By Portfolio Editor Roz Hamlett
The New York/New Jersey region isn’t ‘lightning alley’ – that distinction belongs to Tampa, Fla. Being home to One World Trade Center, the tallest skyscraper in the Western Hemisphere, does mean the metropolitan area experiences its share of intense lightning strikes, especially on hot, humid days. Lightning is drawn to the tallest of buildings like tourists to New York City attractions. Does that mean that being anywhere near One WTC during a storm is particularly dangerous? In most instances, the answer is no, not really.
“One WTC being the tallest building in North America will attract more lightning than the Memorial Pools or Liberty Park because its height significantly reduces the insulating air gap between the ground and the clouds,” said Alan Reiss, director of WTC construction.
In fact, there even was concern in the aftermath of 9/11 that Lower Manhattan would become more vulnerable to lightning strikes in the absence of the towers, which averaged more than 20 strikes a year. Even before One WTC opened to the public, its spire had attracted multiple strikes.
Rather than increasing the risk of a lightning strike in its vicinity, One WTC actually protects the surrounding area due to a phenomenon known as “the degree of influence.” Notwithstanding lightning’s preference for tall objects, the general rule of thumb is that an object will only attract lightning at a distance that is at or less than the object’s height.
“Because One WTC is 1776 feet high, the tower essentially protects anything within a circle centered around it with a radius of 1776 feet,” said Reiss. “Perhaps one in 100 lightning strikes might occur within that zone, but I never heard of lightning ever striking the pools.” One WTC is safe during lightning strikes because of its state-of-the-art protection system, which is based on the same concepts pioneered by Benjamin Franklin. Lightning rods now are mounted on the roof tops of buildings, houses and 4 World Trade Center.
Following Franklin’s modern lightning protection system, One WTC is a super-sized Faraday cage that distributes electrical current around the outside of the tower, with none of it passing through the interior space of the building. The current discharges into the bedrock below the tower and dissipates into the earth. A Faraday cage is an enclosure made of conductive material that blocks electric fields. Elevators, MRI scan rooms and aluminum insulated bags are all examples of Faraday cages.
Reiss offers the following safety tips for keeping safe during lightning strikes:
- If thunder is heard or lightning is seen, get inside a completely enclosed building or a metal car.
- If you cannot reach shelter, avoid being the tallest object in the area.
- Never shelter beneath a tree. If you’re in the woods, shelter beneath the shortest trees.
- If only isolated trees are nearby, crouch down on the balls of your feet.