* Within-day price surges 11 pct to 51.00 pence per therm
* Demand 44 mcm above seasonal norm-National Grid data
LONDON, Nov 7 (Reuters) - British wholesale gas prices climbed on Monday morning, boosted by increased demand due to colder weather and falling wind output.
Gas for instant delivery climbed by 5.00 pence or 10.9 percent to 51.00 pence per therm at 0914 GMT, a couple of pence under a one year and nine month high of 53 pence hit last week.
The day-ahead price was 1.40 pence higher at 51.25 pence per therm.
Forecast demand was 303.8 million cubic metres (mcm), around 44 mcm more than seasonal normal demand, according to National Grid data.
Temperatures are expected to be below normal this week in Britain, with wind speeds at low to moderate levels, increasing gas demand from combined cycle gas turbine plants and for heating.
Peak wind generation is forecast at 2,664 megawatts (MW) on Tuesday, compared to 4,034 MW on Monday, Elexon data shows.
Windier weather is expected next week, which could lower demand from gas-fired power plants.
France’s tight power system could also be boosting demand for gas, traders said.
France is usually an exporter of power to Britian but there are persistent concerns that France is short of nuclear power supply due to extended outages that have left available capacity at less than 70 percent.
French spot electricity prices hit a record high on Monday due to news of more delayed nuclear reactor restarts in France and rising demand due to colder weather.
Meanwhile, the UK gas system was actually oversupplied by around 17 mcm/day on Monday as Norwegian pipeline Langeled flows were near full capacity and supplies through Vesterled were also strong.
The InterconnectorUK has also been in import mode for several days, currently nominated at 23 mcm. Thomson Reuters Point Carbon analysts expect IUK import flows to drop to around 10 mcm/day after the coldest days this week.
In the Netherlands, the day-ahead gas price at the TTF hub was 0.48 euro higher at 18.73 euros per megawatt hour.
In the European carbon market, the benchmark Dec. 16 contract was 0.09 euro higher at 6.50 euros a tonne. (Reporting by Nina Chestney)