The intersection is controlled by give way signs.
The motorbike collided with the Nissan Sentra car in the middle of the passenger's side, causing the side of the car to be pushed in.
Mr Hawthorn described it as a "big impact".
The driver and sole occupant of the car was not injured. It's believed he was a Waipu local.
Northland's rescue helicopter landed in a nearby paddock and flew the injured man to Whangarei Hospital. After an initial survey of the crash scene Mr Hawthorn said skid marks indicated the motorcyclist had applied the brakes, locking the bike up prior to impact.
He said investigations were continuing and it was likely charges would be laid.
Northland's road toll is now 14 - double the region's record low of seven fatalities in 2011.