We usually read weather maps--correctly--as displaying current conditions and/or short term predictions about upcoming weather patterns. This map from the National Climatic Data Center at NOAA (via @APHumanGeog's Seth Dixon) does something different: it displays the probability of a white Christmas (that is, snow on December 25) across the continental United States based on past weather patterns.
With Rogers Hall, Emily Shahan, Jennifer Kahn, and Emily's math literacies students, we've been thinking this semester about the mathematics behind data displays like these. How were these data generated? What do they mean? What is our impression, as readers, when we come across a thematic map like this?
The metaphor we've used to think about unpacking the mathematics is "dissection." If we dissect this data display, what can we determine about its constituent parts? What would young people need to know in order to read, make sense of, and act on a map like this? How is the mathematics more/less hidden here than when we're looking at a more traditional weather map? How do our expectations for the genre of "weather map" play into what we can read and understand with this map?
Via Seth Dixon