How does a tornado form? A simple explanation

Warm, moist air can fuel a thunderstorm. If it is lifted and the air above is suitably layered, it continues to rise. As it rises, it cools. Water vapour condenses into tiny droplets and the cloud grows. Condensation releases heat, which can support the upward motion. This rising air current is called an updraft.

Thunderstorms also contain sinking air. Rain and hail fall; evaporation can cool the air further. The arrangement of the updraft, downdraft and incoming air influences how the storm develops. The simple idea that “warm air meets cold air and a tornado forms” does not explain enough. Met Office: conditions and development.

A thunderstorm with a persistent rotating updraft extending through a deep layer is called a supercell. The broad rotation of that updraft is known as a mesocyclone. A tornado can form beneath it, but most supercells do not produce one.

Even without a tornado, a supercell can bring large hail, heavy rain and damaging wind gusts. Its organised airflow allows fresh air to reach the updraft for a long time. Which parts of the cloud are visible and how much rain surrounds the updraft differ from storm to storm. A striking cloud shape alone therefore proves nothing. NOAA/NSSL: structure of a supercell.

Several processes may contribute. Air may already be rotating around the storm. Within the storm, temperature differences and downdrafts can also create or redirect rotation. Interaction with the ground matters too. Their relative contributions differ from case to case.

A 2024 simulation study by Paul Markowski shows this. In the turbulent surrounding air studied, rotating structures were already present near the ground. Beneath the updraft, they could strengthen into a tornado-like vortex. Earlier models often assumed smoother, more uniform surroundings. This result shows another possible route. It does not prove that every real tornado forms this way.

Measurements add to the picture. A 2025 study by Satrio and colleagues tracked a supercell in Nebraska for 96 minutes. Air paths reconstructed from radar data showed contributions to the low-level mesocyclone from both surrounding air and a rain-cooled part of the storm during its most active phase. Temperature differences mattered for some of that air. This was one storm, and the study examined the larger rotation low in the storm. It does not establish a fixed recipe for all tornadoes.

The TORUS research project shows how demanding such measurements are. Its 2026 project overview describes observations of 46 supercells during field campaigns in 2019, 2022 and 2023. Researchers combined mobile radar, measuring vehicles, weather balloons, crewed aircraft and drones. This lets them study wind, temperature and humidity where standard observation networks miss detail. The 2026 publication date does not mean the storms were observed in 2026.

Air itself is invisible. In a tornado, falling pressure can cool the air enough for water vapour to condense into tiny droplets. These droplets make the cloud funnel visible. How far down it extends depends partly on humidity.

The air vortex may already reach the ground even if the visible funnel ends above it. Swirling dust or debris can then show rotation near the ground. If the rotating air column itself does not reach the ground, it is a funnel cloud. The length of the visible funnel alone cannot reliably distinguish the two. Rain may further obscure the view. NOAA: air vortex, condensation and ground contact.

Updated on 29 October 2026. Thomas Sävert’s German tornado list gathers observations and documents cases under review. It distinguishes confirmed tornadoes, plausible cases and suspected cases. The figures below reflect the list at the time it was checked.

2025: 46 confirmed tornadoes

For 2025, the list records 46 confirmed tornadoes, one plausible case and 92 suspected cases Together these make 139 entries, not 139 proven tornadoes. Confirmed cases include Mussum near Bocholt on 3 September, Siebersbach on 23 October and Illingen on 24 November. All three are rated F1.

View the full 2025 tornado list →

2026: 35 confirmed tornadoes so far

For the still ongoing year 2026, the list contains 35 confirmed tornadoes, one plausible case and 100 suspected cases That is 136 entries in total. The most recent confirmed case in the annual overview concerns Horrenberg and Balzfeld in Baden-Württemberg on 25 October. It is rated F1.

View the full 2026 tornado list →

A current suspected case on the Lower Rhine

The case of Twisteden near Kevelaer on 22 October 2026 is listed. Significant damage was reported in a wooded area. At the time of checking, the case was marked as suspectedThis means a tornado has not yet been confirmed.

The annual lists continue to be revised. New evidence may add entries or change classifications, even retrospectively for 2025. The totals for the completed year 2025 and the ongoing year 2026 cannot therefore be read simply as an increase or decrease. The two links lead directly to the lists for later updates.