Tornado

Tornadoes

Nature's Most Violent Weather Phenomenon

Rotation

Violently rotating column of air extending from thunderstorm to ground

Wind Speed

65 to 200+ mph depending on EF scale rating

Extreme Danger

Most violent storms - instant devastation in path

What is a Tornado?

A tornado is a violently rotating column of air extending from a cumulonimbus cloud to the ground. With wind speeds exceeding 200 mph in the strongest tornadoes, they are the most violent of all atmospheric phenomena. Most tornadoes occur in supercell thunderstorms, though weaker tornadoes can form in other storm types.

Formation and Development

Mesocyclone Formation

Rotating updraft forms at mid-levels of supercell. Wind shear tilts vertical rotation into horizontal, then lifts it to vertical again.

Tornadogenesis

Rotation descends from cloud base. Wall cloud forms and tightens. Funnel cloud appears. Tornado occurs when it touches ground.

Dissipation

Tornado weakens as circulation tightens and storm structure changes. Most tornadoes last 5-30 minutes total.

EF Scale Classification

EF0: Weak (65-85 mph)

Damage: Roof surfaces, trees snapped, mobile homes pushed off foundation

EF1: Moderate (86-110 mph)

Damage: Windows broken, roofs severely stripped, mobile homes overturned, moving vehicles blown off road

EF2: Significant (111-135 mph)

Damage: Roofs torn off, walls collapsed, trees snapped/debarked, light objects become missiles

EF3: Severe (136-165 mph)

Damage: Most trees debarked, heavy vehicles lifted off ground, structures severely damaged

EF4: Violent (166-200 mph)

Damage: Well-constructed houses completely leveled, steel-framed buildings mangled

EF5: Extreme (200+ mph)

Damage: Total devastation, steel structures twisted, grass stripped from ground (1% of tornadoes)

Tornado Types and Origins

Supercell Tornadoes

Most dangerous. Develop from rotating supercells with strong mesocyclones. Often long-lived with strong rotation.

Account for most violent tornadoes (EF3-EF5)

Non-Supercell Tornadoes

Develop from multi-cell clusters or squall lines. Generally weaker but can be violent.

Include landspout and gustnado variations

Waterspouts

Tornadoes over water. Usually weaker but can become dangerous if moving onshore.

Form from warm water and unstable atmosphere

Anticyclonic Tornadoes

Rotate opposite to primary tornado. Often weaker and shorter-lived.

Occur alongside strong supercell tornadoes

Geographic and Seasonal Patterns

Tornado Alley

Oklahoma, Kansas, Nebraska, Texas experience most tornadoes due to geographic positioning for supercell formation.

  • • Oklahoma: ~56 per year
  • • Kansas: ~50 per year
  • • Texas: ~150+ per year total

Peak Season

Most US tornadoes occur April-June when cool dry air aloft meets warm moist air below.

  • • April: Spring storm peak
  • • May: Peak tornado month
  • • June: Secondary peak

Hazards and Damage

Wind Damage

Extreme winds (65-200+ mph) demolish structures, snap trees, and lift vehicles.

  • • Complete home destruction
  • • Multi-story buildings leveled
  • • Vehicles become projectiles
  • • Path width: 10 yards to 2+ miles

Flying Debris

Most tornado injuries from flying debris - wood, metal, glass becomes deadly projectiles.

  • • Debris clouds impenetrable
  • • 2x4 boards piercing trees
  • • Windows shattered instantly
  • • Most fatalities from debris impact

Low Pressure Effects

Rapid pressure drop can cause explosive damage to buildings.

  • • Roof explosions outward
  • • Windows implode
  • • Internal pressure imbalance
  • • Structural failure cascade

Casualties

60-80 tornado deaths annually in US, thousands injured.

  • • Strong tornadoes most deadly
  • • Mobile homes most vulnerable
  • • Early warnings critical
  • • Underground shelters safest

Detection and Warnings

Radar Detection

Rotation Signatures
  • • Velocity couplets
  • • Hook echo shape
  • • Rapid rotation increase
Debris Signature
  • • Debris aloft indicator
  • • Confirms tornado ongoing
  • • High reflectivity from debris
Warnings
  • • Tornado Warning: Immediate
  • • Tornado Watch: Hours ahead
  • • Lead time: 5-15 minutes

Safety During Tornadoes

Immediate Action - Tornado Warning

  1. 1. Go to basement IMMEDIATELY if available
  2. 2. Small interior room on lowest floor if no basement
  3. 3. Away from windows and exterior walls
  4. 4. Cover yourself with mattress, blankets, helmet
  5. 5. Stay put until all-clear given

Preparation and Readiness

  • ✓ Know your shelter location in advance
  • ✓ Practice tornado drills
  • ✓ Keep emergency supplies ready
  • ✓ Have multiple alert methods
  • ✓ Know difference between Watch/Warning
  • ✓ Monitor weather closely in spring
  • ✓ Secure mobile home or evacuate

Key Facts

  • 1,200+ tornadoes annually in US
  • Peak month: May
  • Peak time: 3-9 PM
  • Average path: 7 miles long
  • Average width: 400 yards
  • Average duration: 10-20 minutes
  • Fastest forward speed: 70 mph
  • Strongest: EF5 exceeds 200 mph
  • 60-80 deaths annually
  • 1000+ injuries annually