Smoke from a prescribed burn set this morning over southern Ohio county made an appearance on the National Weather Service Dual Pol radar operating out of Hopkinsville, Kentucky. The image below goes through a few of the products we get from the Dual Pol radar. The smoke is seen as a plume originating over southern Ohio county and heading southeast.
In the image above, the reflectivity (or measure of returned power from the radar beam) topped out at 38 dbZ. This reading is roughly what you would get from a moderate rain shower. The differential reflectivity is fairly noisy in the smoke plume, but ranges from roughly 2 to 7 dbZ. This range is similar to what we see in large rain drops (which incidentally come down in roughly the shape of a hamburger bun). For correlation coefficient, the values are around 0.4, which indicates that the objects reflecting the radar beam are of varying sizes. Combining the three different inputs indicates the target that we are seeing likely is either smoke or chaff, but given that we know a prescribed burn is going on under that site, the radar here is seeing smoke.
The National Weather Service provides weather support to agencies in charge of running prescribed forest fire burns. The Kentucky Department of Fish and Wildlife Resources requested a Spot Forecast for the time they expected to start this fire and into the evening hours. They use these forecasts to determine if a prescribed burn can safely be executed.
Weather conditions were fairly dry this afternoon, with relative humidities bottoming out in the upper teens in some places (as indicated on the image below). The higher values over south central Kentucky were as a result of mid to high clouds across the region. These clouds helped keep temperatures down a little, but more importantly prevented much drier air just above the surface from mixing down, as it did across the line from Breckinridge county to Casey county, and even in the Louisville metro area.