Wind

Wind is horizontal movement of air caused by difference in temperature of adjacent air masses, that is, changes in distribution of air pressure. Wind blows from higher-pressure areas to lower-pressure areas. It is one of the variable meteorological elements. It is a vector defined by direction and speed.

Standard measuring of wind in meteorology is performed 10 m above the ground. Instead of measuring the speed of wind it is its strength that is usually evaluated based on its effect on objects and vegetation; it is expressed in Beaufort. Meteorological stations determine the central direction from which the wind originates; it is expressed in compass directions. Wind speed is the distance travelled in an interval of time; it is expressed in m/s or km/h. Wind force is the force the wind applies to objects in the environment; it is expressed using the Beaufort scale. Wind may whiffle, with strong gusts. Windless atmosphere is called calm - calma (C).

Winds in Bosnia and Herzegovina are usually caused by general distribution of atmospheric pressure in certain months, depressions (cyclones) transiting over our territory, or their proximity, uneven warming and cooling of land and water masses, that is, due to changes in horizontal temperatures caused by different relief (Milosavljević).

The wind regime of Bosnia and Herzegovina is under several different influences: the Dinaric Alps stretching in the NW-SE direction, the proximity of the Adriatic Sea, and the influence of the Pannonian Plain. The wind regime is modified at certain locations, depending on the orographic obstacle, but also on the terrain exposure, concavity or convexity of the relief, altitude, etc.

Bora and ‘jugo’ (southerly wind) are typical of the south of the country with the Mediterranean climate. Bora is a strong, dry and cool wind blowing mostly from the north-east quadrant in the (NNE-ENE) direction. Since it blows from the mountains, it is very unpleasant.

Jugo is warm and humid, originating from the southern quadrant in the ESE-SSE direction. It is formed in conditions of high atmospheric pressure above Africa and low pressure above a part of the Mediterranean Sea. Crossing over the Mediterranean Sea, dry and warm African air picks up some of the maritime characteristics, mainly humidity, and when it reaches the mountains in the south of the country it goes up, and goes through adiabatic cooling, which results in forming of clouds and major precipitation.

In addition to these winds that, less frequently, occur in other parts of the country as well, the mountainous areas of Bosnia, especially in the west with more prominent mountains, are dominated by SE winds resembling föhn winds. Air masses forming föhn winds come from the Adriatic Sea across the Dinaric mountains and descend into karst fields and valleys of the Sava tributaries. Air temperature on a föhn day is, on average, several degrees higher. The difference is more obvious in winter, and less obvious in summer; föhn is very important in the spring - it facilitates snow melting and vegetative processes. Föhn winds reach all the way to Sarajevo, where west wind holds a share of 12.8% in the annual distribution of winds.

The continental part of the country is dominated by weak to moderate winds of variable direction. Strong winds are very rare in this area, and they are usually caused by cool air coming from polar areas; they sometimes occur during summer storms. Dominant wind direction depends on the openness and shape of the surrounding terrain. Winters usually record winds originating from the northern quadrant, since the low-pressure zone is above the Mediterranean Sea. In summer, air pressure decreases going from NE to SE, causing the winds to take the same direction. In summer, under unstable atmospheric conditions, due to turbulent mixing of air, thunderclouds are formed out of strong upward currents (cumulonimbus). Under such conditions, heavy rain, showers, and thunderstorm occur usually in the afternoon, often bringing hail and gale.

Wind frequency distribution and wind speed

The analysis of frequency distribution of different wind directions was based on winds dominating the months of January and July, as well as on annual distribution.

In January, dominant wind directions in the south of the country are N and NE, with a share of 50%. On Bjelašnica, where the relief has no effect due to the altitude, dominance of these directions is much weaker with the total below 40%. January winds coming from the south (S, SE) are much less frequent in the south of the country. It is interesting to note that winds coming from the south are mostly recorded on Bjelašnica with a share of 16.2%, in Neum (10.1%), while in Mostar, this direction has a share of only 4. The SE wind (true jugo) is most frequent in Neum with a share of 12.7%, then in Bihać with 12.1%, while in Mostar, its share is merely 2.2%.

The percentage of calm on Bjelašnica is only 4.3, which clearly shows that it is rather windy in winter months. It is typical of Neum compared to other stations that it has the highest frequency of north and southerly winds; that, and merely 8% of calm, indicates that this area is rather windy during the winter period. Mostar and Bihać record small percentage of calm - 17.1 and 13.2%, respectively. In January, the karst fields of Livanjsko polje stretching in the NW-SE direction, record true jugo (SE) with a share of 19%. The share of wind originating from the north is 8.4%, while the share of the true bora wind (NE) is even smaller at 4.9%.

