Bond Markets are seeing the sharpest reversal of morning weakness since--well, there's not a recent example that measures up. That's because most big moves in the morning are either products of economic data or significant headlines and in those cases, the movement follows the suggestion of the data.
In today's case, we have markets initially moving in the direction suggested by the data (weaker bond markets), but more than reversing that weakness for no apparent reason. Yes, we've seen/heard the excuse that Ukraine headlines are in play, but people who actually trade enough money to move markets saw these headlines more than half an hour before the move started! You might see a 30 second gap between news and movement from time to time, but never 30 minutes.
All we have at the moment is an aggressive morning sell-off in stocks and aggressive bond-buying in Europe (which still exerts some force on US Treasuries at this time of day). 10yr yields are back in line with yesterday's latest levels and MBS are 4 ticks into positive territory.