The teller complied and the robber left the bank with an undisclosed sum of money.
Initial reports that the man had fled the scene on a bicycle were incorrect, said Mr Ralph. It was not clear if the man actually had a weapon or if he was driving the Subaru.
Mr Ralph said the offender was described as Maori and aged in his mid-20s.
He had a thin build and was about 1.8m tall.
CCTV footage from the bank showed the man with his face covered, wearing shorts and clutching the wine cooler bag as he fled the bank.
No one was injured during the robbery.
When approached for comment, an ASB Bank spokeswoman sent a statement to the Herald that said: "Our only comment at this stage is that all staff are unharmed and the matter is being investigated by the police."
Anyone with information about the robbery can phone Detective James Ralph on 09 261 1300, or leave an anonymous tip via Crimestoppers on 0800 555 111.