Rain Scanner Radar and Optical Flow Combination For Early Identification of The Incoming Bow Echo Heavy Precipitation

Abstract

In this study, heavy precipitation in the form of bow echo is observed, identified, and tracked using a rain scanner and optical flow method. Two case studies of bow echoes with a range of properties from 15 to 33 km were observed in the afternoon on 1st February and 4th February 2021. The rain scanner developed based on X-band radar could obtain the first detection of the bow echo shape. The difference between these two bow echoes events is from their initiation. The first bow echo cases are initiated from weakly organized cells. Meanwhile, the second case of bow echo is initiated from a squall line event. Bow echo is initially observed in the western part of Bandung city. Approximately twenty minutes after the first detection, the bow echo passed the center of Bandung city. Image processing using edge detection could track the bow echo from the radar data. Applied Lucas-Kanade optical flow was then used to retrieve the bow echo movement. Vector flow from optical flow showed the dominant movement toward the east direction in both case studies. A simple method to predict the incoming time of the bow echo using the estimated speed from vector flow and the image translation is also presented.