WeatherBlog 7 2016/17 | Outlook and glacier excursion

Current situation and outlook

All right, let's take a closer look. By and large, nothing has changed since last week. Only details of the pressure distribution in Europe have changed. After a brief visit from a small cold front in the north-east at the beginning of the week, it's now sunny again, at least wherever it's not permanently foggy.

This will remain more or less the same up to and including the weekend. Then there are signs of a dripping process in which a small "blob" will drip off the large low to the south "and get stuck in the area of the Iberian Peninsula. This would mean that the snow conditions in the Pyrenees would no longer look so bad. Whether, how, when and where exactly the "blob" will become active is still very speculative. Whether and to what extent the whole thing could also be relevant for the Southern Alps is just as speculative. If you want to speculate in the Eastern Alps, you can take a look at a currently partially simulated cold air drop from the east, which could possibly move a little to the west next week and theoretically provide a sugar coating, or ideally move far enough retrograde to join forces with the low in the south.

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500hPa geopotential and ground pressure (13.12.16): There is another high pressure system in the Arctic Ocean to the west of Alaska. On the eastern flank of this high, cold air is sliding into Canada. On the eastern flank of our high, cold air is sliding towards Turkey. — 500hPa geopotential and ground pressure (13.12.16): Mirroring the local high, there is another one in the Arctic Ocean west of Alaska. On the eastern flank of this high, cold air is sliding into Canada. On the eastern flank of our high, cold air is sliding towards Turkey.

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It remains to be seen whether this potential development should be described as a major weather change (change in the large-scale pressure distribution, disappearance of the persistent high in Central Europe). What we would need for something to happen on a large scale would be a shift of the frontal zone further south (ice in the European Arctic Ocean would probably be helpful for this), or a gradual push of the high to the east. Until then, Mediterranean lows, supported by cold air from the east, are the most likely scenario. Towards the end of the medium term, the various models are currently very divided on possible further developments.

In any case, the WeatherBlog is still rather bored. In one of the relevant weather forums, someone put it this way: Winter is still lurking in Siberia and will have to come at some point - sometime between Christmas and probably Christmas. It's not yet possible to say exactly which Christmas...

Something different.

We will therefore briefly look at a completely different topic: on July 17, 2016, a glacier in the west of the Tibetan Plateau collapsed. This resulted in a huge ice avalanche that killed nine shepherds and hundreds of animals in the alpine pastures below. The reasons for this event are still unclear. Ice avalanches of this kind are very rare. These are not ice avalanches in the sense of seracs breaking off, but rather shallow glaciers (the one in question was a full 15° steep), where large sections suddenly collapse, break off and rush down into the valley.

After the Tibet event, all available satellite data was accordingly analyzed in the hope of finding clues as to the causes. It was found that the glacier showed characteristics of a "surge" process before the collapse. This means that the flow velocity increases sharply. Surge glaciers are otherwise rare in Tibet and in areas where they are more common, they do not simply collapse. Moreover, surges usually occur periodically, alternating with slower resting phases. While analyzing the satellite data in the weeks following the ice avalanche, someone noticed that a neighboring glacier was also undergoing rapid changes. Huge crevasses had opened up in a similar pattern to the one that had just collapsed. The European scientists informed their Chinese colleagues. Just a few hours after making contact, the Chinese informed them that the second glacier had just collapsed. Fortunately, no one was injured in the second avalanche on September 22, although the warning was only received by the local authorities after the ice avalanche had occurred.

500hPa geopotential and ground pressure, exemplary map for Tuesday, 20.12.16. Potential for Mediterranean low with persistent high pressure block north of it.

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Two such events in the same area in such quick succession are an absolute novelty. The search for possible explanations is correspondingly exciting. In a recently published paper (pdf), Chinese scientists suggest that the glaciers in the area, which were previously considered cold (below zero degrees, frozen solid on the ground), could be in a transitional phase towards a polythermal or warm (on average zero degrees, liquid water between the ice and the ground) state. They also suspect that the rapid rise in temperature in the region in recent years has affected the ice temperature. In combination with very precipitation-rich weather, this has resulted in a marked destabilization. The European researchers also suspect, based on model simulations, that water played a decisive role between the ice and the ground. It stands to reason that other glaciers in the area could also be at risk. Efforts are underway for international cooperation to develop an early warning system.

As mentioned, the WeatherBlog finds this more interesting than the current weather and hopes that a turnaround of some kind will actually manifest itself by next week.