No stone will be “left unturned” by search and rescue teams hellbent on finding missing 18-year-old hiker Lily Hooper six days after she was reported missing, rescuers have vowed.

Ms Hooper left her home about 8am last Wednesday on a hike in Nattai National Park, but did not returned.

Search and rescue teams are now narrowing their scope to locate the missing hiker in a “much smaller area” in the Bonnum Pic trail area in Sydney’s southwest.

“Lily is an experienced bushwalker, we are relying on her experience to get her through this ordeal and we are still hoping that she will be found alive and safe,” chief inspector Brendan Bernie said.

“This is an ongoing search and rescue operation, we will be here as long as it takes.”

“She’s an 18-year-old, she’s very fit and she’s an experienced bushwalker and we’re hoping that holds her in good stead.”

SES teams searching through “incredibly arduous” terrain have said “there’s no stone being left unturned”.

The update follows Ms Hooper’s father emotionally phoning breakfast radio to plead for public support.

While 2SM Breakfast Host Tim Webster was fielding calls on Monday morning, a man who identified himself as the father of missing hiker Lily Hooper said he had decided to “bite the bullet” and speak publicly about the search.

Audibly choking back tears, Ms Hooper’s father said he was “very upset” and he wanted people to “cross their fingers” as the search for the missing teen entered its fourth day.

“We’re going to find her today. I’m going back to her now, I’m just putting my boots on, and I just want everyone to throw love and energy because we’ve gotta go and find her,” he said.

“We’ve got to find this kid. She’s got to be in there somewhere.”

Ms Hooper’s father has searched for his missing daughter but until now has refrained from directly addressing the media.

“I’ve been very quiet, I don’t post anything on social media or anything like that and I thought … I’m just going to bite the bullet and ring up,” he said.

“I just want everyone out there to cross their fingers and hope we find her today because it’s been too long.”

“About 11pm, Lily’s car was found parked on Wanganderry Rd, near the start of the Bonnum Pic Walking Trail at High Range, and a command post was established,” police said.

“Initial inquiries indicate Lily reached the summit of Bonnum Pic about midmorning; however, there’s been no further contact since that time.”

“It’s quite dense with bushland and there’s a dense tree canopy which also hinders our aerial searching. However, we’re on the ground, there’s a good support from the local community and our volunteers are doing a fantastic job,” he said.

According to AllTrails, the Bonnum Pic track “requires significant self-reliance” due to post-bushfire regrowth, making parts of the trail overgrown and difficult to follow.

Police Rescue, NSW Ambulance, Fire and Rescue NSW, SES and members of Lily’s family have been working throughout the weekend to find her.

Volunteer rescue squads from as far north as Cessnock have also been mobilised to help in the search.

The search will continue on Monday.