Lightning Detection or Prediction Systems
April 07, 2011
Tim Stoecklein, Assistant Director
Kansas State University
It has been said that the weather is the most popular topic of conversations across the world, and if you think about it, that is probably a fairly accurate statement. To play or not to play is often the question we face when it comes to our recreational programs. Typically the decisions focus on the rain, the snow, the wind, or the lightning. Sometimes it can be a combination of several as once I had to cancel a softball game due to snow AND lightning! Of all the elements served up by the environment, lightning is the second most deadly, behind floods.
Making the call to halt activities due to lightning, or when to resume, can be one of the most challenging because of the nature of the beast. Lightning is most random in its behavior, and statistically speaking it cannot be ignored.
- Lightning strikes the ground approximately 25 million times each year in the U.S. (National Weather Service)
- It can travel 1,000 ft in a millionth of a second (National Lightning Safety Institute)
- Each bolt will average 25,000 amps with a voltage in the hundreds of millions (National Lightning Safety Institute).
Many institutions have turned to technology to assist them with these decisions by purchasing equipment in the form of lightning detectors or predictors. Each of the systems mentioned have their advantages and disadvantages.
Lightning detectors, like those used by many recreation programs, determine lightning strikes have occurred through the detection of electromagnetic emissions or low frequency radio signals (think of the static crashes on your AM radio). The direction and/or distance are calculated using a direction-finding antenna and the strength of the signal received. The data is processed within the unit and the results are displayed, often in terms of a set range. Manufacturers such as BOLTEK and SkyScan have created user-friendly units that can be used in many applications. Some units act as a stand-alone device that can be used in a portable application, while others require computer hardware and software.
Another option is lightning prediction. Systems such as THOR GUARD are designed to predict lightning within a set parameter before it occurs rather than measuring the presence and distance once a strike has occurred. The THOR GUARD system does this by measuring and analyzing the electrostatic field in the atmosphere. Once the processor detects parameters conducive to a strike, an alarm is sounded in varying fashions. This system is more elaborate, requiring more fixed hardware.
Each system has a long list of references, and they can be researched on the internet or over the phone. Do your homework to see which option could be best for your programs!
What is a proper distance at which to suspend activities, and equally important is at what point is it safe to resume activity? The National Lightning Safety Institute (NLSI), the (NWS), and the National Federation of State High School Associations (NFHS) all recommend the “30-30 Rule”. The 30-30 Rule states that when you see lightning, count the time until you hear thunder. If this time is 30 seconds or less, go immediately to a safer place. If you cannot see the lightning but hear thunder, the thunder alone means the lightning is likely within striking range. Wait at least 30 minutes or more after the last thunder or lightning before resuming activity.
Many people may be think that 30 minutes is a long time to wait after a storm has passed. The NLSI reports that, statistically, more lightning originates from the backside of a storm than the front side. The use of lightning detection or prediction devices should help you determine at what point a threatening storm has breached or exited a safe distance from the event venue. However, the 30-30 rule can help you determine the possible settings for your device. The NLSI and NWS both suggest a safe distance of six to eight miles, which is concurrent with their 30-30 rule. Keep in mind that storm velocity and other atmospheric elements can alter the results of the 30-30 rule in relation to actual distance of the threat, and should also be considered when determining your device settings.
As your program shapes its policies with regards to the weather, and more specifically lightning, one should investigate the equipment and information thoroughly as it applies to your situation. Keep in mind that while your local weather agency will issue watches and warnings for thunderstorms, tornadoes, and flooding, they do not have such indicators for lightning.
For more information on lightning safety, check the following links:
THOR GUARD – http://www.thorguard.com/
SkyScan – http://www.skyscanusa.com/
To assist in the decision, here are a few comments from other recreation professionals who utilize either the SkyScan or THOR GUARD system:
– Almost no false reports, very accurate warning
– Automated system that takes the decision-making out the hands of the employees
– Warning tones and strobes provide a clear cut and consistent indication of when to clear the venue
– Produces an “all clear” signal
– Can be networked and displayed with computer software
– Warnings can be issued via computer network in addition to on-site signals
– No estimate on time before storm arrival or warning
– Ease of use
– Mobility, ability to use at multiple venues
– Accurate enough to confirm proximity of the storm
– Likely to produce false reports depending on proximity to surroundings
– Requires personnel to make to call to clear or determine “all clear”
Contributors to this article includes:
– Lance Freeman, Senior Associate Director — Operations, Colorado State University
– Brian Stillman, Assistant Facility Coordinator, University of Texas at Austin
– Jason Adamowicz, Associate Director, Ball State University
– Scott Wagner, Intramural Recreational Sports Director, Truman State University