True winter days are ahead of Bosnia and Herzegovina

By Nedim Sladić

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On New Year's Eve, cold, clean air, light snowfall, and moderate northwesterly winds, at the beginning of January 2019, a cold wave from the north will hit Bosnia and Herzegovina, with temperatures on some days up to 10°C lower than the long-term average of 1981-2010.

According to the analyses of the forecast models ICON-DWD, GFS, and ECMWF, true winter days are ahead of Bosnia and Herzegovina. On the last day of 2018, Bosnia and Herzegovina, synoptically speaking, is located at the boundary between a vast area of high atmospheric pressure from the west and low pressure from the east, with an anticyclone over Great Britain and a cyclone over Eastern Europe allowing colder air to infiltrate via the northern high-altitude stream (northerly winds) towards our regions and for colder air masses to remain over most of the Balkans. At ground level, the edge of a cold front positioned east and southeast of our regions is visible, bringing a small amount of precipitation to our country. Precisely because of this cold front, after three years of stable weather, an unstable New Year's Eve is predicted, accompanied by occasional moderate northwesterly and northerly winds, so we will finally have clean air in the valleys after a series of days with dangerous levels of pollution. However, the front is not felt in central and southern Herzegovina due to its more easterly position, so these areas will not experience precipitation.

On New Year's Eve, cloudy weather is expected in Bosnia, with light rain in lower areas, and sleet in hilly and mountainous areas, gradually turning into snow in the afternoon, and snow in the mountains. Partly sunny in northern Herzegovina, and mostly sunny in central and southern Herzegovina. Larger amounts of precipitation, where snow cover of 5 to 10 cm is predicted, are expected in eastern, southeastern, and partly central parts of Bosnia, and locally over 20 cm in mountain centers. The gradient between the north and south of our country will cause wind, moderate northwesterly and northerly in Bosnia, with stronger gusts expected in central Herzegovina and southwestern Bosnia. On New Year's Eve, dry weather is predicted in Herzegovina, Krajina, western, southwestern, and northern Bosnia, with occasional light precipitation, mostly in the form of snow and sleet, in central and eastern parts of Bosnia. Air temperatures on New Year's Eve should range between -4 and 0°C in Bosnia, and up to 4°C in central and southern Herzegovina.

A temporary improvement in weather is expected with the strengthening of an anticyclone from Western Europe on January 1st, but on January 2nd, new cloudiness will arrive in the afternoon, accompanied by a small amount of precipitation, primarily in central, eastern, and southeastern Bosnia, and in northern and eastern Herzegovina. Already on January 2nd, a strong anticyclone will retrogressively retreat to Western Europe, leaving space for Eastern Europe to allow extremely cold air masses from the north to descend into our regions. In the current circulation, the cold, likely dry, will be strongest in our areas between January 3rd and 5th, weakening briefly on the 6th, and intensifying again slightly on January 7th and 8th. The temperature deviation will be greatest around January 4th and 5th. After January 4th, precipitation in our regions will be very light and only sporadic and local. However, this cold wave will not be nearly as strong in all aspects as was the case in January 2017, when temperatures dropped to -27°C. This time, we expect temperatures to reach up to -18°C in the mountains, -16 to -11°C in hilly and mountainous areas, and -11 to -7°C in the lowlands of Bosnia. In northern Herzegovina, temperatures are predicted to be between -7 and -4°C, and in central and southern Herzegovina from -4 to 2°C, while the highest daily temperatures will range from -7 to -2°C in Bosnia, and from 1°C in its northern part to 5°C in its southern part in Herzegovina.