1924 Great Twin Tornadoes
The twin tornadoes near Ann Arbor
Date of tornado outbreak: August 14, 1924
Duration1: 18 minutes, 25 seconds
Maximum rated tornado2: EF5 tornado
Tornadoes caused: 2
Damages: $985,000,000 (2016 USD)
Fatalities: 327
Areas affected: Ann Arbor, Brighton, Howell, and Lansing

1Time from first tornado to last tornado
2Most severe tornado damage; see Fujita scale

On August 14, 1924, the dealiest and costliest tornadoes ever recorded at the time touched down near Ann Arbor at 4:09 PM. Killing 327 and causing over $900 million (2016 USD, $250 million 1924 USD), the twin tornadoes devastated parts of eastern and central Michigan.

The tornadoes

Tornado Twin #1

EF5 (violent) tornado (NWS)
Duration 4:08 PM – 4:35 PM
Intensity 405 km/h (255 mph) (1-min)
At 4:08 PM, the tornado twin #1 touched down just 13 seconds before tornado twin #2. The weaker twin, this tornado caused the weaker damage, although it still killed 109 and caused $350 million (2016 USD, $95 million 1924 USD) in damages. This tornado was the left side tornado.

Tornado Twin #2

EF5 (violent) tornado (NWS)
Duration 4:09 PM – 4:36 PM
Intensity 480 km/h (300 mph) (1-min)
At 4:09 PM, 13 seconds after the touchdown of twin tornado #1, twin tornado #2 touched down just in front of the twin tornado #1. Causing the other $550 million (2016 USD, $155 million 1924 USD) and killing 218, twin tornado #2 may have had over 310 mph winds after a recent discovery that a citizens anemometer measuired 312 mph winds. This was the tornado on the right side of the picture.