Atmospheric Phenomenon (Weather)

1. Atmospheric Phenomenon(Weather) Thunderstorms, hurricanes, tornados, blizzards, drought

2. Tornados Tornados From 1992-2002 killed aver. of 57 people/yr Form under large barometric pressure gradients Increased danger because of material inside spinning vortex Funnel clouds vs tornado (vortex must touch ground) Fujita or F-scale classification system Based on post storm damage survey Central U.S. has more than anywhere else

3. Tornados A violent rotating column of air in contact with the ground and a cumliform cloud Condensation funnel Family Multiple events from same storm Outbreak No break in activity Types Multiple vortex Satellite Waterspout Landspout

4. Supercell Relationship • Tornadoes often develop from a class of thunderstorms known as supercells • Supercells contain mesocyclones • An area of organized rotation a few miles up in the atmosphere, usually 1–6 miles (2–10 km) across • Most tornadoes from supercells follow a recognizable life cycle • Formation • Maturity • Dissapating • Dissapation begins when > rainfall drags an area of quickly descending air known as the rear flank downdraft (RFD) • RFD completely wraps around and chokes off the tornado's air supply • Vortex weakens • Becomes thin and rope-like • During this stage the shape of the tornado becomes highly influenced by the winds of the parent storm, and can be blown into fantastic patterns.

5. Multiple Vortex TornadoDallas, Texas, 1957 • Tornado in which two or more columns of spinning air rotate around a common center • Very often observed in intense tornadoes • Satellite tornado is a weaker tornado which forms very near a large, strong tornado contained within the same mesocyclone • The satellite tornado may appear to "orbit" the larger tornado

6. Funnel Clouds • Tornados are not necessarily visible • Intense low pressure caused by high wind speeds & rapid rotation usually causes water vapor in the air to become visible as a funnel cloud or condensation funnel • Most tornadoes produce strong winds at the surface while the visible funnel is still above the ground • It can be difficult to discern the difference between a funnel cloud and a tornado from a distance

7. Tornados Usually travel NE Most have wind speeds between 40 mph & 110 mph ~ 250 ft across Travel a few mi before dissipating Few attain wind speeds of more than 300 mph More than a mile across Travel more than 10’s/100’s of mi Observed on every continent except Antarctica

8. Tornados Spring in the Central Plains, t-storms frequently develop along a "dryline,“ Separates very warm, moist air to the E from hot, dry air to the W Along the Front Range, Texas panhandle, and southern High Plains, t-storms frequently form as air near the ground flows "upslope" toward higher terrain If other favorable conditions exist, these t-storms can produce tornadoes Occasionally accompany tropical storms and hurricanes that move over land Most common to the right and ahead of the path of the storm center as it comes onshore

9. Tornado Alley Area of U.S. likely to see tornadoes Highest density of storms in world

10. Detection Storm spotters There are more than 230,000 trained Skywarn weather spotters across the US Doppler radar Measures motion Green indicates areas where the precip is moving towards the radar dish Red areas are moving away Radar is in the bottom right corner Adjacent areas of bright green and bright red are mesocyclonic areas and usually indicate an imminent or occurring tornado

11. Fujita Scale

12. Waterspouts Weak tornadoes Form over warm water Most common along the Gulf Coast & SE states In W US occur with cold late fall or late winter storms A time when you least expect tornado development Occasionally move inland May become tornadoes

13. Mitigation Forecasting Prediction Mitigation

14. Mitigation Forecasting Behavior unpredictable Models aren’t perfect Prediction Doppler radar Geosynchronous satellites Climate change? Mitigation Preparedness Evacuations Warning systems Zoning laws Building codes Flood and control systems

15. Myths • Opening windows will lessen the damage caused by the tornado • Low pressure but not enough to cause implosion • Highway overpasses provide adequate shelter from tornadoes • On the contrary, a highway overpass is a dangerous place during a tornado • The small area under the overpasses is believed to cause a wind tunnel effect • Areas which people believe to be protected from tornadoes like a major river, a hill or mountain • Tornadoes have been known to cross major rivers, climb mountains, and affect valleys • As a general rule, no area is "safe" from tornadoes • The southwest corner of a basement provides the most protection during a tornado • The safest place is the side or corner of an underground room opposite the tornado's direction of approach (usually the northeast corner), or the central-most room on the lowest floor

16. Homework – pick oneDue Tuesday • Tri_state Tornado • Daultipur-Salturia Tornado in Bangladesh • Super Outbreak • 1999 Oklahoma Outbreak

17. Blizzards Severe winter storms with: Blowing snow Wind Very low visibilities  Heavy snowfalls & severe cold not required   Winds pick up snow that has already fallen  Officially, National Weather Service defines a blizzard as large amounts of falling OR blowing snow with winds in excess of 35 mph and visibilities of less than 1/4 of a mile for an extended period of time (> than 3 hrs) NWS may issue "Blizzard Warning“ Or less severe, but still dangerous, "Winter storm watch”

18. What makes a winter storm? Cold Air Below freezing temps in clouds & near ground are necessary to make snow and/or ice Moisture To form clouds and precipitation Air blowing across a body of water, such as a large lake or the ocean Lift To raise the moist air to form clouds & cause precipitation Warm air colliding with cold being forced to rise over the cold dome Boundary between the warm and cold air masses is called a front Air flowing up a mountainside

19. BlizzardsWinter Deaths Related to ice and snow: About 70% occur in automobiles About 25% are people caught out in the storm Majority are males over 40 years old Related to exposure to cold: 50% are people over 60 years old Over 75% are males About 20% occur in the home

20. BlizzardsWinter Deaths Frostbite Damage to body tissue caused by that tissue being frozen Causes loss of feeling and a white or pale appearance in extremities fingers, toes, ear lobes, or the tip of the nose Hypothermia Low Body Temperature Uncontrollable shivering, memory loss, disorientation, incoherence, slurred speech, drowsiness, and apparent exhaustion Warm the body core first Do not warm extremities (arms and legs) first as this drives cold blood toward heart & can lead to heart failure

21. Notable Blizzards The Great Blizzard of 1888 Paralyzed the NE US for several days 400 people were killed 200 ships were sunk Snowdrifts 15 to 50 ft The Midwestern “Armistice Day Blizzard” in 1940 Caught many people off guard with rapid & extreme temperature change 60 °F in the morning by noon snowing heavily Caught unprepared died by freezing to death in the snow and trapped in cars 154 people died “Storm of the Century” U.S in 1993 105 yrs to the day (March 12) after Great Blizzard of 1888 Snow over 26 states as far north as Canada and as far south as Mexico In many southern U.S. areas (Alabama, etc.) more snow fell than in an entire winter Spawned 15 tornadoes in Florida Affected at least 1/2 U.S. population 270 people died 48 were reported missing at sea