There is a ~0.15 % chance that a block will take longer than one hour.

Proof: Taking the total hash rate you provided above and the probability to find a block with just one hash, gives a probability of approximately 0.18 % to find a block in one second.
http://i.imgur.com/3K7jjlp.png
http://i.imgur.com/pT38wqA.png

Consequently the probability to find a block in the n-th second is:
http://i.imgur.com/3eDl8Hc.gif

(Side-Note: Given the above formula, one can expect a block every 551 seconds:)
http://i.imgur.com/2gepSo0.gif

The said probability that a block will take longer than one hour (3600 seconds) is:
http://i.imgur.com/gjYfi0H.gif