LONDON (Reuters) The British gas market could be caught short this winter as an early cold snap sees suppliers tapping into storage a month earlier than last year, eating into stocks needed for when demand usually peaks early in the year.

Wholesale gas traders started withdrawing from Rough Britain’s only long-range storage facility two weeks ago and supplies have been sinking since to about 17 percent below levels seen this time last year, data from network operator National Grid showed.

The premature and pronounced drain on the site under the North Sea, which holds the vast majority most of Britain’s back-up gas, could spell supply jiters early next year.

“If you do the numbers, storage will be empty some time in early February if it stays this cold,” said Jason Durden, energy trader at Energy Quote JHA.

Gas for delivery over the first quarter of 2011 has gained 12 percent since the onset of cold weather in the middle of November, according to one broker, and spot prices have nearly doubled in the last two months as temperatures have dived.

“If January and February demand is as high as it is now, storage will not be enough and prices will spike,” one British gas market analyst said.

Temperatures fell to a new record low for November over the weekend, Britain’s official weather forecaster, the Met Office said, while gas demand is around 25 percent higher than the same time last year, according to National Grid data.

The spot market’s premium over the first-quarter contract, around 1.45 pence yesterday morning, does not incentivise suppliers to hold gas in storage for later this winter.

Another gas market analyst expected withdrawals from Rough to drop by more than 10 percentage points over the coming two weeks if weather forecasts are consistent and assuming maximum withdrawals during the week and that weekend withdrawals will halve.

“Going into this winter with less-full storage and using it earlier could mean an uneasy time if we have a cold Q1,” he said.

The Met Office expects temperatures in southern parts of Britain to become less abnormally cold in late December, although bitterly cold weather is expected to continue in northern parts of the country keeping up pressure on storage to top up supplies coming in from the North Sea gas fields and liquefied natural gas terminals.

But beyond the end of 2010, latest forecasts by US company Weather Services International (WSI) are for temperatures in Britain to average warmer than normal in January and February, which could limit demand spikes and take pressure off stocks to help meet demand.