a) February is the "weak link" in the "Best Six Month" theory because it is one of the weaker months of the year;
b) we are dealing with several unfavorable trends: a stronger yen, up over 3 percent in January, with the Nikkei is down 10.3 percent for the year; and emerging markets are in tatters, particularly the major indexes in the BRICs (Brazil, Russia, India, China): Russia is down 9.8 percent, Brazil has fallen 8.2 percent, China's Shanghai has shed 4 percent, while India is down 3.1 percent.
The yen strength is particularly troubling, because many economic model are based on the yen weakening for the year.
There is some hope emerging markets may stabilize in February. Thailand, for example, just held relatively uneventful elections, the stock market rallied 1.5 percent there.