Wetterblog 9 2024/25 | Der Atlantik kocht uns frisches Wetter

Weather situation

Yesterday, winter arrived late on the southern side of the Alps. An extensive trough in a south-westerly flow brought long-awaited snowfall from the Maritime Alps to Trentino. As announced by our colleague Orakel, the snowfall in the border triangle of Italy, Austria and Slovenia was generous. The Lavinal Lunc measuring station has now measured more than 60 cm of fresh snow, which fell at a snow line of around 1500 metres. The first snowfalls on the western side of the Alps and on the northern slopes of the Alps had already caused wintry conditions on Monday night. Due to warm temperatures, the SLF unfortunately reported more wet avalanches, and many a conditions reporter also noticed the slowing effect of wet snow. But we are looking ahead.

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Good chances of significant snowfall throughout the Alps.

PG-ICON-Wetter

PowderGuide.com

ICON-EU-EPS

Outlook - Cold air intrusion

In the course of Wednesday, the upper-level current will turn back to west-north-west with the arrival and deepening of a new trough. This means that renewed precipitation is expected in the northern western Alps, with a snow line between 1500 and 2000 metres. This will be followed by an outbreak of cold air that will bring long-awaited wintry temperatures to the Alps over the weekend. The Dinaric Alps in Croatia will also receive snowfall and the possibility of a leeward cyclone in the Adriatic cannot yet be ruled out. So anyone who has been waiting for good conditions to unpack their winter sports equipment should make the most of the weekend - because after that the Azores high will catch up with us and it will get warmer again.

850 hPa temperatures and sea level pressure: from Friday onwards, the Alpine region will be enveloped in Arctic air masses.

Uni Innsbruck

ECMWF-IFS

Weather kitchen North Atlantic

In the North Atlantic, the Gulf Stream transports warm water along the east coast of the USA near the surface from the tropics to the Arctic and then to Europe. When it collides with cold Arctic air masses, the water masses in the Labrador Sea cool down and (convectively) sink, which then flow southwards again as part of the "conveyor belt" in deep layers of the ocean. Cyclones are fuelled by sensitive and latent heat and moisture flows, which is why the North Atlantic is also known as Europe's weather kitchen. Of course, Europe lies in the mid-latitudes, i.e. in a westerly wind zone. It is due to favourable Rossby wave numbers when the circulation reaches us from the east. For almost two years now, sea surface temperatures in the North Atlantic have been feverishly high - in some cases they have been 5 standard deviations (0.16°C) above the climatological mean. This study documents that marine heatwaves, i.e. locally strongly increased sea surface temperature anomalies, are triggered as a result of this fever. The causes of the fever are, of course, global warming, but also a transition to the warm phase of the multi-decadal Pacific-Atlantic-Arctic (PAA) mode and the transition from La Niña to El Niño. I have never heard of the PAA mode myself, and find it somewhat disappointing when such phenomena can only be explained statistically and not mechanistically - unfortunately that is often all that is left. Cause and effect are sometimes simply inseparable in the complex but always balanced earth system. The sea surface temperatures in the North Atlantic are still very high and we can only hope that nothing burns in the weather kitchen.