Brazil produces 33% of the worlds coffee . There is a strong relationship between the price of coffee and the value of the Brazilian Real. Future changes in Brazilian monetary policy might have an effect on coffee prices.
I still believe a correlation exists, but I think the recent price movement is a result of the drought in Brazil, which has also had the same effect on sugar. Seeing how the price movement isn't very gradual I would be expecting some type of convergence or correction... but probably after the drought.