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The generation of the sub-seasonal and seasonal forecast signal relies on few major steps, illustrated by a flowchart in Figure 1. The forecast anomaly and uncertainty signals are derived by comparing the real time forecast (top left section in Figure 1) to the 99-value percentile climatology (bottom left section). The climatology is generated using reforecasts over a 20-year period, which provides range-dependent climate percentiles that change with the lead time. The climate generation is described in the bottom left corner of Figure 1.
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