Forecasting a Continuum of Environmental Threats (FACETs): Verification of the Tornado and Lightning Plumes

Forecasting a Continuum of Environmental Threats (FACETs) is a proposed framework that will modify the current watch and warning system to communicate clear and simple hazardous weather information to serve the public. Probabilistic plumes were created by forecasters using automated guidance in the NOAA Hazardous Weather Testbed (HWT) as a part of FACETs. These probabilistic plumes are produced using the storm size and speed to determine the width and length of the plume. A Gaussian smoother from the center point is used to provide a visualization of the forecast threat area and region of uncertainty. A method of forecast evaluation is needed to determine the accuracy of these plumes. However, there currently is not a clear method of verification of the tornado and lightning plumes. Cases were taken from the HWT from various years. For each case, the maximum probability of the lightning and tornado plumes at all timesteps for a case were merged together. The verification data used for the lightning plumes is the National Lightning Detection Network. The tornado plumes were verified by tracking the mesocyclone coordinates. Attributes diagrams were created for the lightning and tornado maximum plume values for each case. Practically perfect plumes were created for each of the cases. Increasing the grid size around the mesocyclone track changed the reliability shown on the attributes diagram. For each of the tornado cases, it was found that using a 9 km and/or a 15 km grid around the mesocyclone point was where the attributes diagrams indicated the plumes were the most accurate. Additionally, the lightning and tornado attributes diagrams were found to be significantly different from each other. We hypothesize that this difference is at least partially due to the different climatological base rates of occurrence.