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Tornado Risk Calculator — Understanding CAPE and Wind Shear
A tornado risk calculator estimates the likelihood of tornado development using two atmospheric measurements: CAPE and wind shear. These are the same values meteorologists watch when a severe weather outbreak is possible.
Tornado Risk Calculator — Understanding CAPE and Wind Shear
A tornado risk calculator estimates the likelihood of tornado development using two atmospheric measurements: CAPE and wind shear. These are the same values meteorologists watch when a severe weather outbreak is possible.
CAPE — Convective Available Potential Energy
CAPE measures atmospheric instability — how much energy is available to fuel a thunderstorm updraft.
Wind Shear
Wind shear is how much wind speed and direction change with altitude. High shear tilts a thunderstorm's updraft, allowing it to persist and rotate. That rotation is how supercell thunderstorms form — and supercells are responsible for nearly all significant tornadoes. Learn more in Wind Chill Chart — How Cold It Actually Feels at Any Wind Speed. Learn more in Fog Day Predictor — How to Know If Fog Will Form Tonight.
The combination is everything.
High CAPE with low shear equals heavy rain and hail but not tornadoes. High shear with low CAPE equals severe wind gusts but no rotating updrafts. It's high CAPE and high shear together that creates tornado conditions.
The calculator gives a relative risk index, not a specific forecast. Always follow official watches and warnings from the National Weather Service.
