The merger of a supercell and squall line in the Great Plains: 2. Formation of a bow echo

On 23–24 May 2020, an isolated supercell formed ahead of a squall line and subsequently evolved into a bow echo through their merger. Utilizing a 10‐min update four‐dimensional variational data assimilation system that integrates radar and surface observations, we investigated the convective‐scale processes that led to the formation of this bow echo.

Our findings indicated that as the squall line advanced eastward, its inflow was initially obstructed by the supercell, causing the weakening of both the squall line and its associated cold pool. However, during the merger, a strong rear inflow jet (RIJ) rapidly developed ahead of the squall line's leading edge and behind the supercell. Unlike a classic RIJ that typically expands rearward over the cold pool, this RIJ accelerated forward toward the supercell.