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Severe Weather Phenomena: Tornadoes, Cyclones, and Hurricanes Explained

Explore the fascinating world of extreme weather events such as tornadoes, cyclones, and hurricanes. Learn about the formation and impact of these natural disasters, including the stages of development, unique characteristics, and destructive potentials. Dive into the science behind thunderstorms, snowstorms, and mid-latitude cyclones, and discover the intricate processes that trigger lightning, blizzards, and torrential rainfall. Gain insights into forecasting techniques, historical data, and how climate factors influence the frequency and intensity of severe weather occurrences. Prepare to be amazed by the forces of nature at play in these spectacular phenomena.

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Severe Weather Phenomena: Tornadoes, Cyclones, and Hurricanes Explained

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  1. Weather Thunderstorms Snow / Rain storms Mid-latitude cyclones Tropical cyclones

  2. Types of Severe Weather • Thunderstorms • Snow / Rain storms • Mid-latitude cyclones • Blizzards • Tornadoes • Tropical cyclones • Typhoons in the western Pacific • Cyclones in the Indian Ocean • Hurricanes in the U.S.

  3. Stages in the development of a thunderstorm

  4. Thunderstorms • How Lightning Works

  5. Thunderstorms

  6. Lightning Varieties cloud-to-ground Cloud discharge Ball lightning Blue jets Red sprites Elves (NOVA: Science Now – Lightning http://www.pbs.org/wgbh/nova/sciencenow/3214/02.html)

  7. Lightning Varieties Volcanic Lightning Nuclear Lightning Triggered Lightning (NOVA: Science Now – Lightning http://www.pbs.org/wgbh/nova/sciencenow/3214/02.html)

  8. Severe weather types • Tornadoes • How a Tornado Forms • Moist air from Gulf of Mexico • Fast moving cold, dry air mass from Canada • Jet stream moving east at 150 mph • Sets up shearing conditions

  9. Severe weather types • Tornadoes • How a Tornado Forms • Warm moist Gulf air releases latent heat, creates strong updraft • Updraft sheared by polar air, then twisted in a different direction by jet stream

  10. Tornado Wind Patterns

  11. Severe weather types • Tornadoes • Why do some thunderstorms spawn tornadoes while others do not? • Super Cell Thunderstorms

  12. Severe weather types • Tornadoes • The Fujita-Pearson Scale • The size of a tornado is not necessarily an indication of its intensity!

  13. Tornadoes • “Tornado Capitol of the World” • CNN’s “10 deadliest U.S. tornadoes” Source: cnn.com

  14. Tornadoes • Why don’t tornadoes strike large cities? • Occur over large regions • Cities are relatively small targets • Oklahoma City Tornado (1999)

  15. Mid-latitude Cyclones • Idealized weather • Middle-latitude cyclones move eastward across the United States • First signs of their approach are in the western sky • Require two to four days to pass over a region • Largest weather contrasts occur in the spring

  16. Mid-latitude Cyclones

  17. Mid-latitude Cyclones • Blizzards • Form when a long cyclone brings • Cold 60 km/hr winds • Freezing temperatures • Lots of snow • Can travel very slowly • Storm itself usually doesn’t kill • Shoveling snow, auto accidents, etc.

  18. Mid-latitude Cyclones • Ice Storms • Formation: • Falling snow and ice melt, change to rain, then freeze again as they reach the ground • Sleet • Freezing rain

  19. Hurricanes • Only natural disaster that is given a human name • Actually large tropical cyclones • Convert heat in the ocean into winds • Exports excess heat from the tropics to the midlatitudes

  20. Hurricanes • How a Hurricane Works • Tropical disturbance • Low pressure zone develops and draws in clusters of thunderstorms and winds

  21. Hurricanes • How a Hurricane Works • Tropical disturbance • Tropical depression • Surface winds strengthen, move about the center of the storm • Central core funnels warm moist air up towards stratosphere • Air cools, vapor condenses, latent heat released • Fuels more updrafts, cycle repeats, storm grows

  22. Hurricanes • How a Hurricane Works • Tropical disturbance • Tropical depression • Tropical Storm • Storm has sustained surface wind speeds of +39 mph

  23. Hurricanes • How a Hurricane Works • Tropical disturbance • Tropical depression • Tropical Storm • Hurricane • Surface winds consistently over 74 mph

  24. Hurricanes • How a Hurricane Works • Tropical disturbance • Tropical depression • Tropical Storm • Hurricane • The Eye • As wind speed increases, winds are spiraled upwards prior to reaching the center • A distinctive clear “eye” is formed • Strongest winds are located on the walls of the eye

  25. Hurricane Wind Patterns

  26. Hurricane Origins • Form in the tropics ~ 5° and 20 ° latitude • Cannot form at the equator (Coriolis effect = 0)

  27. Hurricanes • Hurricane Damages • Storm Surges • Large mound of water builds up beneath the eye • Reaches land as a surge of water

  28. Hurricanes • Hurricane Damages • Storm Surges • Wind speed varies depending upon which side of the hurricane you’re on • Amount of damage on the coastline will vary accordingly

  29. Hurricanes • Hurricane Damages • Heavy Rains • Mudflows and Debris Avalanches • Flooding

  30. Hurricanes • Hurricane paths • Curves due to Coriolis affect • Storms must go around high • Strong and large – storms to Atlantic seaboard • Small and to the north – storms may miss the U.S.

  31. Hurricane Paths

  32. Forecasting the Hurricane Season • Frequency of hurricanes in the North Atlantic is affected by climate • Wet Sahel region in Africa = more thunderstorms • Warm SST = more energy for tropical depressions • Low atmospheric pressure in Caribbean = more cyclones

  33. Forecasting the Hurricane Season • The La Nina / El Nino Connection • La Nina present in Pacific = more winds to move storms • El Nino present in the Pacific = less winds, disrupts storms

  34. El Niño

  35. Normal conditions in the tropical Pacific Ocean • Surface winds move from east to west • From high pressure in S. America to low pressure in Australia • Drags water westward • Warm water pools in the western Pacific

  36. Every 3 – 8 years, system reverses • Called the Southern Oscillation • Trade winds weaken or reverse • Warm water migrates from Australia to S. America • Arrives in time for Christmas – Corriente del Niño

  37. El Niño and La Niña

  38. What is El Niño? • Basically, it's a giant puddle (or pod) of heated water that sloshes across the Pacific Ocean • Similar to an iceberg • Bulge on the surface • Most of “pod” beneath the surface • Due to difference in density • National Geographic’s Model

  39. ENSO - El Niño-Southern Oscillation • Typically lasts 1 year • May last up to 3 • In multi-year events, first year not as affected • Affects both hemispheres

  40. Recognizing an El Niño • Sea Surface Temperatures (SST) • Normal: 6-8° C warmer in the western tropical Pacific than in the eastern tropical Pacific • Check SST to see if in “normal” range

  41. La Niña • Return to “normal” conditions from an El Niño strong • Produces: • Strong currents • Powerful upwelling • Chilly and stormy conditions along S. American coast • Eastern Pacific cools rapidly, Western Pacific warms rapidly • Renewed Trade Wind activity spreads the cooler eastern Pacific waters westward

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