In-depth Notes on Tornadoes

What is a Tornado?

  • A tornado is a violently rotating column of air (vortex) that extends from a cumulonimbus cloud to the ground.
  • Characteristics:
    • Circulation touches the Earth's surface.
    • Can vary in size and intensity.
  • Tornadoes are a type of cyclone, which includes hurricanes and low-pressure systems on large scales.

Tornado History

  • Tri-State Tornado:
    • Most violent tornado on record.
    • Date: March 18, 1925.
    • Traveled 219 miles from Missouri across Illinois into Indiana.
    • Diameter: up to 0.75 miles, with wind speeds reaching 73 mph.
    • Fatalities: Approximately 635 people.
  • Salt Lake City Tornado:
    • Date: August 11, 1999.
    • An F2 tornado lasting 10 minutes.
    • Fatalities: 1, injuries: over 80, damages over $170 million.
    • Most destructive tornado in Utah's history.

Conditions for Tornado Formation

  • Tornadoes most commonly form from thunderstorms, needing:
    • Warm, moist air from the Gulf of Mexico.
    • Cool, dry air from Canada.
  • When these air masses meet, they create instability conducive to severe weather.
    • North America's geography, lacking a major east-west mountain range, allows for more collisions of these air masses.

How Tornadoes Develop

  1. Wind Shear:
    • Change in wind direction and speed with height creates horizontal spinning.
  2. Updraft Formation:
    • Rising air tilts the rotating air vertical.
  3. Rotation Area:
    • Development of a strong rotation area 2-6 miles wide, often leading to strong tornadoes.

Characteristics of Tornadoes

  • Occurrence:
    • Average of 1,200 tornadoes annually in the U.S., causing around 70 deaths.
    • High-risk region known as "Tornado Alley" includes states like Texas, Oklahoma, and Kansas.
  • Physical Attributes:
    • Duration: can last from minutes to over an hour.
    • Average diameter: 0.4 km, path length: 6 km.
    • Rotate predominantly counterclockwise in the Northern Hemisphere.

Tornado Intensity and Damage

  • Fujita Scale:
    • Developed by Dr. Fujita to categorize tornadoes based on wind speed and resulting damage.
    • Categories include:
    • F0: 40-72 mph (light damage).
    • F1: 73-112 mph (moderate damage).
    • F2: 113-157 mph (considerable damage).
    • F3: 158-206 mph (severe damage).
    • F4: 207-260 mph (devastating damage).
    • F5: 261-318 mph (incredible damage).
  • Enhanced Fujita Scale (since 2007): Similar classifications with adjusted wind speed estimates.
  • Damage Mechanism: Tornadoes can throw or ram objects against one another, causing destruction.

Tornado Safety Tips

Before a Tornado:
  • Have a disaster plan, including a supply kit.
During a Tornado:
  • Seek shelter in a basement or an interior room, and protect your head.
After a Tornado:
  • Stay indoors until it's safe. Watch for hazards like downed power lines.

Myths and Misconceptions

  • Taking shelter under a highway overpass is safe.
  • Opening windows helps balance pressure during a tornado.
  • Shelter is best sought in the southwest corner of a house.

Additional Information

  • Waterspouts: Weak tornadoes over water that can cause damage if they move inland.
  • Gustnado: Short-lived whirlwind that forms along a gust front, often mistaken for tornadoes.
  • Tornado Forecasting: Meteorologists utilize Doppler radar and atmospheric data to predict tornadoes.

Tornadoes in Time and Space

  • Most common in spring and summer; peak times vary by region.
  • Can occur any time of day; however, they are most frequent between 3 p.m. and 9 p.m.

Tornado Detection

  • Warning Systems: Alerts issued by the National Storm Prediction Center, including watches (conditions are favorable) and warnings (tornado detected).

Conclusion

  • Understanding tornadoes, their formation, categorization, and safety protocols can save lives and reduce property damage in affected areas.