These “hook echos” on reflectivity mode can sometimes be more well defined and help to indicate the presence of a tornado. In this case, the circled area on the reflectivity mode (the left side of the example below) is in a part of the storm where it’s possible that a tornado could form, below a bit of a hook, or curvature, of the higher reflectivity values. Sometimes, a lowering of the correlation coefficient can be “noise” on the radar, which can be a bit misleading when trying to identify if there is actually lofted debris from a tornado. In order to verify that there is actually a TDS, we need to match up the correlation coefficient radar data to the normal reflectivity mode information to see if the TDS is in a position within the storm that makes sense. Meteorologists call this signature on the correlation coefficient product a tornado debris signature (TDS). This dual-polarization product helps meteorologists confirm that there is a confirmed tornado on the ground, and the height in the atmosphere that this debris is being lofted can help to determine the intensity of the tornado. This example is from 2016 when an EF-2 tornado tracked through parts of Rolette and Towner Counties, and the circled area is where the radar sensed a low correlation coefficient due to lofted tornado debris in that area. These objects are dissimilar from the surrounding precipitation, such as rain and hail, within the storm, and the correlation coefficient product plots this as a blue area compared to the surrounding yellow and red areas, as shown below on the right side. Tornadoes can tear apart trees, homes, etc., and lift pieces of them thousands of feet up in the atmosphere. With severe weather, this can serve as a “debris tracker” for detecting where lofted debris from tornadoes is to confirm that a tornado is on the ground and doing damage. Differential reflectivity explanation and example (KFYR/NWS Bismarck)Ī second very useful dual-polarization product is called the “correlation coefficient.” This product works by determining how similar or dissimilar particles in the atmosphere are compared to their surroundings.
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