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Severe and Unusual Weather ESAS 1115

Learn about the different types of severe weather, including thunderstorms, lightning, hail, and tornadoes. Discover the criteria for a storm to be considered severe and how to stay safe during severe weather events.

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Severe and Unusual Weather ESAS 1115

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  1. Severe and Unusual WeatherESAS 1115 Spotter Training and Radar Meteorology Part 1 – Introduction to Severe Thunderstorms ESAS 1115 Severe and Unusual Weather

  2. Convective HazardsWind, Hail, Floods, Lightning, Tornadoes ESAS 1115 Severe and Unusual Weather

  3. Severe Thunderstorms are Severe Many times, the media uses the word “severe” when the storm is something less than the actual meaning of “severe”. ESAS 1115 Severe and Unusual Weather

  4. Severe Thunderstorm Criteria • Hail greater than 1” in diameter • Winds greater than 50 kts (58 mph) • Tornadoes • Lightning and heavy rainfall, although posing a great threat to life, are not criteria used to determe whether or not a storm is severe ESAS 1115 Severe and Unusual Weather

  5. Lightning ESAS 1115 Severe and Unusual Weather

  6. Lightning ~25 million CG lightning strikes per year in the US making it the second deadliest aspect of thunderstorms ESAS 1115 Severe and Unusual Weather

  7. Lightning Safety • Lightning Stats • Lightning Safety Video • Lightning Safety Tips ESAS 1115 Severe and Unusual Weather

  8. Flash Floods – Turn Around Don’t Drown • Water is an incompressible fluid • 1000 kg/m3 • Results in buoyancy – 2 feet of water can move an SUV • Kills more people than lightning – approximately 100 annually in the US, 50% associated with drowning in vehicles • From 1988-1997, average annual cost is $3.7 billion • Flash flooding vs. river flooding ESAS 1115 Severe and Unusual Weather

  9. Flash Flood Threat ESAS 1115 Severe and Unusual Weather

  10. Flash Floods – Turn Around - Don’t Drown ESAS 1115 Severe and Unusual Weather

  11. Hail – Big Chunks o’ Ice ESAS 1115 Severe and Unusual Weather

  12. Tarrant County, TX May 5, 1995 • 10,000 people at Mayfest • Baseball hail – 10 miles wide50 miles long • 14 people killed by flooding and collapsed roofs • $2 billion (estimated) ESAS 1115 Severe and Unusual Weather

  13. We Know First Hand ESAS 1115 Severe and Unusual Weather

  14. Damaging Winds • Strong outflow from a thunderstorm enhanced by evaporative cooling and downward momentum transfer ESAS 1115 Severe and Unusual Weather

  15. Downbursts • A strong and potentially destructive thunderstorm downdraft • Microbursts are less than 2.5 miles in diameter • Macrobursts are greater than 2.5 miles ESAS 1115 Severe and Unusual Weather

  16. Rain Foot and Dust Foot ESAS 1115 Severe and Unusual Weather

  17. Dust Foot ESAS 1115 Severe and Unusual Weather

  18. Microbursts ESAS 1115 Severe and Unusual Weather

  19. Aviation Hazards ESAS 1115 Severe and Unusual Weather

  20. Danger on Takeoff and Landing • On the glide path, too much lift is generated with headwind gain • With the loss of a headwind, lift is limited ESAS 1115 Severe and Unusual Weather

  21. Beaufort Scale Winds based on visual observations ESAS 1115 Severe and Unusual Weather

  22. First Microburst ESAS 1115 Severe and Unusual Weather

  23. Microburst within a Macroburst ESAS 1115 Severe and Unusual Weather

  24. Microbursts ESAS 1115 Severe and Unusual Weather

  25. Microburst Evolution ESAS 1115 Severe and Unusual Weather

  26. Tornado and Hail Climatology There are more than 1000 tornadoes in the US per year. Hail results in over $1 billion of damage annually. Harold Brooks - NSSL ESAS 1115 Severe and Unusual Weather

  27. 61 Years of Tornado Tracks ESAS 1115 Severe and Unusual Weather

  28. Tornado Frequency All Tornadoes Significant Tornadoes Deadly Tornadoes ESAS 1115 Severe and Unusual Weather

  29. Tornado Threats • Violently rotating column of air in contact with the ground and pendant from a cumulonimbus cloud (thunderstorm) • Tornadoes are ranked on the Enhanced Fujita damage scale: from EF0-EF5 • Appearance is deceiving with small tornadoes sometimes having high destruction potential and large tornadoes having low potential ESAS 1115 Severe and Unusual Weather

  30. EF0, EF1 – Weak Tornadoes • Approximately 70% of tornadoes are in this category • Well-built houses offer adequate safety for these tornadoes • Cars and mobile homes are still very vulnerable to these tornadoes • Wind speeds:65 – 110 mph ESAS 1115 Severe and Unusual Weather

  31. EF2, EF3 – Strong Tornadoes • Approximately 28% of all tornadoes are considered strong • Well-built houses will be severely damaged but still can provide adequate life-protection • Wind speeds:111 – 165 mph ESAS 1115 Severe and Unusual Weather

  32. EF4, EF5 – Violent Tornadoes • Only 2% of all tornadoes are violent • Will completely level a well-built house • The last EF-5’s to hit the US were May 3, 1999 (Moore, OK,) May 24, 2007 (Greensburg, KS,) and May 25, 2008 (Parkersburg, IA.) • Wind speeds:166 - >200 mph ESAS 1115 Severe and Unusual Weather

  33. Rating a Tornado ESAS 1115 Severe and Unusual Weather

  34. Wind Damage vs Tornado Damage • Microburst • Damage is divergent • Large or diffuse area • No signs of rotation • Tornado • Damage is convergent • Narrow path • Rotation about vertical axis ESAS 1115 Severe and Unusual Weather

  35. Swirl Marks ESAS 1115 Severe and Unusual Weather

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