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A siren blares screaming a warning that a tornado approaches. How do you know whether the storm is life threatening or if you're safe in your home? What are the characteristics of weather that lead to the development of severe storms such as tornadoes? Your challenge is to determine which atmospheric conditions support the growth of dangerous tornadoes. It's time for you to take a spin into this investigation.

Planning and Carrying Out Investigations

Tornado Brochure

Tornado Brochure

What is severe weather?

Severe weather is weather that could cause loss of life, damage to property, or require authorities to intervene. Examples of severe weather include blizzards, hurricanes, severe thunderstorms, tornadoes, and floods.

What is a tornado?

A tornado is a column of violently rotating air that extends from clouds to the ground in a thunderstorm. Tornadoes usually form in storms in the central United States. An area of air horizontal to the ground begins spinning due to winds from the storm, and then one of the ends of this horizontal column is picked up into the storm by updrafts. Tornadoes may then form in this area of rotation in the storm.

What is the Fujita Tornado Intensity scale?

The Fujita Tornado Intensity scale is a scale to measure the intensity of tornadoes based on their wind speed and the damaged caused. The scale ranges from category F0, the weakest category, to F5, the strongest category.
Category Wind Speed (mph) Damage Examples of Damage
F0 47-72 Light Slight damage, branches broken off of trees.
F1 73-112 Moderate Moving cars pushed off the road, surface peeled off of roofs.
F2 133-157 Significant Mobile homes destroyed, large trees knocked down.
F3 158-206 Severe Roofs torn off of houses, cars picked up and thrown.
F4 207-260 Devastating Houses destroyed, structures with weak foundations blown off some distance.
F5 261-318 Incredible Houses picked up and carried, objects the size of cars are thrown through the air more than 100 meters.

How does pressure impact storm strength?

The lower the pressure in the center of a storm, the more powerful the storm is. The normal air pressure usually ranges between 970 and 1000 millibars, and in the middle of a hurricane can be 870 to 960 millibars. It is estimated that the pressure in a tornado is the same or possibly even lower than that of a hurricane.

How do temperature gradients affect storm strength?

The temperature gradient is the difference in temperature at the bottom of the tornado and at the top of the tornado. The bottom is usually cooler than the top. A wider temperature gradient with cooler temperatures on the ground and warmer temperatures up higher will create a more intense storm than if there was a narrower temperature gradient.

How can property damage from tornadoes be reduced?

One way to reduce property damage from tornadoes is to secure any items that could potentially become missiles in high winds. Patio furniture, grills, and other outside objects should be tied down and secured so that they can't be picked up by the wind. Make sure that trees are pruned so that dead branches cannot be thrown by the wind. Consider reinforcing weak structures such as garage doors that could possibly give in to high winds and sealing any openings around doors and windows to prevent winds from entering your house.
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