The miner is also expecting approval for its Vickery project by the end of 2019.
"The issues which hampered production in the March 2019 quarter, namely ‘weighting events' at the Narrabri longwall and coal seam quality at Maules Creek, were largely resolved by mid-April," Bell Potter said.
"However, the Narrabri longwall then transitioned through a fault during the June 2019 quarter, which is typically a risk to volumes.
"The September 2019 quarter should be a strong one, with the next major disruption a longwall change-out scheduled for November-December 2019."
According to Bell Potter, from FY20, Whitehaven expects to start in-pit dumping of waste at Maules Creek, substantially reducing haulage distances and therefore unit costs.
"In FY20, around 20% of waste is expected to be in-pit dumped, growing to 100% over a five year period," it said.
According to Bell Potter the Vickery project will have a 12-18 production ramp-up, with material volumes from this project not expected to be produced until FY21.