Line echo wave pattern
From AMS Glossary
line echo wave pattern
(Abbreviated LEWP.) A special configuration in a line of convective storms that indicates the presence of a low pressure area and the possibility of damaging winds and tornadoes.
In response to very strong outflow winds behind it, a portion of the line may bulge outward forming a bow echo.
Nolen, R. H. 1959. A radar pattern associated with tornadoes. Bull. Amer. Meteor. Soc.. 40. 277–279.