On these days where there are no relevant economic reports in the early morning hours, and especially when that has been the case for 2 days in a row, we tend to notice an increased level of activity around the various "opening bells."  

There is no bell at the CME at 7:20am Chicago time (8:20am ET), but there might as well be.  That's the unofficial start of the day for a majority bond traders, and the official start of the day for Treasury options pit trading.  Between the the two, themes often emerge.

Today is one such day, where the 8:20am CME open has served as a starting pistol for selling pressure.  Granted, all this is happening in a micro-range, considering 10yr yields are only up 1.3bps at the moment, but the 8:20-8:35am move did seem abrupt in context--especially because there was no obvious catalyst other than the clock.