Christine Hudnall

JUNE 22nd - 28th 2008

This week is lightning safety week and because I live in Florida, I thought I would talk a little bit about it.

For those that are new to Florida and for the those that do not live here, Florida is known as one of the top lightning capitals of the world.

The number one weather killer in the U.S. is floods, with lightning right behind it standing in the No. 2 spot. In Florida though, lightning is the No. 1 killer. Lightning kills more people each year, on average, than do tornadoes and hurricanes… combined.

REMEMBER - ALL thunderstorms produce lightning.

Before we go further though, let’s understand some basics.

We will start with what thunder is and then move on to the rest:

Thunder

From the bone-jarring clap to the distant rumbling roar, we have all heard thunder. But what is it? Simply put, thunder is the audio part of a bolt of lightning. When a bolt of lightning passes through air it rapidly heats and expands and it is this rapid expansion that creates a sonic wave or sonic boom. This is because this heated air expands faster than the speed of sound.

• If you hear a drawn-out rumbling, the lightning strike is further away. But if you hear a loud CRACK, then it is close by.

What is lightning?

If you have ever walked across a carpeted floor and touched someone or your pet and received a shock, then you had an electrostatic discharge that was caused by friction. Multiply that many, many, many times and you get lightning, which is a very large electrostatic discharge.

What causes lightning

This answer is a little more complicated, because it is not fully known yet. There are many theories, but no exacts. However, bits and pieces of the conditions are known. Let’s go back to the walking on carpet example. We know that friction caused our shock. Well, inside a thunderstorm cloud there is a lot of friction happening between a positively charged top and a negatively charged base.

This positive and negative comes about from strong updrafts and downdrafts, where the updrafts are carrying small water droplets from the lower areas to the upper areas, anywhere between 35,000 to 70,000 feet. And the downdrafts are carrying hail and ice from the upper frozen areas to below.

When particles from the within these drafts collide the water droplets freeze and as is freezes it releases its heat. This heat in turn slightly warms the surface of the hail and ice, keeping it warmer than the surrounding areas, allowing soft hail to form. As this soft hail collides with even more water droplets and ice, our storm cloud with a positive top and negative base forms because negative charged electrons are shaved off the rising particles and attach to the falling particles.

When the positive and negative areas grow larger within the cloud an electric field is created between the top and the base. (Note - negative and positive charges attract each other.) Now, we know that our atmosphere is a great insulator, and from that we can surmise that the electric charge between the positive top and negative base has to build up enough to overcome our natural atmospheric insulation. When this happens the discharge is seen as lightning.

To further complicate matters though, positive charges beneath the ground start to build and basically follow the storms. If this charge beneath the ground is stronger than the charge in the storm then instead of Cloud-to-Cloud or Intra-Cloud lightning, the negative charge comes down meeting with the positive charge that is rising up from below the ground. This is what we see as Cloud-to-Ground lightning.

• CC - Cloud-to-Cloud
• IC - Intra-Cloud
• CG - Cloud-to-Ground

Lightning is the first to arrive and the last to leave, so always follow the 30/30 rule.

30 seconds / 30 minutes

If the time between a thunder clap and lightning flash is 30-seconds or less, seek proper shelter immediately and remain there until at least 30-minutes after the final clap. (See definition of proper/substantial shelter below.) Lightning can strike more than 10 miles from the storm and has been known to strike over 50 miles if all conditions are right. Do not wait until the last minute to seek shelter. Most people are struck before and after a storm has peaked, and this is when most lightning deaths occur.

Think about it - the visible part of the sun that we can see is between 10,000° F - 11,000° F (depending on your source) a mere pittance compared to up to 50,000° F from a single lightning bolt. If it is hot enough to melt sand, turning it into a naturally formed glass, do you really want to test it out on you, or your loved ones?

Substantial shelter is defined as: A building or large enclosed area with a roof, walls, plumbing and electrical wiring. The reason for all of these things is because lightning will always take the path of least resistance. The plumbing and wiring act as a conductor or conduit, guiding the discharge.

Sheds, pavillions, tents, porches, are not considered safe.

If you have no safe shelter to get to, then an enclosed vehicle will work. Here is the catch though: it has to be a metal vehicle, meaning, metal roof and metal sides. The reasoning is the same as a building/shelter, the metal acts as a conductor. Those rubber tires are no match for lightning.

What this means is: plastic & fiberglass vehicles offer no protection. An open-cabbed tractor offers no protection. And neither does a convertible, even with the top up.

Just remember though, whether in a building, house, car, truck or bus - do not touch any of the metal or anything electrical, including the radio, CB, and more - because then you will become part of the channel through which lightning will seek a route through.