Photo: U.S. Department of Education
The more we learn about lightning, the more difficult crafting simple safety rules seems to be. Until the last five years or so, we didn't realize that lightning from "anvil crawlers" can travel as far as 30 miles from the core of the thunderstorm yet still induce cloud to ground lightning.
|Anvil crawlers (foreground) with cloud-to-ground lightning.|
Photo: Norway Meteorological Institution
At this point, there is no perfect lightning warning technique. What to do?
A federally approved technique is the “flash to bang method.”
- If you see lightning and the thunder arrives in less than 30 seconds (six miles) you are in danger. Less than 15 seconds is high danger.
- The danger continues until 30 minutes have passed after the last thunder is heard
- This requires people to keep track of each peal of thunder and restart the clock each time thunder occurs.
This can result in some difficult situations. There was the Orlando school last August that held students – even with the parents demanding to take their children home – for five hours after the scheduled dismissal because of the “flash to bang” rule.
The best way to handle for schools, offices, campuses, etc., to keep their employees safe is to contract with WeatherData for its SkyGuard® service which will keep this type of situations from occurring. We use the National Lightning Detection Network® and we are looking at the 3-D structure of the storm on radar. We can keep situations like Orlando’s from occur as well as making sure you have plenty of notice if lightning is moving in.
If that is not done, then the “flash to bang” rule will work most of the time.
Whichever you choose, make the decision on a “fair weather” day then stick to it. Ad libbing during a storm always seems to create problems.