Severe and Unusual Weather ESAS 1115

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

2. Meteorological Sensors • Two types of two types of sensors: • Remote vs. In-situ • Active vs. Passive • Our passive eyes can only see features of the storm • In order to see the inner workings of a thunderstorm, and to understand it better, we need an active remote sensor – weather radar • Radar will allow us to interrogate information about the storm by detecting precipitation and wind information within ESAS 1115 Severe and Unusual Weather

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

4. 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

5. Severe Thunderstorm Criteria • Hail greater than ¾” in diameter • Winds greater than 50 kts (58 mph) • Tornadoes • Lightning, although posing the greatest threat to life, is not a criterion to determining whether or not a storm is severe ESAS 1115 Severe and Unusual Weather

6. Lightning ESAS 1115 Severe and Unusual Weather

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

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

9. 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 – more than 100 annually in the US. • Flash flooding vs. river flooding ESAS 1115 Severe and Unusual Weather

10. Flash Flood Threat ESAS 1115 Severe and Unusual Weather

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

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

13. 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

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

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

16. 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

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

18. Dust Foot ESAS 1115 Severe and Unusual Weather

19. Microbursts ESAS 1115 Severe and Unusual Weather

20. Aviation Hazards ESAS 1115 Severe and Unusual Weather

21. 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

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

23. First Microburst ESAS 1115 Severe and Unusual Weather

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

25. Microbursts ESAS 1115 Severe and Unusual Weather

26. Microburst Evolution ESAS 1115 Severe and Unusual Weather

27. 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

28. 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

29. 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

30. 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

31. 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

32. Rating a Tornado ESAS 1115 Severe and Unusual Weather

33. 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

34. Swirl Marks ESAS 1115 Severe and Unusual Weather