site.btaJet Stream Helped Spare Bulgaria from Europe's Heatwaves, Says Climate Scientist

Bulgaria has escaped the extreme heat that has gripped much of Western Europe this summer because it has remained on the cooler side of the jet stream, according to Prof. Emil Gachev, head of the Hydrology Section at the Climate, Atmosphere and Water Research Institute at the Bulgarian Academy of Sciences (BAS).

While Bulgaria has seen seasonally warm weather, countries further west have endured repeated heatwaves. Since May, Western Europe has experienced four major heatwaves, with temperatures exceeding 40°C in Spain and France and climbing above 35°C in England.

"These are exceptional values," Gachev said, noting that southern England and parts of Wales recorded their first-ever July without measurable rainfall since climate records began.

According to Gachev, the unusual weather patterns are linked to the exceptionally low extent of Arctic sea ice this year. Although the global average temperature has risen by about 1.4°C since the pre-industrial era, the Arctic has warmed by around 3.3°C, significantly faster than the rest of the planet.

This rapid warming is weakening the temperature contrast between the Arctic and the tropics - a key driver of the jet stream, a fast-moving band of westerly winds about 10 to 12 kilometres above the Earth's surface.

When that temperature difference is strong, the jet stream follows a relatively straight path, allowing weather systems to move quickly and bringing a regular mix of sunshine and rainfall. As the contrast weakens, however, the jet stream slows and develops larger meanders, allowing warm air from North Africa to surge northward while colder Arctic air spills south.

The northward shift of the jet stream, driven by Arctic warming, means African heat that once affected mainly Spain now reaches France and even the United Kingdom, Gachev explained. Bulgaria, by contrast, spent much of June and July on the cooler side of the jet stream's bends, limiting the arrival of extreme heat despite the broader warming trend across Europe.

The country's weather is expected to become warmer in August, with temperatures forecast to remain above the seasonal average, though not dramatically so. On Wednesday, authorities issued a yellow warning for high temperatures in 22 regions.

It is worrying that the Danube River is at a record low level in Bulgaria, the reason for this being the drought in Central Europe, where the watershed is located. The weather in our country actually has very little effect on the level of the Danube River, said Gachev. Because of the drought in Central Europe, paradoxically, even the increased melting of glaciers in the Arctic failed to help improve the river level during the summer months, summarized Gachev.