Presentation on theme: "October 20, 2014 Objective: I will be able to explain how, where, and why tornadoes form. Entry Task: DO NOT UNPACK – be ready for a new seating chart."— Presentation transcript:
October 20, 2014 Objective: I will be able to explain how, where, and why tornadoes form. Entry Task: DO NOT UNPACK – be ready for a new seating chart. Agenda: Intro to Storms - Tornadoes 1)At home SLCs – 2 nd & 3 rd only 2)Tornado notes
What is a tornado? What is a Tornado? A violently rotating column of air Extends from a thunderstorm to the ground. What is a thunderstorm? A local storm Produced by a cumulonimbus cloud Always accompanied by lightning and thunder Usually with strong gusts of wind, heavy rain, and sometimes with hail.
Tornadoes are found most frequently in the US Average year in USA: 1,200 tornadoes 70 fatalities 1,500 injuries Tornado Alley: States at the highest risk of getting a tornado Includes: Arkansas, Iowa, Kansas, Louisiana, Minnesota, Nebraska, North Dakota, Ohio, Oklahoma, South Dakota, and Texas.
Most tornadoes form from thunderstorms Ingredients: Warm, moist air Cool, dry air When these two air masses meet, they create instability in the atmosphere. North America has no major east- west mountain range to block air flow between these two areas. This allows for many collisions of warm and cold air; creating the conditions necessary for tornadoes to form. How does a tornado form? Tornado Alley
How does a tornado form? Step 1: Wind Shear Wind shear (a change in wind direction) Creates an invisible, horizontal spinning effect in the lower atmosphere. Step 1: Spinning in the lower atmosphere
Step 2: Up Drafting Rising air within the updraft tilts the rotating air from horizontal to vertical. How does a tornado form? Step 2: Lifted and tilted from horizontal to vertical
Step 3: Formation & Extension An area of rotation, 2-6 miles wide, now extends through much of the storm. How does a tornado form? Step 3: Extending and Forming
Weak Tornadoes F0-F1 88% of all tornadoes Less than 5% of tornado deaths Lifetime 1 - 10+ minutes Winds less than 110 mph Tornadoes Take Many Shapes and Sizes Strong Tornadoes F2-F3 11% of all tornadoes Nearly 30% of all tornado deaths May last 20 minutes or longer Winds 110-205 mph Violent Tornadoes F4-F5 Less than 1% of all tornadoes 70% of all tornado deaths Lifetime: Hour + Winds: 205 mph +
Fujita Scale of Tornado Intensity SCALE WIND SPEED POSSIBLE DAMAGE F0 40-72 mph Light damage: Branches broken off trees; minor roof damage F1 73-112 mph Moderate damage: Trees snapped; mobile home pushed off foundations; roofs damaged F2 113-157 mph Considerable damage: Mobile homes demolished; trees uprooted; strong built homes unroofed F3 158-206 mph Severe damage: Trains overturned; cars lifted off the ground; strong built homes have outside walls blown away F4 207-260 mph Devastating damage: Houses leveled leaving piles of debris; cars thrown 300 yards or more in the air F5 261-318 mph Incredible damage: Strongly built homes completely blown away; automobile-sized missiles generated
Where and when tornadoes occur? Any time of the year Any time of the day Most likely to occur between 3 and 9 p.m. Have occurred in every state Most common east of the Rocky Mountains during the spring and summer months. Deport, Texas Hoxie, Kansas Northeast, Nebraska
Weak tornado that forms over water. Common along the Gulf Coast. Waterspouts can sometimes move inland, becoming tornadoes causing damage and injuries. Waterspouts
Red: Tornado Warning Purple: Flash Flood Warning To see if there are any active warnings in your area, go to: http://www.weather.gov/view/largemap.php TORNADO WATCH Tornadoes are possible in your area. Stay tuned to the radio or television news. TORNADO WARNING A tornado is either on the ground or has been detected by Doppler radar. Seek shelter immediately Tornado watch and warning
Tornado Facts Tornadoes may appear nearly transparent until dust and debris are picked up or a cloud forms within the funnel. The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction. The average forward speed is 30 mph but may vary from nearly stationary to 70 mph. The strongest tornadoes have rotating winds of more than 250 mph. Tornadoes can accompany tropical storms and hurricanes as they move onto land.