Looking at the radar signatures yesterday of the super-cell thunderstorm near Cisco, TX I could tell that this was not a good situation for anyone in the path of this storm.
Unfortunately, there was one confirmed fatality and others were injured when the tornado moved through the populated areas south of Cisco.
However, there are things to learn by looking at the radar data.
The top picture shows the obvious hook echo created by the tornado, and the red color in the middle of the hook could well be debris.
The second picture of base velocity shows the strong inbound winds (in green) right next to the outbound winds (in red). The brighter the colors, the higher the velocities.
The third picture shows us some new technology from the “dual pol” upgrade of the NEXRAD doppler radar. This product is called “Correlation Coefficient” and can be used to detect debris. A low correlation coefficient means that the targets the radar beam is reflecting off of do not correlate because they are different shapes and sizes (as opposed to raindrops which usually are similar and correlate well, hence a high correlation coefficient). The dark blue in the circle is indicating debris, since it is right where the inbound/outbound winds and the hook are.
This product is very important since debris confirms that a tornado is on the ground, something the radar used to not be able to tell us. Since only about 25% of the “radar indicated” tornadoes end up reaching the ground, anything that verifies that is extremely helpful, especially at night and/or in hilly and tree covered terrain.
However, it should be noted that Correlation Coefficient needs interpretation by an expert. Look at all the dark blue in other areas outside of the storm. That is NOT debris. Only if the low CC lines up with the velocity “couplet” and the hook with high reflectivity (the red/orange) should it be interpreted as debris.