The last thing to consider when using any of these methods is that no forecast is ever perfect. The best one can hope for is a high degree of accuracy. There is an entire area of this discipline related to determining the accuracy of forecasters. The process of doing so is Forecast Verification. There are several methods for verification, just as there are several methods for forecasting, and many of them involve statistical analysis. Verification of some sort is performed at almost every weather forecasting entity - both public and private; although frequently the accuracy findings are not made publicly available.
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