LONDON (Reuters) - Unseasonably cold weather is likely to grip northern Europe again from late February into spring, after a relatively mild spell in late January, U.S.-based Weather Services International (WSI) said on Monday.
WSI expects the moderation in temperatures seen in late January -- after the coldest December since records began for the UK -- to last into early February.
But the specialist in forecasts for the weather-sensitive energy industry sees abnormally cold weather returning to much of northern Europe towards the end of next month, dragging down the average temperature for the February-April period.
WSI said that the current mild spell for most parts of northern Europe was due to the North Atlantic Oscillation (NAO) flipping from negative to positive in January.
Meteorologists say a negative NAO usually points to colder winters in northern Europe and WSI warned in October the negative value for the pressure difference between areas of the north Atlantic would likely mean a very cold start and end to winter with a mild spell in the middle.
"At some point later in February or early March, we do expect a return to more strongly negative NAO conditions," said WSI Chief Meteorologist Todd Crawford.
"At that point, we expect a return to more severe and widespread below-normal temperatures across much of Europe, lasting well into spring."
Crawford said the biggest uncertainty for his February forecast was that the strong negative NAO could return more quickly than expected.
Bitterly cold weather in much of northern Europe at the end of 2010 drove up natural gas prices in Britain, where about two thirds of homes rely on gas for heating, as demand surged to record levels -- draining stocks early in winter.
Demand for heating has ebbed in late January, taking some pressure off gas stocks, but the return of unusually cold could put upward pressure on wholesale energy prices towards the end of winter.