The final move is often a volatile event without the strength and conviction of previous surges. Tools can be written to evaluate the nature of these surges and objectively quantify the strength of the price moves. This is frequently done by using an oscillator like RSI or Stochastics in conjunction with the price. However, price of one commodity can also be compared with another price if they are expected to be correlated. The tool used to discover market weakness is called divergence.
Divergence usually requires price to be moving into a strongly overbought or oversold region.
We then look to see when the price previously displayed similar strong movement. Ordinarily we require the price to move to an even more extreme level than the previous peak. Then we look at the oscillator peaks. If the oscillator fails to follow prices to new extremes we say the price diverges from the oscillator. Nothing works every time and the same can be said about divergence.