Little Known Lightning Facts

The Average Distance Between Successive Flashes Is Greater than Previously Known.

Old data said successive flashes were on the order of 3-4 km apart. New data shows half the flashes are about 9 km apart. The National Severe Storms Laboratory report concludes: "It appears the safety rules need to be modified to increase the distance from a previous flash which can be considered to be relatively safe, to at least 10 to 13 km (6 to 8 miles). In the past, 3 to 5 km (2-3 miles) was as used in lightning safety education."

Source: Separation Between Successive Lightning Flashes in Different Storms Systems: 1998, Lopez & Holle, from Proceedings 1998 Intl Lightning Detection Conference, Tucson AZ, November 1998.

A High Percentage of Lightning Flashes Are Forked.

Many cloud-to-ground lightning flashes have forked or multiple attachment points to earth. Tests carried out in the US and Japan verify this finding in at least half of negative flashes and more than 70% of positive flashes. Many lightning detectors cannot acquire accurate information about these multiple ground lightning attachments.

Source: Termination of Multiple Stroke Flashes Observed by Electro- Magnetic Field: 1998, Ishii, et al. Proceedings 1998 Int'l Lightning Protection Conference, Birmingham UK, Sept. 1998.

Lightning Can Spread out Some 60 Feet After Striking Earth.

Radial horizontal arcing has been measured at least 20 m. from the point where lightning hits ground. Depending on soils characteristics, safe conditions for people and equipment near lightning termination points (ground rods) may need to be re-evaluated.

Source: 1993 Triggered Lightning Test Program: Environments Within 20 meters of the Lightning Channel and Small Are Temporary Protection Concepts: 1993, SAND94-0311, Sandia Natl Lab, Albuquerque NM.

Lightning Protection Systems Provide Limited Protection.

"What we found out was that the lightning protection system played a limited role in directing current from a lightning strike…current traveled through the rebar, through concrete, through pipes, through cables, through vent stacks, and through the electrical system…" - Results of rocket-triggered testing.

Source: Marvin Morris, Electromagnetic Test and Analysis Dept., as quoted in Sandia Lab News, April 25, 1997, Sandia Natl Lab, Albuquerque NM.

This factsheet courtesy the National Lightning Safety Institute, Louisville, CO. Tel. 303-666-8817. http://www.lightningsafety.com

Lightning Trivia

• Cape Canaveral Air Force DStation/Kennedy Space Center has documented anvil lightning travelling 76 NM.
• How far can you see lightning? According to Cape Canaveral/Kennedy Space Center, up to 100-km flashes.
• Lightning Causes Forest Fires. Can Forest Fires Cause Lightning? Yes, smoke and carbon micro-particles, when introduced into the upper atmosphere, can become the initiators of static. Sufficient atmospheric static can spark discharge as lightning. Reports of massive lightning storms in coastal Brasil, Peru and Hawaii have been linked to burning of sugar cane fields. The late 90's Mexican forest fires resulted in unusual lightning activity in the USA High Plains area (Lyons, et al.) So too can dust in an enclosed grain elevator create a static discharge. Recent reports (Orville, et al) show the Houston TX petrochemical industry, discharging copious amounts of hydrocarbons into the upper atmosphere, may be responsible for higher-than-normal lightning activity in that area. (National Lightning Safety Institute)