The subject of wind, or the Latin term “Ventus”, exerts a not inconsiderable influence on seafaring in the areas of Croatia, Slovenia and northern Italy, depending on the strength measured in Beaufort. For this reason, skippers should familiarize themselves with the peculiarities of the particular area in which they are sailing, because anyone who is not familiar with the harbingers and warning signs of Jugo and Bora, as well as the regional hotspots of these weather events, can literally be shipwrecked. The third wind typical for the region, the maestral, is somewhat more harmless.
Winds blow from high to low pressure areas
Winds such as maestral, jugo, nevera / neverin or bora occur whenever the air tries to escape from an area of higher air pressure to an area of lower air pressure, or, as the fundamentals of thermodynamics define it quite simply, to ensure an even distribution of air particles in the given space, but also in the area of thunderstorm cells. The greater the difference between areas with low air pressures and high air pressures, the stronger the respective wind. In this context, mountains and valleys provide natural obstacles, but if they reach the sea, they also influence the wind strength in a similar way to a funnel. Not only sailors know the problem from the Velebit mountains near Senj, where the bora presses strongly on the sea again and again.
Bora or Bura – probably the most feared wind in Croatia
Among the most feared wind in the Adriatic, especially in the months of October to April, is the bora. It is generally distinguished between the black bora (cyclonic bora) and the white bora (anticyclonic bora) It occurs when cold air reaches the northern Balkan regions, especially the area of the side of the Dinaric Mountains facing away from the sea, and here the air pressure rises, while in southern regions, i.e. over the Adriatic Sea low air pressure prevails. In these cases, it is called the white bora.
White bora and black bora
Bora also occurs on the northern Italian coast, predominantly when a strong low-pressure area spreads over northern Italy, attracting air masses from the high-pressure areas. This is usually the “black bora”.
Velebit transverse valleys act like nozzles
Since, as mentioned at the beginning, the air masses always strive to create a balance between high and low air pressure, the winds blow towards the sea during bora when low air pressure prevails there. The Dinaric mountain ranges in the interior of the country are a natural obstacle to this. In this scenario, passes and cross valleys, which reach the Adriatic Sea, act as a kind of nozzle, intensifying the cold winds that fall from the mountains or from the cross valleys onto the Adriatic Sea. The bora blows from the northeast and east and can be extremely gusty, as numerous sailors, but also skippers on motor yachts had to experience on their own bodies.
When there is a bora, the SeaHelp operations center is usually very busy, because the sudden winds occur in gusts and without much warning. They reach wind forces of 5 to 7 Beaufort, in gusts also clearly more. At Krk, it is reported, a bora gust reached 248.4 km/h, at Makarska on 26 January 1996 even 250.2 km/h, it is said to have been the strongest wind gust measured in the area of the Adriatic. In the area of Kvarner up to Rijeka, sometimes, but rather rarely up to Istria, skippers should in any case approach a safe harbor in case of Bora.
The Bora – the unpredictable wind
The deceptive thing about the bora: the Adriatic usually presents itself at its best for photographers, while skippers have to contend with extreme swell and almost unpredictable winds.
First signs of the bora
Skippers should be warned, however, when visibility on the Adriatic improves significantly and the source clouds, or cloud towers in the sky first build up, only to turn into lenticular formations virtually blown by the wind. Then it will not be long before the bora sends the first spray streets across the Adriatic.
But there are warning signs of an impending bora that the skipper should keep an eye on. The bora usually follows the jugo, especially when the air pressure drops sharply. Meteorologists estimate five to 10 hPa within six to 12 hours. Then the air pressure rises again by two to three hPa and it clears up from the north. At the same time, the temperature drops sharply. If then in the morning the usual morning dew on deck is missing, there is no haze in the air and the clouds over the mountains in the hinterland partly turn into lenticular formations, the messages are considered as an unmistakable sign of a soon to start bora.
It becomes especially dangerous in the southern part of the Gulf of Trieste, in the Gulf of Rijeka and the Kvarner Bay, as well as on the coast between Senj and the strait between Krk and Prvic. But also between the Velebitski Channel and the east coast of Rab and Jablanac, as well as between Sibenik to Cape Ploca and areas between Omis and Makarska are threatened by the bora. The bora blows strongest in the nozzle of Baska, in the south of the island of Krk and in the area of the island of Maun.
