Using different formats for your Sprint Retrospective is a great way to help a Scrum Team inspect their process through different lenses and perspectives. The Liberators came across the Weather Forecast Retrospective by Barry Heins and shared their experience and (slightly modified) approach here: https://medium.com/the-liberators/predicting-the-weather-a-weather-forecast-retrospective-for-scrum-teams-9bbb02105ea4