Greenfield, Iowa tornado had some of the strongest winds ever recorded

300+ mph: Greenfield, Iowa tornado had some of the strongest winds ever recorded, radar data shows

Mobile radar measured wind speeds above 300 mph in the deadly twister.

300+ mph: Greenfield, Iowa tornado had some of the strongest winds ever recorded, radar data shows

Mobile radar measured wind speeds above 300 mph in the deadly twister.

EIGHT NEWS, IOWA’S NEWS LEADER. WE ARE LEARNING NEW DETAILS TONIGHT ABOUT THE DEADLY GREENFIELD TORNADO. IT’S BEEN OVER A MONTH SINCE THE EF4 TORE THROUGH THE TOWN. IT DAMAGED ALMOST EVERYTHING IN ITS PATH. HERE TO EXPLAIN THE NEW AND SURPRISING DATA IS ��vlog METEOROLOGIST ZANE SATRE STACY. YOU MIGHT HAVE HEARD RECENTLY FROM AROUND THAT THERE WAS, YOU KNOW, THAT GREENFIELD TORNADO WAS THE STRONGEST EVER RECORDED. WELL, HERE’S WHERE THAT’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

300+ mph: Greenfield, Iowa tornado had some of the strongest winds ever recorded, radar data shows

Mobile radar measured wind speeds above 300 mph in the deadly twister.

Recently released data determined winds in the Greenfield tornado topped 300 mph, making it one of the strongest tornadoes ever recorded.The data came from a mobile radar truck called a Doppler On Wheels. The mobile radar, operated by researchers from the University of Illinois, was located just east of Greenfield as the tornado tore through town on May 21. WATCH: Drone footage shows destruction, path of Greenfield tornado Scanning 100-160 feet above the ground, the radar measured wind speeds of 263-271 mph in the tornado. Those measurements were then used to calculate ground-level winds of 309-318 mph. Mobile radars have only found 300+ mph winds in two other tornadoes. In 1999, a Doppler On Wheels estimated 321 mph winds in the Bridge Creek-Moore, Oklahoma, F5 tornado. In 2013, another radar truck calculated 313 mph winds near the El Reno, Oklahoma, EF3.Does this change the tornado's EF4 rating?The National Weather Service rated the Greenfield tornado an EF4, with peak winds of 175-185 mph. This new radar measurement will not change that rating.The Enhanced Fujita scale estimates tornadic wind speed using damage, not direct readings from radars or anemometers. Anemometers don't usually survive being hit by a strong tornado, and mobile radars only collect data on a limited number of storms.This leaves damage as the best way to determine the strength of most tornadoes.WATCH: Greenfield woman says she's 'lucky to be alive' after being trapped under houseWATCH: 'We're going to rebuild': Greenfield holds vigil one week after deadly tornadoWATCH: Greenfield residents begin storm cleanupWATCH: Raw video of tornado on the ground heading toward GreenfieldWATCH: 'It's a miracle that she survived': family of Greenfield tornado survivor share updates

DES MOINES, Iowa —

Recently released data determined winds in the Greenfield tornado topped 300 mph, making it one of the strongest tornadoes ever recorded.

The data came from a mobile radar truck called a Doppler On Wheels.

The mobile radar, operated by researchers from the University of Illinois, was located just east of Greenfield as the tornado tore through town on May 21.

WATCH: Drone footage shows destruction, path of Greenfield tornado

Scanning 100-160 feet above the ground, the radar measured wind speeds of 263-271 mph in the tornado. Those measurements were then used to calculate ground-level winds of 309-318 mph.

Mobile radars have only found 300+ mph winds in two other tornadoes.

In 1999, a Doppler On Wheels estimated 321 mph winds in the Bridge Creek-Moore, Oklahoma, F5 tornado. In 2013, another radar truck calculated 313 mph winds near the El Reno, Oklahoma, EF3.

Does this change the tornado's EF4 rating?

The National Weather Service rated the Greenfield tornado an EF4, with peak winds of 175-185 mph.

This new radar measurement will not change that rating.

The Enhanced Fujita scale estimates tornadic wind speed using damage, not direct readings from radars or anemometers.

Anemometers don't usually survive being hit by a strong tornado, and mobile radars only collect data on a limited number of storms.

This leaves damage as the best way to determine the strength of most tornadoes.

WATCH: Greenfield woman says she's 'lucky to be alive' after being trapped under house

WATCH: 'We're going to rebuild': Greenfield holds vigil one week after deadly tornado

WATCH: Greenfield residents begin storm cleanup

WATCH: Raw video of tornado on the ground heading toward Greenfield

WATCH: 'It's a miracle that she survived': family of Greenfield tornado survivor share updates

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300+ mph: Greenfield, Iowa tornado had some of the strongest winds ever recorded, radar data shows

Mobile radar measured wind speeds above 300 mph in the deadly twister.

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