Sailing in Croatia

The weather in Croatia is a little cooler than that of Greece but summertime is beautiful and moderate from May to October. Winds can be from a variety of directions and are moderate but fluctuate daily. In midsummer, expect occasional stronger blows of the Bora wind which lasts for a few days at a time, from the north.

The Bora

The bora is heralded by a clear blue sky above the harbour and thick white clouds with a clearly outlined horizontal edge over the mountains. Sometimes tiny clouds separate from the white cloud and are carried towards SW by the bora.

Bora winds are most common during the cold season (October through March). In general, the frequency of gale force winds varies from less than one day per month in the summer to two or three days per month during winter months. The average duration of a continuous gale force Bora over the Adriatic is about 12 hours but the winds sometimes will last up to two days. The average duration of a Bora that reaches gale force some time during its history is 40 hours with a maximum duration of 5 days.

The Bora is most common in the Adriatic Sea where it flows mainly from the northeast through gaps in the Dinaric Alps. On occasion, the Bora can be very localized, extending only a few miles offshore. At other times the Bora will dominate the entire Adriatic Sea; when the pressure differential is large enough the Bora can extend as far south as Malta.

In the northern Adriatic, the wind direction associated with the Bora is generally northeasterly but can vary in local areas due to the terrain. The strongest winds occur along the eastern shore of the Adriatic from Trieste to the Albanian border. It is most intense to the north, decreasing somewhat moving southward. The greatest intensity of the Bora occurs where the mountain peaks are at least 2000 feet above sea level and inland not more than two or three miles. Over the open water of the Adriatic, winds are usually less intense but gale force winds (30+ kt) are common. The frequency of the gale force Bora in the open sea is greater for the cyclonic type of pattern than for the anticyclonic pattern. 

During the cyclonic pattern, the strongest winds are usually found in the southern Adriatic.

The Sirocco

Sirocco winds occur year-round even if the most common months are October through January. These winds usually last one or two days and often bring rain, (sometimes mixed with Saharan dust) or fog. Wave heights can reach 4 m (13 ft) at the anchorage.

The Sirocco is a southeasterly to southwesterly wind over the Mediterranean originating over North Africa and sometimes affecting the Adriatic Sea area. The Sirocco normally occurs within the warm sector of a cyclone passing either north or west of the region. These cyclones originate either over North Africa or south of the Alps. Sirocco conditions occur when the circulation extends far enough southward to draw air from the North African region. The onset of the Sirocco is more gradual than the onset of a Bora. It occurs more frequently in the southern part of the Adriatic with a decrease in frequency northward. Although the Sirocco is not as strong as the Bora, winds can reach gale force (30+ kt), especially in winter and spring. The average duration of continuous gale force winds during a Sirocco is 10 to 12 hours with rare occurrences as long as 36 hours. The maximum wind speed likely during a Sirocco is about 55 kt.