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.

This satellite image shows Cyclone Narelle forming off the north-west coast of WA. Map from: Higgins Storm Chasing Facebook page.

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.

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.