Hey it seems to be happening again right now. Similar time to yesterday.
EDIT: Its much worse today, lag spikes of up to 3 - 10 seconds or more long, with brief smooth pauses lasting 20 seconds in between. Someone or something is doing something at this time to cause this, I wonder what. Its quite suspicious actually.
EDIT2: I had to reconnect twice because of this lag. On the third time I decided to wait 30 seconds so it would appear I had left the server. After rejoining, the lag had stopped. I suggest you put effort into looking into this because it suggests somebody targeted the server while I was there.