Lightning in Slow Motion

Here's a video may change your understanding of lightning, http://vimeo.com/28457062
It shows a strike at 7,207 frames per second and begins with a "negative leader" forking its way down trying to find something to "ground" it. Note how the tendrils branch out like tree roots. Then one branch touches ground and something remarkable happens. All the other branches vanish as a positive return stroke follows the lightning path back up to the cloud. I was also surprised at how long the return strike lasted - I thought the movie was over but the frame counter at the bottom was still going.

Here's how Wikipedia describes a lightning strike:

In a typical cloud-to-ground strike, electrons descends from cloud base to ground. Just before the strike leader reaches the ground, the charge in the step leader induces a huge electric potential in objects connected to the ground (some 10's of million volts), that brings up spikes of positive charge flow from high sharp objects, lightning rods, people, trees, etc. connected to the ground. Once the descending and rising charge paths have met massive amounts of charge flows in the 1 cm thick ionized channel of air centered in a lightning bolt channel--this massive flow of charged particles heats the air and gives the brightest part of a lightning strike. The stepped leader of a bolt of lightning may take on average about 20 milliseconds to reach the ground. Occasionally much longer lightning strokes occur which take more time. Once the downward and upward current flow impulses meet--a few meters or tens of meters above earth—a much more conductive connection is established between the cloud and the ground and the front edge of the return stroke electrons zip from the cloud at about 0.3-0.5 times the speed of light, c, on the highly ionized lightning stroke path. Return currents may continue for several microseconds or even repeat.The return stroke with its much larger current flow produces the highly visible intense main lightning strike as it heats and ionizes the surrounding air in the lightning channel to about 30,000 degrees C (54,000 degrees F).

Extreme Weather Preparation

Here's some extreme weather advice from USA.gov.

Summertime can bring a range of weather challenges and potential dangers. Some of these threats can occur with little warning, so do what you can to prepare by assembling an emergency kit and forming a plan of action. Find out what you should do if faced with the following weather dangers:

Lightning: In the U.S., lightning kills more people each year than tornadoes and hurricanes. If you can hear thunder, you are within striking distance and should seek shelter in an enclosed building or vehicle. While indoors, don't use a corded phone, a computer or other electrical appliances; and avoid contact with plumbing (don't shower, wash hands, do laundry, etc.). Learn more about lightning safety and get tips on what to do if you're outdoors during a thunderstorm.

Floods: If you have time, move essential items to an upper floor. Do not touch electrical equipment if you are wet or standing in water. Do not walk through moving water that is six inches or higher. If floodwaters rise around your car, abandon the car and move to higher ground. Learn more about what to do before, during, and after a flood.

Hurricanes: If you can't evacuate, get inside and secure external and internal doors. Stay away from windows and doors and take refuge in a small interior room, closet, or hallway on the lowest level. Learn more about what to do before, during, and after a hurricane.

Tornadoes: Storm cellars and basements are the safest locations, but if they aren't available, go to an interior room, closet, or hallway on the lowest level. Stay away from windows, doors, outside walls, and corners. If you are in a trailer or mobile home, go to a sturdy, nearby building. Learn more about what to do before, during, and after a tornado.

Extreme Heat: Stay indoors as much as possible. Consider spending the hottest part of the day in an air-conditioned public building, such as a library or shopping mall. Never leave children or pets alone in vehicles. Learn more about what to do in extreme heat.

Wildfires: If your home is threatened by a wildfire, you must evacuate. If you have time, bring an emergency kit that includes copies of important documents. Learn more about what to do before, during, and after a wildfire.

Earthquakes: If you are indoors, stay away from windows, doors, and outside walls and get under a sturdy table or desk. If you are outside, keep away from buildings, streetlights, and utility wires. If you're in a moving vehicle, safely stop the vehicle in an open area and stay inside. Learn more about what to do before, during, and after an earthquake.

Lightning Strikes!

According to the National Weather Service, lightning is the MOST UNDERRATED weather hazard.

Here are some lightning do's and don'ts...

Where to Go
The safest location during a thunderstorm is inside a large enclosed structure with plumbing and electrical wiring. These include shopping centers, schools, office buildings, and private residences.
If lightning strikes the building, the plumbing and wiring will conduct the electricity more efficiently than a human body. If no buildings are available, then an enclosed metal vehicle such as an automobile, van, or school bus makes a decent alternative.

Where NOT to Go
Buildings with exposed openings are NOT SAFE. These include beach shacks, metal sheds, picnic shelters/pavilions, carports, and baseball dugouts. Porches are dangerous as well.
Convertible vehicles offer no safety from lightning, even if the top is "up". Other vehicles which are NOT SAFE during lightning storms are those which have open cabs, such as golf carts, tractors, and construction equipment.

What To Do
Once inside a sturdy building, stay away from electrical appliances and plumbing fixtures. As an added safety measure, stay in an interior room.
If you are inside a vehicle, roll the windows up, and avoid contact with any conducting paths leading to the outside of the vehicle (e.g. radios, CB's, ignition, etc.).

What NOT to Do
Lightning can travel great distances through power lines, especially in rural areas. Do not use electrical appliances, ESPECIALLY corded telephones unless it is an emergency (cordless and cell phones are safe to use).
Computers are also dangerous as they usually are connected to both phone and electrical cords. Do not take a shower or bath or use a hot tub during a lighning storm.

