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
Source: Separation Between Successive Lightning Flashes
in Different Storms Systems: 1998, Lopez & Holle, from Proceedings
1998 Intl Lightning Detection Conference, Tucson AZ, November
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
Source: Termination of Multiple Stroke Flashes Observed
by Electro- Magnetic Field: 1998, Ishii, et al. Proceedings
1998 Int'l Lightning Protection Conference, Birmingham UK,
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
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
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
- 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)