The Bora is a local wind system along the Adriatic coast between Slovenia! and Montenegro, which occurs particularly in winter. As a rule, polar cold air flows from the northeast! towards the Balkans between a high over Central Europe and a low over! Southeast Europe. The Dinaric Mountains act as a barrier, so that the cold air accumulates! to the east of them. Once this “lake of cold air” has reach a certain height, it flows over the mountain range and falls as a stormy downdraft (also call katabatic wind) to the Adriatic coast.
There are two categories of downdrafts: warm dry katabatic winds, such as the Foehn in Switzerland, or cold dry katabatic winds, to which the Bora belongs.
The foehn and the bora arise
in the lee (windward side) of a mountain range. They are caus by a wind current that is bas on a horizontal pressure gradient across the mountains. The mountains block this and cause an overflow.
In the classic foehn, the air mass is forc to rise, whereby the air first cools dry adiabatically (-1°C/100m) until clouds form and then moist adiabatically (-0.6°C/100m). This can lead to precipitation (lifting precipitation, accumulation precipitation). The turkey phone number library now drier and colder air mass flows back down the other side of the mountain and warms up by 1 °C per 100m (dry adiabatically). This results in a warmer air mass than before it rose.
Elevation map of the Dinaric mountain range
Some typical Bora incursion regions have been mark (Wikimia Commons, Felix Reimann)
The Dinaric mountain range is significantly lower than the Alps. In the you can find more information here north, the highest peaks are between 1000 and 1500 m above sea level and in the south between 1500 and 2000 m above sea level. There are also much lower passes (below 1000 m above sea level) over which the air can flow. Due to the lower pass heights, the condensation point is rarely reach and, if at all, only dry adiabatic cooling takes place (-1°C/100m). The cooling (rise) and the warming (sinking) balance each other out and the downdraft usually has the same temperature as before it rose. This also explains why the Bora is known as a cold downdraft.
The temperature of the air mass is shown at 900 hPa, approx. 900 m above sea level. aero leads The high brings dry polar air (blue shades = cold air mass between -2 and -8 degrees) with a north-easterly flow. (MeteoSwiss)
The air mass is now damm up by the easterly flow. This can be clearly seen from the satellite perspective as a wall of clouds along the mountain range. As the air sinks on the other side, the clouds disperse again, so it stays dry and visibility is good.
Satellite image at 09:58 UTC (Meteoschweiz)
Wind and pressure situation at 09 UTC (11 LT). The average wind (in knots) is shown as a wind feather and the gust peak (in knots) as a number. (MeteoSwiss)
High gusts were already measur in the coastal region this morning. The Croatian Meteorological Service has issu a wind warning and expects gusts of 35 to 95 knots or 65 to 175 km/h depending on the region.