Actually, to be blunt, you look at clusters rather than the means. If you were to teleport inside the Met Office you'd find they use a product called Decider, amongst other things, which does a grand job of producing and analysing clusters. The pros only give mean charts a glancing look, we should be doing the same.
Fixating on a mean chart which shows a continuation of the current pattern is like sticking your fingers in your ears and saying "I can't hear you!" when someone's explaining something to you. The scientific way is to look at all the output (and yes, that means being creative with free trials, or simply paying the 25 bucks a month in order to see more of ECM) and then work out what's likely to happen based on percentages.
Just looking at a mean chart and going "oh, that's going to happen because it's what's happened for the last couple of weeks" is daft IMO.
I would have much more respect for the mean-chart users if they would quote percentages, but they never do!
Originally Posted by: Retron