130/150Kmph Bora/Bura Gusts Lifted the Sea Surface of Bakar Bay During the February 26, 2023 Episode; Bakarac, Bakar Municipality, Primorsko-Goranska Županija, Hrvatska
26-February-2023
Describing the Bora, an orographic wind, therefore local, katabatic, therefore falling from areas at higher altitudes, ALWAYS coming from E/NE towards W/SW, would require a degree thesis and in any case would never be complete.
I've been traveling around all these areas for the past 40 years, but I always discover something new, so I won't go into the specifics of the area, which has so many variables and unknowns (within a very few kilometres, there are areas where it doesn't blow, despite being similar and contiguous to those around, where instead it even prevents standing), but a brief general description.
The Bora (international term in Italian), called Bura in Croatian and Burja in Slovenian, is considered the strongest and most frequent local/orographic wind in the Mediterranean (once there were dozens of episodes like this every winter and as many in the other seasons combined), but in some episodes, close to 200km/h, is probably one of the strongest orographic winds in the world at SEA LEVEL. It can be compared, at least isobarically, to the winds that are generated along the Atlantic coast of Greenland, which "fall" from the frozen plateau to the ocean, when the strong Greenlandic thermal anticyclone is present, in the heart of the island.
The Bora generally activates when a mass of cold and stable air, coming from the EAST or NORTH/EAST, tends to press on the Dinaric Alps and the eastern Julian Alps, seeking an outlet towards the sea where, in the meantime, a depression is generated.
Within a few hours between the Dinaric watershed and the coast (generally around 6-15km in northern Croatia and 20-25km for Trieste) a strong isobaric gradient is created between the high pressure in the 'danubian hinterland and low on the Adriatic, to the point of having a difference of 15hpas in a few kilometers of thickness.
This generates the wind, but then it is the orography that makes it gusty, violent, irregular; this happens because the colder air is denser than that which rises from the sea and tends to be channeled into the Dinaric gates (the first is actually in the Julian Pre-Alps, Cividale area) which are (at least) 9 from north to south, but the main ones are certainly the "Triestina" one (from Postojna-Ravbarkomanda), the one Podkraj-Col-Vipava (Vipavska dolina) the one from Gornje Jelenje towards Grobnik (Rijeka racetrack), the one from the Lić-Fužine plain towards Bakarac-Kraljevica and Most Krk and the Senj one, from above Vratnik pass.
Channeling itself and physically rolling down the mountains/reliefs, the wind strengthens by friction, turbulence and depressurization, thus becoming the Bora.
130/150Kmph Bora/Bura Gusts Lifted the Sea Surface of Bakar Bay During the February 26, 2023 Episode; Bakarac, Bakar Municipality, Primorsko-Goranska Županija, Hrvatska
26-February-2023
Describing the Bora, an orographic wind, therefore local, katabatic, therefore falling from areas at higher altitudes, ALWAYS coming from E/NE towards W/SW, would require a degree thesis and in any case would never be complete.
I've been traveling around all these areas for the past 40 years, but I always discover something new, so I won't go into the specifics of the area, which has so many variables and unknowns (within a very few kilometres, there are areas where it doesn't blow, despite being similar and contiguous to those around, where instead it even prevents standing), but a brief general description.
The Bora (international term in Italian), called Bura in Croatian and Burja in Slovenian, is considered the strongest and most frequent local/orographic wind in the Mediterranean (once there were dozens of episodes like this every winter and as many in the other seasons combined), but in some episodes, close to 200km/h, is probably one of the strongest orographic winds in the world at SEA LEVEL. It can be compared, at least isobarically, to the winds that are generated along the Atlantic coast of Greenland, which "fall" from the frozen plateau to the ocean, when the strong Greenlandic thermal anticyclone is present, in the heart of the island.
The Bora generally activates when a mass of cold and stable air, coming from the EAST or NORTH/EAST, tends to press on the Dinaric Alps and the eastern Julian Alps, seeking an outlet towards the sea where, in the meantime, a depression is generated.
Within a few hours between the Dinaric watershed and the coast (generally around 6-15km in northern Croatia and 20-25km for Trieste) a strong isobaric gradient is created between the high pressure in the 'danubian hinterland and low on the Adriatic, to the point of having a difference of 15hpas in a few kilometers of thickness.
This generates the wind, but then it is the orography that makes it gusty, violent, irregular; this happens because the colder air is denser than that which rises from the sea and tends to be channeled into the Dinaric gates (the first is actually in the Julian Pre-Alps, Cividale area) which are (at least) 9 from north to south, but the main ones are certainly the "Triestina" one (from Postojna-Ravbarkomanda), the one Podkraj-Col-Vipava (Vipavska dolina) the one from Gornje Jelenje towards Grobnik (Rijeka racetrack), the one from the Lić-Fužine plain towards Bakarac-Kraljevica and Most Krk and the Senj one, from above Vratnik pass.
Channeling itself and physically rolling down the mountains/reliefs, the wind strengthens by friction, turbulence and depressurization, thus becoming the Bora.