Tornado, funnel, wall cloud, waterspout
The current definition of a tornado, the rule that you do not wait for a funnel to reach the ground, and the moment a waterspout becomes a tornado.
The definition, and the one it replaced
The American Meteorological Society revised its definition of a tornado on 2 November 2020. Current wording:
A rapidly rotating column of air extending vertically from the surface to the base of a cumuliform cloud, often with near-surface circulating debris/dust when over land or spray when over water.
The wording it replaced, which is still printed in a great deal of training material, read "a violently rotating column of air, in contact with the ground, pendant from a cumuliform cloud, and often (but not always) visible as a A rotating condensation funnel hanging from a storm base with no ground contact and no debris beneath it. Reportable, and a different report from a tornado.."
Note what the definition does not require: a visible funnel. The column of air is the tornado. The The visible funnel of a tornado, formed where the pressure drop is enough to condense the moisture present. It is optional: a tornado can be doing full damage with no funnel visible at all. is weather happening inside it, and whether you can see it depends on the humidity, the light and where you are standing.
Do not wait for the funnel
This is the single most consequential sentence in the field guide, and it exists because waiting costs How long between a warning being issued and the severe weather arriving. Quoted two ways: counting only the warnings that beat the event, or averaging in the events nobody warned at all, which roughly halves it. that cannot be got back:
storm spotters should NOT wait for a condensation cloud to reach the ground before reporting a tornado. Instead, spotters should look for a rotating dust/debris cloud on the ground below the funnel.
So the thing to look for at the surface is rotating debris, not a funnel touching down. Dust, dirt, vegetation, spray, roofing. If it is going round underneath a rotating cloud base, the circulation is reaching the ground whether or not anything has condensed.
What is reportable, and what is not
- Tornado
- Report immediately. Rotating debris at the surface under a rotating cloud base is enough; a visible funnel is not required.
- Funnel cloud
- Report it. A rotating condensation funnel aloft with no surface circulation. Say that it is a funnel cloud and say what you can and cannot see at the surface.
- Wall cloud
- Report it only with rotation. The field guide is specific: wall clouds "should be monitored visually for signs of persistent, sustained rotation and/or rapid vertical motion." A A localized, persistent lowering beneath the updraft base, on the rear inflow side of a storm, marking where air is being drawn up. Not all of them rotate, and a rotating one is what you report. sitting there doing nothing is not a report.
- Waterspout
- Report it. Over water it is filed as a The over-water equivalent of a landspout. Usually weak, and a genuine hazard when one moves onshore., a marine event. What happens when it reaches land is below, and it is the reason this section exists: both coasts, the Gulf and the Great Lakes all produce them.
- Shelf cloud
- Not a rotation report, ever. A A low, wedge-shaped arcus cloud on the leading edge of a storm, attached to the cloud base above it. It is an outflow feature, it means damaging wind rather than rotation, and it is the feature most often misreported as a wall cloud. is outflow on the leading edge of a Air descending through and out of a storm, driven by the weight of the precipitation and by rain evaporating into drier air below. It is what produces the gust front and the damaging winds.. It can look alarming and it can roll about its horizontal axis, and neither of those is the vertical rotation a tornado report describes. Report the wind it brings, not the cloud as rotation.
When a waterspout becomes a tornado
NOAA states the rule in one line: "when a waterspout moves from water onto land, then it is called a tornado." It is not a technicality. The warning changes and the event type in the record changes. It is worth knowing wherever there is water: both coasts, the Gulf, the Great Lakes, and any large inland lake or reservoir.
The official national archive of significant weather events and their impacts, published by NOAA and built largely from local storm reports. It is the source almost every long-term severe weather statistic comes from. handles the transition explicitly, with worked examples in the directive for both directions: a waterspout that became a tornado, and a tornado that went out over water and became a waterspout. Your job is not to file the paperwork. It is to say clearly where it was over water, when it crossed the shoreline, and where it was after that.
One documented example, chosen because the office published its full survey. On the morning of 10 May 2025 three waterspouts came ashore in the Florida panhandle within a few hours:
.Pensacola Beach Tornado... Rating: EF1 Estimated Peak Wind: 100 mph Path Length /statute/: 0.37 miles Path Width /maximum/: 150 yards Fatalities: 0 Injuries: 0 Start Time: 06:21 AM CDT Start Location: Pensacola Beach / FL Start Lat/Lon: 30.3304 / -87.1406 Survey Summary: A waterspout moved onshore Pensacola Beach just east of the pier.
You are watching a rotating cloud base half a mile away. Dust is being picked up and turning beneath it. There is no condensation funnel at all. What do you report?
The field guide names exactly one thing to look for at the surface, and it is not a funnel.Rotating debris at the surface under a rotating cloud base is a tornado, and the field guide tells spotters in capitals not to wait for a condensation cloud to reach the ground before reporting one. The circulation is what the definition describes; the funnel is just the part of it you can sometimes see.