Scientists Confirm 300+ MPH Winds in Greenfield Tornado!
Scientists Confirm 300+ MPH Winds in Greenfield Tornado!
July 2024
Hello, Friend! Hope you're enjoying the weekend.
After an amazing severe weather season, we're finally enjoying some quiet in the Plains. So there's no better time to look back at one of the most intense tornadoes of the year!
GREENFIELD TORNADO MAX WINDS
Recently, the Center for Severe Weather Research confirmed that the EF4 Greenfield, Iowa tornado had some of the most intense winds ever observed. Based on Doppler on Wheels (DOWs) data, they estimate that the tornado contained winds of 309-318 mph!
As the 2024 #BEST field season ends, a glimpse into the data collection during the Greenfield, IA tornado. Peak wind speeds as high as 309-318 mph were calculated in a narrow region 100-160 feet ARL. These are among the highest wind speeds ever determined using DOW data. https://t.co/CM09J3VSOB pic.twitter.com/fuxfdyoi9d
— Doppler on Wheels (DOW) (@DOWFacility) June 22, 2024
These winds were measured near the end of the tornado's 44-mile march through southwest Iowa on May 21st.
Reed Timmer and his crew took extraordinary video of the tornado around the time these data were captured. Large vortices explosively rotated around the center of the 1/2 mile-wide circulation.
STRONGEST #TORNADO IN HISTORY? 300+ mph wind confirmed in Greenfield, Iowa tornado. Check out this new drone footage from this prior to this measurement! WATCH: https://t.co/hIgQ4RVSws pic.twitter.com/g4m5QmBFec
— Reed Timmer, PhD (@ReedTimmerUSA) June 23, 2024
These intense winds rank highly in the pantheon of radar-sampled violent tornadoes. Only two tornadoes had stronger winds.
The highest winds in history were measured in the historic Bridge Creek, Oklahoma F5 tornado on May 3, 1999. Radar scientist Josh Wurman and his collaborators originally reported a 302 mph max velocity. Later, using modern post-processing techniques, Wurman adjusted this max to 321 mph.
The second most intense radar-sampled tornado struck the rural area south of El Reno, Oklahoma on May 31, 2013. Howie Bluestein and his collaborators measured 313 mph winds in the 2.6 mile-wide funnel. Josh Wurman's DOWs also measured intense winds, and estimated that the gusts may have been as high as 336 mph.
Unlike the Bridge Creek tornado, the max velocities in the Greenfield tornado didn't last very long at any given location - around 1 second. And since the Enhanced Fujita damage scale is calibrated to 3-second gusts, it's likely that the highest winds were too short-lived to cause more intense damage.
This is similar to the El Reno tornado, which "only" produced EF3 damage. The strongest winds in this tornado were limited to extremely fast-moving sub-vortices that passed over locations in less than a second.
Nevertheless, it's apparent that the Greenfield tornado was an elite tier tornado. And one that will be discussed by storm chasers for years to come.
CHASE TIP OF THE MONTH
On an early spring chase day, it's easy for chasers to want to jump on the first radar echo.
But often, these days are characterized by fast storm motions -- sometimes greater than 50 mph. So if you get to the storm took quickly, it may mature after it passes you. And once it passes you, it is almost impossible to catch up.
So, on those early spring days, I recommend positioning considerably downstream -- say 25-50 miles -- to allow the storm time to mature. Then, when it's producing the big tornado, you'll be there to capture it in all its glory!
TORNADO SCIENCE MINUTE
Mobile radar-measured wind speeds often exceed damage-estimated wind speeds in violent tornadoes.
But did you know that radar may underestimate true wind speeds? It's true.
One reason is that radars measure "scatterers" -- a.k.a., what the wind moves -- not the true wind speeds. And since the real wind is often faster than what it moves, the wind is often faster than radar.
Another reason is that wind gusts measure a volume of air -- not just a point. So, slower-moving air can bring down the average velocity of the volume.
That said, EF scale wind estimates are based on 3-second gusts. And since radar velocities are effectively instantaneous, it partially explains why radar measurements are generally greater than damage wind speed estimates.
ANNOUNCEMENTS
The long-anticipated sequel to the 1996 hit movie Twister is coming out on July 19th. I plan to post a full breakdown of the movie next month!
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Well, that's all for now. Hope you enjoyed it!
- Gabe Garfield
WxGabe on X/YouTube/Facebook/Instagram
