An Exceptional Case of Freezing Rain in Bucharest (Romania)

Abstract

A high-impact freezing rain event affected parts of southeastern Romania on 24−26 January 2019. The freezing rain caused extensive damages in Bucharest, the capital city of Romania. The meteorological analysis highlighted the presence of a particular synoptic pattern involving a high-pressure system advecting cold air mass at low levels, while at mid-levels a warm and humid intrusion was associated with a low-pressure system of Mediterranean origin. At Bucharest, the vertical profiles from ERA5 and radiosondes emphasized the presence of a thick warm layer between 1000−1400 m above the re-freezing layer close to the surface. A climatology of freezing rain events in Bucharest was built to understand the frequency and intensity of this phenomenon. On average, there were approximately 5 observations of freezing rain in Bucharest per year between 1980−2018. The number of consecutive freezing rain days was used as a proxy for the event severity. Moderate-duration events (2 consecutive days) represented 16 periods of all 59 non-overlapping freezing rain periods in Bucharest and long-duration events (3 consecutive days) represented 3 periods. The monthly distribution showed that freezing rain occurs more frequently between December−February with a maximum in December. The moderate and long-duration freezing rain events were associated with two main sub-synoptic patterns related to the Carpathians lee cyclogenesis.

Keywords

• freezing rain
• high-impact meteorological event
• carpathian lee cyclogenesis
• climatology