Weather 101: Tornadoes with no warnings - CBS46 News


Weather 101: Tornadoes with no warnings

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(Source: WGCL) (Source: WGCL)

Every now and again, you might hear about tornado damage despite never actually seeing a warning. That was the case Monday when an EF-0 tornado was confirmed in Forsyth County only after damage was reported by emergency management.

So why would a tornado not be warned?

While rare, it's actually not unusual to see a few tornadoes a year in north Georgia without warning. Unless someone literally sees a tornado on the ground, we typically detect them by looking at the wind in Doppler radar. Most tornadoes are easy to spot, but every once in a while, you may see a weak, or very quick "spin up" twister that can evade the radar.

Shower was too shallow

The radar beam that picks up rain, storms and tornadoes shoots out of the radar at an angle that gradually goes up (see attached image). Typically, tornadoes develop in large, well-organized rotating thunderstorms that the radar beam can easily see. These severe storms typically rise to about 60,000 feet off the ground.

But in the case of Monday's tornado, it developed in a shower (not even a storm) that was so small, it was only about 20,000-30,000 ft. tall, according to the National Weather Service, which is typical for a summer shower in the South. Because the shower was so small -- or shallow -- rotation from the weak tornado was below the radar beam, and never even showed up on radar.

Imagine a security camera pointed directly at you as you walk into a room. If the camera is setup to see an adult, the baby standing next to you will be too short, and not appear. While rare, Monday's twister out of a baby shower vs. a stronger storm. 

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