SEVERE WEATHER

SEVERE WEATHER NOTES

TORNADOES

• Wind shear - a sudden change of wind velocity and/or direction

  • Can be vertical or horizontal or a mixture of both

• When the air becomes unstable, wind shears form resulting in a large thunderstorm. Inside the clouds, warm humid air rises, while cool air falls. Rain or hail may be falling.

• The cycling of warm and cool air rising and falling within the thunderstorm causes spinning air currents.

• These currents shift from a horizontal direction to a vertical direction and drop down from the cloud. Once these currents touch ground, it becomes a tornado.

• Fun fact: The winds inside of tornadoes have been clocked at over 300 mph!

• Enhanced Fujita Scale (EF Scale)

  • EF Ratings

    • ​0 65-85 mph

    • 1 86-110 mph

    • 2 111-135 mph

    • 3 136-165 mph

    • 4 166-200 mph

    • 5 Over 200 mph

HURRICANES

• Hurricane - a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, low-level circulation (wind speeds reach 74 mph)

• A low pressure area moves through the tropics (moisture-rich)

• As this weather system moves west, warm ocean air rises into the storm, forming an area of low pressure underneath allowing more air to rush in

• As the air rises and cools, clouds and thunderstorms form. As water condenses and forms rain, this releases more heat, which powers the storm

  • There are a few things that make hurricanes more likely to occur:

    • A pre-existing weather disturbance

    • Warm water: at least 26.5 degrees C over a depth of 50 meters

    • Thunderstorm activity

    • Low wind shear: small or no difference in wind speed and direction

BLIZZARDS

• Blizzards - a storm with large amounts of snow/blowing snow, winds greater than 35 mph, and visibility of less than ¼ mile for at least three hours.

• Blizzard conditions usually form on the northwest side of a powerful storm system.

  • Strong winds form due to a large difference in pressure between the low pressure of the storm and the high pressure beyond the storm.

  • There are three things needed to make a blizzard:

    • Below freezing air

    • Moisture is needed to form clouds and precipitation

    • Moist air needs to rise over very cold air making clouds and snow

Find the following 3 on your own with the button below.

DROUGHTS

FLOODS

LIGHTNING STORMS