Nomura analyst Masanari Takada earlier this month warned of a “Lehman-like” plunge in the stock market. On Monday, he gave some urgency to that warning.

“ ‘The U.S. stock market especially is facing its greatest test of the year.’ ”

Bearish sentiment currently correlates well with sentiment before the collapse of investment bank Lehman Brothers in 2008, Takada argues. So investors should prepare for carnage in the stock market due to “panic-selling by fundamentals-oriented investors and systematic selling by trend-following technical investors.”