The impact of dry thunderstorms in Southwestern Romania

Dry thunderstorms occur in low humidity conditions and thus there are no significant precipitation at the ground. While there is no threat regarding heavy rainfalls, there are some associated phenomena that can produce severe damages: dry lightning – cloud-to-ground lightning and dry microburst. During the hot summer days, when convection initiates, the falling precipitation evaporates below the high base cloud because of the dry and very warm air. The evaporative cooling in turn contributes to negative buoyancy fueling strong downdrafts, resulting strong winds at the surface. These dry thunderstorms represent the main cause of wildfires. Also, due to strong lightnings power outages can occur and household appliances can be damaged.

Southwestern Romania is the region with the strongest lightning activity between 2012–2022 and, also, the heat waves here have among the highest frecquency and intensity in the country. The increasing air temperature led to an increase in the frequency of the heat waves in this region, considering that 68% of the heat waves during 2001–2020 period occured in the last 10 years. Thus, in the summer in Southwestern Romania the optimal conditions for dry thunderstorms occurrence are met. In this study, dry thunderstorm cases that produced severe wind gusts (up to 29 m/s), strong lighning activity but light rainfalls (les than 5 mm) are analyzed with the aim to assess the social and economic impact of lightning and wind gusts in such type of storms, improving the awareness of the public and local authorities. The synoptic features showed that dry thunderstorms precede shallow cold fronts and their associated phenomena can become severe when an intense heat wave is present.