How Do Tornadoes Form and How Do You Stay Safe?
Most strong tornadoes form when a supercell's updraft tilts and stretches spin created by wind shear. Forecasters find them on radar by hook echoes, velocity couplets and debris signatures, and rate them afterward by damage on the EF Scale. When a tornado warning is issued, go to the lowest, most interior room you can reach.
Tornadoes are the storm everyone wants to understand and nobody wants to meet. This unit walks through the whole story: where the spin comes from, how radar finds it, how the damage gets rated, and what to do when the warning hits your phone. The science parts are fun. The safety part is not optional.
What You’ll Learn
- How wind shear, the mesocyclone and stretching produce a tornado.
- How landspouts, waterspouts and QLCS tornadoes differ from supercell tornadoes.
- What EF0 through EF5 mean and how NWS damage surveys assign a rating.
- How to spot a hook echo, a velocity couplet and a tornado debris signature on radar.
- Why radar can miss tornadoes far from the radar site.
- The difference between a tornado watch, warning and emergency.
- Where to shelter at home, in a mobile home and in a vehicle.
Lessons In This Unit
- 8.1How Tornadoes FormMost strong tornadoes form in supercell thunderstorms. Wind that changes speed and direction with height creates horizontal spin. A storm's updraft tilts that spin upright into...Advanced · 10 min
- 8.2Rating Tornadoes: The Enhanced Fujita ScaleTornadoes are rated after they hit, by the damage they cause. National Weather Service surveyors match damaged buildings and trees to 28 damage indicators, judge construction...Intermediate · 9 min
- 8.3Finding Tornadoes On RadarRadar usually can't see the tornado itself. Forecasters look for a hook echo on reflectivity, a tight couplet of bright green (toward) and bright red (away) winds on velocity,...Advanced · 10 min
- 8.4Tornado SafetyThe safest place is an underground storm shelter, basement or FEMA-rated safe room. With no basement, go to a small windowless interior room on the lowest floor, get under...Beginner · 9 min
Questions People Ask
How many tornadoes does the US get each year?
Around 1,200, more than any other country.
Are tornadoes measured by wind speed?
Rarely. They are rated by damage on the Enhanced Fujita Scale, which estimates the wind needed to cause it.
What should I do during a tornado warning?
Take shelter immediately in a basement, safe room or small interior room on the lowest floor, and protect your head and neck.
Learn the spin, read the radar, and when the NWS says go, you go. — Jen
