Tornadoes Destruction from the Barrie Tornado Thunderstorms In

Tornadoes Destruction from the Barrie Tornado Thunderstorms In order to understand tornadoes, we must consider where they are formed. The thunderstorm is usually a storm composed of one or more cells. Each cell is a few kilometres in diameter and develops from clouds that grow rapidly upward and produce thunder and lightning. A thunderstorm often brings heavy precipitation, such as rain or hail, as well as strong gusty winds. Sometimes thunderstorms can become quite violent and may generate flash floods or tornadoes.

Thunderstorms have three stages of development: Cumulus Stage initial stage of cloud development, as warm, humid air rises and water vapour condenses to form the cloud; characterized by upward motion throughout the cloud Mature Stage cloud reaches maximum vertical development, precipitation starts to fall, creating a downdraft; this is the stage with the most violent weather and the occurrence of thunder and lightning Dissipating Stage precipitation-induced downdraft is observed throughout the cloud; the cloud sinks and evaporates away. Tracking Storms

Just as a searchlight beam picks out and reflects off an object, weather radar sends out microwave pulses that bounce off rain, hail and snow. The radar measures the pulses reflected back by precipitation and relays the patterns to a video screen for a meteorologist to interpret. Conventional weather radar can show the type, amount and rate of precipitation. Doppler radar, can also measure the speed at which precipitation is moving in the area the radar covers. While the actual tornado is usually too small for the Doppler radar to see, it does detect wind shifts, gust fronts and cyclonic patterns that are the

signature of tornadoes. Storm Safety 30 Seconds: 30 Minutes: When there are fewer than 30 seconds between the flash of lightning and the rumble of thunder, you should seek immediate shelter in a well-constructed building. If no such building is nearby, then the best choice is to get into a hardtopped vehicle such as a car, van or RV. If you are caught outside and cannot quickly get to a building or vehicle, then you should do the

following: Avoid being the tallest object around; Avoid being NEAR the tallest object around (i.e. an isolated tree); Avoid being near objects that conduct an electrical charge (metal fence, power lines, golf clubs, fishing rod, etc.); Get out of, or off, the water. Maintain lightning safety precautions for 30 minutes after the last flash of lightning or rumble of thunder. There have been a number of documented cases of lightning

striking the ground many kilometres away from a thunderstorm, even though the storm may be moving away. One wellknown lightning guideline is the "30-30" rule: Take appropriate shelter when you can count 30 seconds or fewer between lightning and thunder, and

remain sheltered for 30 minutes after the last thunder. Volunteer Weather Watchers All across Canada, thousands of volunteers watch the skies. When they spot tornadoes, thunderstorms, or other severe weather, they report it to Environment Canada. What is a Tornado? The typical tornado first appears as a rotation in a huge thunder cloud, behind a shroud of heavy rain or hail.

The sky usually turns green, yellow or black. The tornado descends as a violently rotating funnel cloud and sounds like the rumble of a freight train or a jet and can be quite deafening. A tornado can last just a few minutes or a few hours and usually leaves a wake of destruction. Fujita Scale Rating the Severity of Tornadoes The Fujita scale is used to rate the severity of tornadoes as a measure of the damage they cause. The scale was devised in 1971 by the JapaneseAmerican meteorologist Tetsuya (Ted) Fujita. It classifies tornadoes using the following scale. Fujita Scale

Rating the Severity of Tornadoes F0 - light winds of 64 to 116 km/hr; some damage to chimneys, TV antennas, roof shingles, trees, signs, and windows and accounts for about 28 percent of all tornadoes. F1 - moderate winds of 117 to 180 km/hr; automobiles overturned, carports destroyed, and trees uprooted. F1 tornadoes account for about 39 percent of all tornadoes. F2 - considerable winds of 181 to 252 km/hr; roofs blown off homes, sheds and outbuildings demolished, and mobile homes overturned. F2 tornadoes account for about 24 percent of all tornadoes. F3 - severe winds of 253 to 330 km/hr; exterior walls and roofs blown off homes, metal buildings collapsed or severely damaged, and forests and farmland flattened. F3 tornadoes account for about six percent of all tornadoes. F4 - devastating winds of 331 to 417 km/hr; few walls, if any, left standing in well-built homes; large steel and concrete missiles thrown great distances. F4 tornadoes account for about two percent of all tornadoes. F5 - incredible winds of 418 to 509 km/hr; homes leveled or carried great distances. F5 tornadoes can cause tremendous damage to large structures such as schools and motels and can tear off exterior walls and roofs. Tornadoes of this magnitude account for less than one percent of all

