Bow Echo Formation Mechanisms: An Analysis of 293 Events

Bow echo formation mechanisms are examined using the sample of 293 bow echo cases whose predictability was studied in two recent prior works (Mauri and Gallus, Wea. Forecasting, 2021; Gallus and Duhachek, Wea. Forecasting, 2022). That sample of cases included events without severe wind, events with marginal severe wind, and events with high-end severe wind, and it also separated events into nocturnal and daytime periods. The bow echo formation mechanisms explored included interaction of a line of storms with a boundary, interactions of a line with individual cells in front of it, and the presence of strong line-normal inflow into the main line of storms. The degree of curvature for each case also was calculated to assess its correlation with wind severity and the possible influence of bowing mechanisms on this curvature. This metric, calculated through the haversine function, offers a novel approach to quantifying storm morphology and its relationship to wind damage.

A statistical analysis of this dataset revealed a strong correlation between bowing curvature and wind severity, corroborating some past results. Preliminary analysis suggests that specific bow echo formation mechanisms may also be associated with stronger winds. However, roughly half of all cases did not involve an interaction with a boundary or individual cells in front of a line, suggesting that more complex interactions or storm-scale processes often lead to bow echo formation. Work is ongoing to classify the line-normal inflow for each case, as some prior research suggested numerical models are more able to predict bow echoes in environments with stronger line-normal inflow. The current research contributes to ongoing efforts to enhance forecasting and understanding of bow echoes.