This satellite image shows Cyclone Narelle forming off the north-west coast of WA. Map from: Higgins Storm Chasing Facebook page.
People in the Pilbara are preparing for dangerous weather conditions, as Cyclone Narelle bears down ominously on WA's north-west coast
The eye-catching photographs accompanying this story were captured by Brett Martin just before sunset on Wednesday afternoon, 25 nautical miles north-west of Onslow.
They depict a "tropical squall line" and a "gust front ahead of a storm line", with the red tinge resulting from dust picked up in the Pilbara on the way out to sea.
Picture taken 25 nautical miles NW off Onslow just before sunset on Wednesday. Photo: Brett Martin, courtesy perthweatherlive.com
Mr Martin, whose images were posted on www.perthweatherlive.com, reported conditions were glassy and flat before the storm hit but when the weather arrived, the swell lifted to two metres, winds increased to 40 knots and visibility was reduced to 100 metres.
According to Mr Martin, the storm was accompanied by an awesome lighting show.
Meanwhile a "blue alert" remains in place with regards to Cyclone Narelle for people in or near an area from Whim Creek to Mardie including Wickham, Roebourne, Point Sampson, Karratha and Dampier.
Conditions before storm hit were glassy and flat. The dust caught in the storm reduced visibility to 100 metres. Photo: Brett Martin, courtesy perthweatherlive.com
Narelle is a category three severe tropical cyclone which is likely to develop further as it moves on its south-south-west track towards the Northwest Cape.
Although there is no immediate danger people are asked to start preparing for dangerous weather.
Karratha tavern manager Becky Macneal said although the tavern was slightly busier than usual for a week day, people were still pretty calm at this stage.
Taken by mobile phone inside a boat 25 metres off Onslow, in WA's Pilbara. Photo: Brett Martin, courtesy perthweatherlive.com
"It's still pretty far away," she said.
She said some workers had come in to the bar after having already been sent back into town from offshore rigs.
"Mine sites are doing tie downs and making sure things are safe but there doesn't really seem to be much of an urgency right now."
"The town is still quiet from the Christmas break, so it's mostly just locals."
Ms Macneal said those who were new to town usually headed straight to the shops when there were cyclone warnings to stock up on food and water supplies.
"I went down to the shop yesterday and the shelves were a little bit emptier than usual," she said.
At 3pm on Thursday, Narelle was 740 kilometres north of Exmouth and 610 kilometres north-northwest of Karratha, moving south-southwest at 19 kilometres per hour.
It has continued moving south south-west overnight and is expected to slowly develop as it continues towards the Northwest Cape.
Gales with gusts of up to 100km/h are expected to develop in coastal areas between Whim Creek and Onslow including the Karratha area on Friday morning, then extend west to Exmouth and Coral Bay later Friday or early Saturday.
Winds are likely to increase further during Saturday about the west Pilbara coast.
Thunderstorm activity will increase about the Pilbara coast on Friday with isolated heavy falls possible, mainly in coastal parts.
The Department of Fire and Emergency Services is urging people to secure or remove loose material from around their homes, ensure emergency kits are complete and check everyone knows what to do.
Water over the road has been reported at various floodways along the North West Coastal Highway near Minilya Roadhouse.
Road users are advised to approach floodways with extreme caution and obey road closure signs and not to drive into water of unknown depth and current.
Resources companies are beginning to take precautions in preparation for the cyclone.