Major Storms Chapter 10 continued Three Major Type of Storms Thunderstorms Hurricanes Tornadoes Thunderstorm Brief, but intense, storm with rain, lightning and thunder, gusty and often strong winds, and sometimes hail Develop in warm, very moist, and unstable air Thunderstorm Stages Cumulus Stage Mature Stage Dissipating Stage Cumulus Stage Heat from earth’s surface warms the air around it The warm air rises (updraft) Moist air condenses to form cumulus cloud Cloud grows in height as long as warm moist air rises Mature Stage Large cumulus cloud has heavy, large water droplets which fall Cool ,dry air enters cloud and descends (downdraft) Pulls water droplets downward forming rain Mature Stage Cumulus cloud has become cumulonimbus It has updraft, downdraft, and precipitation Lightning and thunder begin Dissipating Stage Downdrafts begin to dominate the updrafts Prevents warm, moist air from rising and forming cloud droplets Storms dies out with light rain Lightning Giant electrical discharge that occurs when the insulating ability of air separating positive and negative charges breaks down Lightning In thunderstorm, electric charge is separated Positive charges at top of cloud Negative charges at bottom Earth’ surface has positive charge Charge at bottom of cloud overcomes air resistance from updrafts Lightning Negative charge rushes toward earth (stepped ladder) Positive charge from earth flows into air and meets negative charge Current carries positive charge up into cloud THIS CURRENT IS LIGHTNING WE SEE!! Fort Smith, Arkansas Thunder Lighting discharge produces extremely high temperatures – 54,000 deg F Travels through air and heats it quickly –causing it to expand at explosive rate Expansion creates shock wave that creates booming sound—THUNDER!! LIGHTNING CAUSES THUNDER!!!!! Hurricanes Large, violent circular storm that develops over the warm, tropical ocean near the ____________ Hurricane They are cyclonic Winds swirl around central eye Wind direction ______________ – in _____________ Hemisphere ____________ – in ____________ Hemisphere Hurricane They are low-pressure systems. Eye of a hurricane is always low-pressure area. Lowest barometric pressures ever recorded have occurred inside hurricanes. Hurricane Wind speed At center of storm must be sustained ____ _______ Hurricane Season ________ through _____________ Stage of Formation Tropical wave – wind speeds less than 25 mph Lacks closed circulation Tropical depression – sustained winds between 25 – 39 mph System still disorganized ___________ _______ – winds are sustained _____-74 mph Closed circulation Hurricane – winds sustained 74 mph or greater Closed circulation becomes eye Factors in Hurricane Development ____ __________ ___________ _____ ______ ______ or greater Fuel source is the moist, warm air Light westerly winds aloft hurricanes travel east to west so light westerly winds prevent shearing and tearing apart of thunderstorms Rotation (spin) Without spin, the wave is just another area of low pressure Hurricane Formation Low atmospheric area moves off ________ and into the Atlantic Air moves toward these atmospheric lows from all directions and curves under the influence of the Coriolis Effect, initiating rotation Hurricane Formation Hot, moist air masses meet and rise up into the atmosphere above the low pressure area, establishing a self-reinforcing feedback system Parts of Hurricane _____ - the low pressure, calm center of circulation _____ ______ - area around the eye with the fastest, most violent winds _____ _________ - bands of thunderstorms circulating outward from the eye Part of the evaporation/condensation cycle that feeds the storm Hurricane Damage huge amounts of rain high sustained winds storm surge - wall of water tornadoes __________-__________ __________ (know there are 5 categories) Category 1 -wind speed (_____ - 95 mph) Category 2 - wind speed (_____ - 110 mph) Category 3 - wind speed (_____ - 130 mph) Category 4 - wind speed (_____ - 155 mph) Category 5 - wind speed ( > _____ mph) little or no structural damage and some flooding trees down and roof damage (shingles ripped off) mobile homes damaged and severe flooding major structural damage and severe inland flooding serious damage to most wood structures and severe flooding further inland Historic Hurricanes ____________ hurricane Hurricane __________ October 19, 2005 Lowest pressure 884 mb Highest wind speed 175 mph Dropped in pressure from 970 mb to 884 mb and increased wind speed from 80 mph to 175 mph in a 12 hour period Strongest Hurricanes Tornadoes A tornado is defined as a violently rotating column of air in contact with the ground and pendent from a ____________ cloud ________ _________ __________ disturbance on Earth Tornado Formation Violent updrafts and strong winds combine and form whirling vortex of air Updrafts tilt it vertically Air must be blowing in same direction at all levels of atmosphere How Tornadoes Form one way the rotation appears to happen is when winds at two different altitudes blow at two different speeds creating