tornadoes and have never been officially recorded in Canada. Tornadoes in Canada On average, Canada experiences 1000 severe thunderstorms per year. Approximately 80 tornadoes are recorded every year but this does not account for unseen twisters. Canada's Worst Tornadoes Regina, Saskatchewan - June 30, 1912 - 28 dead, hundreds injured Edmonton, Alberta - July 31, 1987 - 27 dead, hundreds injured Windsor, Ontario - June 17, 1946 - 17 dead, hundreds injured Pine Lake, Alberta - July 14, 2000 - 12 dead, 140 injured

Valleyfield, Quebec - August 16, 1888 - 9 dead, 14 injured Windsor, Ontario - April 3, 1974 - 9 dead, 30 injured Barrie, Ontario - May 31, 1985 - 8 dead, 155 injured Sudbury, Ontario - August 20, 1970 - 6 dead, 200 injured St-Rose, Quebec - June 14, 1892 - 6 dead, 26 injured Buctouche, New Brunswick - August 6, 1879 - 5 dead, 10 injured When a tornado threatens:

Take shelter immediately, if available, preferably in the lower level of a sturdy building. Stay away from windows, doors and exterior walls. Flying glass is extremely dangerous. Don't waste time opening windows to keep pressure from building up in the house. It's unlikely to help anyway. Outdoors, with no shelter available, lie flat in a ditch, ravine or other low-lying area, and shield your head with your arms. Don't get caught in a vehicle or mobile home, which the tornado can lift. Choose a location where your vehicle won't be hurled or rolled on top of you. More than half of tornado deaths occur in mobile homes. Beware of flying debris. Even small objects such as sticks and straw can become lethal missiles. In heavy rain, be on the look out for flash floods.

When swimming or boating, always head to shore at the first sight of a storm. Remember that damaged and weakened structures, fallen debris, downed electrical wires, and gas leaks are potential dangers after a storm has passed. Tornado Safety - Shelter In a house, go to the basement and take shelter under a stairway. In a house with no basement, the safest spot is the ground floor in the centre of the house. Small rooms tend to be more structurally sound so seek shelter in a hallway, small room, closet or bathroom (the plumbing may provide some structural stability).

Avoid wide-span buildings, such as barns, auditoriums, shopping centres and supermarkets with large roofs. In high rise buildings, move to lower levels, small interior rooms or stairwells. Stay away from elevators and windows. Camping

Lightning, Strong Winds and Large Hail: If in a tent or tent-trailer, move to the closest comfort station/washroom or your hard-topped vehicle. If no shelter is available, seek refuge deep in a thick stand of trees. If no trees or only solitary trees are nearby, then find the lowest-lying area. Crouch down and cover your head. Heavy Rain/Flash Floods:

Avoid camping close to streams or rivers as heavy rain can cause water levels to rise rapidly. Never cross rain-swollen streams or rivers as the undercurrents could carry you downstream. If flash flooding does occur, get to higher ground immediately. Tornadoes: Move to a campground comfort station/washroom. Crouch and cover your head. If there is no comfort station or washroom nearby, evacuate your tent or camper van. Lie down flat in a low-lying area and cover your head with your hands. DO NOT get into your vehicle to escape a tornado! Strong tornadoes can overturn vehicles Case Study: Barrie Tornado Barrie Events Centre

Track of all tornadoes associated with the May 31, 1985 outbreak News Report: Barrie Tornado, 1985

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