UK GAS-Prompt prices fall on lower demand

* System is slightly undersupplied

* Wind power output seen to rise by 450 MW

June 4 (Reuters) - British prompt gas prices fell on Thursday on expectations for a fall in demand and lower exports to Belgium, while the system was close to balanced.

Gas for day-ahead delivery was down 0.83 pence at 43.85 pence per therm at 0845 GMT, while prices for immediate delivery were down 0.60 pence to 44.65 pence per therm.

National Grid (LSE: NG.L - news) data showed supply was forecast at almost 180 million cubic metres (mcm) on Thursday, while demand was expected at nearly 183 mcm, meaning the system was only slightly undersupplied.

"Within-day situation is less tight due to lower exports to Belgium and lower consumption, and is a bearish driver for the day-ahead contract," analysts at Thomson Reuters Point Carbon said.

Demand for gas was expected to fall due to higher output from wind power and warmer weather.

Maximum temperatures were expected to rise to a maximum of 25 degrees Celsius on Friday from some 23 degrees Celsius on Thursday, but dropping as low as 6-10 degrees overnight in northern Scotland, the UK's Met Office said.

Daily average wind power output was expected to increase by some 450 MW from Thursday to Friday, Point Carbon's data showed.

LNG terminals were nominated to inject 34 mcm/day on Thursday, with a new cargo from Qatar expected to arrive at the South Hook terminal on Saturday (Shenzhen: 002291.SZ - news) .

However, to keep the same injection rate for the rest of June, another four cargoes were needed, Point Carbon analysts said.

Norway's gas system operator, Gassco, said on Thursday planned maintenance at Zeebrugge terminal would end by Friday, three days earlier than previously planned, and some capacity would be available from 1600 GMT on Thursday.

Further along the curve, gas for delivery in July was down 0.09 pence at 42.71 pence per therm.

In the Netherlands, day-ahead gas at the TTF hub was down 0.23 euros at 20.05 euros per megawatt-hour, also due expectations for lower consumption on the Continent.

The benchmark European Union carbon price was up 0.03 euros at 7.55 euros a tonne on ICE Futures Europe. (Reporting by Nerijus Adomaitis; editing by Jason Neely)