There are definite cyclical patterns in commodities. I believe that MRCI is the best source for seasonal cyclical trading of commodities. Check their website for comprehensive discussions.
Yes! Some commodities have recurring seasonal patterns. "Particularly the grains softs." There is a really good book on seasonal trading & spread strategies with grains softs. Here is the link http://www.amazon.com/exec/obidos/tg...books&n=507846
I'm not sure about energy seasonals. Im sure there has to be a book out there covering energy seasonals.