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How we use our Radar to See the Heart of Thunderstorms




Since we got our own live radar in 2020, we've definitely put it through the ringer - it's seen rain, sleet, hail, snow, tornadoes, and more, and it's not gonna stop anytime soon. One of the most helpful tools, however, is the ability to - instead of spinning 360 degrees around - look vertically, up and down, and analyze the structure of thunderstorms in extreme detail. Above is a radar image from a severe thunderstorm that dropped large hail in Southern Tennessee, as seen from a vertical scan from our live radar. The white arrow indicates the location of the strong updraft, a local area of winds surging upwards, in this case in excess of 70mph! Notice how, inside this updraft, there is lower rain and precipitation values due to it getting thrown up into the storm.


Besides the rain intensity product you commonly see on air, we also make regular use of a product called "Velocity".

It looks daunting, but in fact is a simple tool that measures wind speeds - the wind is measured relative to the radar, so in this case, green winds = towards the radar, and red winds = away from the radar. The brighter the colors, the faster the winds. It's as simple as that! In this velocity image of the same storm, you can see very clearly the strong, bright intense area of high winds in the center of the updraft, which is winds surging upwards at 80mph at it's highest point. This is how hail is formed, and formed the hail certainly was on this day... some areas got hail larger than baseballs from this storm!


Another exceptionally useful way to utilize vertical scans includes analyzing what we call the freezing line, which, as it explains, is the point at which precipitation freezes into ice or snow. Everything above this line is ice and snow, and everything below it is typically rain. The transition zone between the snow and rain appears brighter on vertical scans, as you can see in the image above - this is because, as it snow is melting into rain, it becomes a mixed form of precipitation which reflects radar beams better. This feature is known as a bright band.


To help analyze this so called bright band, we also have 3 dimensional tools that can help figure out what exactly the beam is reflecting. This image shows the bright band, denoted by the yellow-green line of returns across the screen, on the correlation coefficient product. It too sounds daunting, but fear not! It is a 0% to 100% scale, with 100% (reds) indicating 100% similarity of objects, and 0% (closer to blue) indicating no similarities in objects. Rain is typically close to 100%, as raindrops aren't very different, but the image here shows the mixed area as yellow - about 50% - indicating that it is indeed a mixture of rain, ice, and snow! This same tool can be used to analyze tornado debris in the core of tornadoes, birds, and more. With all of this technology at our disposal, we have access to truly to the second data across the Tennessee Valley, and we never miss a thing thanks to it.

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