conveyor belt
n.— «At the moment, we’re experiencing a series of weather fronts producing a series of depressions—what’s known as a conveyor belt system. “Until a high pressure system can build from another direction, you just get a seamless run of weather fronts bringing rain and gales and thunder and not very nice conditions. It’s just a natural phenomenon.”» —“Wet, wet, wet” by Linda McKee Belfast Telegraph (Ireland) May 23, 2006. (source: Double-Tongued Dictionary)