Sladić analyzes: How was our summer this year

By Nedim Sladić

Although it seems strange and unreal at first glance, this summer we had the same number of rainy days as last year, but the visible difference this time was in the African heat - unlike last year when it mercilessly occupied the entire Balkans and baked it at temperatures up to 42 degrees for fifteen consecutive days, this time it seemed reluctant to move beyond Bosnia and Herzegovina.

At the same time, the border between African heat and oceanic coolness was often around Zagreb. Therefore, northwestern Croatia, Slovenia, and Austria were the countries that had an extremely humid, rainy, and cool summer with very few hot days due to being "connected" to a cooler air mass and constant incursions of weakened frontal disturbances from northwestern Europe. 

This year, summer was not supposed to miss Bosnia and Herzegovina. And it truly didn't. We had two out of four perfectly aligned parameters for a good summer - a strong Azores maximum and an unimpeded influx of heat from North Africa with southwesterly flows, as well as potential heatwaves. 

For example, in 2014, we didn't have a single condition that makes a summer a summer, which was the reason for a catastrophic and one of the rainiest summers in Bosnia, and in Dalmatia and parts of Herzegovina, the rainiest ever recorded, which later reflected in a very poor tourist season in Croatia. 

However, the only "handicap" of this summer in Bosnia and Herzegovina was precisely these constant incursions of cool oceanic air coming from northwestern Croatia. As we were on the border of hot and cooler air simultaneously, during the incursions of cooler air masses, the northernmost parts of Bosnia were often cooler, but received less precipitation than the heated central and eastern parts of the country, and the reason is obvious - the heating of the ground. And therefore, it is logical that the central parts of Bosnia bore the brunt and experienced very strong thunderstorms, which were indeed abundant this summer. 

However, we also had a couple of periods with upper-level/secondary cyclones that lingered over our regions for several days, locally affecting certain areas and bringing large amounts of precipitation and thunderstorms. So, although we had a small number of days with precipitation (for example, in June and July, only about nine to ten on average, and in August around eight), the amounts of precipitation will not confirm that, as they could be much higher. Namely, in the warmer period of the year, precipitation is unevenly distributed, mostly characterized by showers of variable intensity and local character, making them almost impossible to predict in terms of quantity or exact location during the summer. If we take Sarajevo, it can happen simultaneously that there isn't a drop of rain in Grbavica, Otoka, and Hrasno, while there is a downpour with a large amount of precipitation in Dobrinja, Ilidža, and Hadžići. This is characteristic of local showers and thunderstorms. 

In my opinion, this summer had its drawbacks, but also its advantages. Why? Precisely because the summer in Bosnia and Herzegovina from June to the end of July was accompanied by considerable drought and moderate heat, summer lovers, including myself, got their due at the very beginning. June was a relatively dynamic, but also fickle month in which literally within 24 hours there was a reversal from spring to summer and vice versa. Specifically, we are referring to the legendary night, which in my assessment is the "highlight of the summer of 2016," when on the night of June 16-17, an extreme influx of heat from Africa occurred at high altitudes in the form of strong winds and heat that Sarajevans will remember for the warmest night ever recorded in their city, followed by heatwaves that continued until the end of the month and into July, until mid-July. But then came an unexpected turn. 

In mid-July, with the influx of cold air and increased northeasterly winds, it noticeably cooled down, and temperatures dropped to almost single digits. Although it didn't last long, the period of temperature recovery was rapid, and by the end of July, the last serious heatwaves of the summer arrived. In fact, the beginning of August marked a turning point when, on August 5-6, a cold air mass broke through, catapulting fresh air and northeasterly winds from northern Europe and dominating the Balkans. The cold front shifted south of Croatia, so Bosnia experienced extremely cool weather for that time of year. 

The period of below-average and occasionally significantly below-average temperatures, lasting almost eight days, made this August preliminarily a cooler August than average or within normal limits, while precipitation was average. As the stronger heatwaves were absent, the end of the month began to resemble late summer, with temperatures barely exceeding 32 degrees. It was felt that the Azores maximum was losing its strength, which turned out to be true, because instead of summer in the first half of September, an Ionian cyclone nullified all of that. Had it been absent, I am sure we would have had heatwaves, and temperatures would have exceeded 35 degrees here, as all conditions were in place for it. 

One of the advantages of this summer was the shower-like precipitation, which helped keep river levels at a somewhat bearable level. Last year's dry and hot summer, as well as a mild autumn, was followed by a dry and atypically warm winter and only a slightly wetter spring, causing very low river levels in our country. I am sure of the following: had we lacked precipitation and had only slightly higher temperatures, the Miljacka River in Sarajevo would have been dry in many places in the city! The advantage of this summer goes to mushroom pickers, who can be satisfied with this year because there was enough moisture, which helped mushrooms grow. 

Overall, this summer was meteorologically average in terms of precipitation, but significantly above average in terms of temperature, with June and July contributing the most with slightly more pronounced deviations from the average (2-3 degrees), while August was average or only slightly below average, but significantly milder than last year's, which was characterized by a large number of heatwaves.
The turbulent, humid, and amplitudinous summer of 2016 is behind us. However, let's be fair and admit the fact that "summer is summer" and that it should be hot and sunny, so let's hope that summer 2017 will be much calmer, more stable, warmer, and much more beautiful.

Bosnia and Herzegovina was on the border of hot and cooler air all summer, and unlike 2014, this year's summer did not disappoint as it might have seemed at first glance.

Four synoptic conditions for a good summer

For a sunny, stable, and hot summer, it is necessary to meet four synoptic conditions: 

- The retention of all frontal disturbances significantly north of us, from the United Kingdom all the way across Scandinavia and Russia. More precisely, the bulk of bad weather should be hundreds, even thousands of kilometers away from our regions.

- Cooler air should be directed towards the aforementioned areas so that incursions of cooler air accompanied by pronounced northeasterly winds do not reach our regions from the northwest of the continent, either over the Alps or over the Mediterranean, depending on the position of atmospheric pressures.

- The dominant and long-term influence of low atmospheric pressure is necessary.

- The establishment of a very strong Azores maximum is the most crucial factor for a warm summer. It is the main conductor of summer, which will form its center over the Atlantic coast, somewhere near the coasts of Portugal and Spain, and will later spread eastward across France, Italy, Austria, towards the western Balkans and parts of Eastern Europe, along with the withdrawal of hot Saharan air.

These are the four main conditions that, in the last twenty-five years, have led to very warm and relatively stable summers in Bosnia and Herzegovina. We had them in the war year of 1992, and in 1998, 2000, 2003, 2007, 2011, 2012, 2013, and 2015.