switch to velocity image
This radar image is from the approximate time the photo was taken. The approximate location of the photographer is shown. Notice that just southwest of the core of the storm, there are a few pixels of weak reflectivity (in green and blue, near the photographer). This is known as the weak echo region, and is a sign of a strong updraft in the storm. Since tornadoes typically develop at the base of an updraft, this also marks the location of a potential tornado. Click the link above to view the unusual velocity pattern in this storm.