Co‐development of a cyclone family and an atmospheric river over the North Atlantic: a synoptic evolution with associated moisture transports

Atmospheric rivers, identified as narrow strips of high moisture transport, emerge and evolve with the synoptic‐scale dynamics. Here, the co‐development of a well‐defined extensive atmospheric river crossing the North Atlantic Ocean and a cyclone family during the period of 18–20 September 2018 is presented from its initiation to the end from this perspective. The high moisture state of atmospheric rivers is maintained by the local supply of moisture over a short timescale of less than 24h by convergence and divergence not only associated with the synoptic‐scale evolution of the cyclones but also associated with extensive horizontal transport.