100 Tornado Facts

Basics

A tornado is a violently rotating column of air in contact with both the ground and a cumulonimbus cloud.
The average tornado is on the ground for less than 10 minutes.
Most tornadoes travel at 30-40 mph forward speed.
The average tornado moves southwest to northeast in the US.
Tornadoes rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
The typical tornado is 100 to 200 yards wide.
A tornado's peak damage path is usually near its center.
Most tornadoes never produce a visible funnel — they're wrapped in rain or dust.
Tornado warnings are issued by the National Weather Service.
The average lead time for a tornado warning is 13 minutes.

The widest tornado ever recorded was the 2013 El Reno tornado at 2.6 miles wide.
The highest measured wind speed on Earth was 301 mph during the 1999 Bridge Creek-Moore tornado.
The longest tornado path on record is 219 miles, from the 1925 Tri-State Tornado.
The deadliest US tornado killed 695 people in 1925 (Tri-State).
The deadliest single-day tornado outbreak was April 27, 2011 with 316 deaths.
The largest tornado outbreak in US history was April 25-28, 2011 with 360 confirmed tornadoes.
The deadliest tornado worldwide killed 1,300 in Bangladesh in 1989.
Bridge Creek-Moore is the only US tornado ever measured above 300 mph.
The 1974 Super Outbreak produced 148 tornadoes in 18 hours.
The most tornadoes in a US calendar year was 1,817 in 2004.

The Enhanced Fujita Scale (EF) replaced the original Fujita Scale in February 2007.
EF0 tornadoes have winds of 65-85 mph.
EF5 tornadoes have winds of 200+ mph.
About 54% of US tornadoes are rated EF0.
Fewer than 0.1% of US tornadoes are rated EF5.
There is no EF6 — the scale caps at EF5.
The Fujita Scale was proposed by Dr. Ted Fujita of the University of Chicago in 1971.
The Enhanced Fujita Scale uses 28 damage indicators.
EF ratings are based on damage, not measured wind speed.
Only about 20% of supercells produce tornadoes.

Supercell thunderstorms produce most significant tornadoes.
A supercell has a persistent rotating updraft called a mesocyclone.
Wind shear tilts the updraft away from the rain shaft in supercells.
The wall cloud is a lowering of the rain-free base where tornadoes form.
The RFD (rear-flank downdraft) helps tighten the mesocyclone into a tornado.
Waterspouts form over water and can move onto land.
Landspouts form from non-supercell thunderstorms and are usually weak.
Gustnadoes are short-lived swirls on thunderstorm outflows and are not true tornadoes.
Multi-vortex tornadoes have several smaller vortices rotating around the main circulation.
The 'hook echo' on radar is caused by rain wrapping around the mesocyclone.

The safest place in a tornado is an underground shelter or storm cellar.
Without a basement, shelter in an interior room on the lowest floor.
Mobile homes are the deadliest place in a tornado.
Overpasses are dangerous — they funnel wind and offer no protection from debris.
Opening windows to 'equalize pressure' is a myth.
A NOAA weather radio can wake you up during a nighttime warning.
The FEMA-recommended safe room can withstand EF5 winds.
Bicycle helmets can reduce head injuries from flying debris.
Never try to outrun a tornado in a car unless it's clearly far away.
Post-storm hazards include downed power lines, broken glass and gas leaks.

Joplin, Missouri suffered 158 deaths in a 2011 EF5 tornado.
Greensburg, Kansas was 95% destroyed by a 2007 EF5.
Moore, Oklahoma has been struck by two F5/EF5 tornadoes since 1999.
The Xenia, Ohio F5 killed 32 during the 1974 Super Outbreak.
The Jarrell, Texas F5 in 1997 is one of the most complete tornadoes ever documented.
The Hackleburg-Phil Campbell EF5 in 2011 tracked 132 miles.
The Tuscaloosa-Birmingham EF4 in 2011 tracked 80 miles.
The Flint-Beecher F5 killed 116 in Michigan in 1953.
The Tri-State Tornado stayed on the ground for 3.5 hours.
The Elie, Manitoba F5 is the only confirmed F5 outside the US.