The following is a personal account from the survivor of a tornado that flattened a campground in Pine Lake, Alberta, killing 11 and injuring 136.

July 14, 2000 will forever be recorded in my family's memory as the luckiest day of our lives. It was the start of the third week of a family vacation that had been marred by nearly constant rain, and the three hours we'd just spent in a rental boat had been the highlight.

The dark clouds that had appeared overhead seemed to remain northwest of our location and didn't, at the time, represent a real threat of rain or thunderstorm. Storms are common in this area when the temperature is in the 30 degree range, where it had been all day.

The clouds in the sky continued to move overhead and now suggested the possibility of an early evening storm. This prompted me, a paranoid type, to gather up our belongings and prepare the travel trailer and immediately prepare for the impending downpour. When the wind picked up and the first sprinkle of rain appeared, I gathered my family together in our 27-foot trailer and prepared to weather the storm while watching television.

Visitors to this Alberta campground had very little warning before the tornado hit.

My children screamed and reported on what they were seeing outside of our trailer. My eight-year-old daughter watched a trailer that was 75 feet away from us stand up on its back end and tip over on its side. The rain and hail were pelted sideways in the extreme wind that sounded like a freight train with a continuous whistle blowing for the full four minutes that it lasted.

We felt our trailer lift up and strike the large tree we were parked against several times while we felt a continuous shaking for the entire duration of the terrible wind. My fear at this time was that we were going to tip over and roll, and that I needed to get my family to a safer location.

When the winds died, as the eye of the storm arrived at the campsite, I moved my family to our full-sized van and drove behind a large barn that was about 100 feet away. The wind, rain, and hail picked up again and we suffered through the remainder of the storm in the relative safety of our vehicle.

When we emerged we were surrounded by damage and destruction. We saw the overturned trailer and another trailer unit that had a tree fallen on it.

All around us were chaos and destruction, pain, sorrow and death as people picked themselves up in total shock and dismay from this dreadful event that had just turned a pleasant summer evening into a scene from a war zone.

Since tornadoes often strike with little or no warning, you need to be prepared before a severe storm strikes.

One of the most important things you can do, if you live in an area where tornados hit, is to build a safe room in your house.

If a tornado warning is issued for your location, take the following steps immediately if you are at home:

• Go at once to the basement, storm cellar, or the lowest level of the building.
• If there is no basement, go to an inner hallway or a smaller inner room without windows, such as a bathroom or closet.
• Get away from the windows.
• Go to the center of the room. Debris can sometimes come through walls.
• Get under a piece of sturdy furniture such as a workbench or heavy table or desk and hold on to it.
• If you have time, get a mattress or blankets to protect your head and the heads of any children with you. If you don't have time, use your arms to protect your head and neck.
• If you live in a mobile h

A tornado could threaten you when you are away from home, in a car, a building, or a park. Here are several steps you can take:

If at work or school:

• Go to the basement or to an inside hallway at the lowest level.
• Avoid places with wide-span roofs such as auditoriums, cafeterias, large hallways, or shopping malls.
• Get under a piece of sturdy furniture such as a workbench or heavy table or desk and hold on to it.
• Use your arms to protect your head and neck.

If outdoors:

• If possible, get inside a building.
• If shelter is not available or there is no time to get indoors, lie in a ditch or low-lying area or crouch near a strong building. Be aware of the potential for flooding.
• Use arms to protect head and neck.

If in a car:

• Never try to out drive a tornado in a car or truck. Tornadoes can change direction quickly and can lift up a car or truck and toss it through the air.
• Get out of the car immediately and take shelter in a nearby building.
• If there is no time to get indoors, get out of the car and lie in a ditch or low-lying area away from the vehicle. Be aware of the potential for flooding.

DEADLIEST TORNADO: The "Tri-state" tornado of 18 March 1925 killed 695 people as it raced along at 60-73 mph in a 219 mile long track across parts of Missouri, Illinois and Indiana, producing F5 damage.

BIGGEST TORNADO OUTBREAK: 147 tornadoes touched down in 13 U.S. states on 3 and 4 April, 1974.The outbreak killed 310 in the U.S., 8 in Canada, with 5454 U.S. injuries and 23 hurt in Canada. 48 of the tornadoes were killers.

LARGEST TORNADO: It was in Texas -- specifically, in the high plains of the Texas Panhandle near Gruver on 9 June 1971. At times, the tornado was over 2 miles wide, with an average width of about 2500 yards.

MOST TORNADOES IN A MONTH: The record for most tornadoes in any month (since modern tornado record keeping began in 1950) was set in May 2003, with 516 tornadoes confirmed.

Watch the sky, pay attention to local weather forecasts and know the difference between a Tornado watch and a Tornado warning. 

