EAWS-Matrix
EAWS- Matrix
The EAWS Matrix is a tool introduced by the European Avalanche Warning Services with to goal of helping avalanche forecasters in determining the avalanche danger levels in a more objective way. The EAWS Matrix serves to standardize the avalanche danger level assessed and issued by the various warning services and is intended to exclude subjective influences as far as possible when forecasting avalanche danger.
The EAWS Matrix: A tool for an objective assessment of the avalanche danger level in Europe
The EAWS Matrix is used to determine avalanche danger levels based on snowpack stability, frequency of snowpack stability and avalanche size.
The EAWS Matrix is a substitial part of the decisional workflow for avalanche forecasters in Europe. The forecaster approaches the EAWS Matrix with the following thoughts: In a first step she assess snowpack stability by picking one of the classes very poor, poor, or fair and concurrently the frequency of the given class with lowest snowpack stability (many, some, or few) that decribes the avalanche problem best. In a second step the forecaster assesses how large the largest expected avalanche can become and chooses the corresponding field within the selected snowpack stability and frequency chart.
The given avalanche danger levels of the current EAWS Matrix was obtained by a survey of numerous forecasters in Europe. They were asked to assess a danger level for the various combinations of snowpack stability, frequency of snowpack stability and avalanche size. Figure 1 shows that some fields within the EAWS Matrix contain two proposed danger levels. The median danger level is indicated showing the integer value for each danger level (e.g., 1 for 1-Low). If the distribution of responses by the forecasters was rather heterogeneous, a second value is given in brackets, representing the interquartile range, if this value was different from the median danger level. When applying the EAWS Matrix (Figure 1), the forecaster should use the first danger level given in the cell. An optional danger level in parenthesis indicates that forecasters might disagree and a tendency towards a second danger level. These cells should be considered carefully and collected feedback on for future evaluation. For example, if the forecaster assessed that the dominant avalanche problem is best described by the factors poor snow stability on manny slopes and avalanches up to size 3 are expected, the result would be avalanche danger level 4-High.
If you are interested on more detailed information on how the updated EAWS Matrix was derived, go and check the documented explanations presented at the General Assembly of EAWS in Davos in June 2022.
If you are interested on more detailed information on how the EAWS Matrix fields were appointed with their respective avalanche danger leve, go and check the poster presented during the EAWS General Assembly in Davos in June 2022.