However, the company said it remained on track to achieve its group 2017 saleable production guidance of 21Mt to 22Mt.
Whitehaven last issued production guidance for Narrabri at the FY2016 results in August, when it estimated Narrabri would produce 9Mt of saleable coal for the 2016-17 financial year.
“The revised guidance arises from production impacts associated with safely managing a discrete area of adverse geotechnical conditions at the mine,” it said in a statement.
Mining in panel LW06 at Narrabri is expected to be completed in early March with production scheduled to start in LW07 panel, the first 400m wide panel, early in the June quarter.
“Notwithstanding this revision and production impacts caused by wet weather earlier in the year, Whitehaven remains on target to achieve its FY2017 saleable production guidance range,” the company said.
“Further, metallurgical coal sales in the December quarter were 22% of total sales compared to 16% in the September quarter.”
Sales of metallurgical coal in the second half of the year are forecast to grow to 26% of total group sales consistent with the target of achieving 35% of total group sales when Maules Creek reaches full capacity.
Whitehaven will release its December quarter production report next Monday.