There are numerous indications with the SERP trackers that an update to the Google Panda algorithm was rolled out this week, starting around the 28th August and continuing throughout the first week of September.
User "mentat" on Webmasterworld suggested that it may be a slight reversal of the previous Panda Update that rolled out at the beginning of August, saying "Well, for me seems that this week marked a Panda reverse [...] but the miracle lasted only two weeks."
Other users in that forum thread seem to agree, and this thread at Blackhatworld appears to be noticing the same thing.
Maria Haynes, Google Penalty Recovery and Algorithm Consultant, has indicated that it may be related to Google Panda (i.e. content quality), although the signals do not seem to be overly clear at present:
I am possibly seeing some Panda related movement, but it's only affecting a couple of sites so far.— Marie Haynes (@Marie_Haynes) September 1, 2015
...but TBH the changes are so subtle I'm reluctant to call it Panda for sure. Will keep a close eye on things the next couple of days.— Marie Haynes (@Marie_Haynes) September 1, 2015
Glenn Gabe at G-Squared Interactive, a well-regarded SEO agency also noticed a potential reversal of some Google Panda recoveries:
Barry Schwartz at Seroundtable, a website previously hit by Google Panda, seems to indicate that all his gains since Panda 4.2 have been lost. He posted a Google Analytics chart in this post that seems to confirm this:
Google Panda Update subject to Extended Rollout?
Previously, Google has indicated that Google Panda rollout may take months due to "technical reasons". It is possible that all we are seeing is Google Panda still rolling out from last month. Glenn Gabe seems to agree:
Pedro Dias, an ex-member of the Google search quality \ webspam team appears to indicate this is more likely another stage of the Google Panda Update as it rolls out in controlled stages:
@rustybrick I don't believe it's a reversal. More likely a stage as it all rolls in controlled stages— Pedro Dias (@pedrodias) September 1, 2015
With no word directly from Google, we think this is the most logical explanation at present.
How big is the movement?
While there is some forum chatter, it is not that much compared to previous updates. A look at the SERP trackers indicates that the update has been rolling out over some time with spikes on the 28th August and 1st September:
The Rank Ranger Risk Index shows a peak on the 28th August and 1st September, as well as a fair amount of movement over the entire of the last week or so.
MozCast shows a spike on the 31st August, but also several spikes over the previous weeks.
The insight from ex-Google employee Pedro that Google Panda could (it is speculation on his part) roll out in managed stages is kind of interesting. Couple that with the fact it took ten months for Google 4.2 to arrive after the previous update, along with indications that there are technical reasons for a slower roll out, we suspect that there may be more SERP movement to come as they seek to refine what must be a very sophisticated update.
Our advice to webmasters is that we suggest you continue to review and improve the quality of your website to ensure that not only that you improve your Panda Score, but also avoid any future declines in the SERPs as Google continues to find more signals that indicate high-quality content and tweak their algorithm accordingly.