site.btaHailstorms in Bulgaria Occur Most Frequently in May, June

May and June are the months with the most frequent hailstorms in Bulgaria because a large part of the country is in the temperate climate zone, where the peak of rainfall is climatically in these two months, National Institute of Meteorology and Hydrology’s (NIMH) Meteorology Department Director Lilia Bocheva told BTA on Thursday.  

Much of central and northern Bulgaria was hit by hailstorms and strong winds on Wednesday. Populated areas were flooded and property and farmland damaged.

Bulgaria’s hail season itself over the last 30 years can be climatically observed from April to September and even up to October. But there are now hailstorms almost every month, Bocheva said. “The winter hailstorms are in isolated places, mainly in southern Bulgaria, most often in the Eastern Rhodopes, where there are warmer intrusions in the winters, which have also been warmer in the country in recent years,“ she added.

NIMH’s Director reported that until 1991, many of our weather stations had no recorded hail in the winter or colder half of the year. Now, however, hailstorms begin in March and by October they are present.

The largest hailstorms in Europe have been recorded in Italy, which is located almost at Bulgaria’s latitude. "There are even more aggravating circumstances, such as the location of the peninsula and the circumnavigating sea, which gives extra moisture and helps such processes to develop," the expert explained.

A major hailstorm in Sofia hit Sofia on July 8, 2014. It passed through the central parts of the city, was unusually long. Hailstorms are most often up to five minutes in duration. Wednesday’s hail, which fell in Veliko Tarnovo, lasted about ten minutes, and over ten minutes in some places. This makes it significantly more dangerous not only because of the size of the hail grains, but also because of the duration of the process, the meteorologist said.

Forecasting hail clouds is difficult because their processes develop quickly - it can happen within a few hours, or an hour, Bocheva pointed out. She added that the development of a cloud that brings hail develops in one or two hours. "Hail clouds live shorter, but they also develop very quickly, and are very powerful," Bocheva noted.

She explained that humidity and high temperatures contribute to the formation of these powerful clouds. When it rains heavily in Bulgaria in the summer, the rainfall evaporates from the vegetation the next day and in hot weather clouds form in certain places, which can also form hailstones. “Here, they are also formed by the topography because it is very "broken" and the mountains also contribute to the formation of this type of clouds,” Bocheva said.