UK GAS-Within-day price falls on weak demand, oversupply

LONDON, June 12 (Reuters) - The within-day British wholesale gas price fell on Monday morning, hit by high output from the country's nuclear power plants and wind farms. * British within-day gas price was down by 1.25 pence at 36.55 pence/therm at 0810 GMT. * Gas system oversupplied by 6.5 million cubic metres (mcm), with demand forecast at 170.6 mcm and flows at 177.1 mcm/day, National Grid (LSE: NG.L - news) data showed. * Traders said high imports from Norway, combined with weak demand for gas from power plants pushed within-day prices lower, while forecasts for a drop in output from wind farms on Tuesday limited the day-ahead contract fall. * Day-ahead gas price down by 0.85 pence at 36.75 p/therm. * Peak wind power generation is forecast at 8 gigawatts (GW) on Monday, falling to 2.7 GW on Tuesday, National Grid data showed. * Imports from Norway through the Langeled pipeline were around 34 mcm, up from around 20 mcm the previous day. * The Torness 1 nuclear reactor came back online over the weekend after an outage, meaning all of Britain's nuclear fleet is running, and providing almost 30 percent of the country's electricity. * July gas contract down by 0.60 pence at 36.55 p/therm. * The Zarga and Al Mafyar liquefied natural gas (LNG) tankers are due to arrive in Britain on July 2 and July 4 respectively, via the Cape (LSE: CIU.L - news) of Good Hope. * They previously looked to be heading for Britain via the Suez canal but change direction last Thursday, prompting speculation they may no longer be coming to Britain. * Day-ahead gas price at the Dutch TTF hub down by 0.12 euro at 14.95 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract down by 0.01 euro at 5.03 euros per tonne. * Thomson Reuters (Dusseldorf: TOC.DU - news) analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting by Susanna Twidale, editing by Louise Heavens)