The weekly update to the US Drought Monitor was released yesterday with both small improvements and degradation found with the analysis for Iowa. The authoring of the Drought Monitor is a difficult process as precipitation is highly variable in space and time. For example, it is sometimes difficult to balance long term dryness vs short term wetness and arrive at a single drought classification for a given area. The featured map is a new data visualization attempt by the IEM to illustrate the sometimes conflicting precipitation departures over space and time. The colored polygons represent the current US Drought Monitor analysis. For each of the long term climate sites tracked by the IEM, three dots are generated and colored by their standardized precipitation index (SPI) value over 30, 90 and 180 days. The dots are colored using a simple SPI to drought classification cross reference. When SPI is positive, associated "wet" (W classifications) colors are used. So what does this plot show us? For starters, only a small portion of central Iowa has above average precipitation over all three of these intervals. There are developing pockets of dryness over southern Iowa that will likely require introduction of drought classifications if rains do not come. While the worst drought analysis exists over northwestern Iowa, departures are variable over different periods. What do you think of this visualization? You can generate it on-demand via the "generate this chart" link, but be warned that the generation is very slow!

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