Evaluation of WRF Simulations of Snow Storm and Polar Low Over Western Black Sea

Abstract

Snowstorms are the dangerous weather event that effect daily life. In 24th January 2022 Istanbul is affected by a major snow storm, this storm caused financial loses and suspended the both public transportations and flights. For now this phenomena is similar to Polar Lows. Polar Lows are mesoscale phenomena that can produce gust force wind speed, their horizontal scale is 200 to 1000 km, lifetime of Polar Lows last hours to daily scale and they form and intensify in the presence of upper level trough, air-sea or sea-ice temperature difference, potential vorticity anomalies. In this study snowstorm occurred in Western Black Sea will be analyzed using Numerical Weather Prediction model called Weather Research and Forecasting Model and what kind of environment the low developed will be discussed. The upper level cut-off cyclone reached -44 °C in 24 January 2022 which creates a favorable environment for polar low formation and intensifies over the relatively warmer sea. WRF results suggested that wind speed and sea surface temperature minus T500 satisfied the determined criterion for polar lows with 20 m/s and 50 °C respectively. Diabatic processes are another mechanism that enhances the polar lows and, in this study, it is seen they were both equally contributing the polar low and cross sectional analysis showed the warm-core structure and deep moist convection in 24 January 2022 12UTC. However, questions still remaining such as baroclinic instability, condensational heating and other mechanisms that may contribute polar low intensification needs to be investigated comprehensively. From our results the polar low did not intensify because it is not remained over the relatively warm sea long time like the Arctic region and Japan Sea. From our knowledge this is the first study of polar low in Black Sea and it requires more investigation and sensitivity experiments like changing the model parameterization, increasing sea surface temperature etc. to understand polar low structure further more.