In the north-west, on the other side of Plješevica, January records much higher frequency of winds coming from SW, W, and NW with a share exceeding 50%, which is a consequence of barometric depressions transiting above this area. True jugo (SE) at in this part of year is most frequent in Bihać (12.1%). Besides Bihać, jugo is felt in Sarajevo, with a share of 9.8%. Such strong influence of jugo is due to position and proximity of the usual routes of barometric depressions. The usual directions of wind in Sarajevo are E and W, with almost identical share of 12.6% and 10.6% respectively. 

At the remaining stations in the Federation of BiH, the percentage of calm in January exceeds 40%, peaking in Zenica at 61.2%. Interestingly, January southerly winds (coming from S, SE, and SW) are much less frequent in Mostar (10.5%) compared to Bjelašnica where their share is 43.9%. It is possibly due to the relief effects, that is, weakening of southerly streams due to friction caused by uneven terrain, while streams at greater heights remain stronger.

Maximum average wind speeds are recorded on Bjelašnica, ranging from 5.3 m/s (E) to 11.2 m/s (S). In January, north wind (N) records show the average speed of 10.5 m/s. At the remaining meteorological stations, average wind speed in January is below 5 m/s. The highest value was recorded in Mostar, true bora coming from NE at 4.8 m/s. The minimum average values of wind speed were recorded in southeast Bosnia, at the meteorological station in Tuzla; they range between 1.3 m/s (E) and 1.7 m/s (N and S). The most usual wind in this area comes from NE, and its share in the total winds is 14.6%.

Mean January distribution of wind and calm in %

(period 1961-1990)

C

N

NE

E

SE

S

SW

W

NW

Bihać

13.2

6.0

6.2

7.9

12.1

9.4

12.5

18.3

14.4

Bjelašnica

4.3

29.3

8.5

3.7

2.7

16.2

25.0

4.7

5.6

Bugojno

53.0

11.8

2.2

1.9

6.0

10.2

2.0

1.6

11.2

Livno

49.4

8.4

4.9

7.1

9.6

4.3

4.0

4.9

7.4

Mostar

17.1

30.8

22.4

3.5

2.2

4.0

4.3

5.6

10.0

Neum (1982. - 1990.)

8.0

32.5

14.6

5.8

12.7

10.1

2.6

3.4

10.2

Sanski Most

50.9

8.0

3.3

2.0

3.4

4.8

4.8

8.2

14.5

Sarajevo

41.1

2.7

2.2

12.6

9.8

6.4

5.1

10.6

9.5

Tuzla

47.7

5.1

14.6

3.0

3.8

3.1

7.2

9.2

6.3

Zenica

61.2

11.1

2.8

1.9

1.8

5.5

10.8

2.2

2.7

Summer period on the territory of the Federation of Bosnia and Herzegovina is dominated by N, NW, and W winds, although other directions are present as well due to the terrain configuration, however, in a smaller percentage. In July, winds originating from the north dominate Bjelašnica with a share exceeding 33%; the share of this wind direction in Mostar exceeds 25%. This wind direction also dominates at stations in Bugojno, Zenica, and Livno (13-14%).

At the majority of stations in the Federation of Bosnia and Herzegovina, distribution of frequency of different wind directions is almost identical to the winter distribution. The differences are rather small, which is especially evident from the distribution of the north wind. True bora (NE) dominates in Mostar with a share of 21.6%. Bjelašnica is the windiest station at this period, although calm percentage of 6.9% is somewhat higher than in winter when it is 4.3%. Summer period in the south of the country is generally windier; the percentage of calm in Mostar is 11.1%, which is less than 17.1% recorded in January. Sarajevo is also windier in summer than in winter; calm percentage in July is 30.4%, which is much lower than 41.1% recorded in January.

In summer, true jugo (SE) is most frequent in Sarajevo, with a share of 13.2%. Considerable frequency of this direction (11.4%) is recorded in Bihać as well, although the wind dominating this site comes from the east (14.8%). Sarajevo records similar data, with east winds dominating with 16.7% in July. SW, W and NW winds are somewhat more frequent in Bihać, with the total share of 36.6%. In general, differences between summer and winter distribution are rather small; occasionally, they are more prominent due to local conditions.

Mean July distribution of wind and calm in %

(period 1961-1990)

C

N

NE

E

SE

S

SW

W

NW

Bihać

13.0

6.4

9.7

14.8

11.4

8.1

13.2

12.4

11.0

Bjelašnica

6.9

33.7

16.8

3.4

2.2

9.9

17.1

3.9

6.0

Bugojno

47.6

13.9

5.0

2.9

2.8

7.3

5.6

2.6

12.3

Livno

43.0

12.7

5.3

3.8

4.7

5.4

8.2

9.9

7.1

Mostar

11.1

25.7

21.6

5.8

5.9

7.4

9.3

5.6

7.6

Neum (1982. - 1990.)

