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LIGHTNING DETECTORS
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Wxline, featuring Strike Guard™
Wxline, LLC
The Strike Guard™ lightning detection system
employs state-of-the-art technology to address the
most demanding lightning safety and equipment
protection applications.
(General to Advanced Audience)
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LIGHTNING DETECTION RESOURCES
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Convective Weather Hazards (slide show)
MIT Lincoln Laboratory, courtesy of
University Corporation for Atmospheric Research (UCAR)
(Advanced Audience)
(Adobe PDF file)
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An Introduction to the National Lightning
Detection Network
Global Hydrology and Climate Center (GHCC),
National Aeronautics and Space Administration (NASA)
(General to Advanced Audience)
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Lightning & Atmospheric Electricity Research
at the GHCC
Global Hydrology and Climate Center (GHCC),
National Aeronautics and Space Administration (NASA)
(General Audience plus Data Sets)
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Lightning Detection and Ranging System
Thomas O. Britt, Carl L. Lennon & Launa M. Maier,
Kennedy Space Center (KSC),
National Aeronautics and Space Administration (NASA)
(General Audience)
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Lightning Detection From Space:
A Lightning Primer
Global Hydrology and Climate Center (GHCC),
National Aeronautics and Space Administration (NASA)
(General Audience)
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Pacific Lightning Detection Network (PacNet)
Department of Meteorology, University of Hawai`i
(General to Advanced Audience)
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’Spherics for Monitoring Lightning
School of Environmental Science,
Division of Science and Engineering,
Murdoch University
(General Audience)
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OVERVIEW OF LIGHTNING DETECTION EQUIPMENT
by the National Lightning
Safety Institute
Lightning hazards can be mitigated by advanced planning. One part of this
safety program should include an early detection and warning alarm
package. Lightning detectors can give notice to shut down dangerous
operations before the arrival of lightning. They also may signal
“all clear” conditions after the lightning threat has
passed. Some type of detection package may help you with Duty-To-Warn
issues.
Lightning detectors vary in complexity and cost from large dedicated
equipment packages costing in excess of $150,000 to inexpensive $20-$30
Radio Shack portable weather radios. The Flash-to-Bang (F-B)
Method requires no dedicated detector — only counting the time
in seconds from seeing lightning’s flash to hearing the associated
thunder or bang. For each five-second interval, lightning is one
additional mile away. Thus, a F-B of 10 = 2 miles, 15 = 3 miles,
20 = 4 miles, etc.
The distances from lightning Strike A to Strike B to Strike C easily can
exceed more than five miles. How much time is needed to get to
shelter? Three to four minutes is suggested. Suspension of activities
is very site-specific. For general situations, we recommend activating
your lightning defense at a F-B of 30: lightning is six miles away.
We also recommend waiting to resume activities for 30 minutes after the
last observed lightning or thunder. This protocol may seem
excessively conservative in many situations. (“We’ll never
get anything done under such strict guidelines....”). Lightning
safety is a case-by-case risk management decision. And, yes, safety
and productivity sometimes are incompatible. Safety, however,
always should be the prevailing directive.
Available technologies of present day lightning detectors include:
- Radio Frequency (RF) Detectors. These measure energy discharges
from lightning. They can determine the approximate distance and
direction of the threat. See
Boltek Lightning Detection Systems.
- Inferometers. These are multi-station devices, much more costly
than RF detectors. They measure lightning strike data more precisely.
Inferometers usually require a skilled operator. See
Vaisala Lightning Detection.
- Network Systems. The National Lightning Detection
Network and the United States Precision Lightning Network
systems cover all of the USA; each reports lightning strikes to a
central station. Local storm data is available by subscription.
Past strike information is archived and accessible upon request. See
NLDN and USPLN.
- Electric Field Mills. This pre-lightning detection equipment
measures potential gradient (voltage) changes within the earth’s
electric field and reports these changes as thresholds build to
lightning breakdown values. For more on EFMs, see
Mission Instruments and
Campbell Scientific, Inc.
- Optical Monitors. These can provide earlier warning, as they
detect cloud-to-cloud lightning that typically precedes
cloud-to-ground lightning.