Lightning Myths

“There are only three things that can kill a farmer: lightning, rolling over in a tractor, and old age.”-Bill Bryson

According to the National Weather Service, “lightning kills on average more than 70 people and injures at least 300 each year in the U.S. Most people assume they will never get hit and yet they pour money into lotteries where your chance of winning is less likely than your odds of being struck by lightning. So the “Hey, you never know” lottery philosophy needs to be applied to lightning too.

Much about lightning that people think they know is false. Here are some common myths:

• Lightning never hits the same place twice
  False. The top of the Empire State Building is hit a hundred times a year.
  
• I’m safe if there’s blue-sky overhead
  False. Lightning can easily travel more than three miles from the thundercloud. 10-15 miles is rare but can happen. So distant clouds can be a local concern. Don’t wait for rain to stop a sports game. If you see dark, angry clouds approaching, call the game.
  
• A car is safe from lightning because of the rubber tires
  False. After traveling several miles through air, lightning will laugh at two feet of rubber. It is the metal body of the car that directs lightning around you and keeps you safe. This also means that fiberglass cars, bikes, motorcycles, and open cabin tractors will NOT keep you safe. Likewise rubber sneakers or a rubber rain jacket offer NO protection.
  
• Lightning is attracted to metal or take off anything metal
  False. Metal does not act as a lightning magnet; bolts are just as happy to hit trees and stony mountains. HOWEVER, when lightning does strike, it can travel over 100 yards through metal fences, cars, bleachers, etc.
  
• You can become electrified by touching a lightning victim.
  False. Humans are not batteries and do not store electricity. Give CPR immediately.
  
• Trees will protect you from lightning
  False. Anything tall attracts lightning and being under a tree is the second leading place for lightning deaths.
  
• I’m safe from lightning inside my house
  Yes, But… A lightning strike on the house can cause current to run through phone wires, electrical cords, metal window frames, water pipes (even plastic), etc. Stay away from windows and away from phones and appliances.
  
• A surge protector or UPS will protect my computer against lightning strikes
  False. A surge protector is great for normal, everyday spikes in electricity but lightning is off the scale. The only sure way to protect computers, TVs, etc during a storm is to unplug them.
  
• If lightning is about to strike you outdoors, lie flat on the ground
  False. Lightning can travel over 100 feet though the ground so you maximize your exposure by lying flat. Instead use the ‘Lightning Crouch’ – feet together, crouch low, head tucked, ears covered. You want to be low down with minimal ground contact.
  
• Lighting won’t strike water
  False. Lightning can strike water so boaters and swimmers are not safe in a storm.
  
• Stand near a tall object so the lightning will strike it instead of you.
  False. Lightning is very fickle. It prefers tall objects but it can and does strike anything it wants to. Even if the tall object is hit, you can still be fried if within 100 feet of the strike.
  
• Most lightning injuries occur to golfers
  False. Common victims include postal workers on foot, telephone repairmen, farmers in large fields, joggers, hikers, campers and of course, golfers.
  
• A lightning strike is always fatal
  False. A strike will instantly kill 20% to 30% of the time. Sometimes the heart is stopped and immediate CPR is needed. Sometimes lightning just flashes over the outside of a victim, blowing off the clothes but leaving few external signs of injury and few, if any, burns.

Bottom Line

This myth list is for information only. There is still much about lightning that is not understood. No guarantee of lightning safety is stated or implied.

Resources
www.lightningsafety.noaa.gov/pdfs/LightningMyths-1.pdf
www.uic.edu/labs/lightninginjury/ltnfacts.htm
www.wvlightning.com/lmyths.shtml
www.essortment.com/hobbies/lightningthunde_scqd.htm

Overconfidence

"When it comes to old-fashioned risks like weather, we often overestimate ourselves" - The Unthinkable by Amanda Ripley

In a new book called The Unthinkable, the author looks at human response to disasters and emergencies. She points out that people often make the same mistake that FEMA did, we focus on preparing for the "big" but rare events like terrorism or nuclear attack and overlook the common but deadly surprises that mother nature is prepared to send our way.

Consider lightning. The National Weather Service estimates that 100,000 thunderstorms occur in the United States each year. One hundred bolts hit the earth every second and in many years these bolts kill more people world wide than any other kind of weather including hurricanes and tornadoes. In the U.S. 1318 deaths were attributed to lightning from 1980 through 1995, an average of 82 per year. Lightning can occur anywhere and sometimes with little warning; lightning has struck 10 miles away from the rain of a thunderstorm.

Consider hurricanes. Unlike lightning, no one living near a coast should be surprised or unprepared when a hurricane hits your neighborhood. However did you know that the common cause of hurricane death is drowning; some trapped in the attic of their house but many drowned in their own cars trapped by flood waters. As a child growing up in San Antonio, Texas, I recall each rain season, seeing TV news of flood water pouring across roads like a mini river. And every year one or more cars would try to cross this shallow river and be carried off by the flood.

A few weeks ago in Ossining, NY, a torrential rain came down while my wife and I were shopping. We watched as a river of rain water began pouring down the street. The rain was too much for the storm drains and water gushed out instead of going in. Manhole covers in busy intersections were popped off by geysers. To our surprise cars tried to speed through as if everything was normal. They had no clue of the hidden gaping manholes waiting to grab a tire. We saw one manhole cover hit by a car and the cover went flying - luckily no one was hit by it.

Bottom Line
Take storms seriously - both the lightning and heavy rain. Do not drive through any water that you can not see the ground through. There could be hidden potholes or erosion that will swallow your car. Water that reaches the bottom of your car door could flood your engine or make the car buoyant enough to float away in heavy current.