Reading University is working with the Met Office on improving MJO forecasting, he said.

BBC: Met Office three-month forecast was 'not helpful'

Some weather models can predict the MJO three weeks ahead, he said, but others struggle to predict it a week ahead.

BBC: Met Office three-month forecast was 'not helpful'

The "long arm of the MJO" even extends into the middle latitudes.

BBC: Met Office three-month forecast was 'not helpful'

Nick Klingaman from Reading University says that, as it moves east, the MJO influences monsoon rainfall in Australia, India, Southeast Asia, South America and Africa.

BBC: Met Office three-month forecast was 'not helpful'

Forecasts have greater skill when the MJO is already active.

BBC: Met Office three-month forecast was 'not helpful'

He says the MJO can be an important predictor of the state of the North Atlantic Oscillation - which controls much of our weather in the UK - about 2-4 weeks in advance.

BBC: Met Office three-month forecast was 'not helpful'