One explanation I have seen for the $US strength is cheap money is being pulled out of the Emerging markets and it is heading back home.
As for the strong $A, it is possible that some people are having an each-way bet on safety. The Yen and Euro are both heading south ... only guessing but maybe there is a trade out there ... short the Yen/Euro and buy the $US and the $A is getting some of the leftovers. [I don't understand FX trading.... just my guesses]
