Lecture Notes: The 1965 Palm Sunday Tornado Outbreak

Overview

• Date: April 11, 1965
• Event: Tornado outbreak in the Midwest
• Impact:
  • 47 tornadoes across six states
  • Over 200 lives lost
  • 1500+ injured
  • Significant community devastation

Historical Context

• Tornado forecasting was still developing
• First tornado forecast in 1948
• Development of severe storms forecast centers
• Introduction of air raid sirens in 1952
• Public awareness of severe weather was limited

Meteorological Setup

• Date & Time: Began on April 11, 1965, at 7:00 AM
• A closed low advanced towards the Great Lakes
• Conditions included:
  • Warm temperatures (83-85°F from St. Louis to Chicago)
  • High CAPE values (>1000 J/kg)
  • Strong jet stream and wind shear
  • A textbook severe weather setup

Tornado Outbreak Progression

• Initial Tornado: Touched down near Cedar Rapids, Iowa
• Tornado Families: Multiple tornadoes spawned from single supercells
  • Notable tornado families: A, B, C, D, E, F, G, J, K, L
• Significant Tornadoes:
  • Tornado Family B1 caused F4 damage in Spring Brook, Iowa
  • Family F tornado: An F4 twister in Northern Illinois
  • Family J: "White Tornado" with an F3 rating

Key Tornado Events

• 5:45 PM: Severe tornado activity reported in Indiana
• The "Twins": Two funnels merging near Goan, Indiana
• L Family Tornadoes:
  • L1 and L2 caused significant damage and fatalities
  • L2 tornado reached one mile in width

Aftermath

• Casualties: 258 fatalities, 3,148 injuries (American Red Cross)
• Financial Damage: $1.2 billion (2025 inflation estimate)
  • Indiana: $145 million
  • Michigan: $51 million
• Community Impact: Many communities severely affected, some never fully recovered

Societal & Scientific Impact

• Tornado Science Progression:
  • Alan Pearson and Ted Fujita developed the Fujita Scale
  • Improvements in severe weather forecasting and response
• Cultural Impact:
  • Influenced public perception of tornadoes and severe weather preparedness

Conclusion

• The 1965 Palm Sunday Outbreak remains a significant event in meteorological history
• Highlighted need for advancements in forecasting and public safety measures
• Continues to influence how tornado events are perceived and managed today