UK GAS-Prices slide after spike driven by short-covering

LONDON, July 10 (Reuters) - British wholesale gas prices fell on Wednesday, retracing gains of the previous session which had been driven by short covering, despite an undersupplied system as outages in Norway continue.

* The within-day contract fell 0.3 pence to 31.70 pence per therm by 0810 GMT.

* Day-ahead gas prices were 0.15 pence lower at 31.25 pence per therm.

* Both contracts had spiked over 5% on Tuesday morning and early afternoon but began falling towards the end of the day.

* "The short-covering was over. There was no reason prices were up," said one gas trader. "We're not all done yet, we should come off some more."

* Flows to Britain along the Langeled pipeline were 14 mcm lower as a number of outages continued there including on the Nyhamma, Troll and Karsto fields.

* However, Norwegian operator GASSCO said over the weekend the impact from the Nyhamma outage, which will last through August, would be half of the initial estimate.

* That revived concerns that storage tanks would get too full, too quickly during a season of low demand.

* "As long as it looks (like) tank tops, I think people will want to be invested short," said another gas market player.

* Gas send-out from liquefied natural gas (LNG) terminals is lower on Wednesday, at 16 mcm compared to 23 the previous day.

* But an additional tanker declared for Britain, with three tankers now expected in the next two weeks.

* Peak wind generation is expected to be low at 1.7 gigawatts (GW) on Wednesday out of 12 GW of metered capacity, Elexon data showed.

* Low wind generation can increase demand for gas used in power generation. Gas for power demand is seen 5 mcm higher on Thursday at 72 mcm.

* The system was undersupplied by 10 million cubic metres (mcm) with demand forecast at 162.8 mcm and supplies seen at 152.8 mcm.

* Further along the curve, the August contract was up 0.55 pence at 30.50 p/therm

* The September price fell 1.59 pence to 33.10 p/therm, narrowing the spread between the two months.

* In the Dutch gas market, the day-ahead gas price at the TTF hub fell 0.12 euro to 11.43 euros per megawatt hour.

* The benchmark Dec-19 EU carbon contracts was 0.17 euro higher at 26.73 euros a tonne. (Reporting by Sabina Zawadzki Editing by Edmund Blair)