11.02.2020#14: Avalanche bulletins in the Alps: consistency across borders

Regional and national warning services publish daily avalanche bulletins. The descriptions of danger levels leave room for interpretation. Do avalanche warning services in the Alps speak the same language?

In the Alps avalanche bulletins are published daily during winter months. These bulletins are produced by thirty regional, national and military avalanche warning services.

All of these warning services communicate avalanche hazard using the European Avalanche Danger Scale, introduced more than 25 years ago with the aim of increasing consistency in communicating avalanche danger in Europe. However, the descriptions of the five danger levels are short, and leave room for interpretation. A further difficulty arises since avalanche danger cannot be measured, and thus cannot be objectively verified. This gives rises to the question:

Do avalanche warning services in the Alps speak the same language?

We studied how often avalanche danger in neigbouring forecast regions differed when predicted by the same warning services and across borders between different warning services. We found that on around one third of days the forecast differed between neighbouring regions across national borders and where responsibility for forecasting changed between warning services. Moreover, the danger level of some warning services was consistently higher than neighbouring regions, for example when Swiss forecasts are compared with French. Snow climate and mountain topography can only partially explain these differences.

What next?

This analysis demonstrated quantitatively for the first time differences in the application of the avalanche danger scale. It thus provides important information for working groups of the European Avalanche Warning Services aiming to harmonise information provided in avalanche forecasts across Europe.

More information:
Techel, F., Mitterer, C., Ceaglio, E., Coléou, C., Morin, S., Rastelli, F., and Purves, R. S.: Spatial consistency and bias in avalanche forecasts - a case study in the European Alps, Nat. Hazards Earth Syst. Sci., 18, 2697-2716.

Frank Techel, Ross Purves