IT sounded like a freight train and lasted only 20 seconds, but left a trail of devastation in its wake.

Fifteen people were injured when a mini-tornado struck a packed Hornsby Westfield, tearing the roof off a cinema but Fire and Rescue NSW says the toll could have been much worse.

RELATED NEWS: Stores closed, clean up continuing in Hornsby following mini tornado

Luckily, the cinema was between sessions and empty, but elsewhere glass shards rained down on shoppers as the winds shattered glass doors and windows.

A 50-year-old woman suffered lacerations to her face and neck when a shard of glass fell from above. She was transported to Hornsby Hospital in a serious condition, along with fourteen others with minor injuries.

"Apparently a number of the injuries were from the glass, which blew outwards," the spokesman said for Ambulance NSW said.

media_camera A demountable building flipped at Hornsby Station with two Sydney Trains employees inside.

Six Sydney Trains employees were working inside a demountable at Hornsby Station shortly before 3pm when their building was uprooted and tossed on its side.

One member of staff is recovering in Hornsby Hospital with suspected broken ribs, while five others suffered cuts and bruises, a Sydney Trains spokesman said.

"As far as I know, they got out pretty quickly and without too much hassle," the spokesman said.

He said the temporary structure was used for holding train crew before their shift started.

Station guard Ben Shilton, 26, of Lake Haven, was near the demountable when it flipped.

"It came across from Westfield and I could see the shrapnel and corrugated iron flying towards us," said he said. "All the powerlines were sparking up.

"I was at the other end of the carpark and the wind was so strong it pushed a car on its side. The demountable has moorings and it just ripped right off and started wobbling.

"By the time I got over there the blokes in there were already out, a bit sore but they were OK."

"You can see the path of destruction here - about a 15-metre swathe of destruction - and across the other side (of the tracks) as well."

media_camera Roof panels at Hornsby Westfield were dislodged in the wind. Picture: Supplied

The roof of Hornsby's Cinema 3 collapsed during the storm and a search and rescue operation took place before being cleared shortly after 4.30pm.

A NSW Fire and Rescue spokesman said firefighters used handsaws to cut through the debris to see if anybody was trapped.

A glass dome in the shopping centre's roof also cracked, forcing centre management to evacuate.

A spokeswoman for the Westfield Group said the centre was forced to use emergency power.

Hornsby resident Ben Davison was driving on Burdett St when debris began flying around him.

"All of a sudden this wild wind came out of nowhere. A big piece of metal from a roof struck my car," he said.

"Then a large branch came down on top of the car in front of me. The car to the right of me had its back windscreen smashed by another fallen branch. I'm pretty shook up by it all but thankfully no one was injured."

A 25-year-old graphic design student returned to her car to find it was crushed by a fallen tree in Jersey St.

"It's not as bad as the worst of them but I won't be able to drive away," Jessica said. "I'm waiting for someone to pick me up, I guess I'll just have to come back tomorrow.

"I was in class and we just heard this sound like an aeroplane."

media_camera A large tree crushed a car after a mini tornado hit Hornsby

Cindy Cusack, another graphic design student, from Newport, said: "It was basically a tornado.

"There was this huge crack of either a tree or lightning I'm not sure, but we all got away from the windows and then came out. Being graphic design students everyone was worried about their works."

Penelope Bright said the damage was unbelievable and her mum was lucky to escape without injury.

"Just spoke to my mum who is in Westfield Hornsby right now," she said via Facebook.

"They've been evacuated, there's glass everywhere and it looks like a bomb has gone off."

Within 20 minutes of the storm hitting, Westfield had been evacuated, the Pacific Hwy had been closed in both directions and trains on the Northern, North Shore and Newcastle lines were closed.

Hornsby Inn suffered major damage to its roof and Hornsby Library has been closed until further notice.

media_camera Paramedics tend to an injured person in Hornsby. Picture: Supplied

Hornsby state Liberal MP Matt Kean saw the storm land from his office window. He said it sounded like "a freight train".

"It was like a cyclone. It ripped the roof off the building opposite the library. There's stuff everywhere," Mr Kean said.

Berowra fire station officer Wayne Stevens, who was standing on the Pacific Highway amid the fallen trees, said: "To the best of our knowledge we've had a mini cyclone."

Hornsby Council media spokesman Nick Cook was outside when the wind hit.

"I went outside to have a smoke and I had just lit a cigarette and heard this terrifying sound. It came from the railway station and initially I thought a train had derailed. I looked up and there were pieces of corrugated iron flying through the air. I just thought 'woah'.

"I dropped my full cigarette and just ran back inside. I tried to pull the door shut and couldn't because of the wind. As I was running something landed just behind my leg, which I thought was just wet cardboard or something. When I went back out it was a whole piece of wall, I thought 'woah, that could have killed me'."

media_camera Damage from the mini tornado in Hornsby. Picture: Supplied

Did you see what happened? Tell us your experience by commenting below

Hornsby police Supt Jeff Philippi said the corridor of damage extended from Alexandria Pde and Romsey St in Waitara through Westfield Hornsby to Bridge Rd.

"From our information this is the only area that suffered any significant damage," he said.

The Pacific Hwy was closed in both directions at Hornsby and trains on the Northern, North Shore and Newcastle lines were also closed temporarily.

Penelope Bright said: "Just spoke to mum who is in Hornsby Westfield. They've been evacuated and there's glass everywhere. It looks like a bomb went off".

media_camera Look closely at this image and you'll see one car which doesn't belong... on its side. Picture: Supplied

Jenny Creek said: "I am in Orara st - ground floor of a high rise and I never hear the wind or rain (partly because of hearing loss as well) and I was shocked when my windows all rattled and the trees were blowing horizontal - it was def a tornado as it went through ......"

The owners of Hornsby's Odeon Theatre said on Facebook: "I just watched a hurricane funnel land on top of Westfield Hornsby! it was so noisy, it was funnel shaped and started throwing roof panels every direction. It came towards the Odeon and the turned up the railway line towards Asquith. Scary. Hope all are well".

Becca Anne wrote on the Hornsby Advocate's Facebook page: "My mum was in the middle of it! Thankfully she was sitting in her car but tree branches fell all around her, a woman had to cling to pole and a man was knocked unconscious! Absolutely terrifying!"

Elise Toyer from Spendless Shoes in Westfield said: "I didn't see much but heard it. It sounded like a really bad thunderstorm, like hail. Then everyone was staring up (at the Centre roof) and it was raining clumps of lint out of the roof. Luckily no one seemed to get hurt. There were some ladies sitting (below the damaged roof) and they got a bit of a scare I think."

media_camera Not even charity clothing bins were spared the force of the wind.

media_camera Roofing was torn from a number of buildings during Hornsby's mini tornado. Picture: Supplied

Lyn Johnstone, of Epping, who works for Hornsby Council said: "We had just been laughing at the rain and how bad it was when there was this huge sound and we thought 'oh now there's thunder'. But then we thought oh, hang on, was that thunder? It seemed to come from the station, so I looked outside (towards Jersey St) and just saw the trees literally being shredded, they were being shredded by the wind."

media_camera Work crews move to remove trees brough down by the wind.

Just Jeans' Jess Margerum said it all happened in a few seconds.

"I just heard this gust of wind and I thought what the hell is this"

"Seems like a huge burst of wind came through the entry doors forming a wind tunnel and went up to the ceiling pushing the glass panels out."

Originally published as Mini tornado hits, 15 people hurt