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Thunderstorms

Learn about the different types of atmospheric stability and how they contribute to the formation of thunderstorms. Discover the life cycle of a thunderstorm and the various factors that can influence their development. Gain insight into the effects of severe thunderstorms and the challenges associated with forecasting them.

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Thunderstorms

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  1. Thunderstorms Spring 2016 Kyle Imhoff

  2. Atmospheric Stability • A Matter of Stability • bubbles of air vs. the atmospheric environment • bubbles change temperature by either • dry adiabatic lapse rate (9.8C/1km) (5.5F/1,000ft) • moist adiabatic lapse rate (5C/1km) (3.5F/1,000ft) • Environment lapse rate varies • Stability - a measure of whether an air bubble moves when prodded (heated or forced lift) • unstable - moves and never returns • stable - may move, but returns to same place

  3. Stable Air Characteristics clear or stratiform clouds generally light surface winds smoke, haze, smog accumulate Inversions are common (morning fog) Unstable Air Characteristics clear or cumuliform clouds generally gusty winds lack of haze Thunderstorms can develop if enough moisture is available Atmospheric Stability

  4. Thunderstorms • Thunderstorms always form in an unstable air mass - and are associated with Cumulonimbus Clouds (Cb) • Most thunderstorms occur in the spring and summer (with a maximum in frequency around the solstice - June 22) • The majority of thunderstorms occur between 2-8pm due to daytime heating

  5. Initial Stage Cumulus to Mature Strongest Vertical Motions (25 m/sec) Cloud grows from 15,000-35,000 ft Electrification occurs Downdraft starts Heaviest rain and hail Life span: 20 minutes Mature Stage Mature to Dissipating Weaker Vertical Motions (5-10 m/sec) Cloud reaches maximum height - spreads out into Anvil Downdraft spreads far Lighter rain Less Electrification Thunderstorm Evolution

  6. Life Cycle of a Thunderstorm

  7. Where Storms Form • Formation Zones • Differences in Temperature and Moisture • Clear/Cloudy regions • Sea/Lake Breeze • Mountain vs Valley • Edge of Fog areas • Dry line - West U.S. • Large River Valley

  8. T-storm Types • Types of T-Storms • Air mass, single cell • Clusters • Supercell (HP or LP) • Squall Lines • Derechoes • Mesoscale Convective Complexes (MCC’s)

  9. Squall Line

  10. Squall Line/Air Mass Thunderstorms

  11. Effects • The Effects of Thunderstorms: • Gust Front • Straight-line winds • Derecho • Microbursts • Tornadoes • Mini and Maxi • Fujita Scale • Flash Flooding • Hail • pea to softball sized

  12. Severe Thunderstorms • Four main ingredients: • Instability • Moisture • Lifting Mechanism • Wind speed changes direction/speed with height (called wind shear)

  13. Forecasting Thunderstorms • Storm Prediction Center • Issues watches, outlooks, discussions regarding potential severe thunderstorms and tornadoes • NWS Forecast Offices • Issue warnings on severe thunderstorms and tornadoes

  14. Summary • Thunderstorms come in many shapes and sizes – all produced by convection • Key ingredients are instability, moisture, and a lifting mechanism • Very difficult to predict timing and location of thunderstorms • Important due to their potential socioeconomic impacts

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