ATMO 10/7 Thunderstorms and Tornadoes

Up drafts and Down drafts:
- Instability aka potential (energy)

Difference between SW and SE thunderstorms:
- SW has higher temperature and lower dew point temperature
- SW has higher elevation (even in the valley)
- SW has much higher cloud bases (must cool more for condensation to occur)
- SW has less water vapor to condense, and less latent heat addition from condensation, resulting in weaker up drafts
- SE has low cloud base, more water vapor, more latent heat, resulting in stronger up drafts
- SW rain falls through a deep unsaturated layer below cloud base with very low relative humidity, resulting in evaporitive cooling and strong down drafts
- SW rain falls through a shallow unsaturated layer, with high relative humidity, resulting in weaker down drafts because there is less evaporitive cooling

Required for T-Storm Formation:
- Wind shear assists in keeping up and down drafts separated

Super cell:
- Extremely large (20-30 mi. diameter) single cell thunderstorm with extremely strong up draft (up to 100 mph with counter-clockwise rotation)
- Dome cloud is formed from momentum of up draft "punching" through the stable layer (anvil) of the atmosphere

Tornadoes:
- Violently counter-clockwise rotating column of air which descends from a thunderstorm
- Tornado center is typically 10-20% lower pressure than the surrounding area
- Tornado outbreak: many tornadoes occurring over a short period of time
- 75% of all tornadoes form in the US

Know: "Summary of Tornado Characteristics" table:

Tornado Safety:
- Deaths and injuries commonly caused by flying debris

Tornado Formation:
- Unstable atmosphere able to form strong t-storm formation
- A lifting force (most common: surface heating and weather fronts)
- Vertical wind shear to provide rotation

Inversion Layer / Convective Cap:
- Inhibits formation of thunderstorms in the morning
- Allows atmosphere to heat up in the lower part, then break the cap and form very severe t-storms or super cells
- Holds back convection until a lot of energy and water vapor build up in the lower atmosphere