This is how fire and smoke appear on the weather radar
CHARLOTTE, N.C. — When a five-alarm wildfire began burning Thursday in Charlotte’s South Park neighborhood, it sent smoke and particles into the air that were so thick they could be seen on weather radar.
Appearing in the same yellow-green color that precipitation is typically imaged as it does on radar, the smoke plume appeared as if it were a storm. However, what the radar was really seeing were tiny particles of burning material lifted into the air by the 2,000-degree fire.
Whether you’re a certified meteorologist or a weather enthusiast looking at your favorite smartphone app, the radar images would have shown the same thing.
While Chris Mullachy, a meteorologist at WCNC in Charlotte, was using the TV station’s weather center to view the radar, chief meteorologist Brad Panovich was also able to post images to Twitter from a publicly available app.
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Radar was a good way to see where the smoke plume was headed.
Images showed how easterly winds were carrying smoke west toward Interstate 77 and the Starmount neighborhood.
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How do radars work?
As WCNC Charlotte’s Weather IQ series explained, RADAR is short for Radio Detection And Ranging.
Radar sends radio waves or energy pulses from the antenna. These energy beams eventually collide with an object and reflect some of that energy directly back to the radar.
This object can be rain, snow, hail, or smoke particles.
The larger the size of any of these details, the more energy it reflects back. Normally, this is how gravity is assigned and then shown in red on the radar image.
The longer it takes for that wave to return, the further away the object is from the radar source.
For Charlotte, the closest National Weather Service radar is in Greer, South Carolina, which is near the cities of Greenville and Spartanburg.
As the radar beams travel from Greer to South Carolina, the curvature of the Earth causes the surface to dip away from the atmospheric beam. This in turn makes the beam measurement of the atmosphere higher and higher.
By the time the radar beam reaches Charlotte’s South Park neighborhood, the beam is approximately 5,000 feet above the ground. With the smoke plume appearing on the radar on Thursday, knowing this element helps us understand how high the smoke plume is.
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A lower-quality radar operated by the Federal Aviation Administration north of Charlotte Douglas International Airport also gave a perspective of the fire in the lower atmosphere.
Residents miles away from the fire in south Charlotte reported they could see smoke. Some residents even told WCNC Charlotte that ash and debris were raining down on their homes despite being miles away from the fire.
The radar scans one beam every 1,000 milliseconds at the speed of light and continues to scan the area to give us an accurate picture of what is happening.
A typical radar will complete a full scan of the sky every four to six minutes, thus providing a new look at the movement of the smoke plume.