![Tornado producing supercell
[insert fig 11-29]](https://image.slidesharecdn.com/prezentacjaglennamcmanawayathunderstormsandtornadoes-131218070218-phpapp01/85/Thunderstorms-and-tornadoes-24-320.jpg)
![Global tornado frequency
[insert fig 11-32]](https://image.slidesharecdn.com/prezentacjaglennamcmanawayathunderstormsandtornadoes-131218070218-phpapp01/85/Thunderstorms-and-tornadoes-26-320.jpg)
![[insert table 112]](https://image.slidesharecdn.com/prezentacjaglennamcmanawayathunderstormsandtornadoes-131218070218-phpapp01/85/Thunderstorms-and-tornadoes-27-320.jpg)
![Distribution of lightning strikes
[insert fig 11-23]](https://image.slidesharecdn.com/prezentacjaglennamcmanawayathunderstormsandtornadoes-131218070218-phpapp01/85/Thunderstorms-and-tornadoes-29-320.jpg)
Thunderstorms and tornadoes
- 1. Thunderstorms and Tornadoes By Glenn McManaway
- 3. Types of Thunderstorms 1. Airmass or Ordinary Cell Thunderstorms •Limited wind shear •Often form along shallow boundaries of converging surface winds 2. Supercell / Severe Thunderstorms •Precipitation does not fall into the updraft •Cluster of cells at various developmental stages due to cold outflow undercutting updraft
- 4. ORDINARY CELL THUNDERSTORMS 1. CUMULUS STAGE • Sun heats the land • Warm, humid air rises • Condensation point is reached, producing a cumulus cloud • Grows quickly (minutes) because of the release of latent heat • Updrafts suspend droplets • „Towering cumulus‟ or cumulus congestus
- 5. 2. MATURE STAGE • Droplets large enough to overcome resistance of updrafts (rain/hail) • “Entrainment” Drier air is drawn in • Air descends in downdraft, due to evaporative cooling and falling rain/hail • Anvil head when stable layer reached (cloud follows horizontal wind) • Strongest stage, with lightning and thunder
- 6. Mature, ordinary cell thunderstorm with anvil head
- 7. 3. DISSIPATING STAGE • Updrafts weaken as gust front moves away from the storm • Downdrafts cut off the storm‟s “fuel supply” • Anvil head sometimes remains afterward • Ordinary cell thunderstorms may pass through all three stages in only 60 minutes
- 8. Microbursts create aviation hazards
- 9. Review of Stages: Developing (cumulus), mature and dissipating
- 10. Converegence / Divergence Left Diagram: Not conducive for Thunderstorm activity (High Pressure System) Right Diagram: Associated with Thunderstorm activity (Low Pressure System / Oragraphic lift / Air mass boundry lift / Frontal Lift
- 11. Thunderstorms Typical conditions: 1. Conditional instability 2. Trigger Mechanism (eg. front, sea-breeze front, mountains, localized zones of excess surface heating, shallow boundaries of converging surface winds)
- 12. 1. External trigger mechanism forces air parcels to rise to the lifted condensation level (LCL) Clouds form and temperature follows MALR 2. Parcel may reach level of free convection (LFC). Parcel accelerates under own buoyancy. Warmer than surroundings - explosive updrafts 3. Saturated parcel continues to rise until stable layer is reached
- 14. A squall line
- 15. Radar image of squall line
- 16. Wind shear and vertical motions in a squall line thunderstorm
- 17. Mesoscale convective complex (MCC)
- 19. Tornado Development 1. Pre-storm conditions: Horizontal shaft of rotating air at altitude of wind shift (generally S winds near surface and W winds aloft) 2. If capping is breached and violent convection occurs, the rotating column is tilted toward the vertical
- 20. Supercell Thunderstorms •Defined by mid-level rotation (mesocyclone) Highest vorticity near updraft core •Supercells form under the following conditions: High CAPE, capping layer, cold air aloft, large wind shear
- 24. Tornado producing supercell [insert fig 11-29]
- 26. Global tornado frequency [insert fig 11-32]
- 28. Lightning Source of lightning: the cumulonimbus cloud •Collisions between supercooled cloud particles and graupel (or hail) cause clouds to become charged •Most of the base of the cumulonimbus cloud becomes negatively charged – the rest becomes positively charged (positive electric dipole) •Net transfer of positive ions from warmer object to colder object (hailstone gets negatively charged & fall toward bottom - ice crystals get + charge) •Many theories exist: open area of research •Heats up to 50,000 Degrees F
- 29. Distribution of lightning strikes [insert fig 11-23]
- 33. •Intracloud Discharges •Cloud to Ground Discharges - death and destruction of property - disruption of power and communication - ignition of forest fires - Lightning is an excellent source of soil nitrogen!