I emailed the Port Hedland Met Office some time back about this issue and below is a portion of the reply.
I have had a lot of inquiries about this. And I am glad you looked at the sat pic as it is a radar issue.
Our radar is very sensitive and can pick up different sizes of airborne particles including sea haze, dust haze, smoke and precipitation.
You will find that when we have onshore winds (from west to north east) there may be false echoes on the radar image from the sea haze. We call this anomalous propagation.
Lately we have had reduced visibility all day due to the haze, misty mornings and ongoing fires.
The Bureau has tried to minimize these false echo's but are unable to eliminate them altogether without interfering with real echo's.