UK GAS-Prices mixed on forecasts for warmer Tuesday, colder Wednesday

May 15 (Reuters) - British prompt gas prices were mixed on Tuesday morning, with revised forecasts for higher temperatures depressing within-day prices and expectations for a cooler Wednesday lifting day-ahead gas.

* Day-ahead gas rose by 0.75 pence to 56.50 pence per therm at 0837 GMT

* Within-day contract was down 0.60 pence at 55.90 pence/therm.

* Changes in the weather forecasts were behind the price moves, as Tuesday's weather is projected to be warmer than forecast before and Wednesday's colder, affecting demand, said a trader.

* Average daily temperatures in Britain are seen at about 13.5 degrees Celsius on Tuesday and are forecast at 11.5 C on Wednesday, Thomson Reuters Eikon data shows.

* The gas market was oversupplied on Tuesday morning, as Norwegian supplies remained steady while demand declined, driven by the warmer weather.

* National Grid (LSE: NG.L - news) data shows gas demand is forecast at 169.7 million cubic metres (mcm), 32.2 mcm lower than the seasonal norm. Flows are forecast at 190.6 mcm/day, 20.9 mcm over the demand.

* Gas supply from Norway to Britain was flowing at 70 mcm/day, 1 mcm lower than Monday and 50 percent below the pipeline system's maximum capacity of 141 mcm/day.

* The June contract was up 0.25 pence at 55.10 pence/therm.

* Day-ahead gas at the Dutch TTF hub rose by 0.17 euros to 21.70 euros per megawatt-hour.

* The benchmark Dec (Shanghai: 600875.SS - news) -18 EU carbon contract grew by 0.25 euros to 14.89 euros a tonne. (Reporting by Lefteris Karagiannopoulos in Oslo, editing by Louise Heavens)