A
line echo wave pattern (
LEWP) is a
weather radar formation in which a single line of thunderstorms presenting multiple
bow echoes forms south (or equatorward) of a
mesoscale low-pressure area with a rotating "head". LEWP often are associated with a multiple-bow serial
derecho and often produce tornadoes, some of which can be strong. The existence of a LEWP on radar means that a serial
derecho has developed or is likely to develop soon, much as a
hook echo indicates the same for a
tornado.