Map of May 20 and 31 Oklahoma Tornadoes with Population Density

Posted on June 4, 2013 by Doug McCune

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The past two weeks have been devastating for Oklahoma. Multiple tornadoes have touched down in and around Oklahoma City, causing massive damage and the loss of 42 lives. First, on the afternoon of May 20, 2013 an EF5 tornado hit Moore, Oklahoma. Then only 11 days later a series of tornadoes hit the same general area, striking El Reno/Yukon (to the west of Oklahoma City) and multiple sites within Oklahoma City (the western, central, and eastern areas of the city were all hit).

SpatialKey has been working to analyze the destruction of these tornadoes. Our data partner, Weather Decision Technologies (WDT), has created hand-drawn paths of the affected areas. These paths paint a grim picture of the destruction in Oklahoma. We've overlaid these paths on a population density map to allow us to understand how many people were impacted, and which strikes had the most effect.

View the map below or view a larger version.

Interacting with the map

At high zoom levels the map shows the storm tracks overlaid on a dot-density population map. Mouse over the storm tracks to see a tooltip that shows how many people and housing units are within that track.
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When you zoom in the map will change to show satellite imagery. The census blocks switch to colored shapes that are colored based on the population of that block. Mouse over those blocks to see a tooltip showing the stats for that individual census block.
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Estimated population impact

Overall we estimate that approximately 34,000 people were within the affected paths of these tornadoes. This is a rough estimate based on the intersection of the tornado paths with census data.

Affected area Estimated Population Date
Moore/Newcastle 9,000 5/20/2013
El Reno/Yukon 300 5/31/2013
West Oklahoma City 800 5/31/2013
Central Oklahoma City 17,500 5/31/2013
East Oklahoma City 6,500 5/31/2013

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About the map

The map shows the paths of the tornadoes overlaid on a population dot density map. The population data is from the 2010 US census, and is granular to the census block level. Each tiny dot represents a single person.

Red dots are used for people within the tornado paths, while blue dots are used for people outside the paths. By layering the population dots we can get a picture of population density. We can see that the tornado that hit central Oklahoma City tore through a populated area, versus the tornado that hit El Reno or east Oklahoma City missed dense areas.

About the data

The tornado paths for the storms on May 31 were provided by WDT and were hand-drawn by their meteorologists. The path for the May 20 Moore tornado was created by NOAA.

The population and housing data comes from the 2010 US census. The census data provides polygon block shapes with population counts and the number of housing units within each block. We have converted that polygon data to point data by filling the shapes with a random distribution of points, one for each person, throughout each individual census block.

The map also uses the Toner basemap from Stamen Design, as well as satellite imagery from MapBox.

If you're a SpatialKey customer, you already have access to the tornado path data, both from WDT and NOAA, which is available in the SpatialKey Data Mart.

Posted in weather, damage assessment, tornado, Event response | Leave a reply