Doppler Radar

Doppler radar image showing circulation in a storm

How do the 6 Storm Team meteorologists track snow, rain, wind and hail?

They do that through the use of Doppler radar on Storm Tracker 6.

Radars have been in used for more than 150 years ago. The kind that track storms employ what's called the Doppler effect, or Doppler shift. It's a principle of physics named after an Austrian physicist, Christian Doppler, who found that the occurrence produced by a moving source of waves created an shift in the frequency of those waves.

When the source is approaching approaching the observer, that frequency shift is rising. When the source moves away from the observer, the shift in frequency is downwards.

An easy way to understand and remember the principle of the Doppler effect is to think of a car on a road. As it approaches you, the driver honks the horn. You can hear the high pitch sound of the horn, but suddenly after it passes by, the pitch drops.

This same effect is how Doppler radar works in tracking weather. The radar sends out a pulse of energy, which then reflects off an object, such as a raindrop.

Some of the energy reflects away into the air, but the majority of it goes back to the radar. Equipment at the radar calculates how far away the raindrop is, how intense the rain is and which way the raindrop is moving in relation to the fixed radar site.

That is where the Doppler effect comes in.

6 Storm Team meteorologists use the data sent from the most powerful radar in East Tennessee, which is located at the National Weather Service office in Morristown.

Data is sent to their 6 Storm Tracker computer, where they can follow storms and show you when the rain, sleet and snow is headed your way.

During severe weather situations, the wind speed and direction is what is most important. If the wind picked up on radar is going away from the radar in one area and nearby is going towards the radar, this can mean there is rotation within the storm. That means there is a possibility the storm could produce a tornado.

Doppler radar can also show the meteorologists how strong the winds are over a given length of a line of storms. This can help them determine if the storm could produce straight line line winds.

With 6 Storm Tracker, the meteorologists also have access to all the National Weather Service Doppler radars sites across the country, including Nashville, Northern Alabama, southeast Kentucky, and northern Georgia. This gives a complete view of building storms that may be headed to East Tennessee.