According to Wikipedia, the Japanese tsunami was caused by an Earthquake who's "surface energy" (which I imagine is what's relevant for tsunamis) was about 2 orders of magnitude more than the expected 2 megaton impact of this asteroid, so it probably wouldn't lead to a huge tsunami.
Additionally there'd be a much more obvious and earlier warning than for a "conventional" tsunami, allowing more people to reach safety in time.
http://neo.jpl.nasa.gov/risk/2012da14.html
http://rt.com/news/paint-asteroid-earth-nasa-767/
Seems like a good opportunity to bring up existential risks. And A friendly reminder that NASA is in fact pretty damned important.
Thoughts?