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Tornado vs. Waterspout

By: Martha Spencer
By: Martha Spencer

This morning at 8:59 a 'Tornado Warning' popped up in Coastal Walton County. My immediate thought when seeing the warning, was that it was a waterspout along the coast. Oscar and I got to chatting about it today, and agreed that in an ideal world, warnings should be distinguished between actual tornadoes, and water spouts. Granted, some waterspouts can be tornadic, but most are not, and it gives a false sense of danger when one sees a Tornado Warning on TV.

So what's the difference? The obvious assumption would be that a water spout must develop over water. This is not necessarily true.  By simple definition, a water spout is a column of rotating wind over water that has characteristics of a tornado or dust devil. That would be the rotation. But many times water is picked up and becomes highly visible, sometimes a lot more than just the dust seen in tornados. This can give the impression that they are a lot stronger than they really are.
 

Now we must make the distinction between a tornadic waterspout and a non-tornadic waterspout. A tornadic waterspout is one that originated as a tornado over land, and eventually moved over water. These become very dangerous for boats and marinas, and especially boats not anchored or tied down. Tornadic waterspouts are typically more dangerous than "fair weather waterspouts", and are usually much larger. Non-tornadic waterspouts average between 3-100 meters, and have rotating winds less than 45 kts. which would make it an F0 tornado had it been over land.

What occured in Walton county this morning was most likely a non-tornadic waterspout that moved inland for a brief period of time, and then fizzled. The storms at that time were moving South to North, and the 'Tornado Warning' was only issued for fifteen minutes. Tornado warnings for land based tornadoes are generally issued for 45 minutes, and dropped early if the storm loses its rotation.

Waterspouts not only form over the sea, but can also develop over larger lakes. One of the biggest misconceptions about waterspouts is that it is assumed that a waterspout draws up water from the body of water it is over. This is NOT true. The water that makes a waterspout visible largely comprised of the same things that tornadoes are made visible by, condensed water vapor and dust with converging winds that rise around a core. However, some of the water you see at the very bottom of the waterspout is spray from that body of water, but only goes up a few meters.

Waterspouts are very common in areas where there are daily convective thunderstorms, like the Florida Keys. Tornadic waterspouts are far more dangerous, less common and more damaging. Today, this was not the case.

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