WeatherBlog 5 2020/21 | Mild, windy, future uncertain

Both sides will have to continue to cope with the current situation. Central Europe lies in a slight SW flow between a low to the west of the British Isles and a high over North Africa. Anyone who thinks that the next dump is due in the south will be disappointed. Compared to the PowderAlert south, the current flow is much weaker and has a clear westerly component. In addition, the core of the low is positioned "wrong", i.e. too far to the north and west. This means there is no chance of tapping into warm, humid Mediterranean air. Minor disturbances here and there will bring high clouds, but no significant precipitation. On the mountains, the Föhn will make itself known with strong gusts, but even this will be far less extreme than last time. The wind may penetrate the valleys in places, but it is likely that the cold air lakes will not be cleared out everywhere and the high fog cover may persist in places.

The image on the left shows an ECMWF ensemble forecast for Innsbruck from December 15 to 24. The top panel shows the temperature in 850 hPa, in the middle is the precipitation (6-hour total), at the bottom is the geopotential. The thick lines are the main run and the control run. The main run is a high-resolution run without changes to the initial conditions, as used for the normal weather forecast. The control run starts with the same initial conditions, but has a lower resolution, as do the ensemble runs. This saves computing time.

You can clearly see in all three plots that the uncertainties increase from Sunday/Monday: At the beginning, the thin dashed lines are quite close to each other. There is little change in our boring SW current. From about Sunday night, the lines diverge. There are warmer and cooler options, some with precipitation and some without. It does happen that the ensembles for forecasts agree much better in a week. The fact that they don't here shows how uncertain the development is.

The graphic comes directly from the ECMWF website. You can enter city names or coordinates to view your own location, set the start time and the display format. These images, as well as many others, have only been freely available for a few weeks. The ECMWF has taken a big, very valuable step towards open data and made many forecast products freely available that were previously reserved for weather services and other professional, paying users. Thank you for this, please keep it up and make the rest accessible too!

And to Ms. Holle, Ullr and anyone else who might be responsible: Please keep the snow coming!