http://recode.net/2015/04/27/twitter-is-testing-a-new-look-for-search/:

The new design moves a lot of the filter options from the left-hand side and consolidates them as tabs on the top of the page. That bumps up the trends section, leaving more room for the new summaries that accompany them. You can see what the current version looks like below.

I’ve been receiving this new search UI on one of my accounts, and I agree that it’s a much cleaner, usable UI for search.