To view this update, after logging into your Google webmaster tools panel, navigate to "Search Traffic" > "Search Queries", on the graph displaying impressions and clicks ratio in blue and red lines you can now see a vertical line dissecting that contains the word "Update", when I hovered it, it said:
"An improvement to our top search queries data was applied retroactively on 12/30/13"
Here is the image:
Since the word is out, it seems like Google will let the webmaster know about the specific dates a new update from Google has been implemented and the the exact date on which the search query data was applied.
It seems to be like a good initiative because previously the webmasters seemed to be rather confused about not knowing when exactly the Google update was implemented but now they can clearly know about the statistics of their sites before and after the update is released and know if the update brought positive results or negative results in terms of traffic on their site.
If you are a webmaster, check your webmaster tools now to inspect weather your site got jumped up or down after the update.