Happy Friday!
I hope you had a good weekend! I was awakened by booming thunder and flashes of lightning early this morning before sunrise that lasted hours, accompanied by torrential rain. My attempts to go to the gym were thwarted by streets partially underwater, and at least 2 inches of rain in the gym parking lot. Fearing flooding (well known to occur in Dallas), I turned around and went back home (and exercised).
Today we take a closer look at these sleep intruders.
Thunderstorms most commonly begin early in the day when the sun starts to hit the ground causing warm air to rise into the atmosphere. Over time, these pockets of air form cumulus clouds that continue to grow vertically in the atmosphere, the so called "towering cumulus", eventually becoming anvil-shaped (wider at the top, narrower at the bottom).
Precipitation forms within the cloud, with small ice crystals on top, a mixture of small ice crystals and hail in the middle, and a mixture of rain and melting hail in the lower levels (archived Happy Friday about hail available upon request). Air movements and collisions between the precipitation in the middle layers cause them to be charged. The lighter crystals are positively charged and move upward with the rising air. The heavier hail is negatively charged and is either suspended or drifts to the lower part of the cloud. Thus, the top of the thunderstorm cloud is positively charged and the lower part is negatively charged. A small positive charge also develops at the bottom of the thunderstorm cloud. The negative charge in the middle of the cloud causes the ground beneath it to become positively charged, and the positively charged lower part of the cloud causes the ground beneath it to become negatively charged. And as you know, opposites attract.
Lightning is a giant spark of electricity either in the atmosphere or between the atmosphere and the ground. Initially, air insulates these positive and negative charges in the cloud and between the cloud and the ground. However, when the differences in charges exceeds a certain threshold, the insulation breaks down, with a rapid discharge of electricity known as lightning. Lightning can occur within the cloud (intra-cloud lightning) or between positive and negative charges between the cloud and the ground (cloud-to-ground lightning).
Two different types of cloud-to-ground (CG) lighting occur depending on the charge in the cloud where it originates. The most common type, a channel of negative charge called a stepped leader, zig-zags downward in a forked pattern. As it descends toward the ground, it causes streamer channels of positive charge to reach upward. As they connect, a powerful current flow creates a bright luminosity trailing 60,000 miles per second back to the cloud, causing a visible lightning flicker. Less commonly, a positive charged leader travels downward, with an upward return of a lower positive charge to earth with a single return stroke.
A "bolt from the blue" is CG lightning that starts inside a cloud, goes outside the storm and travels horizontally away from the cloud then goes to the ground.
Intra-cloud (IC) flashes do not reach the ground. Cloud-to-air (CA) flashes have visible channels that extend into the air around a storm. An IC flash that stays within a cloud is called sheet lightning, producing a sheet of luminosity during a flash.
Heat lightning is any type of lightning that is too far away for the thunder to be heard. It can have a reddish color to it.
Cloud-to-cloud, or spider lightning produces long horizontal flashes, often seen under stratiform clouds.
Thunder is the sound made by the flash of lightning. When lightning passes through the air, it heat it quickly, producing temperatures of 50,000 degrees Fahrenheit (5 times hotter than the sun's surface)! The extreme change in heat causes the air to expand and creates the sound of thunder.
Fun facts and myths about thunder an lightning:
Lightning can strike as far as 10 miles (16 km) from a thunderstorm; if you hear thunder, you are within striking distance from the storm.
There are about 25 million lightning flashes every year.
Lightning is one of the top weather-related killers in the U.S. and causes more injuries than deaths (about 10% of people struck are killed).
The odds of being stuck by lightning in a given year are 1 in 1,222,000 and the odds of being struck in your lifetime are 1 in 15,300. Much higher odds than winning the Powerball jackpot (1 in 292 million) or dying of a hornet, wasp or bee sting during your lifetime (1 in 46,744).
Pets can often tell that a storm is coming before humans are able to. Thunderstorms can cause pets to panic or flee (lesson: microchip your pet). It's always safer to have them inside.
You should never shelter under a tree during a thunderstorm – this is one of the leading causes of lightning-related casualties. Lightning likes to strike the tallest, most isolated objects, also including picnic pavilions and bodies of water. For this reason, lightning often strikes the same place twice (so much for that myth).
Lightning can spread out for 60 feet after striking earth. Therefore, it's true – showering or touching plumbing during storm is dangerous (metal is a great conductor). This includes doing dishes and washing your hands or face. Wait at least 30 minutes after you hear the last rumble of thunder before taking a shower or running the water.
Touching a victim who has been stuck by lightning will not electrify you. (People stuck by lightning have died because bystanders were afraid to offer CPR.)
If it takes 30 seconds or less to hear thunder after you see lightning, the storm is within 6 miles (9.7 km) and close enough to be dangerous.
Being in your car does not protect you from being stuck by lightning! The rubber tires do not you safe. Hard-topped vehicles are safest because the shock is dispersed in the metal shell of the car.
It just started to thunder again. As lightning storms threaten computers through surges and travel through cables, I'm unplugging my computer right now.
Have a good weekend and Happy Father's Day to all of the dads!
Deb
https://www.youtube.com/watch?v=8KjxXvBDTOo&t=184s