12.6

13.9

8.1

2.9

9.4

5.7

5.6

19.8

22.0

Sanski Most

51.8

8.8

6.3

2.8

2.2

2.9

4.9

5.2

15.0

Sarajevo

30.4

3.3

2.7

16.7

13.2

4.0

6.2

15.0

8.6

Tuzla

50.3

4.3

12.5

3.3

5.0

2.5

5.7

8.8

7.5

Zenica

61.3

13.0

4.7

2.6

2.1

3.2

8.6

2.9

1.6

Concerning the annual fluctuations of wind direction, winter and summer season are almost identical. The annual distribution shows that Bjelašnica is the windiest with calm at 5.8%. Windy locations include Bihać with 12.5% of calm, and Mostar with 17.2% (C). The remaining stations show that the share of calm ranges between 30.9% in Sarajevo and 63.1% in Zenica. The annual distribution is dominated by N and SW winds with a share above 20%. True bora (NE) is most frequent in Mostar (19.3%). True jugo (SE) dominates in Sarajevo, with a share of 13.3%. Wind speed is not as constant as the annual wind direction. Maximum average annual speeds for different directions are recorded on Bjelašnica with the following values: N 8.3 m/s, SW 9.0 m/s and S 9.3 m/s.

Mean annual distribution of wind and calm in %

(period 1961-1990)

C

N

NE

E

SE

S

SW

W

NW

Bihać

12.5

5.6

7.1

11.5

12.9

9.8

14.0

15.0

11.5

Bjelašnica

5.8

27.1

10.7

3.9

2.5

16.1

24.2

4.2

5.4

Bugojno

46.4

11.7

3.8

2.1

5.1

11.1

5.1

2.5

12.2

Livno

42.5

9.9

5.5

6.1

10.0

6.2

6.3

7.1

6.4

Mostar

17.2

24.2

19.3

4.6

4.6

7.7

8.3

5.6

8.4

Neum (1982. - 1990.)

8.3

23.3

11.0

4.4

10.7

12.2

4.6

10.4

15.1

Sanski Most

49.3

8.2

4.8

2.2

3.8

4.9

5.0

6.5

15.2

Sarajevo

30.9

2.8

2.6

16.7

13.3

6.5

6.3

12.8

8.1

Tuzla

46.1

5.1

15.0

3.7

5.5

2.6

5.8

9.3

7.0

Zenica

63.1

11.6

3.5

2.4

5.1

9.7

2.1

2.4

Majority of the Federation of Bosnia and Herzegovina territory, settlements and river valleys, is dominated by winds with average annual speed of 4 m/s. Winds with mean annual speed between 4 and 10 m/s are recorded in the highlands of the central parts of the country. Extreme wind gusts may reach 40 m/s, and stormy winds of 17.2 m/s occur several times a year. In the mountain climate zone, extreme winds occur at higher altitudes, i.e. mountain tops, while valleys mostly remain protected.

Mean annual wind speeds in m/s

(period 1961-1990)

N

NE

E

SE

S

SW

W

NW

Bihać

1.7

1.8

1.9

2.6

2.6

2.0

1.7

1.7

Bjelašnica

8.3

6.5

4.7

4.8

9.3

9.0

5.0

5.2

Bugojno

2.6

2.6

2.4

2.8

2.9

2.5

1.9

2.3

Livno

3.4

3.2

2.4

2.7

2.6

2.2

2.2

2.5

Mostar

3.9

4.1

3.2

2.3

2.7

2.4

2.3

2.9

Neum (1982 - 1990)

2.8

2.2

2.4

3.3

3.5

2.8

2.6

2.5

Sanski Most

2.5

2.2

1.8

2.7

3.1

2.4

1.7

2.0

Sarajevo

2.2

2.3

2.4

2.7

3.3

2.2

2.0

1.9

Tuzla

1.7

1.5

1.6

1.6

1.9

1.9

1.6

1.6

Zenica

2.7

2.4

2.0

2.5

2.1

2.4

2.3

The average annual number of days with stormy winds (wind measuring 8 or higher on the Beaufort scale) ranges between 0.1 day in Gradačac and 17 days on Bjelašnica. In the central mountain-basin part of the country, such strong winds occur 2-3 days a year, up to 4 in the south.

For the purpose of this Atlas, the number of strong wind days (wind measuring 6 - 8 on the Beaufort scale) was also taken into consideration. According to the multiannual data sets for the period 1961-1990, the far northeast of the country records an annual average of 0.4 days, with 4 to 8 days in the central basin area, 11 to 14 days in the southern parts of the country, and 24 to 28 days a year at altitudes above 1000 meters.