Every six hours a numerical forecast model shows the changing weather, by quarters of an hour for up to 3 or 7 days. It provides forecast maps for Europe at various altitudes at 3, 6 or 9 hour intervals.
This very complex model with millions of pieces of information requires very powerful computers ; supercomputers capable of billions of operations a second.

The forecasting maps are interpreted by the forecaster, who adapts and refines them until they are as accurate as possible for his area of competence. This interpretive work remains indispensable for achieving bulletins of a high standard. In fact, the forecasts on the model are often approximate, barely taking local phenomena into account (storms, banks of fog, wind acceleration in valleys…).
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