John Nelson’s map of tornado migration in the United States, showing the seasonal variations in tornado occurrence, is a master class in data visualization and design—in deciding on the right way to present geographic information. The map combines three styles—impressionistic choropleth, weighted mean centre movement diagram, and small multiple—to present month-by-month information all at once; in the accompanying text (also here), Nelson discusses some of the alternatives he could have chosen instead. And in a separate post he talks about how he made the map. [Esri]

Previously: Mapping Tornado Tracks.