Radar Imagery for Northwood, ND EF 4 Tornado

Below are radar images from the Doppler radar at Mayville, ND, with Northwood, ND indicated with a white dot.  The Northwood EF4 tornado was sampled at 18 miles from the radar, or about 900 feet above ground level. Therefore, very fine resolution of both reflectivity and Storm Relative Motion (SRM) images were obtained from the radar.  Strong tornadic signatures were detected in SRM imagery, with winds away from the radar (red), and winds toward the radar (green) indicating the intense cyclonic (counterclockwise) circulation of the tornado.  In fact, a rarely seen debris signature was detected in base reflectivity imagery at 849 and 853 pm.  This feature was debris from the surface being drawn up into the tornado, and seen in reflectivity imagery just like rain or hail would be detected.  Note the reflectivity image at 844 pm has a pronounced hook echo with less than 50 dbz (non red returns) near the hook, this was likely right before the tornado struck Northwood. 

Radar picture
Reflectivity 840 pm
Radar picture
Reflectivity 844 pm
Radar picture
Reflectivity debris ball 849 pm
Radar picture
Reflectivity 853 pm
 
Radar picture
SRM 840 pm
Radar picture
SRM 844 pm
Radar picture
SRM 849 pm
Radar picture
SRM 853 pm

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