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- What are Bura winds?
Bura winds are the dry, very cold Adriatic northern (from NNE to ENE) winds characterized with intense wind gusts.
It is considered a katabatic wind (from Greek, it means “down hill” or “fall wind”) and it derives from the word “Boreas” – Βορέας, the North.
Bora (Italian) winds occur through all the year and blow over the slopes and coastal mountains. The cold NE’er air accelerates simultaneously once it blows over the mountains due to it’s weight and hits the seas surface with Gale force. The bora is often associated with a typical “sea dust” caused by the gushes that temporarily lift drops of water and a sea foam that reaches with big amounts on shore.
- Common locations;
The strongest winds occur along the coastal areas from Trieste to the Albanian border, but along the Adriatic shore the Bura has it’s favorable locations where it is both intense and more common specifically in; the Gulf of Trieste, the Kvarner Gulf, Velebit Channel, Šibenek area, the Kaštela Bay, Makarska and surroundings Žuljana cove on the Pelješac peninsula. Further from the coast, the Bura appears to be increase in both directional regularity and force, thus in the area of i.e. Palagruža Isle it reached storm force winds. The town of Senj near Rijeka is known for the location where Bura affects with strongest disruptive winds in excess of 220 km/h.
Obviously the strongest winds occur along the E side of the Adriatic, the W side is affected by much weaker winds.
- White or black bora?
The Bura winds are classified into the white – and black Bura, associated with two significant weather patterns.
Initially the Bura winds are most commonly accompanied by a cold pool that extends at least over the mountainous areas of the Balkans, from which the pressure gradient is higher east of the mountains than over the Mediterranean.
When the dense cold pool next reaches the altitude of the mountains, or the level of that specific geopotential height, the Bura initiates to break through, while the two divided airmasses tend to equalize.
The light or white Bora (Italian; Bora Chiara) is evolved by the anticyclonic pattern, while a high is persistent over C Europe and a shallow low is centered over the S of the Mediterranean. Generally the white Bora is characterized by its dry, clear but cold weather accompanied by good visibility in the lee of the coastal mountainous areas. Additionally, thick clouds occur along the crests of the mountains during upward motions while the air descends next on the lee sides in the west. The clouds subsequently disappear in the descending air and appear to be as a cap cloud or lenticular cloud. Clear Air Turbulance (CAT) has been reported with the existence of the Light Bora.
The dark or black Bora (Italian; Bora Scura) is associated with the cyclonic pattern and most often occurs when a Genua low is shifting towards Adriatic – or Ionian Sea. Accompanied weather across the area are clouds and rain. While the Dark Bura appears to be less intense than the Light Bura, but it can bring widespread disruptive cold rain and substantial snow amounts. During most situations the visibility is poor and the Dark Bura is associated with rain/drizzle and stratus.
- Bura in numbers;
The Bura can reach up to 220 km/h winds, but had been recorded as high of 304 km/h. The strongest Bura tends to occur in Senj, because of its position and the orography, the Bura is able to blow in multiple directions. In 1956 a gust in excess of 231 km/h was measured.
Other winds of the Adriatic;
- Jugo – warm Adriatic wind.
Jugo is a SE’ly wind and blows across the Adriatic when a cyclone develops over that specific area. It bring clouds and rain while the low matures and pressure deepens. The development is relatively slow and it can usually be noticed three days in advance and last generally longer than Bura, 5-7 days and even longer in winter. Unlike Bura, Jugo is a continues wind that gradually gains strength.
The mistral is considered the friendly wind and usually blows from the NW which is an evolvement by the differences of temperatures between the mainland and sea. It’s most common from Spring to Autumn. It usually commences at 9-10 in the morning, peaks at the afternoon and decreases again during sunset.
The name is derived from the Latin word “transmontanus” which means “a wind that comes across the mountains”. This name is widely used across the Mediterranean and blows usually with a moderate strength accompanied by cold winds during clear weather. It reveals or announced fair weather in general.
This refers to an E wind and derives from the Italian word “Levante” which means “east”. The Latin word means “uplift, elevate”. Most commonly it’s a moderate wind that lifts clouds, moisture and precipitation. A very common location Levanter insist is the area of Gibraltar, where these typical multilayer (lenticular) clouds form over the famous Rock of Gibraltar.
Ostro is a S wind, from which it’s name derives from the Latin word “Auster” which means “South”. Despite the fact it doesn’t insist long the wind could gain considerable strength.
This is a SW Adriatic wind and is usually dry and warm. This wind rises across the Adriatic after Jugo, when the Mediterranean low arrives from the Sea and reaches the W and C coastal areas of Croatia. Usually the wind doesn’t last long but it can be significant enough since it causes considerable squalls. In particularly in harbors estimated sea surface levels rise that are open to the SW.
At least until Thursday afternoon the Bura insists, until the long wave trough descends towards Iberian Peninsula, things gradually settle during the evening.