The weather is crazy because of the jet stream


The weather is crazy: cold and rainy here, sweltering heat in the north

Heat records fall, we drown in the rain and freeze. But the opposite could be true. SRF meteorologist Felix Blumer explains why these strange weather conditions occur around the world.

The intense heat in Lytton, Canada is causing many things to catch on fire.

BILD: James MacDonald/Getty (Lytton, 3. Julie 2021)

We pull the jacket over our shirt and want to go back to summer. At the same time, temperatures are declining around the world. 49.6 °C was measured in a lytton unit, and it has never been hot in Canada before in living memory. The heat meant that the entire village was burnt down and the forest fires never ended.

It is very hot north of the Arctic Circle. In Banak, Norway, the thermometer showed 34 degrees, warmer than at any time since the weather was recorded. Record heat in the north, bad weather and heavy rains in central Europe. The weather is crazy.

Felix Blumer, meteorologist and coordinator at SRF Meteo.

Felix Blumer, meteorologist and coordinator at SRF Meteo.

Oscar Alessio / SRF

Canada is located at latitude 50, which is no further south than Switzerland. Would such thermal records be possible for us, too? Meteorologist Felix Blumer of SRF Meteo compares the current heat stage in Canada to the summer of 2003 in Switzerland. Bloomer says:

“The jet stream curved farther north over western Canada and carried sweltering air into the region from the south.”

The jet stream is a group of westerly winds that circulate around the North Pole at great altitudes, affecting the movement of areas of high and low pressure. The situation in Western Canada remained stable for several days, so the heat increased, similar to the hot summer of 2003 in Switzerland, when we felt like we were in Bella Italy.

Heat waves can also happen with us

But no one wants temperatures a little over 40 degrees, and this is also possible in Switzerland in the coming years. “Values ​​in the 45-degree range are only possible for a very special or southwestern region, and only very local over a short period of time,” Blumer says.

We’re freezing right now, but Canada is getting hot. However, Blumer puts registry values ​​into perspective. Lytton also had something to do with the temporary drying effects. Outside the Fohn, temperatures in the region ranged between 40 and 45 degrees. “It’s still very hot, but it happened earlier in similar climatic conditions,” the meteorologist explains. The region is located approximately at the same latitude as Valencia.

Warming and jet stream as drivers

There is no doubt that extreme temperatures are increasing, especially in the north. According to Bloomer, there are two phenomena at play together. As a result of global warming, the amount of snow in the polar regions is decreasing, and the snow is melting faster in the spring.

Because tribal land warms faster than snow-covered land, the air warms much more. “This increased warming at higher latitudes and corresponding smaller temperature difference between middle and high northern latitudes appears to weaken the jet stream,” says Felix Blumer.

jet stream looms

The pulsating jet stream of the wave is diverted to the north and south. Because of this northward deviation, it gets hot in summer for weeks in the polar regions. However, in the south, due to the deflecting jet stream, there is wet and cold weather instead of warm. This jet stream phenomenon has occurred quite often in recent years and is effective in various places. In 2010 in Western Siberia or in 2014 in large parts of Scandinavia, when it was as hot there as it is now.

However, we complain with us about dampness and coldness. However, according to Bloomer, the summer wasn’t that bad: “If we ignore devastating thunderstorms, the summer of 2021 in Switzerland has so far been better than its reputation.” In many places in Switzerland, June has been among the five warmest since measurements began in 1864. However, the distribution of rain has been very uneven. From Lake Geneva to western Lake Constance, June has been the wettest month since measurements began. However, June in the south and parts of Graubünden was drier than usual.

Moisture in the central plateau had to do with the aforementioned belly of the jet stream, which turned westward into the Atlantic Ocean. This resulted in a frequent current from the southwest to the southeast, bringing warm air in June, but also many thunderstorms with heavy rain. Little has changed in July, and in the coming days we will often be at the eastern edge of the cold air over the British Isles. So the winds continue with southwest winds and thunderstorms, says Bloomer.

Wetness and cold delay the ripening of the fruits

With such prospects, one wonders what this is doing with the fruit in our country. Because of the weather, the start of the local fruit season has been delayed by about two weeks, says Beatrice Rottemann of the Swiss Fruit Association. Thus, the fruits generally ripen after two weeks. Rain also increases the risk of plant diseases and rot. Fruit producers are making more effort to sort the fruit.”

Basically, water promotes fruit development, and the fruit grows larger. In professional fruit farming, crops are usually protected from water and cold by foil surfaces. The start of the season was delayed by the cool, wet, sunless spring, but the warm June made up for it somewhat, which is why the quality of the fruit is still good.

However, we would like to see some dry shower days at the start of the holiday. It will not be lost in southern Europe. Next weekend, a desert heat wave will blast across the Mediterranean.

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