Severe Weather, Explained

Every way to receive a tornado warning: Wireless Emergency Alerts, NOAA Weather Radio, weather apps, outdoor sirens, and phone-call alert services — what each channel covers, where each one fails, and how to layer them so a warning always reaches you.

A tornado watch means conditions are favorable for tornadoes; stay alert. A tornado warning means a tornado has been spotted or is imminent — take shelter immediately. Watches cover wide areas for hours; warnings cover small polygons for 30-60 minutes.

A Tornado Emergency is the highest tier of tornado warning, reserved for a confirmed, damaging tornado moving into a populated area with a severe threat to human life. It sits above the base tornado warning and the PDS tornado warning.

Tornado warnings are issued by 122 local NWS offices when Doppler radar shows strong rotation or trained spotters confirm a tornado. The warning is a storm-based polygon, typically 30-60 minutes, delivered within seconds through WEA, EAS, and apps.

The average tornado warning gives roughly 8-10 minutes of lead time before the tornado arrives. Some warnings give 30+ minutes; quick spin-up tornadoes can give zero. Here's where those minutes come from and how to use them.

Wireless Emergency Alerts are free government warnings broadcast from cell towers to every compatible phone in a warned area. Tornado warnings, destructive severe thunderstorm warnings, and high-end flash flood warnings all trigger WEA automatically.

NOAA Weather Radio All Hazards broadcasts NWS warnings from 1,000+ transmitters on seven VHF frequencies, with a tone alarm that wakes you and battery backup that survives power and cell outages. Here's what it does that your phone can't.

Outdoor warning sirens are designed to alert people outdoors, not to wake you inside a modern home. Activation policies vary by county, there is no standard all-clear signal, and sirens fail in exactly the storms they warn about.

Nocturnal tornadoes are roughly 2.5 times more likely to kill than daytime tornadoes: people are asleep, storms are invisible, sirens don't reach indoors, and silenced phones stay silent. The Mid-South faces the most nighttime tornado risk.

A severe thunderstorm warning means a storm with 58+ mph winds or 1-inch hail is occurring or imminent. The 2021 damage-threat tiers — base, considerable, destructive — tell you how bad, and "destructive" warnings now buzz phones via WEA.

A flash flood warning means flash flooding is imminent or occurring — move to higher ground and never drive through floodwater. A flash flood emergency is the rare top tier: catastrophic flooding with a severe threat to human life.

Tornadoes form when warm, moist air at the surface meets cold, dry air aloft, with strong wind shear that tilts a horizontal vortex into a vertical one inside a supercell thunderstorm.

A supercell is a thunderstorm with a persistent rotating updraft called a mesocyclone. Supercells are a small fraction of thunderstorms but produce nearly all violent tornadoes and most giant hail. Anatomy, types, and why rotation changes everything.

The shapes and species of tornadoes explained: rope, cone, stovepipe, and wedge profiles; supercell vs QLCS vs landspout formation; waterspouts and satellite tornadoes; and why a tornado's appearance doesn't reveal its strength.

A tornado is a violently rotating column of air in contact with the ground; a funnel cloud is the same rotation not yet reaching the surface. How to tell them apart — and how wall clouds, shelf clouds, and scud fool eyewitnesses.

A multi-vortex tornado contains 2-6 small "suction vortices" rotating inside the parent funnel. They cause the most extreme wind speeds and explain how some tornadoes destroy one house and leave the next standing.

The three classic radar signatures of a tornado: the hook echo on reflectivity, the velocity couplet marking rotation, and the debris ball / Tornado Debris Signature (TDS) that confirms a tornado is on the ground lofting debris.

The Enhanced Fujita scale rates tornadoes EF0 to EF5 based on damage to 28 structure types. EF0 is 65-85 mph; EF5 is over 200 mph. The scale replaced the original Fujita scale on February 1, 2007.

The Storm Prediction Center's five severe weather risk categories — Marginal (1), Slight (2), Enhanced (3), Moderate (4), High (5) — and what each level actually means for tornado, wind, and hail threat where you live.

US tornado activity peaks nationally in May and June, but "tornado season" depends on where you live: late winter and spring in the Gulf South, April-June in the southern Plains, June-July in the northern Plains, and a real November second season in the Southeast.

Tornado Alley covers the central Plains (Oklahoma, Kansas, Texas, Nebraska); Dixie Alley covers the Mid-South (Mississippi, Alabama, Tennessee, Arkansas). Both produce many tornadoes but with different timing, structure, and risk profiles.

The National Weather Service calls a thunderstorm "severe" only if it produces hail 1 inch or larger, wind gusts of 58 mph or greater, or a tornado. Why those exact numbers, why lightning and rain don't count, and how reports are verified.

Large hail forms when a thunderstorm updraft suspends ice through supercooled water long enough to grow it past an inch — supercells grow the giants. Hail is America's costliest severe-storm hazard, causing tens of billions in damage yearly.

Straight-line winds — downbursts, microbursts, and gust fronts — cause more widespread damage than tornadoes in a typical year, with gusts that can top 100 mph. How they form, how surveys tell them apart from tornadoes, and how to stay safe.

A derecho is a widespread, long-lived windstorm from a fast-moving line of thunderstorms — a damage swath at least 240 miles long with 58+ mph gusts, often embedding 75-100+ mph. The August 2020 Iowa derecho was the costliest US thunderstorm on record.

The safest place during a tornado is a basement or storm shelter. If unavailable, go to the lowest floor, an interior room with no windows, and cover yourself with a mattress or helmet. Mobile homes and vehicles offer almost no protection.