When people talk about Big Data, they often talk in terms of Messianic solutions for economy-size systems. Roads and highways. Diagnoses and treatments. Buyers and sellers. But some of the most interesting work being done with data addresses a different kind of complex system. The information for this system is neither private nor proprietary: In fact, its ownership is a little more evergreen. It’s the weather. And this week, one of the more interesting recent online weather data products opened to the public and explained itself.