Here are 3 blow-off tops and 1 failed attempt which all occurred in the last 7 months. Successful completions are marked in solid black. The failed attempt is shown in dotted black.
On all 4 attempts, the price accelerated upwards to different degrees. Each target can be roughly measured based on the price move.
Notice how the failed blow-off begins closer to a price bottom than the successful ones did.
Volume was either steadily increasing or declining during successful blow-offs, compared to the unsuccessful attempt when volume was not clearly trending.
ROC (momentum) was increasing with all 4 attempts. The blow-offs were successful when momentum was at 0 or positive at the start of each blow-off.
Disclaimer: This is my opinion. This is not advice. Trading involves risk.