordinate.