National Weather Service United States Department of Commerce

Severe Thunderstorm, Flash Flood and Heat Threats Lead up to Independence Day

Severe thunderstorms capable of mainly large hail and severe wind gusts are possible late this afternoon and into tonight over eastern Montana and parts of the western Dakotas. Excessive rainfall may result in flash flooding today over northern New Jersey, southern New York and western Connecticut. Heat Advisories have been issued today for the Twin Cities of Minnesota and the Artlatex region. Read More >

Slide 14

The Reality of a Tornadic Circulation in the Real Atmosphere

The reality of a tornadic circulation in the real atmosphere (which just happens to be where people live!), is that the wind has a very strong horizontal component. In fact, in most cases, the strongest horizontal *and* vertical components of the wind can be found not far above the surface. In addition, in almost ALL tornadoes, the very strong wind extends outside the diameter of the visible funnel – and in many cases, a considerable distance outside the visible funnel. It also needs to be emphasized (and this will come as no surprise to those who are well educated about tornadoes) that not ALL tornadoes exhibit a visible funnel cloud! Many tornadoes have been filmed where there is no visible condensation funnel connecting the cloud base to the ground. The only evidence that the tornado circulation exists at ground level in these cases is usually a dirt or debris cloud at the surface underneath a funnel cloud aloft, giving the illusion that the tornado is not ‘on the ground.’

Explicit illustration of this idea can be seen by looking once again at the KFOR-TV video image captures displayed on the right of Slide 9. Notice the incredible amount of flying debris - some of it being huge pieces of buildings - that would take very intense wind speeds to take airborne. This is despite the fact that the edge of the visible condensation funnel has not yet moved into the frame of reference. These intense winds are occurring OUTSIDE the visible condensation funnel of the tornado!

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