A funnel cloud is a vortex of condensated water vapor and air spinning at high velocity. Funnel clouds can form under cumulus clouds if there is enough humidity and vorticity in the air. Landspouts and waterspouts are funnel clouds which reach to ground level, but are usually weak, as opposed to tornadoes. A tornado by definition is a funnel cloud created by mesoscale storm rotation rather than the small vorticity in the air which is responsible for funnel clouds.
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