UK GAS-Within-day down on wind and Norway flows, day-ahead up on colder weather

Sept 21 (Reuters) - The British within-day gas price fell on Friday due to increased imports from Norway and strong wind power production, but forecasts for approaching colder weather helped lift the day-ahead contract.

* Within-day gas price down 1.10 pence at 74.50 pence per therm by 0904 GMT

* Day-ahead gas rose by 1.85 pence to 75.75 pence per therm

* Strong wind on Friday and an increase in gas flows from Norway were behind the price fall in the within-day contract, a British gas trader said

* As temperatures and wind output are both forecast lower on Monday, the day-ahead saw gains, added the trader.

* Peak wind generation was forecast to be strong on Friday at 10.1 gigawatt (GW), but output is expected to decline a bit from the following day

* Strong output from wind turbines typically reduces demand for gas-fired power generation

* Gas supply from Norway to Britain rose to 68 mcm per day, 11 mcm/day higher than Thursday, as flows through the Langeled pipeline increased.

* The market is oversupplied, with demand forecast at 146.0 million cubic metres (mcm) and flows at 157.5 mcm/day, National Grid data show

* Average daily temperatures in Britain are seen around 12.7 degrees Celsius on Friday and are forecast to fall to 10.1 C on Monday

* October contract up 0.36 pence at 74.75 p/therm

* In the Dutch gas market, the day-ahead price at the TTF hub was up 0.27 euro at 28.50 euros per megawatt hour

* The benchmark Dec (Shanghai: 600875.SS - news) -18 EU carbon contract rose by 0.08 euro to 22.11 euros a tonne (Reporting by Lefteris Karagiannopoulos in Oslo; Editing by Adrian Croft)