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Expected forecast anomaly category computation
The Each of the 51 ensemble forecasts have 51 members, which will be members are assigned an extremity rank each. Using these 51 ranks, the forecasts will be put in one of the 7 anomaly categories (as described in Table 1). This is done based on , and the arithmetic mean of the 51 ensemble member rank values , which all can be from 1 to 100 (rank-mean) can be calculated (see also Figure 4) :and the result assigned to one of the 7 anomaly categories (as described in Table 1).
This The rank-mean will also be is a real number between 1 and 100, but this time a real (not integer) number. If the anomaly rank-mean is 50.5, that is exactly the normal (median) condition, i.e. showing no anomaly whatsoeversignal. If the anomaly rank-mean is below 50.5, then the forecast shows drier than normal conditions are forecast, if the rank-mean is above 50.5, then thee forecast shows wetter than normal conditions. The lower/higher the rank-mean anomaly value is below/above 50.5, the drier/wetter the conditions are predicted to be. The lowest/highest possible value is 1/100, if all ensemble members are 1/100 (the most extremely dry/wet). Then, based on this rank-mean, we define the expected forecast anomaly category (one of the 7 categories in Table 1) for the whole ensemble forecast, by placing the rank-mean into the right categories, as defined in Table 1 above. For example, all rank-mean values from 40.0 to 60.0, interpreted as 40.0<= <60.0, will be assigned to 'Normal', or category-4.
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