* Gas follows down oil, coal, power markets
* Spot gas market moves sideways
LONDON, Sept 26 (Reuters) - British natural gas prices for delivery in the upcoming winter season dropped to their lowest level since the beginning of August on Wednesday morning, reacting to bearish sentiment that has already gripped power and coal markets.
The NBP winter 2012/2013 gas was trading at 63.75 pence per therm at 0800 GMT on Wednesday morning, the lowest level since the beginning of August.
Traders said the slump was a result of weakness that has already befallen other key energy products such as coal and power. Front-month Brent crude prices dropped below $110 per barrel on Tuesday morning, trading around $109.65 at 0830 GMT, as economic concerns pull prices down.
"We're seeing rising resistance against further state cuts in southern Europe, and the big economies like the U.S., China, Japan and Germany are also not looking very good ahead of this winter, so energy prices are giving in," one energy trader said.
In coal markets, the API2 2013 futures contract fell below $100 per tonne in September.
Currently trading around $97, the contract has dropped almost 30 percent in value since the product's current downtrend began in summer 2011.
In power markets, the mood is also bearish.
Wholesale electricity or baseload (24 hours) supply in the first quarter of 2013 have dropped below 49.50 pounds per megawatt-hour (MWh) for the first time since early August.
And in Germany, the benchmark 2013 baseload power contract is currently trading around 47.50 euros per MWh, down 5.5 percent since mid-August and close to a two-year low.
On the front-end of the gas price curve, prices moved broadly sideways as lower Norwegian gas flows were balanced by higher British production and imports from continental Europe, analysts said.
"Our latest model forecasts consumption to be higher and Langeled flows (from Norway) have dropped and may remain at the current level. These are bullish factors for the NBP day-ahead contract," analysts at Thomson Reuters Point Carbon said.
"On the bearish side, UK flows have increased and IUK (pipeline) is nominated to import gas from Belgium to the UK today."
Gas demand in Britain was expected to be 172.5 million cubic metres (mcm) on Wednesday, over 30 percent below the seasonal norm, according to data from National Grid.
With flows seen at 169.2 mcm, the system would be slightly undersupplied, implying the need for higher imports or storage withdrawals.
Gas storage sites in Britain are filled to an average of around 92.6 percent, according to data from Gas Infrastructure Europe, down from almost 98 percent in August. (Reporting by Henning Gloystein; Editing by Catherine Evans)