1. one that goes ahead and makes known the approach of another; herald.
2. anything that foreshadows a future event; omen; sign.
I love this addition and how it adds a bit of context to the photos. Each photo has a solitary cloud that definitely adds to their interestingness. I also like the choice of making the photos black and white. It helps to create a sharp contrast between the cloud and its surroundings. If you like this series, I definitely suggest checking out the rest of his portfolio.