Left the FT-817 running RX for several days now.
First time I've encountered this. Too bad I can't see the waterfall since I'm still in the office now and by the time I arrive at my apartment the waterfall would've scrolled past.
2015-05-14 09:04 VK4TVL 50.294534 -1 1 QH30jq +43 19.953 JI1KBF PM95tp 6158 3826
2015-05-14 09:04 VK4TVL 50.294582 -23 0 QH30jq +43 19.953 JI1KBF PM95tp 6158 3826
2015-05-14 09:04 VK4TVL 50.294488 -23 0 QH30jq +43 19.953 JI1KBF PM95tp 6158 3826
http://wsprnet.org/olddb?mode=html&band=all&limit=50&findcall=&findrepor...
A search of the forums suggests that this is a rare occurence.
With explanations ranging from AC hum (http://wsprnet.org/drupal/node/1033) to weird tropo propagation phenomena (http://wsprnet.org/drupal/node/488) or to possibly very strong signals.