I am reluctant to write something about this because the chatter in the SEO community is all over the place. It seems like many are saying that Google is testing the new Penguin 4.0 update in the wild. Some are saying they see rankings for Penguin impacted sites jump up and down over the course of the same day.
It is possible that Google might be testing Penguin 4.0 on some users but I am not sure if that is how this algorithm release can work. I suspect it can, but again, it is hard to tell.
The Black Hat Forums thread on page 14 started to spike up again with people saying their sites were going up and down over the course of 24 hours. There is also some chatter about this in the ongoing WebmasterWorld thread.
The tools are hit or miss, it depends on when they run and if they hit the Google Penguin test (if there is a test). For example, Mozcast has been on fire all week:
But some of the other tools are steadily high or just all over the place.
Here are some quotes from the threads:
Right now it's just dancing around bit, but in all likelihood these small patch updates are warning sings of an impending penguin 4.0
It is my opinion that Google is probably testing a filter on those weird days, and some people are winners and other are loosers. Since our company is expecting a Penguin recovery (due to recent NSEO disavowels), and since Penguin is imminent, and since we have good days when others report bad days, this behavior is most likely Penguin testing. About a year ago, Google said Penguin was coming soon. That's about the time "Zombies" started getting reported.
I am seeing many tweets from folks and I have tons and tons of emails from people asking me what is up.
@rustybrick lot's of serp changes that we're seeing. Tons of bouncing all over the place.— Online Advantages (@OnlineAdMatt) September 22, 2016
Again, it is too early to tell but it wouldn't surprise me if Google is testing a Penguin refresh.
Update: As the day goes on, it seems more and more like Google is indeed testing the new Penguin update. No confirmation from Google on this.
Update #2: Friday at 8am ET, Google confirmed the roll out of Google Penguin 4.0, the real time version.