[tash9]

One piece of context to note here is that models like ECMWF are used by forecasters as a tool to make predictions - they aren't taken as gospel, just another input.

The global models tend to consistently miss in places that have local weather "quirks" - which is why local forecasters tend to do better than, say, accuweather, where it just posts what the models say.

Local forecasters might have learned over time that, in early Autumn, the models tend to overpredict rain, and so when they give their forecasts, they'll tweak the predictions based on the model tendencies.