The area of Ajdovščina, a town in Vipava Valley (Slovenia), is highly exposed to strong and cold wind, called Bora, which occurs 42 days per year on average. The peak frequency occurs in the cold season (November - March). Its strongest gusts exceed the speed of 200 km/h; in winter 2010 the wind gust was measured at a record speed of 295 km/h. It blows mostly from the northeastern direction, but due to the surface of the relief, it deviates locally also to the east and to the north. Because the region separates the lower Adriatic coast from the Julian Alps range, extreme Bora winds often occur there.
Bora affects people’s everyday lives, causes damage in agriculture, traffic and destroys buildings. In the periods of extremely strong wind people are advised not to leave the buildings due to the safety reasons. Kindergartens, schools, other public buildings, factories and even medical center are closed.
Furthermore, strong wind easily tears down the electricity and telephone cables. Lack of the electrical power affects also the supply of the drinkable water. Inevitable Bora’s consequences are smaller or bigger damages on the buildings, most common consequences are uncovered roofs. Although the local population is well adapted to this local meteorological phenomenon, injuries and damage due to flying objects blown away by wind may occur. When the wind speed exceeds 100 km/h the traffic is obstructed. The highway is closed
for the truck trailers because of the risk of overturning, which brings negative consequences on the local economy. Bora can also break or uproot trees. Damage most likely occurs in winter and spring, when Bora shakes off the tree blossoms. Furthermore, local areas where Bora is at its highest, trees grow inclined with asymmetric crowns.