Funnel Cloud
A rotating cone-shaped cloud extending downward from the base of a thunderstorm but not reaching the ground. When a funnel cloud touches the ground, it becomes a tornado.
More Severe Weather Terms
Tornado
A tornado is a violently rotating column of air in contact with the ground, extending from a thunderstorm. Tornadoes are rated from EF0 to EF5 on the Enhanced Fujita scale by the damage they cause. Most last less than 10 minutes, but the strongest can stay on the ground for more than an hour.
Supercell
A supercell is a thunderstorm with a deep, persistently rotating updraft called a mesocyclone. Supercells are the most dangerous type of thunderstorm: they produce nearly all significant tornadoes in the United States and most hail larger than golf balls, along with damaging winds and flash flooding.
Mesocyclone
A rotating vortex of air within a supercell thunderstorm, typically 2-6 miles in diameter. Mesocyclones are detected by Doppler radar and indicate the potential for tornado development.
Derecho
A derecho is a widespread, long-lived windstorm produced by a fast-moving line or cluster of severe thunderstorms. Under the criteria the Storm Prediction Center uses, the swath of wind damage must be at least 250 miles (about 400 km) long, with gusts of at least 58 mph along its length and several well-separated gusts of 75 mph or greater.
Microburst
A localized column of sinking air that produces damaging divergent winds at or near the surface. Microbursts can produce winds exceeding 100 mph in an area less than 2.5 miles across and are particularly hazardous to aircraft.
Downburst
A strong downdraft that induces an outward burst of damaging winds at or near the surface. Downbursts can be either microbursts (less than 2.5 miles) or macrobursts (larger than 2.5 miles) and can cause damage similar to a tornado.
Wall Cloud
An isolated lowering of a rain-free cloud base, typically found on the south or southwest side of a supercell. Wall clouds often rotate and may produce a funnel cloud or tornado. They usually precede tornado formation by 10-20 minutes.
Enhanced Fujita Scale
The Enhanced Fujita (EF) scale rates tornadoes from EF0 to EF5 based on the damage they cause. Surveyors compare the damage to 28 kinds of buildings, structures, and trees against expected levels of damage, then estimate the 3-second wind gust responsible. EF0 means estimated gusts of 65 to 85 mph, and EF5 means over 200 mph.
Flash Flood
A flash flood is a rapid and extreme flow of high water into a normally dry area, or a rapid rise in a stream or creek above flood level, that begins within about six hours of its cause. The usual cause is intense rainfall, but a dam failure or an ice jam can also trigger one.
Squall Line
A squall line is a line of active thunderstorms, either continuous or with breaks, together with the rain areas the storms produce. Squall lines can extend for hundreds of miles and last for many hours. Their main hazard is straight-line wind damage, though tornadoes sometimes form along the leading edge.
Shelf Cloud
A shelf cloud is a low, horizontal, wedge-shaped cloud attached to the base of a thunderstorm along its gust front, the leading edge of the storm's rain-cooled outflow. Rising cloud motion is often visible on its leading edge, while the underside looks turbulent and wind-torn. It means gusty winds are about to arrive.
Funnel Cloud: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
Weather Education
How Tornadoes Form: Types, EF Scale, and Safety
Learn how tornadoes form from supercell thunderstorms, the Enhanced Fujita scale, types of tornadoes, and critical safety steps to protect yourself.
Weather Education
Watch vs Warning vs Advisory vs Outlook: NWS Weather Alerts Explained
Learn the difference between a weather watch, warning, advisory, and outlook, what a Special Weather Statement means, and when to prepare versus take immediate action.
Weather Education
Weather Fronts Explained: Cold Front vs Warm Front, Occluded Fronts, and Map Symbols
What cold, warm, stationary, and occluded fronts are, how each is drawn on a weather map, and the clouds, rain, wind shift, temperature, and pressure changes to expect before, during, and after one passes.
Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Feature
Severe Weather
Follow outlooks, watches, warnings, and storm signals in one severe-weather workflow.
Guide
What Causes Thunder and Lightning?
How lightning forms through charge separation, what causes thunder, and how to stay safe.
Guide
Lightning Safety Guide
Know when lightning becomes dangerous, how far away it can strike, and when to move indoors.
Seasonal Hub
Tornado Season Guide
Peak tornado timing by region, safety planning, and how warnings work.
Explore Other Terms
El Niño and La Niña
El Niño and La Niña are the warm and cool phases of a recurring climate pattern in the tropical Pacific called the El Niño-Southern Oscillation (ENSO). During El Niño, the trade winds weaken and the central and eastern tropical Pacific runs warmer than average. During La Niña, the trade winds strengthen and the same waters run cooler. Both shift weather patterns worldwide.
Kp Index
The Kp index is a 0 to 9 scale of global geomagnetic activity, reported in 3-hour intervals from ground-based magnetometers. A Kp of 5 or higher indicates a geomagnetic storm, and the values map onto NOAA's G-scale from G1 (Kp 5) to G5 (Kp 9). The higher the Kp, the farther from the poles the aurora can be seen.
Liquefaction
A process in which water-saturated, loosely packed soil temporarily behaves like a liquid during strong shaking and loses its ability to bear weight. It can tilt or sink buildings, float buried tanks and pipes upward, and cause the ground to crack and spread sideways. Reclaimed land, river deltas, and sandy fill are especially vulnerable.
Drizzle
Very light precipitation consisting of tiny water droplets less than 0.5mm in diameter that appear to float in the air. Drizzle typically falls from stratus clouds and reduces visibility more than light rain of the same intensity.
Wind Shear
A change in wind speed or direction over a short distance, either horizontally or vertically. Strong wind shear is essential for supercell and tornado development but is also a significant hazard to aircraft during takeoff and landing.
Reflectivity
A measure of how much radar energy is reflected back by precipitation, measured in dBZ (decibels of Z). Higher values indicate heavier precipitation or larger particles. Values above 50 dBZ typically indicate heavy rain or hail.
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