* Fortescue plans 55 million-tonnes-per-yr iron ore run rate
* Says takes into account threat of wet weather over current quarter
* Iron ore average sale price $122/dmt in Dec qtr
* Market readies for solid iron ore output figures from bigger rivals Rio, BHP
SYDNEY, Jan 17 (Reuters) - Fortescue Metals Group December-quarter iron ore shipments rose 19 percent from the previous quarter to 14.8 million tonnes as it continued to expand in Australia, beating its own guidance, the company said on Tuesday.
Fortescue also said it plans to maintain a 55-million-tonnes-per-year run rate over the current quarter, noting that the period covers the traditional northern Australian wet season when cyclonic conditions can disrupt production.
The company had previously provided December quarter guidance of 13.5-14 million tonnes.
The total shipment figure includes ore transported by Fortescue from other mining companies operating in Australia's Pilbara iron ore belt.
A four-day shut down of Indian Ocean port operations at the end of January for maintenance would also affect production schedules, Fortescue said.
Fortescue, Australia's third-biggest iron ore miner after Rio Tinto and BHP Billiton , also said it sold its iron ore at an average CFR price of $122 per dry metric tonne between Oct. 1 and Dec. 31. Total costs per tonne of ore over the period averaged $46.43, the company said.
The company forecast a "reasonable" price range for ore of between $135-$145 per dmt in the current quarter.
It said index-linked ore prices had been relatively stable recently, with the average for the month of December being $138 per dmt.
Fortescue shares were up 2.8 percent to A$4.75 at 0118 GMT, outpacing a 1 percent gain in the broader market
Rio Tinto and BHP Billiton are also set to report solid iron ore output growth in the December quarter as they continue to expand mining in Australia, betting any loss in China's appetite for the steelmaking material is only temporary.
Rio's production figures are due later on Tuesday and BHP is scheduled to report on Wednesday.