The eye-catching pictures accompanying this report were captured by photographer Brett Martin just before sunset on Wednesday afternoon, 25 nautical miles north-west of Onslow.

Martin, whose images were first posted on perthweatherlive.com, reported conditions were glassy and flat before the storm hit, but when the wild weather arrived, the swell lifted to two metres, winds increased to 40 knots and visibility was reduced to 100 metres.

Then, he said, came the most awesome light show.

A ''blue alert'' remained in place for people in or near an area from Whim Creek to Mardie, including Wickham, Roebourne, Point Sampson, Karratha and Dampier.

Narelle is a category 3 severe tropical cyclone which is likely to develop further as it moves on its south-south-west track towards the Northwest Cape. Although there was no immediate risk, people in the area were asked to start preparing for dangerous weather.

Karratha tavern manager Becky Macneal said said some workers had come to the bar after being 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.''

Narelle was about 760 kilometres north of Karratha overnight and expected to arrive in the town on Friday or early Saturday.

WA TODAY