Unpleasant short steep waves
Unpleasant for all skippers in Bora prove to be the short, but steep waves, which do not even turn out to be particularly high, with a wave height of 1 to 2.5 meters
Jugo brings rain and thunderstorms
The exact opposite of the bora is provided by the jugo, which often goes by the name of sirocco and originates in Africa as a southerly wind. Unmistakable sign of the Jugo: a brown-yellow dust on deck, which testifies that the wind transports absorbed Sahara sand. The Yugo often occurs in spring and autumn, rather rarely in gusts, and reaches up to five Beaufort at its peak, but usually stays in the range of three to four Beaufort. It is characterized by a mix of sun and clouds with a sometimes unpleasant sultriness and limited visibility due to a hazy veil that lies over the Adriatic Sea.
Waves up to five meters high at Jugo
As the wind acts from the south on the Adriatic Sea in its entire longitudinal extension, there are strong swells of up to five meters at Jugo, which can cause problems for the skipper at Jugo, especially off the coast of Istria. Once Jugo has reared its head for the last time, it is followed by relatively strong thunderstorms, especially from August onwards. And, when a cold front approaches, the jugo can often quickly turn into a bora. Anyone who has then survived the jugo in a bay should keep a close eye on the weather, because the southerly wind is then followed by the northeasterly wind and the skipper is well advised to adjust his anchorage according to the new conditions.
The maestral subsides to the evening in
To the delight of most sailors, the maestral blows from west to northwest with strengths of two to four Beaufort, especially during the summer months. Since the land heats up more than the Adriatic under the influence of the sun, onshore winds are added during the day and the maestral can reach up to five Beaufort before dying down again in the evening.
Typical for the maestral are the fair weather clouds, which provide a nice contrast against the background of the Adriatic Sea, while over the mountains isolated thunderstorms are unloading, but in most cases they do not reach the coast. Spring clouds over land, which collapse towards evening, announce the good news that the next day at sea will also be marked by beautiful weather.
The underestimated Nevera or Neverin occurs locally dangerous
Considered probably the most dangerous wind in the Adriatic, according to the long experience of the staff in the SeaHelp operations center, the Nevera or Neverin. It comes from the west and is almost impossible to predict. Its wind gusts often reach hurricane force and start abruptly. Where the Nevera or Neverin suddenly strikes, it leaves a trail of devastation, depending on its characteristics, even if the spook lasts only 45 minutes at most. Mostly the Nevera says goodbye with heavy, cloudburst-like rainfalls. Damage to boats and yachts, torn buoys and sometimes capsized sailing yachts are among the common Nevera deployment scenarios at SeaHelp.
The omens should not remain hidden from experienced skippers: Nevera / Neverin, which occurs more frequently in the summer months, especially in August and September, announces itself by sudden calm, light thunder coming from the west, followed by first visible lightning, until suddenly the thunderstorm strikes with full force. Especially after longer periods of warm and sultry days, but also partly cloudy horizon, it seems advisable to be on guard against the Nevera.
Those who can, should call at ports on the east coast at the first signs of the Nevera, mooring at ports open in the west direction is not advisable.
Nevera is a storm at sea that occurs suddenly (a storm with thunder and lightning or a storm with thunder and rain), a short-term weather disaster caused by extreme heat. It always comes from the direction of the open sea (west) and, unlike the bora, it is not locally predictable.
Neverin (a kind of more violent and shorter nevera of local type), can cause unpleasantly high waves for a short time. Neverin is almost regularly accompanied by thunder and lightning, which makes it easier to locate at night when the storm clouds are not visible.
Thunderstorms – dangerous, but usually predictable
From August onwards, it can become locally uncomfortable when the first thunderstorms announce the end of summer. They move up from the northwest, west or southwest, can be accompanied by sudden strong winds, violent lightning and occasionally even by waterspouts. Often, regular thunderstorms can be seen in the sky. Their heralds come in the form of differently layered cloud formations, which thicken downward and in which isolated lightning flashes already twitch. After a good two hours, the impressive spectacle in the sky usually ends and the sun comes out again. These weather phenomena are encountered mainly on the east coast of Istria and in the area of Kvarner, but occasionally further south.
SeaHelp app warns of sudden weather changes
Those who want lasting protection from the unpredictable weather phenomena should at least download the SeaHelp app, which is free for iOS– and Android phones is available. Through the app, in addition to the usual service applications, you will be informed by weather alerts in the event of sudden, unforeseen weather changes and also always have the current weather situation at your fingertips with just two clicks.
Be on the safe side with a SeaHelp membership
Of course, a practical complement to this is a membership with SeaHelp, Europe’s leading nautical breakdown service, whose response boats are designed to still be able to provide assistance in almost any weather. With up to 600 hp at the stern, they are equipped for almost any task and weather phenomenon, whether Jugo, Bora, Nevera, Maestral or thunderstorms.