“Tornadoes … the dimensionless point at which parallel lines met and whirled and blew up. They made no sense.” – David Foster Wallace

Overview

The tornado is one of the most fascinating, destructive, and mysterious storm systems that occur in the United States. With data that only dates back to the 1950’s, long-term trends in the records are very difficult to identify, but it can be observed that the frequency of large-scale outbreaks are increasing. In fact, the number of tornadoes in the most extreme outbreak in a five-year interval doubled over the last half-century.

Tornadoes continue to mystify scientists on the exact conditions of their formation; atmospheric instability and wind shear are the building blocks for this fierce storm, but how these variables interact with our warming climate has led to many questions. Atmospheric instability occurs when warm, moist air is wedged under drier cooler air, and wind shear refers to the changes in wind direction and speed at different elevations in the atmosphere.

It is likely that a warmer, more humid world would lead to more frequent instability in the atmosphere, but a warmer climate could also lessen the chances for wind shear. Researchers have also found that the increase in outbreaks were driven by storm relative helicity, which is a measure of vertical wind shear. However, this factor has not been projected to increase under a warming climate, leaving us even more unsure regarding the correlation between a warming climate and increased tornado activity.

This data raises new questions about how climate change will impact the severity of thunderstorms and specific weather events. The lack of direct correlation between our warming climate and the increase of tornado activity leaves two possibilities: either the recent increase in severity is not due to global warming, or global warming has implications for tornado activity that we do not understand.

Data Description

The data points visualized above were collected by the National Weather Service1 field offices found in the Storm Data2 publication. The storms are broken up in five year periods, starting in the year 1950 and ending in 2015.

The initial data was in a comprehensive CSV file, and a script written in the Python3 programming language was used to group the data in five year increments and keep only those tornadoes recorded as a 3 or greater on the Fujita4 Scale.

For each five year period, the data was visualized in ArcGIS Pro5 using the same mapping properties and exported to PNG6 image format. The image files were loaded into GIMP7, optimized and exported as an animated GIF8. The animated GIF was converted to a video using FFmpeg9.

Author: Morgan E. Brickey. Last edited: 2019-12-11

  1. National Weather Service. weather.gov. Accessed 2019-11-30.Online: https://www.weather.gov↩︎

  2. Storm Data Publication. data.gov. Accessed 2019-11-30. Online: https://catalog.data.gov/dataset/storm-data-publication↩︎

  3. Python. Copyright (C) 2001–2019. Python Software Foundation. Accessed 2019-11-30. Online: https://www.python.org↩︎

  4. Fujita Scale. Weather.gov. Accessed: 2019-11-30. Online: https://www.weather.gov/oun/efscale↩︎

  5. ArcGIS. Single Desktop GIS Application Part of Esri Geospatial Cloud. Accessed 2019-11-30. Online: https://www.esri.com/en-us/arcgis/products/arcgis-pro/overview↩︎

  6. Portable Network Graphics (PNG). Copyright 1995–2019 Greg Roelofs. Accessed 2019-11-30 Online: http://www.libpng.org/pub/png/↩︎

  7. GNU Image Manipulation Program (GIMP). Software released through CC-BY-SA by The GIMP Development Team. Accessed 2019-11-30 Online: https://www.gimp.org/↩︎

  8. Graphics Interchange Format (GIF). Copyright 1987–1990 CompuServe. Accessed 2019-11-30. Online: https://www.w3.org/Graphics/GIF/spec-gif89a.txt↩︎

  9. FFmpeg is a trademark of Fabrice Bellard. Software released under GNU LGPL 2.1. Accessed 2019-11-30. Online: https://ffmpeg.org/↩︎