Jamie Dimon warned against predicting what's next for the economy. AP Photo JPMorgan's Jamie Dimon said central banks' outlook from 18 months ago was "100% dead wrong." He cautioned against making definitive economic forecasts, and said to prepare for a range of outcomes. Dimon is doubtful that central banks and governments can manage the coming turmoil. Jamie Dimon, the billionaire chief executive of JPMorgan Chase and one of Wall Street's most-watched commentators, said forecasters have missed the mark on their economic outlooks, and there's still reason for caution moving forward. In a panel at the Future Investment Initiative Summit in Riyadh, Saudi Arabia, the banker called out governments and central banks, and said some more humility should be in order. "Prepare for possibilities and probabilities, not calling one course of action, since I've never seen anyone call it," Dimon said, per multiple media reports. "I want...