This is what we see on the radar when we see squalls. In this case the squall has passed us (and I got a little wet). The line up the screen is our course. The dotted line is the course to Pitcairn. The line angled bottom left is an Electronic Bearing Line - something we use to mark items on the radar. If the object moves down the line directly towards us, it's going to hit us. If it moves off the line, the it will miss us. We have to take into account our course changes but that's the basics of it.

We are fortunate that we have the power to run the radar all the time as its useful not just to see squalls, it shows other vessels and land too. It's the thing we watch most at night, even more so when we get into the atolls of the Tuamotus...