Skyviper, you are correct in one respect. You are looking at a heavy rain storm approaching from the vessel's port side. I happen to know that this boat is tied up at its slip in a small marina.
Notice the diagonal line near the center of the display ? That's the land and docks in that marina, and in the surrounding area. The target at 8 o'clock traces back from a thin line and then gets "thicker" as it goes along. The antenna sweeps every 3-4 seconds. To make a line like that at that distance (given the seep interval) requires a bit of headway. Hint: It's not another vessel.
I'll try setting it up on X Padder, Maybe i need more time to adjust to the Layout of the buttons. I like having the Throttle but everything just feel weird to me somehow. May be i just got too used to the Logitech+GamingMouse set up.