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GEOL 1301 – Thunderstorms and Lightning

GEOL 1301 – Thunderstorms and Lightning. Characteristics Occurrence Conditions for Formation Stages of Development Severe Thunderstorms Lightning. Thunderstorms. Characteristics. Cumulonimbus cloud with lightning and thunder. Characteristics.

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GEOL 1301 – Thunderstorms and Lightning

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  1. GEOL 1301 – Thunderstorms and Lightning

  2. Characteristics Occurrence Conditions for Formation Stages of Development Severe Thunderstorms Lightning Thunderstorms

  3. Characteristics • Cumulonimbus cloud with lightning and thunder

  4. Characteristics • Cumulonimbus cloud with lightning and thunder • Heavy rain and gusty winds

  5. Dry Thunderstorms with Virga

  6. Structure of a Thunderstorm

  7. High Winds – Gust Front

  8. Characteristics • Cumulonimbus cloud with lightning and thunder • Heavy rain and gusty winds • Some storms – hail and tornadoes

  9. Hail

  10. World Record - Aurora, NE June 20037” diameter (volleyball size) and 1.7 lbs. Storm > 70,000 ft. high

  11. Characteristics • Cumulonimbus cloud with lightning and thunder • Heavy rain and gusty winds • Some storms – hail and tornadoes • Individual thunderstorm cells • Av. 15 mi. (25 km) diameter • Last 30 minutes • Multicell clusters very common

  12. Multicell ClusterDowndraft from one cell forms another

  13. 100,000+ Thunderstorms in U.S. Each Year

  14. Conditions for Formation • Daily heating – air mass thunderstorm

  15. Conditions for Formation • Daily heating – air mass thunderstorms • Frontal boundary (primarily cold, stationary or occluded) - may form a squall line

  16. Squall Line

  17. In Advance of Cold Front

  18. Conditions for Formation • Daily heating • Frontal boundary • Dryline

  19. Dryline

  20. Conditions for Formation • Daily heating • Frontal boundary • Dryline • Sea breeze convergence

  21. Sea Breeze Convergence

  22. Conditions for Formation • Daily heating • Frontal boundary • Dryline • Sea breeze convergence • Outflow boundary

  23. Outflow Boundaries from Large Storms

  24. Stages in Development Cumulus Mature Dissipative

  25. Severe Thunderstorms • Characteristics - any or all: • Wind gusts > 58 mph (93 km/hr)

  26. Severe Thunderstorms • Characteristics - any or all: • Wind gusts > 58 mph (93 km/hr) • Hail > 1” (2.5 cm) diameter (quarter size)

  27. HailstreakWest Texas Severe Thunderstorm

  28. Large Hail

  29. Severe Thunderstorms • Characteristics - any or all: • Wind gusts > 58 mph (93 km/hr) • Hail > 1” (2.5 cm) diameter • Tornado

  30. Severe Thunderstorms • Characteristics - any or all: • Wind gusts > 58 mph (93 km/hr) • Hail > 1” (2.5 cm) diameter • Tornado • Common features: anvil top

  31. Anvil Top

  32. Severe Thunderstorms • Characteristics - any or all: • Wind gusts > 58 mph (93 km/hr) • Hail > ¾” (1.9 cm) diameter • Tornado • Common features: anvil top, frequent lightning

  33. Severe Thunderstorms • Characteristics - any or all: • Wind gusts > 58 mph (93 km/hr) • Hail > ¾” (1.9 cm) diameter • Tornado • Common features: anvil top, frequent lightning, and mammatus clouds

  34. Mammatus Clouds

  35. Most Dangerous Severe Thunderstorms • Supercells

  36. Supercell Thunderstorm - Eastern Colorado

  37. Training Effect Can Produce Flooding

  38. Most Dangerous Storms • Supercells • Mesoscale convective systems (MCS’s)

  39. LightningAn Underestimated Hazard

  40. Central Texas – 8 to 12 strikes/ mi2 / year

  41. 80% of Lightning is Cloud-to-Cloud

  42. Lighting Development • Large electrical charge imbalance

  43. Lighting Development • Large electrical charge imbalance • Within the storm

  44. Lighting Development • Large electrical charge imbalance • Within the storm • Between storm and ground

  45. Lighting Development • Large electrical charge imbalance • Within the storm • Between storm and ground • Collision - droplets and ice crystals • Ice crystals +

  46. Lighting Development • Large electrical charge imbalance • Within the storm • Between storm and ground • Collision - droplets and ice crystals • Ice crystals + • Water droplets –

  47. + Charge Induced Below Thunderstorm

  48. Stepped Leader of Ionized Air Branches Downward

  49. Spark Jumps from Tall Object to Stepped Leader

  50. Flowing + Charges Create Return Stroke

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