- Hybrid Designs. These monitors use a combination of the other
single-technology designs. Two or more sources of information
(C-C, C-G, optical recognition, EFM) may be better than just one.
See Wxline.
- Subscription Services. NLSI Recommendation:
Rent a meteorologist. Here hired professionals make the critical
decisions and advise you. This method may blunt claims of negligence
if something goes wrong. And some subscription weather services
provide windspeed, rain, hail, tornado and other data sets. Off-site
lightning detection by subscription is available from several vendors,
including Skyview Weather,
AccuWeather, Inc.,
DTN/Meteorlogix.com
(Weather Sentry) and
WeatherData Services, Inc.
(Sky Guard).
Lightning Detection Options
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Accuracy vs. Cost vs. Complexity
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| Source of Info |
Accuracy |
Cost |
Complexity |
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Hearing
Thunder |
Danger
Is Near |
No Cost |
Simple |
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TV Weather
Channel |
General
Info. |
No Cost |
Simple |
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Weather
Radios |
General
Info. |
Up to $40 |
Simple |
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Handheld
Detectors |
50-60%
Accurate |
Up to $500 |
Moderate |
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Boltek
System |
70-80%
Accurate |
Up to $1500 |
Moderate |
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Wxline
System |
90-95%
Accurate |
Up to $7000 |
Moderate |
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Subscription
Service |
95%+
Accurate |
Monthly Fee |
Simple |
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Beware of a false sense of confidence imparted by detectors; none of
them will detect all lightning all of the time. None of them will
provide “first strike / Bolt Out of the Blue” information
or forecast in advance the precise locations of lightning strikes.
Various detection receiver algorithms operate at different frequencies
and wavelengths: Boltek Stormtracker in the Low
Frequency Range 100-700 kHz; Vaisala GAI NLDN at 100-400
kHz; NMT Lightning Array at VHF 60-78 mHz; NASA LIS
and OTD optical at 777.4 m; Vaisala SAFIR VHF at 109-119
mHz; Vaisala GAI LDAR II at 50-120 mHz; GAI VLF at
20-50 kHz; the UK Meteorological Office RDI at 9.8 kHz; etc.
An excellent summary of families of lightning detectors and future research
is available at NASA’s
Lightning Detection Instruments.
Detectors can display early warning of lightning conditions to hazardous
operations. Some detectors can start/stop standby power
generators. A signaling or alarm notification method is essential to
alert field personnel of developing dangerous circumstances. Two-way
radios, remote-activation siren packages, strobe lights and other methods
are available.
Essential companions to any type lightning detector include:
- A written Lightning Safety Policy;
- Designation of Primary Safety Person;
- Determination of When to Suspend Activities;
- Determination of Safe/Not Safe Shelters;
- Notification to Persons at Risk;
- Education: At a minimum consider posting information about
lightning and your organization’s safety program;
- Determination of When to Resume Activities. For many situations,
if you hear thunder, your (brain) detector is working fine. Since
lightning and thunder always occur paired, the lightning associated
with the thunder you just heard is within your hearing distance —
some seven to nine miles. Immediately go to safe shelter. No place
outside is safe!
Select the detector and/or signaling device that is site-specific to
your requirements, is easiest to use, and which offers the most favorable
cost/benefit to your operation’s budget. No detector is
100% perfect.
Summary: Detectors give advanced notice of the lightning
hazard. Now consider other defenses to mitigate the hazard. Where is
safe refuge? How long to get there? How long to stay there? What about
computers and servers and telecommunications? Is facility bonding and
grounding and surge protection OK? Lightning rods required? Contact
NLSI for assistance.
Authored by the National Lightning Safety
Institute (NLSI). Previously published in print;
Exclusive online publication 25 April 2008 by Ten Spider
Enterprises; modified for the web. Article Copyright
National Lightning Safety Institute;
Used with Permission.
Follow links to the right to learn more about lightning detection and lightning detectors.
At the left margin, Related Links address topics of interest
pertaining to lightning and thunderstorms, including lightning protection, lightning safety,
and other lightning and severe weather topics. View the
Weather & Meteorology SiteMap
for a complete list of meteorology and weather-related topics.
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