Google says a Panda refresh began this weekend, but will take months to fully roll out.
The last time we had an official Panda refresh was almost 10 months ago: Panda 4.1 happened on September 25, 2014. That was the 28th update, but I would coin this the 29th or 30th update, since we saw small fluctuations in October 2014.
The rollout means anyone who was penalized by Panda in the last update has a chance to emerge if they made the right changes. So if you were hit by Panda, you unfortunately won’t notice the full impact immediately but you should see changes in your organic rankings gradually over time.