The broker raised its benchmark forecast almost two weeks ago and Newcastle spot prices have since eclipsed the $US100/t mark.

The higher demand for Australian thermal coal comes as heavy rain has slowed output from Indonesia and Colombia while Chinese domestic prices have surged.

But the big surprise was South Africa’s record export shipments of 1.12 million tonnes to China in September.

“Data just released for October shows that Richards Bay had a record month in October with exports surging to 7.38 million tonnes,” Goldman said in a commodity update report.

“It will be interesting to see how much of this shows up in China over the next couple of months – we suspect quite a lot.”

In September, only 45% of China’s thermal coal imports came from Indonesia, down from an average of more than 60% for the previous months of 2010.

Higher prices in China will help support Australian thermal coal exports as well.

Goldman took note of a base price of about $US122/t for high-grade Shanxi coal of around 6000 kilocalories per kilogram (net as received).

“If we assume spot freight from Australia to China at $18 per tonne, this nets back to a free-on-board Newcastle price of about $104 per tonne, which gives us some confidence that current spot prices are sustainable,” the broker noted.

“As ever, the key things to watch are Chinese domestic coal prices heading into the winter and the true extent of rain-related constraints on Indonesia exports.”

Goldman expects total Chinese imports of thermal coal to exceed its earlier forecast of 85Mt and will soon revise this estimate.

Japan remains the dominant importer of Australian thermal coal with annual benchmarks set according to the Japanese financial year, which starts in April.

Signalling the strength of the resurgent seaborne thermal coal market since the global financial crisis, back in March 2009 thermal coal benchmarks struck with Japanese power companies were in the range of $70-72/t.