UK GAS-Prices down on ample supply in warm weather

LONDON, June 29 (Reuters) - British wholesale gas prices fell on Friday as a week-long heatwave dampened demand and left ample supplies to offset the start of exports to Belgium after a planned outage.

* Within-day gas prices fell 0.63 pence to 53.90 pence per therm (p/therm) at 0800 GMT.

* Day-ahead gas fell a penny to 53.50 p/therm.

* Weather forecasters monitored by Reuters have tweaked their average temperature forecast for Friday lower by 0.2 degrees Celsius to 18.5 degrees Celsius.

* But the heatwave across the country continues, with average temperatures for the weekend and early next week expected at around 20 degrees C.

* The warm temperatures reduce gas consumption for heating and are not strong enough to increase power demand through more use of air conditioning systems.

* The system was oversupplied by 8.4 mcm with demand at 167.8 mcm, in line with seasonal averages, and supply seen at 176.2 mcm, according to National Grid (LSE: NG.L - news) data.

* Wind generation is expected to pick up to reach a peak of 3.7 GW on Friday compared to around 1 GW earlier this week, and to rise further to almost 6 GW on Saturday (Shenzhen: 002291.SZ - news) .

* UK Continental Shelf gas supplies are higher at 132 mcm compared to 128 mcm on Thursday, helped by more supplies at the Bacton SEAL and Barrow North terminals, returning from outages.

* Gas exports out of Britain to Belgium through the IUK pipeline are expected at 38 mcm on Friday after a two-week planned outage was completed on Thursday.

* The maintenance had trapped excess gas in the country although much of that was put away in storage.

* "We do expect higher IUK exports as the return of Norwegian production from Troll/Kollsnes loosens the NBP (Shanghai: 601018.SS - news) (British) system," Thomson Reuters (Dusseldorf: TOC.DU - news) gas analysts said in a daily note.

* The July contract was down 0.7 pence at 53.30 p/therm.

* Day-ahead gas at the Dutch TTF hub fell 0.17 euro to 21.73 euros per megawatt-hour

* The benchmark Dec (Shanghai: 600875.SS - news) -18 EU carbon contract was down 0.08 euros at 14.92 euros a tonne (Reporting by Sabina Zawadzki; Editing by Jan Harvey)