To produce weather forecasts for two to 30 days ahead, we use a variety of techniques:
We use our high resolution UK and European model, which runs out to day five
Our global forecast model which runs out to day six
Our global ensemble model which runs out to day six
We use our long range models, such as Decider, to look ahead to day thirty, as well as output from the European Centre for Medium-Range Weather Forecasts, which the UK Met Office is a contributer towards.