GOT IT,

OK. Would you believe "50% in the next 100"??  And a "low" probability in the next 20.  What's low?  I don't know.  If its 1 out of 2 in the next 100, couldn't it easily be 1 in 4 in the next 20?  Sounds high to me in any case, especially if  you consider the Gulf of Mexico just experienced a supposedly 500 year wave height.  And, the a typical model of storm frequency of return, it does not say that it CAN'T happen in ANY particular year.

http://www.bbc.co.uk/science/horizon/2003/bigchilltrans.shtml

If these things follow a line plot of Probability on the log of Time, it is 25% chance in the next 10 years.