Friday night there were numerous warnings for severe thunderstorms, but the only major damage was from a storm that produced a powerful "downburst" that did some terrible damage in the Bladensburg area (as you can see in this photo gallery).
- Courtesy Hieu H. Nguyen/University of Texas
Three weeks ago, on June 1, there was an equal number of warnings for tornadoes during a dangerous afternoon and evening, and there were a number of small, short lived tornadoes later confirmed by the National Weather Service.
But here in the Washington area, severe thunderstorms, downbursts and straight line winds have done more damage over the years than any tornado. Terrific advances in radar meteorology over the last 20 years (now with dual-pol) have allowed us to see storm structure in small detail. But while Doppler can "see" rotation in storms and even very small whirlwinds in the air above us, which technically might produce a small tornado and trigger a TORNADO WARNING and result in some minor damage, downbursts can produce winds of 100mph or higher and cause major damage. More damage than a small tornado if they hit a metro area as we saw last night. Downbursts happen as the rain and hail generated in a thunderstorm cell begin falling and drag the air toward the ground, cooling the air as the precipitation melts and evaporates. As a result, a falling bubble of cold air that can reach speeds of 100 miles per hour is generated. Then BANG, the racing cold bubble of air hits the ground and causes the damage we saw. Remember, the severe storm that generated a big downburst, or macroburst, that caused major damage in Great Falls, Potomac, Bethesda, Chevy Chase, NW D.C. and in Prince George's County on June 14, 1989?
- Courtesy Chevy Chase Historical Society
- More than 250,000 residents lost power. It was days before the damage was cleaned up. A number of homes were destroyed. Year after year, severe thunderstorms and downbursts cause more damage and take more lives due to flash flooding, lightning and wind than tornadoes in our area. NWS Doppler image of tornado near Yazoo City, MS April 2010
Doppler radar can detect spin and horizontal winds, but really can't measure vertical winds or rapidly descending cold air that will become the downburst when it hits the ground. Many thunderstorms or individual "cells" within a line of thunderstorms may last for only 30 minutes. They rapidly grow with rising warm, humid air, produce rain and rise to 5-7 miles high, where the temperature may be 20 to 30 BELOW ZERO in a few minutes. I still like a Snickers bar every once in a while. OK I admit it. A Snickers has about 120 calories. Imagine 1 TRILLION snickers. That is how many calories or energy an average thunderstorm can generate in its 30 minute average life. Surprised that this atmospheric monster with all those Snickers can cause damage like the folks in Bladensburg experienced? About 50 years ago we didn't have the knowledge and tools to be able to accurately predict things like floods, snow storms, hurricanes and tornadoes.
Predicting downbursts and microbursts is still a challenge but I predict that 50 years from now we will not only be able to better see these terrible winds, but give 20-30 minute advance warning for a local town and even neighborhood, such as Bladensburg. While we can't stop the damage, people can be well protected and ready for what some described as a bomb blast. In the future, I predict we may hear a 'DOWNBURST WARNING" and know here in our area it might be more serious than "TORNADO WARNING"