The weatherman caught in a media storm

It's surely one of the more sensational weather forecasts of the last few years – the prediction that next month will be the coldest May in Britain for a century.

It was splashed all over the front page of the Daily Express on Thursday and doubtless sent a shiver down the spines of many people already fed up with the chilly spring.

But it didn't come from the Met Office. No, this prophecy of a truly out-of-season wintry month came from an independent weather forecaster, Piers Corbyn, using what he terms his "solar weather technique" which involves calculating how solar particles will interact with the Earth. However, Mr Corbyn, 65, who has a degree in physics and runs a company named WeatherAction from an office in south London, declines to disclose his methodology in detail.

He specialises in long-range forecasts, especially those concerned with extreme weather events, and four days ago, in dramatic headlines on his website, he prophesied "the coldest or near coldest May for 100 years in central and east parts with a record run of bitter northerly winds ... spring put into reverse." He added that his confidence regarding mean temperatures in east and south-east England was 80 per cent for them being the coldest in 100 years, and 90 per cent for them being in the coldest five years of the century.

Contrast this with the current Met Office 30-day forecast, which says that temperatures up to mid-May "will generally be close to or slightly above the seasonal average". This is arrived at by using numerical weather prediction, the technique employed by all the world's meteorological services – running mathematical models of the weather on supercomputers.

There doesn't seem to be a meeting point between the Met Office and Mr C, and indeed, if you mention him to the chaps down in Exeter, the response is a world-weary sigh. "Piers Corbyn has never been able or willing to publish," says a spokesman, "detailed analysis of how he forecasts the weather".

Mr Corbyn's response to this is robust. "They're lying scum!" he snorts. "Because basically, whenever I've had meetings and invited them along, they've refused to come."

On his methods, he says: "We've published detailed results, or others have published detailed results..."

But the methodology...?

"We have published certain ideas..."

But not the whole thing in detail?

"Well why the f**k should I? The methodology is owned by the company, right? Why the hell do you drink Coca-Cola when the recipe is secret?"

Mr Corbyn will, though, give a generalised outline. "It's based on the fact that the weather and climate are controlled by activity from the Sun, and its modulation by the orbit of the Moon," he says. "It's a solar-magnetic-lunar system."

Reminded that all the world's national weather services use numerical weather prediction, he says: "Well, what they're doing there is delusional nonsense, because the weather is not controlled by the weather. It's controlled by other things, ie external factors.

"Their calling for more money to be spent on computers is just theft. All it will enable them to do is get the wrong answer quicker."