When the big whales Power Down, that means that their Steem Power will get converted into Steem in a few days. This could cause a temporary price increase of Steem that you can profit from by buying before they do.
Powering Down takes a few days to complete, but whenever a big whale or many small whales are due to Power Down the same day there is a profit opportunity.
Use this tool: http://steemdown.com
You will see there the big whales, when they power down, and how much time there is left until they do. If there are many whales that power down in 1 day, then the price of Steem could go up that day.
If you buy Steem 1 day before there is an opportunity to arbitrage this, price goes up, you convert to Steem Dollar, and enjoy some profits.