wind shear How rotation begins is still not completely understood by scientists How Tornadoes Form column gets caught in a supercell updraft, the updraft tightens the spin and it speeds up (like a skater's spins faster when arms are pulled close to the body) funnel cloud is created. How Tornadoes Form rain and hail in the thunderstorm cause the funnel to touch down creating a tornado Tornado Trivia _______ _______ reported per year in United States Can last few seconds to an hour Can remain on ground from a few yards to 100 miles Tornado Trivia Most tornadoes occur in _______ 99% rotate counterclockwise in Northern Hemisphere Most tornadoes occur in the _______ ______ Tornado Trivia occur most frequently in the U.S. between 4 and 6 p.m. average 5 to 10 minutes on the ground. can stand still or move forward up to 70 mph. can be up to a mile wide at ground level. Multiple Choice Q: What is the safest thing to do during a tornado? Leave all windows open to prevent them from breaking Leave all windows closed to keep pressure from building against the roof of the structure. Multiple Choice (KNOW) Q: What is the safest thing to do during a tornado? Leave all windows closed to keep pressure from building against the roof of the structure. _________ __________ ___________ __________ _________ for tornadoes in US Tornado Alley The land in the Great Plains is relatively flat, which allows cold dry polar air from Canada to meet warm moist tropical air from the Gulf of Mexico. It's along the front between the two air masses that most tornadoes form. Fujita Scale _____________ _________________ Scale (know categories) (February 1, 2007) aligns wind speeds more closely with associated storm damage takes into account quality of construction and standardizes different kinds of structures Historic Tornadoes Huntsville, Alabama Tornado (Nov 15, 1989) 259 Homes destroyed 130 Homes with major damage 148 Homes with minor to moderate damage 80 Businesses destroyed 8 Businesses damaged 3 Churches heavily damaged 2 Schools destroyed 10 Public buildings destroyed or heavily damaged $1.9 Million in public utility damage $160 million total damages Historic Tornadoes Huntsville, Alabama Tornado F4 tornado 21 fatalities 463 injured Birmingham Tornado of 1998 Occurred April 8, 1998 F5 category Over 1,000 homes and businesses were destroyed. 33 people killed and 256 injured th 7 deadliest in Alabama history B’ham tornado damage B’ham tornado damage December 16, 2000 Tuscaloosa Tornado F4 tornado Forward speed of 60 mph 11 fatalities and 143 injured 300 homes damaged http://www.youtube.com/watch?v=G3Jyqy7qhsQ Tuscaloosa tornado damage Tuscaloosa tornado damage Remains of mobile home ____________ _____________ _______________ March 21, 1932 Affected Perry, Bibb, Chilton, Shelby, Coosa counties 60 mile path 800 yards wide F4 category ______ __________ and 150 injured Historic Tornadoes _________ ________ (April 3-4, ________) 148 tornadoes in 13 states __________ __________ _________ in US Historic Tornadoes Super Outbreak 315 – 330 fatalities 28 deaths in Guin, ______ _______ tornado Destroyed entire town ________ ________ of Super Outbreak (traveled over 100 miles) ___________, _________ ____________ _____________ ___________ during __________ ____________ started in southwest Greene County just outside the Dayton area at about 3:30PM CDT. Started as a small tornado and intensified while moving northeast at about 50 mph. In early stages, two tornadoes were formed and merged into the main one Two Tornadoes Xenia tornado Xenia Tornado Damage Langs Chevrolet Used Cars Covington Co. Tornadoes MAY 03, 1956 F3 JUN 28, 1957 F2 JAN 05, 1962 F2 DEC 24, 1964 F0 NOV 11, 1974 F1 MAR 13, 1975 F1 MAR 31, 1976 F2 MAY 03, 1978 F1 JLY 11, 1979 F2 MAY 20, 1980 F1 MAY 20, 1980 F1 DEC 28, 1983 F2 JUN 13, 1984 F1 SEP 15, 1984 F1 OCT 28, 1985 F1 FEB 22, 1990 F1 JAN 01, 1994 F0 MAY 09, 1995 F0 OCT 04, 1995 F0 OCT 04, 1995 F0 OCT 04, 1995 F0 … NOV 15, 2006 F2 Deadliest Tornado in US March 18, 1925 695 fatalities and 2027 injured F5 category MO, IL, IN states affected Tornado Myths (KNOW) Opening windows will equalize air pressure and prevent an explosion TRUE FALSE Fact: Most experts agree that tornado-force winds will take care of opening the windows for you. Forget this old advice. Take cover immediately! Tornado Myths (KNOW) Go to the Southwest Corner of your Basement TRUE FALSE Fact: Some studies suggest this might actually be the most dangerous place in your basement. If a tornado hits from the southwest, it could push debris into that area. No matter where you go, try to hide under a mattress or sturdy piece of furniture to maximize protection. Tornado Myths (KNOW) Tornadoes never strike big cities TRUE FALSE Fact: In the past several years, tornadoes have roared through several major cities including Miami, Nashville, Tenn, and Fort Worth, Texas. Despite folklore, no city or town has "Natural Protection" from a tornado. Tornado Myths (KNOW) Highway overpasses are adequate shelter if a tornado approaches while you are on a road.