NOAA's National Weather Service Weather Forecast Office

Lifecycle of a Bow Echo

In the late 1970s, Dr. Ted Fujita, was the first to identify bowing segments (or the bow echo) within a larger squall line.  The lifecycle of a bow echo can be described as a gradual transition from a large, strong and tall echo to a bow echo which often turns into a comma- shaped echo pattern. Initial damaging downburst (DB) winds descend to the surface during the large, strong tall echo stage (A).  The downburst intensifies distorting the echo pattern into a bow-shaped pattern.

Rear Inflow Notches (RINs) (weakness in the reflectivity pattern at the trailing side of the storm) are frequently observed during the early and mature stages of the bow echo.  These notches are a reflection of drier air entraining the storm from the rear towards the leading -forward side of the bow echo. 

Circulations (or mesocyclones) may rapidly form along the leading northern - forward side of a bowing structure.  In some cases, non-supercell tornadoes have occurred in the vicinity of the circulations.  Tornado damage intensity frequently falls in the F0 - F1 category.    However,  tornadic damage of F2 intensity have been documented with some bow echoes. 

We have been studying bow echoes across the Mid-Mississippi Valley Region for the last eleven years.  Check "Science News"  (under Damaging Winds) for more information about our applied research results of bow echoes embedded within larger squall lines.