Satellites provide dramatic views of clouds, but in order to understand the processes that underlie how clouds form and evolve, scientists turn to complex computer models that simulate Earth’s atmosphere. By feeding a range of ground, aircraft and satellite data into Goddard’s Earth Observing System Model (GEOS-5), research meteorologists can see how closely the mathematical equations used to simulate atmospheric dynamics match reality. Such models are by no means perfect, but they have improved tremendously in recent years. The visualizations below, based on GEOS-5 model runs from February 2010, show how well the model reproduced the massive blizzard known as “Snowmaggedon.” In the visualization, watch Snowmaggedon’s sprawling, comma-shaped cloud system—complete with a tail that reaches all the way to the Caribbean—as it churns up the Eastern Seaboard dumping three feet of snow in some areas.