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Fubar512

Anyone care to guess

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Anyone care to guess what caused the return at the 8 o'clock position on this commercial marine radar display?  

It's on a 12-mile range setting, so each ring represents 3 miles across.  That places the target 4.5-5 nm out from the vessel carrying the radar.  

Now, I know what it is, from its track (relative to the antenna's sweep period), and by having encountered such targets before.

 

SUkHM7I.jpg

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No guesses here. I thought I was looking at a weather radar for a second :/. But you do have me interested.

 

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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 sweep interval) requires a bit of headway.  Hint: It's not another vessel.

 

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If that's rain, then that really thick mass seems like a bow echo.

My guess is that it's a waterspout.

 

Waterspout-in-Tampa-Bay-580x773.jpg

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An airliner from the size of the return.  Too bad it wasn't a video, as opposed to a still, then you'd appreciate how fast the return traverses the display.

 

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1 hour ago, Skyviper said:

Well. That makes sense.

So how high or low was it?

To figure that out, one must know the height of the radar, how its mounted (savvy installers place a wedge under the mounting flange to compensate for a boat's running angle), and the vertical beam width (large span open array radar antennas usually have a narrower beam width, than smaller, enclosed dome antennas).

One boat that I used to run had a 72-mile radar mounted on it's bridge top.  The antenna was about 20 feet above the waterline.  On its 12-mile range setting, I used to see smaller, private aircraft departing from a local airport about 6-7 nautical miles away, and at the 36-mile range setting, military transports climbing out of  joint base McGuire -Dix-Lakehurst (once they cleared the ground clutter).

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and here I was going to say "the Hindenburg"....

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