Severe Weather Special: Unpredictable straight-line winds can be devastating

Straight line winds can sometimes be the gusts you feel blowing just ahead of an approaching storm, and other times they can be life threatening events reaching wind speeds of up to 140 MPH.

Straight line winds are winds in a thunderstorm with no rotation. Straight line winds occur due to rain cooled air pushing downward from a storm creating a downdraft. This air then spreads out along the ground in a straight line, oftentimes, reaching speeds between 60 to 80 MPH, but in some cases, these winds can far exceed these speeds.

Melissa Delia of the National Weather Service St.Louis office explains, "Some of the wind speeds with our considerable and catastrophic severe thunderstorms warnings can actually get into the EF1 range."

Most straight line winds occur due to common thunderstorms, but a more rare occurrence known as the derecho can sweep across multiple states spanning at least 250 miles while seeing wind gusts of up to at least 58 MPH.

In 2020, a derecho broke the record for the most expensive single day thunderstorm event at over $11 billion.

Melissa Delia says this event sticks out to this day, "The derecho that went across Iowa in August of 2020 really stuck out to me. Winds in that storm were upwards of 140 miles an hour."

Bill Gallus is a professor of atmospheric sciences at Iowa State and was in the direct path of this event that saw life threatening straight line winds come through his neighborhood.

Bill Gallus, "I'm sitting there as a scientist actually thinking, how is this even possible? How can a thunderstorm generate such strong wind that lasts for so long." Bill Gallus took shelter in his home as the winds roared at an estimated 90 MPH. After the storm passed through, Bill ventured out around his neighborhood, "I took a walk around, an hour or two later, and there was actually a metal light post that had snapped and was down along the ground. There was a stop sign that had bent at a 90 degree angle."

Satellite imagery taken from the 11th following the event shows darkness ascending across state lines after straight line winds left many without powers for days in comparison to many lights later when power would be restored.

Straight line winds are capable of producing such devastating events like the one seen in 2020. It's important to take watches and warnings seriously. The best thing to do if the storm is warned for strong winds is to get into a windowless room on the lowest level floor and on the interior wall.