I bet the site calculates TH/s available based on how quickly the blocks are discovered vs the difficulty level.  I think the pools/miners just got lucky and found a few blocks in a much shorter period of time than was expected for the new difficulty level, and since that's the only statistics available for the website to calculate TH/s on, it calculated them quite high.

Wait an hour or four, then you should get more accurate numbers of current network strength.