They can, but it's best to wait for them to form on the 1 hour - if you're trading the 1 hour that is. Even though big candles will often form on the lower time-frames before a reversal, because they're not made up of as much data - like a 15 min candle only shows 15 mins worth of data... or opinion is probably a better way to put it - they don't have a high probability of being successful, so it's best not to trade them and wait for big candles to form on the hourly instead.

Here's today's update...