Tornadoes & Thunderstorms

Tornadoes & Thunderstorms By: Christian Rossetto, Dan Rutherford, Jordan Provenzano

Table of Contents Introduction………………………………………………………………………..1 Facts about Tornadoes……………………………………………………………..2 How Tornadoes are Formed……………………………………………………….3 When and Where Tornadoes are Formed………………………………………….4 Damage Caused by a Tornado……………………………………………………..5 Tornado Intensity…………………………………………………………………..6 Facts about Thunderstorms………………………………………………………...7 How Thunderstorms are Formed…………………………………………………..8 How Thunderstorms are Formed II………………………………………………..9 How Thunderstorms are Formed III……………………………………………...10 When Does a Thunderstorm Form……………………………………………….11 Different Types of Thunderstorms……………………………………………….12 Different Types of Thunderstorms II……………………………………………..13

Introduction Windsor, Ontario June 17, 1946. 17 dead, hundreds injured. The tornado that caused tons of damage and even tore apart our beloved Devonshire Mall. That was the worst tornado to ever hit Windsor, Ontario. Most people did not know that. In this project you will learn other very interesting facts about tornadoes and thunderstorms that most people didn’t know.

Table of Contents Facts about Tornadoes Many people believe that there is no tornado unless there is a visible funnel cloud. However this is not true, for 'invisible' tornadoes can exist. Its the same thing as a normal tornado, but the funnel cloud does not descend to the ground. The latter situation is extremely rare. This is a simulation of how a tornado forms: Once the tornado reaches the ground, it starts to up debris around it. This can actually change the color of the tornado, because some dirt in the southern states is actually a deep shade of red.

Table of Contents How Tornadoes are Formed At this point in time, formation of tornadoes are not fully understood by scientists. They usually form in a giant rotating thunderstorm called a supercell. Supercells form when cold polar air meets warm tropical air. The result is a great instability caused by the rising warm air. A squall line, or narrow zone of cumulonimbus clouds forms, giving life to the tornadoes. Lightning flashes, and heavy rains and hail begin to fall. Soon after, the easiest recognizable part of the tornado, the funnel, seems to descend from the base of the cloud. In actuality, it does not, but rather the pressure within the cloud drops due to the increasing wind speeds. This is known as Bernoulli's principle. As the pressure drops, it causes moisture in the air to condense. This action continues down the spiral, giving the impression that the funnel is descending from the cloud base. In addition to the visible funnel, there is also a hissing sound, which turns into a loud roar when the tornado touches the earth.

Table of Contents When and Where Tornadoes are formed These are the most common places and times tornadoes occur in Canada and in United States

Table of Contents Damage Caused by a Tornado

Table of Contents Tornado Intensity

Table of Contents Facts about Thunderstorms Thunderstorms have an average lifetime of 20 to 30 minutes. Their size varies from 5 to over 15 miles in diameter. Atmospheric pressure changes near a thunderstorm. The strong updrafts in a thunderstorm cause a small low-pressure area which sucks air in from around the thunderstorm. The air that exits out at the top of the storm causes an increase in pressure in the surroundings.

Table of Contents How Thunderstorms are Formed For a storm to develop, a few boundary conditions are needed. The first one is an unstable column of air. There are different types of instability, but in general it means that the air rises spontaneously. Instability can be the result of heating of the surface (or cooling of the upper atmosphere): a thermal instability. Or it can have a dynamic cause, such as in a frontal system. This type of instability is called dynamic instability. These two types of instability can influence each other. The second condition we need for the development of a storm is moisture. There has to be enough available water in the boundary layer for condensation so a cloud can form. Dry layers in the upper atmosphere can cause entrainment.

Table of Contents How Thunderstorms are Formed II So what happens when a column of air meets these conditions? A hot, humid air package is located at the surface and starts to rise by buoyancy processes. When the ambient air temperature is the same as the dewpoint temperature, condensation starts and a cloud forms. Because of the liberation of condensation energy, the air heats up and rises even faster. If the temperature drops below freezing, ice crystals start to form. If the temperature drops below -23 degrees C., all water droplets become ice crystals. Ice crystal-clouds can be identified as clouds having a smooth appearance.

Table of Contents How Thunderstorms are Formed III Two mechanisms for the development of rain droplets exist:- Bergeron-Findeisen process: transport of water vapor from supercooled water droplets to ice crystals- Collision and Coalescence: bigger droplets capture smaller droplets by their difference in fall speed. If there are enough droplets and they have become big enough, they will fall out of the cloud and reach the surface and we speak of a shower, or storm (Cumulonimbus, CB for short).

Table of Contents When Does a Thunderstorm Form A storm can be called a thunderstorm when enough separation of electrical charge takes place in the cloud to produce lightning. The processes which are responsible for this charge separation are not yet completely understood. The smaller particles in the cloud become positively charged, the bigger particles negatively charged. Because of the different fall speeds of the particles, a spatial separation of electric charge takes place in the cloud: positively charged at the top, and negatively charged at the lower part. The negatively charged bottom of the cloud induces positive charge near ground. If the electrical field, caused by the different charge regions, becomes high enough, a lightning discharge may occur.

Table of Contents Different Types of Thunderstorms The Single Cell Thunderstorm - When there is lack of wind shear, these cells are short lived because the downdraft cuts off the updraft. After a while, only a leftover orphan anvil remains. The Multicell Thunderstorm - If the condensation level is reached and the air becomes buoyant, a new cell may form, which in turn triggers additional cells along the edge of its outflow boundary. The cluster of cells produced by this process is called a multicell storm and is responsible for the relatively long lifetime of such a thunderstorm complex, up to a few hours.

Table of Contents Different Types ofThunderstormsII The Mesoscale Convective System - A large cluster of thunderstorm cells, usually consisting of a line of storms near the front edge, and a trailing stratiform region of medium, persistent rainfall. The spatial extend of the complex is somewhere in the range of 50 to 100 miles in diameter. MCSs form out of generic multicell storms, usually later during the day, and as the lifetime of an MCS is relatively long, they may remain active deep into the night.

FIN .

Tornadoes and ThunderstormsCreditsWork By: Christian RossettoDaniel RutherfordJordan ProvenzanoSubmitted to: Mr. J HalpinSpecial Thanks go out to Jordan for all the splendid hard work he put into this project!!!!!!(JUST KIDDING)and to you for watchingNOW YOU CAN LEAVE!!!!!!! .

Tornadoes & Thunderstorms