This research was supported by National Science Foundation Grants ATM-0637148, ATM-0934307, and ATM-0802888, and by NOAA Grant NA08OAR4320904. Portions of this manuscript were completed while the first author was a graduate research assistant at the School of Meteorology and Cooperative Institute for Mesoscale Meteorological Studies in Norman, Oklahoma, and subsequently, a postdoctoral research associate at the Center for Analysis and Prediction of Storms (CAPS) in Norman.
Two residents of Protection, Kansas, assisted the UMass X-Pol crew in locating truck services and a deployment site. Jeff Hutton and Mike Umscheid of the NWS–Dodge City, Kansas, forecast office provided the damage-track shape files, tornado chronology (Table 1), and a great deal of other useful information about the Greensburg storm and its tornadoes. Dr. Louis Wicker provided computing support. Discussions with Les Lemon, Dr. Chuck Doswell, Dr. David Dowell, Dr. Morris Weisman, Vijay Venkatesh, Jeffrey Snyder, Dr. Alan Shapiro, and Matthew Kumjian were illuminating and helpful. We used the software package ViSky, developed by Gordon Carrie, to generate the image of the dual-Doppler lobes. Robert Fritchie supplied the photograph of the Greensburg tornado. The comments of two anonymous reviewers resulted in substantial improvements to this manuscript.
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One might characterize tornado production modes as a sliding spectrum, rather than discrete categories. It is primarily because of the vast differences in potential human impact (as denoted by their EF-scale ratings) that two modes were delineated in this study.
Historically speaking, the date of the Greensburg storm is 4 May 2007, because the tornado struck Greensburg at about 9:45 p.m. local time (2145 CDT) on that day. For the purposes of this study, however, we will follow meteorological convention and use UTC time hereafter; for example, 2145 CDT 4 May 2007 corresponds to 0245 UTC 5 May.
The Greensburg storm was detected by a number of other WSR-88Ds, including those at Vance Air Force Base near Enid, Oklahoma (KVNX; ~130 km away), and the NWS forecast office in Amarillo, Texas (KAMA; ~330 km away). KDDC was by far the closest in range (~65–75 km away).
However, the low values of