WeatherBlog 2 2023/24 | Continued turbulence, rising temperatures

Current situation and outlook

We are still in the vicinity of a low pressure system over Germany and its influence is causing humid and relatively cold air masses to accumulate along the Alpine arc. The depression will move on in the coming days and the weather will become calmer. Meanwhile, our weekend weather is brewing south of Greenland. The development of low pressure in the Atlantic is in full swing and disturbances will slide directly into Europe as typical westerly weather. The decisive factor for our skiing weather is how far south they can penetrate. The models are currently predicting a strengthening Azores High, which will push the lows further north, giving the westerly flow in the Alpine region a south-westerly component. This will push warmer air masses towards us. From today's perspective, the next wave of precipitation will fall with significantly warmer temperatures than recently. The idyllic winter weather in the lower-lying valleys will probably come to an end (for the time being). The signs are also pointing to westerly weather next week, but as usual, things can still change.

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500hPa and geopotential, GFS, Wednesday 6.12. Remnants of low pressure still clinging to the Alpine arc, intermediate high pressure influence in the coming days. Low pressure development southeast of Greenland
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meteociel.fr

The Austrian weather service (Geosphere Austria) explains that the last time Bregenz, Innsbruck and Salzburg had as much snow at the same time of year was in 2014. It hasn't been as cold as last weekend in the north and east of Austria for over 10 years. A look at the snow maps of the SLF is also pleasing: the snow depths in the north of the Swiss Alps are significantly above average compared to the long-term average, especially at lower altitudes and on the edge of the Alps. New snow depth highs for the beginning of December were consistently achieved at the weather stations of the Bavarian Avalanche Warning Service. Most of the Bavarian LWD stations have been in operation since 1998 and you can click here through the seasonal graphics and compare current snow depth values with those measured so far. The example of the seasonal graph from the Kampenwand in the picture gallery below shows the rapid increase in snow depth in cold temperatures. (We suspect that the low wind in the graph is due to a frozen sensor rather than actual calm). In the meantime, the temperatures have risen again and the snow cover has already settled considerably. In any case, the WeatherBlog is happy about snow in the mountains back home and hopes that the approaching thaw doesn't tear too big a hole in the beautiful statistics!

COP28

We digress briefly from snow and weather and note that another Conference of the Parties (COP) is currently taking place, this time in Dubai under the leadership of Sultan Al Jaber, who also heads the state oil company of Abu Dhabi. The purpose of the COPs is, by and large, to reach an agreement within the global community on how to combat climate change. Sultan Al Jaber attracted attention in the run-up to the event with a video in which he first says: "there is no science out there, or no scenario out there, that says the phase-out of fossil fuel is what's going to achieve 1.5." and then follows up with "please, help me, show me a roadmap for a phase-out of fossil fuels that will allow for sustainable socio-economic development, unless you want to take the world back into caves."

Without going any further into the rather idiosyncratic persona of the Sultan as head of the climate conference or the purpose of the conference in general, let's make a note of it: Yes, in order to somehow achieve 1.5°C, a "phase-out" or a radical reduction in the burning of fossil fuels is necessary. From the IPCC report to the International Energy Agency, there is plenty of corresponding "science". And no, this won't take the world back to the Stone Age and we don't all have to find a cave to live in.

Finally, back to more pleasant topics. Sebastian's second tutorial on the new PG weather deals with ensemble maps. General explanations of ensemble forecasts can be found in this WeatherBlog,

500hPa geopotential and ground pressure, GFS, Saturday 9.12. Strong Atlantic low on the doorstep, Azores high also quite present. Warmer air reaches the Alpine region and the next precipitation is expected to fall at significantly higher temperatures than recently.

meteociel.fr

PG-ICON weather tutorial #2: The ensemble models and their variables

We use the deterministic weather models ICON-D2 and ICON-EU for PG-ICON weather, which are initialized by means of data assimilation of observations with an optimal initial state. For snow depth, rainfall and new snowfall, we also offer you the corresponding ensemble models, ICON-D2-EPS and ICON-EU-EPS. Here, 20 (D2) or 40 (EU) simulations are calculated, each of which deviates minimally from the other in its initial state. This gives us a probabilistic forecast and allows us to use statistics to gain knowledge about the sensitivity of the large-scale weather situation to disturbances. As a standard, we show the mean of all ensemble simulations, which is the most probable forecast. For the amount of new snow, we also provide the ensemble minimum and maximum, which should be considered as the most pessimistic and optimistic forecast, respectively: "There is no such thing as too much snow" (Doug Coombs). Their difference can be regarded as forecast uncertainty, and this naturally increases as the forecast period increases. So, if you want to dream, just look at the maximum! We also note that ensemble mean, minimum or maximum do not represent a physically consistent state, as these arise from multiple simulations.

Finally, we offer the "chance of new snowfall > 15 cm", where we have chosen 15 cm as a relevant amount of new snowfall. This is calculated as the number of simulations in which this 15 cm is reached for a grid point, divided by the total number of ensemble simulations.

In the images (image gallery below the article) we show you the four ensemble variables: Minimum, Mean, Maximum and Chance(fresh snow > 15cm).