page_title: Lightning strike
section_title: Monitoring and warning systems
hierarchical_section_title: Lightning strike / Prevention and mitigations / Monitoring and warning systems
caption_attribution_description: A Thor Guard Lightning Prediction System, as deployed by the Niles Parks District, Niles, Illinois, United States
context_page_description: A lightning strike or lightning bolt is an electric discharge between the atmosphere and the ground. They mostly originate in a cumulonimbus cloud and terminate on the ground, called cloud to ground lightning. A less common type of strike, called ground to cloud, is upward propagating lightning initiated from a tall grounded object and reaches into the clouds. About 25% of all lightning events worldwide are strikes between the atmosphere and earth-bound objects. The bulk of lightning events are intra-cloud or cloud to cloud, where discharges only occur high in the atmosphere. Lightning strikes the average commercial aircraft at least once a year, but modern engineering and design means this is rarely a problem. The movement of aircraft through clouds can even cause lightning strikes.
  A single lightning event is a "flash", which is a complex, multi-stage process, some parts of which are not fully understood. Most cloud to ground flashes only "strike" one physical location, referred to as a "termination".
context_section_description: The exact location of a lightning strike or when it will occur is still impossible to predict.  However, products and systems have been designed of varying complexities to alert people as the probability of a strike increases above a set level determined by a risk assessment for the location's conditions and circumstances.  One significant improvement has been in the area of detection of flashes through both ground and satellite-based observation devices.  The strikes and atmospheric flashes are not predicted, however the level of detail recorded by these technologies has vastly improved in the past 20 years.
  Although commonly associated with thunderstorms at close range, lightning strikes can occur on a day that seems devoid of clouds. This occurrence is known as "A Bolt From the Blue"; lightning can strike up to 10 miles from a cloud.
  Lightning interferes with AM (amplitude modulation) radio signals much more than FM (frequency modulation) signals, providing an easy way to gauge local lightning strike intensity. To do so, one should tune a standard AM medium wave receiver to a frequency with no transmitting stations, and listen for crackles amongst the static. Stronger or nearby lightning strikes will also cause cracking if the receiver is tuned to a station. As lower frequencies propagate further along the ground than higher ones, the lower medium wave (MW) band frequencies (in the 500–600 kHz range) can detect lightning strikes at longer distances; if the longwave band (153–279 kHz) is available, using it can increase this range even further.
  Lightning detection systems have been developed and may be deployed in locations where lightning strikes present special risks, such as public parks. Such systems are designed to detect the conditions which are believed to favor lightning strikes and provide a warning to those in the vicinity to allow them to take appropriate cover.
caption: A Thor Guard lightning prediction system
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