The fed can rock the markets. They know this and act accordingly. Which includes rocking them when needed. They rarely act between meetings and without notice but when they want the markets to get the message, the move in-between meetings. They did this when the markets were dropping after the dot com bubble. They wanted the markets to recognize that they were lowering interest rates and were not unaware of the situation so they cut between meetings and the market jumped but only short term. It still continued to descend over the next months but slower and much more controlled.