I would have loved to write a good analysis of how El Nino will affect the global agricultural system. Luckily (for me), such analyses has already been conducted. What is remaining is for countries, especially those that are going to be directly affected, to work out plans on how they will respond to this calamity.
In my country Malawi, for example, I do no see any serious deliberate actions from the government, households as well the firms in preparations for effects of El Nino despite early warnings of severe famine from the same. I pray that other countries have plans on how they will deal with these climatic event.
I have the following two links that excellently analyze the impacts which El Nino will have on agricultural systems. The first link captures the impacts at a global level whereas the second link leads to a set of videos by FEWSNET that succinctly explain the impact which El Nino will have on Sub Saharan Africa.
I promise to keep informing you on any developments that result from El Nino in Sub Saharan Africa.