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A 200-mile Lightning Bolt And A 7.7-second Flash

Cloud-to-Cloud lightning is the most common type of lightning, but do you know the other types? The National Audubon Society Field Guide to Weather helps us better understand even the rarest types of lightning. Paige Schwahn/The Republic Wochit

ASU professor and Tucson scientists played a role in documenting extreme lightning events.

Imagine being struck in Phoenix by a lightning bolt that originated in a storm near Kingman.

Or picture looking up at the sky during a storm and witnessing a lightning flash that lasts almost as long as it takes an Olympic sprinter to run 100 meters.

Believe it or not, events such as these have taken place in recent years and an Arizona State University professor and a Tucson-based scientific company played key roles in documenting them.

The World Meteorological Organization recently certified two records involving lightning. The organization confirmed that a lightning flash over Oklahoma during a June 20, 2007, storm covered a horizontal distance of 321 kilometers or 199.46 miles. The same study confirmed that the record for the longest duration of a continuous flash is 7.74 seconds on Aug. 30, 2012, over southern France.

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The certification of these records is the first time lightning has been included in the WMO extreme weather and climate archive, according to Randy Cerveny, a professor in the school of Geological Sciences and Urban Planning at ASU.

Cerveny said the big takeaway for the public from these records is that lightning can pose a danger even when a storm isn’t directly overhead.

“We have something called the 30-30 rule,” Cerveny said. “If there is less than 30 seconds between the flash and the thunder, you should stop whatever you’re doing and go inside. The other 30 is you should wait 30 minutes after the storm has passed. Even if the storm has passed, as we just found out here, lightning can travel tens of miles away from where that parent thunderstorm is.”

lightning bolt

Lightning as seen from Lake Pleasant Parkway and 95th Avenue in north Peoria. Daniel Williams/Special for The Republic

Better able to pinpoint

Cerveny, who also is chief rapporteur of climate and weather extremes for the WMO, said it has only been in recent years that meteorologists have had the ability to detect and measure lightning with such precision. Previously, the WMO archives only included extremes in categories such as heat, cold, wind speed, precipitation and other weather phenomena.

“In today’s world, we have these lighting-detection networks that are incredibly sensitive and incredibly precise in identifying exactly where these strikes are taking place,” Cerveny said. “We are much better at positioning these things and telling how long they last than what we were just a few years earlier.”

Much of the science behind these improved lightning detection networks is being done by a division of the Finnish scientific and meteorological instrument company Vaisala. About 30 years ago Vaisala purchased the Tucson company that grew out of University of Arizona research that developed the National Lightning Detection Network.

That work continues at Vaisala’s Tucson facility and it supplied data from its U.S. and global lightning detection networks to help certify the records.

Ron Holle, a meteorologist with Vaisala in Tucson, said the networks detect a radio signal unique to lightning that is emitted by each flash. The networks use information from several antennas within a given area to pinpoint lightning strikes.

“The antenna is tuned to look for that particular signal,” Holle said. “When it hits the ground, it locates the angle and time stamps the time to less than a thousandth of a second. Those times and angles from an average of around 10 antennas are sent to the control center here (in Tucson).”

Cerveny and Holle said it is likely that the two recently certified records may not reflect the true extremes for lightning. The records reflect the extremes known to the WMO for which quality data is available.

In addition to being recent technology, the detection networks are expensive and are most prevalent in the United States and Western Europe.

“We have to start somewhere,” Cerveny said. “We set these up and verified these extremes with the idea we’ll probably be revising them in the future as we find areas that have even more intense lighting. There are parts of South America that really get slammed by lightning. I’m hoping some day we can get a network down there to evaluate those strikes.”

Safety is the big goal

Both scientists also expressed the hope that the attention given to these lightning extremes will help deliver the message that a storm doesn’t have to be directly overhead to be dangerous.

Holle said that is especially true in places like Arizona where dry storms often produce lightning. From 2006-2015, lightning killed 16 people in Arizona. That ranks fourth in the country behind Florida (47 deaths), Texas (20) and Colorado (17).

He said people should be conscious of the threat of lightning whenever storms are known to be in the area.

“One of the things that comes up often in lighting safety is ‘If it’s not raining, I’m safe,’ ” Holle said. “It doesn’t rain a lot with lighting in here Arizona. I estimate here in Arizona, at least half of the time when lighting strikes if the person looks up there is going to be some blue sky. There is not an automatic that signal that everything is OK.”


Source: Lightning records: A 200-mile bolt, a 7.7-second flash


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