the Tornado outbreak sequence and serial derecho event of August 2017 was a significant tornado outbreak sequence and derecho event which spawned many tornadoes...

Tornado outbreak sequence and serial derecho event of August 2017
Date of tornado outbreak: August 4-18, 2017
Duration1: 14 days
Maximum rated tornado2: EF4 tornado
Tornadoes caused: 257 (record most for a continuous tornadic sequence in August)
Total Damages: $5.6 Billion
Total Fatalities: 17 (+52 non-tornadic)

1Time from first tornado to last tornado
2Most severe tornado damage; see wikipedia:Enhanced Fujita Scale

257 180 42 18 11 6 0

The worst days of the outbreak were August 6, August 9, August 13, August 15, August 16 and August 18

Notable Tornadoes

Chapman, Kansas

EF3 tornado (NWS)
Cone tornado.png
Duration 4:26PM – 4:52PM
Intensity 360 km/h (225 mph) (1-min)
This large EF3 wedge tornado originated about 25 miles northwest of Solomon, Kansas...and was the first tornado of the outbreak, the tornado continued to the southeast and struck Chapman, which sustained severe damage from a EF4 tornado the previous year...this event was originally rated a EF5, but was downgraded to a EF3 after lack of damage indicators, but winds still stayed above EF5 intensity, possible EF4 damage was found to farming equipment

Burlington, Oklahoma/Kiowa, Kansas

EF4 tornado (NWS)
Katie Oklahoma EF4 tornado.png
Duration 4:36PM – 6:02PM
Intensity 305 km/h (190 mph) (1-min)

This Long-Track EF4 wedge destroyed many buildings along it's 84 mile long path...the tornado first touched down while the Chapman Tornado was at peak intensity, the tornado moved to the north-northwest at EF0 intensity, around 4:42PM the tornado strengthened to EF1 4:45PM the tornado reached EF2 intensity ripping a few roofs off of houses, around 4:50PM the Tornado started to cause signs of Low-End EF3 intensity, by quickly became a Violent EF4 by 5:00PM, around 5:15PM the tornado briefly weakened to a EF3, but restrengthened...the Tornado grew back into a EF4 and moved into Kiowa causing extensive damage, the tornadoes rating is disputed for EF5...

Springfield, Illinois

EF4 tornado (NWS)
W3381-8c03-704b7-wedge-tornado-bennington-kansas-by-fred-wasmer.jpg October 4, 2013 Wayne, Nebraska EF4 damage.jpg
Duration 6:19PM – 6:54PM
Intensity 370 km/h (230 mph) (1-min)
a isolated cell that formed east of the derecho formed in the perfect area of instability for tornadoes, wind shear and CAPE were also very favorable, as a result...a wedge tornado occurred, some houses were completely swept away as a result...the tornado touched down at 6:19PM...the tornado was rated EF5, but was downgraded...and keeps getting upgraded and downgraded...this is a wip...