That all the models over-estimate moisture content with approaching systems. Ok this does not happen exclusively, but on the whole the vast majority of systems that are progged will over-estimate the moisture/rainfall content. Why is this? Surely if they kept on over-estimating it then that would be added to their database and they would 'learn' from it and the model would predict a rainfall amount that is closer to the real amount in the future. I mean, when was the last time u saw a little system pop by and BANG 30mm+ comes out of it when you were expecting less than 5mm? Not since ive been forecasting. On the other hand how many times in the past months have we seen a system destined to drop 30mm+ and end up with a bee's fart worth of rainfall? Too many times. If data was continously added to the model then shouldnt it realise that its getting it wrong, and from its catalogue of past systems use this data to predict systems more accurately? What im really getting at here is why do models consistently over-estimate the amount of rainfall/moisture instead of under-estimating it?