• Dark, often greenish sky
• Wall cloud
• Large hail
• Loud roar; similar to a freight train

Tornado watch: Atmospheric conditions are favorable for severe thunderstorms to produce tornadoes. Listen for updated forecasts and possible warnings.

Tornado warning: A tornado has been spotted on the ground or is indicated by radar. Take cover immediately!

The aftermath of a tornado can be devastating, but knowing what to do after a tornado strikes will make the recovery effort easier, quicker and safer.

• Listen to local officials, and emergency management personnel.
• Stay away from downed power lines and other harmful debris.
• Remain calm, especially around children.
• Check on the elderly and your pets.
• Use a flashlight and not candles to inspect damage.
• Check for any gas leaks and turn the valves off if there's a leak
• Turn off electricity if there are signs of sparks.
• Watch for any loose debris that could fall.
• Take pictures of your damaged property for insurance claims.

A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long.

A supercell storm is usually the precursor to a tornado.

The United States is the world capital for tornadoes as conditions favourable for tornado development most often occur over the Plains during spring and summer.

From a supercell, a tornado is born

A typical tornado outbreak often features an intense upper-level disturbance moving across the Plains during spring. This disturbance provides the strong vertical wind shear that gives an updraft its twisting motion, turning a normal thunderstorm into a potentially tornado-spawning supercell.

As several friends and I sat down to watch the movie “Twister” at an after-prom party in the early hours of May 4, 2003, little did we know that later that day, our lives would be endangered by an actual twister.

Fast-forward 12 hours to Subway, where I work, in Stockton, Missouri. My co-worker’s mother keeps calling about the bad weather headed our way. Because we aren’t busy, I send my co-worker home at 6 p.m. My mother calls at 6:15 p.m. to remind me what to do if there is a storm: get inside the walk-in cooler.

I try not to worry, telling myself it’s just another thunderstorm. As I sweep near the front of the restaurant, about 6:30 p.m., the power goes out. The wind is roaring, and the front door is opening, closing, opening, closing. To stop rain from blowing in, I run and lock it. In a few minutes, I’ll realize there was no need to lock the door.

I scurry back to the walk-in cooler, grab my purse and cell phone and step into the cool shelter. I try shutting the door, but the wind, which I now realize is a tornado, is sucking the door open. I clench my phone and a tiny bar supporting the shelf inside the cooler. I pray and dial my phone fast, glancing through the cooler doorway every few seconds.

I watch the cabinets in front of the door being sucked across the room. I watch the huge beams that support the whole building crash to the ground. I watch the wall above the cooler collapse right in front of me. I watch as everything from Subway leaves the building and everything from Dollar General Store, right next door, comes in. Debris hits the sides of the cooler, and it shakes. I wonder when this will all be over. I keep praying that God keeps me safe.

After the winds die, I yell to see if anyone can hear me; I don’t want to spend another minute in the cooler. I hear a voice telling me it’s safe to come out. About 30 feet in front of the cooler’s doorway, I can see a glimmer of daylight. I grab my purse and phone and crawl out through the hole.

Sitting on the roof of Subway—now just a few feet from the ground—sirens blare, emergency vehicle lights flash and smoke fills the sky. No trees are left, power lines are down, debris is everywhere, and hardly any buildings are standing.

Knowing that your area is prone to tornadoes is the first step in becoming prepared for one. The key to being safe is to have a plan. Knowing what you will do when a tornado is approaching will help you get out of harm's way, fast.

Some steps to take in order to prepare for a tornado include:

• Plan what you would do in the event a tornado watch or warning is issued.
• Purchase a weather radio
• Designate a tornado shelter and route to it

When forecasters determine that tornadoes are possible in your area, a tornado watch will be issued. This is your clue to:

• Tune into your weather radio and stay tuned to future weather updates and listen for possible warnings.
• Check on the elderly, children that may be in school or at a friend's house, and your pets.
• Stay close to safe shelter in the event a warning is issued and be ready to act quickly.

A tornado watch can turn into a tornado warning within minutes. While improving technology allows forecasters to predict weather further in advance with a greater degree of accuracy, there are still occasions when nature throws a surprise at us, spinning up a tornado with little or no warning. 

Forecasters and researchers use a wind damage scale created by T. Theodore Fujita to classify tornadoes and sometimes the damage done by other wind storms. The F - for Fujita - scale uses numbers from 0 through 5. The ratings are based on the amount and type of wind damage.

• F-0. Light damage. Wind up to 72 mph. Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.
• F-1. Moderate damage. Wind 73 to 112 mph. The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed.
• F-2. Considerable damage. Wind 113 to 157 mph. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated.
• F-3. Severe damage. Wind 158 to 206 mph. Roof and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted.
• F-4. Devastating damage. Wind 207 to 260 mph. Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.
• F-5. Incredible damage. Wind above 261 mph. Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel-reinforced concrete structures badly damaged