2THUNDERSTORMS Caused by quick, upward movement of warm, moist air Occurs along a cold front within a warm air massAir is heated by Earth’s surface
3Thunderstorms Lightning Produced by electrons Flows from a negatively-charged areaTo a positively-charged area
4Lightning: an electric current many bits of ice bump into each othercollisions create an electric chargecloud fills with electrical chargesthe positive charges form at the topthe negative charges form at the bottomopposites attractcauses a positive build up on ground beneath the cloudZAP! Lightning Strikes!
5Thunderstorms Lightning Either in a cloud or on the ground Causes air to expand rapidly – bright flashGround’s electrical charge concentrates around anything that sticks upThe charge coming up eventually connects with a charge reaching down from the clouds
6Thunderstorms Thunder Caused by rapid expansion of air Produced by lightning boltIf you hear the sound of thunder, then you are in danger from lightning.Lightning kills/injures more people each year than hurricanes or tornadoes (between people)
8Thunderstorms SAFETY TIPS You Must Avoidusing electrical appliances (includes telephone)being near tall objects (like under a tree)open spaces (crouch down and hug your kneesbeing near or in bodies of waterall conductors of electricity!Lightning may be about to strike ifyour hair stands up (feels prickly)
10Thunder Is Caused By Lightning Lightning bolt travels (cloud to ground)Opens a channel (a little hole in the air)Super heated air expandsQuickly cooled air collapses back dueSound wave is thunderLight travels faster than soundLightning before we thunderWhich do you think is hotter, a bolt of lightning, or the surface of the sun?Lightning- it is 30,000 degrees Celsius. That’s 5 times hotter than the sun!!
12# Seconds / 5 = how many miles away Can you tell how far away a thunderstorm is?Count the number of seconds between when you see lightning & hear thunder# Seconds / 5 = how many miles awayFor example:If you counted 10 seconds between the lightning and the thunder, the lightning is 2 miles away!
13TORNADO (Twister or Whirlwind) Rotating, funnel-shaped cloudUsually Midwestern USADiameter: several hundred yardsDevelops during a thunderstormAir PressureRapid dropcauses rain & hailWind speed ranges mphLasts about 10 minutes (THANK GOODNESS!)
14TORNADO Tornado Watch Tornado Warning Conditions are right for one to occurWe’re watching for one!Tornado WarningOne has been sightedTake cover!
15Tornado SAFETY TIPS Move to underground area (basement) If outdoors, get in a ditch -- not under a bridgeIf no basement, lie flat beneath a table or bedGo to central part of buildingStay away from windowsGet out of car or mobile homeCrouch in the SW cornerdebris usually fall in the NE corner
16change in wind direction How do tornadoes form? Wind shearchange in wind directionan increase in wind speed with increasing heightcreates an invisible, horizontal spinning effect in lower atmosphereRising air from the updraft of a thunderstorm tilts the rotating air from horizontal to vertical.An area of rotation, 2-6 miles wide, now extends through much of the storm.
18What NOT to do(8 min video)Moore, OK time-lapsed 3 min.
19Where are tornadoes most likely to occur? The Great Plains of the central the United States brings ingredients together.includes TX, KS, and OK.More than 500 tornadoes in this area annually , commonly known as "Tornado Alley".