Something at an unknown distance along the azimuth of the "spoke" on the screen is pushing out RF energy and your weather radar is displaying it, now it might just be another weather radar though as I understand the designers have methods of reducing the chances of that happening, otherwise you'd see them all the time.......OTOH your captain could be correct, it could indeed be something higher powered such as a fighter's radar (they do have them, but not a weather radar, it is used for interception and other purposes) a ground based radar, perhaps military, or perhaps it is the result of a jamming exercise, again for the military.
For some of us who had a another line of work before our civvie flying days those spokes bring back memories (and cold sweats) of time of groping around in the clag and darkness in an attempt to trying to find whatever it was that was producing the phenomenon.
Last edited by wiggy; 31st May 2017 at 14:16.