‘Understanding Clouds’ was the theme of World Meteorological Day 2017 (on 23/03) to highlight the enormous importance of clouds for weather climate and water. Clouds are central to weather observations and forecasts. Clouds are one of the key uncertainties in the study of climate change. Clouds play a critical role in the water cycle and shaping the global distribution of water resources.
Have a look a this video (by Jack G Miller and World Meteorological Organization), that beautifully illustrates the challenge to forecast clouds and solar energy: