WeatherBlog 13 2019/20 | After the storm is before the storm

Sabine in retrospect

Storm depression Sabine, alternatively christened Ciara by the Met Office, initially caused fairly widespread official wind warnings between the North Sea and the main Alpine ridge at the beginning of the week. As soon as the cold front associated with Sabine passed through, it became very windy in many places as forecast, causing various traffic problems, power outages and wind-related damage to buildings.

During Sabine's rendezvous with friends, the WeatherBlog heard that the warnings had once again been totally exaggerated ("It's not windy here at all!") and felt compelled to defend the meteorologists' guild. A warning situation is a warning situation and they are not simply invented by a secret society of conspiracy meteorologists. There are different warning colors from green (everything is ok) to red (PANIC!), depending on the severity of the problem being warned about. In this case it was wind, but there are also weather warnings for heavy precipitation, particularly heavy thunderstorms or extreme temperatures, for example. You can of course find out what the colors mean from the national weather services, for example here at ZAMG (Austria), or here at DWD: Warning criteria, Warning levels.

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Peak gusts between Sunday and Tuesday in Germany. — Peak gusts between Sunday and Tuesday in Germany

DWD

The warnings are issued when corresponding threshold values for wind speeds, precipitation, etc. are exceeded in the forecasts. If a storm Sabine follows a storm Petra, which has already knocked down trees and covered roofs a few days earlier, citizens and the media are probably particularly sensitized and then a weather warning in some headlines quickly turns into an unprecedented monster hurricane. If you expect to narrowly miss the end of the world, the loss of a few roof tiles simply doesn't feel particularly spectacular. Another fundamental image problem with preventive measures is, of course, that you don't usually notice when they work, but you do notice when they fail.

Sabine was a storm that is definitely worth warning about. The ingredients for wind peaks well above 100 km/h, even in the lowlands, were:

Distinctive storm depression with center over Scandinavia
Zonal jet stream over Central Europe
Cold front originating from the steering depression, embedded in the jet, roughly pushed from northwest to southeast.

The wind speeds were already very high in the higher air layers due to the strong high-altitude flow alone, and they made it to the ground with the help of the cold front, as this mixed the events vertically. On the northern edge of the Alps, there was also the "guard rail effect" (well explained by the DWD with graphics). The front is pushed from the north towards the Alps, which leads to channeling effects and slightly higher wind speeds. As the front was dragged along the guard rail of the Alpine arc for longer, the wind in the Bavarian Alpine foothills was still very strong in places on Tuesday.

Calm between Storm Petra and Storm Sabine

LH

Outlook

Sabine has now moved off to the east. The jet stream and the fronts floating in it tend to be pushed a little to the north and we are no longer quite so directly in its path. Nevertheless, it remains changeable (and windy). The southern slopes of the Alps are still much calmer and sunnier. In the north, the clouds will also clear here and there today, but there will always be showers and it won't be really sunny.

Thursday will probably start quite sunny everywhere, but the next disturbance will reach us from the west during the course of the day, initially with clouds, then also with precipitation. Before that, the south föhn may briefly pass by in the more susceptible valleys. On Friday, it will be quite friendly again in the west, but it will remain cloudy in the eastern Alps. Thanks to a strong NW current, north föhn will prevail in the south for a change.

From today's perspective, the weekend will be calmer, much milder and sunnier. High pressure will push the frontal zone a little further north and warm air from the south will spread into the Alpine region. For the coming week, the next front with storm potential is then indicated in the crystal ball.

It will remain consistently unstable (and a very mild winter overall), as can be seen on the maps in the gallery below. Between last Monday and next Monday, details relevant to our local and regional daily weather patterns will change, but the overall large-scale situation (strong polar vortex, very active Atlantic, strong westerly flow in ME) will hardly change at all.