A LEWP, according to the NWASNWS, is defined as "a [[squall line]] that has developed into a wave-like pattern due to acceleration at one end of the line and deceleration along the portion immediately adjacent."<ref>{{cite web | url=http://www.nwas.org/committees/avnwinterwx/doppler_weather_radar_overview.htm | title=Doppler Weather Radar Overview | publisher=NWAS | work=Echo Identification using NEXRAD: Line Echo Wave Pattern | accessdate=July 28, 2012 | deadurl=yes | archiveurl=https://web.archive.org/web/20140404130516/http://www.nwas.org/committees/avnwinterwx/doppler_weather_radar_overview.htm | archivedate=April 4, 2014 | df= }}</ref>
[[File:Illinois-LEWP.jpg|thumb|left|A LEWP in Illinois/Indiana and Arkansas, associated with a [[Tornado outbreak sequence of April 19–24, 2011|very large derecho]]]]
