Thunderstorms and Tornados

Thunderstorms

  • Thunderstorms are common in middle and lower latitude regions, especially during summer.

  • Associated with intense weather phenomena including:

    • Lightning

    • Heavy rain

    • Hail

  • Intense friction between moving ice particles in clouds generates electrical charges leading to lightning.

  • The heat from lightning can reach approximately 45,000 degrees Fahrenheit, creating a shock wave known as thunder.

Structure of Thunderstorms

  • Cross Sectional View: Demonstrates various stages of thunderstorms and air movement.

    • Massive convective uplift can be initiated by a cold front rapidly lifting warm moist air.

    • An uneven distribution of charged particles may occur during uplift, leading to lightning.

Evolution of a Thunderstorm

Cumulus Stage

  • Initiated by:

    • Convective processes or the arrival of a cold front into maritime tropical air.

  • Rising air forms cumulus clouds as warm moist air is forced upward.

Developing Stage

  • Condensation: As the air continues to rise, it cools and condenses, releasing latent heat.

  • This process leads to rapid cloud formation and indicates atmospheric instability.

Mature Stage

  • Characterized by:

    • Strong updrafts and intense precipitation.

    • Development of downdrafts and cold air descending to create severe weather.

  • Storms are most intense during this stage when there are strong updrafts coupled with downdrafts.

  • Formation of the anvil head occurs where convection ceases to continue upward, causing the cloud to spread laterally.

Dissipation Stage

  • Marked by the cessation of updrafts and gradual equilibrium within the storm.

  • Intense precipitation diminishes, and the thunderstorm weakens.

Lightning Formation

  • Lightning results from the separation and collision of electrical charges within clouds:

    • Positively charged ions at the base; negatively charged particles higher up.

  • Types of lightning:

    • Cloud-to-ground: Occurs when a negative charge (leader) from the cloud meets a positive charge (streamer) from the ground.

    • Cloud-to-cloud: Lighting within the clouds as charges redistribute.

  • Most lightning happens within clouds, but it can strike the ground.

Tornadoes

  • Small, intense cyclones characterized by very low pressure and strong converging winds.

  • Tornadoes primarily associated with supercell thunderstorms and exhibit violent updrafts.

  • Tornado Alley: Peak season for tornadoes occurs from April to July, with a concentration in areas like Texas, Oklahoma, Kansas, and Nebraska.

  • Formed from a horizontal vortex that is pulled vertically due to updrafts.

  • Enhanced Fujita Scale used to classify tornadoes based on the damage, with EF0 to EF5 rankings.

Snowstorms and Blizzards

  • Snowstorm: Defined as frozen precipitation.

  • Blizzard: A severe winter weather event characterized by heavy snowfall and strong winds.

    • Common in middle to high latitudes including Michigan.

Lake Effect Snow

  • Occurs when cold arctic air passes over warmer lake waters, acquiring moisture.

  • This air then moves over land, condensing to form clouds and precipitation, leading to heavy snowfall.

  • The process is highly dependent on the temperature differential between the lake and air.

  • Once ice forms on the lake surface, the lake effect snow phenomenon diminishes.