Coal inventories at China's Qinhuangdao port have ballooned to a three-year peak of 7.1 million tonnes due to prolonged vessel traffic restrictions amid extreme weather, Sxcoal's latest data showed.

Coal shipments via railways to the port in northern Hebei province have remained at full capacity in recent days despite heavy snowfall. But strong winds have led to a shipping ban around the Bohai Sea that has subdued coal deliveries out of the port.

Qinhuangdao port has been subject to transportation control since 8:50 p.m. on December 8 due to gales. The sailing suspension has now stretched into a third day, severely limiting vessel turnover at the port.

As a result, daily outbound shipments slumped to 92,000 tonnes on December 10 before falling further to zero a day later, automatically pushing inventories higher to the 7.1-million-tonne peak, according to Sxcoal's data.

Stockpiles have surged by around 1 million tonnes over the past two days alone as outbound volumes plunged while inbound deliveries into the port remained normal. On December 11, coal railings to the port rose from 532,000 tonnes a day ago to 550,000 tonnes, the highest daily volume since December 1.

Traders were closely watching for any signs of when normal operations can resume at Qinhuangdao, which plays a pivotal role in China's coal trade and the security of energy supplies during the key winter period.

The spot market saw a clear rise in offer prices at northern ports, although tradable prices remained conservative. The benchmark 5,500 Kcal/kg NAR coal can be traded at 940-950 yuan/t FOB with VAT at northern ports, while offer prices were around 955-960 yuan/t.