It is usually just called a debris cloud or dust whirl.
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It varies widley. A rapidly developing tornado may only been in
the dust whirl statge for a few seconds, while others may linger in
this phase for several minutes. Some tornadoes never grow beyond
this stage.
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All tornado contain rapidly rotating winds. Most tornadoes
contain a condensation funnel and a whirl of dust and/or
debris.
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Yes, the word 'whirl' is both a noun (whirl, whirls) and a verb (whirl, whirls, whirling, whirled).
Examples:
The star made her entrance in a whirl of excitement. (noun)
The propeller began to whirl then the helicopter began to lift. (verb)