Conceptual models from the MetEd program Meteorology Education and Training Mesoscale Meteorology Severe Convection II: Mesoscale Convective Systems Bow echo evolution Why and how does the bow echo evolve? We talk about the shape of the whole squall line, not about the shape of a single cell radar reflectivity

The echo has the bowed shape due to the mid-level intense flow (rear inflow jet) into the back of the system. The bow echoes are generally indicators of intense winds, not predictors. Large swaths of damaging surface winds are a particular concern with bow echoes. Bow echo evolution For relative short squall lines Yellow lines: Mid-level storm-relative flow

If a bow echo persists for hours, the Coriolis force will intensify the northern vortex (and weaken the southern vortex) creating the often-observed asymmetric evolution by the later stages. Yellow lines: Mid-level storm-relative flow Why does it become asymmetric? Coriolis effect Long-living huge system. MCV

Asymmetric feature