We received a lot of questions about the line of severe thunderstorms that moved through our area yesterday, and a good number of them were about the shape of the line itself.
The line of storms appeared curved on the radar … this is known as a Bow Echo.
A Bow Echo occurs when winds high above increase along part of a line of storms, and that part is pushed ahead of the rest of the line forming a “Bow” like shape.
Aside from the typical gusty winds, excessive lightning, hail and heavy rainfall that accompanies severe thunderstorms, Bow Echoes have higher chances of producing downbursts. A downburst occurs when evaporative cooling creates an area of cold dense air inside a thunderstorm, and then that air plummets to the ground. As the cold air smashes into the ground it spreads out creating gusts of wind that can easily exceed one hundred miles per hour.
Downburst wind damage is often mistaken for tornado damage.
Although tornadoes can form all along a Bow Echo, the most favorable area for tornado development is on the ends of the bow itself, as winds begin to curl around behind the line of storms.
On the whole, whenever a Bow Echo is visible on radar it should not be taken lightly. It is an indication that a very serious weather situation has developed and its progress should be closely monitored.