How Do You Read Weather Radar?
Start with reflectivity, where colors show how much energy returns: greens for light rain, reds for heavy rain, purples for possible hail. Then check velocity, where green is toward the radar and red is away, to find rotation. Remember the beam rises with distance, and always follow NWS warnings.
This is the unit where radar stops being pretty colors and starts being measurements. We start inside the dome and work up to hail algorithms and winds aloft. Some of it is advanced. Take it one lesson at a time, and use the live radar demos as you go.
What You’ll Learn
- How NEXRAD Doppler radar measures distance, strength and motion
- What dBZ and the radar colors really mean
- How to read velocity, spot aliasing and recognize a rotation couplet
- Why the beam rises with distance and what the cone of silence hides
- How dual-pol ZDR, CC and KDP reveal hail, melting snow and tornado debris
- What VIL, MESH, echo tops and rotation tracks measure
- How the VAD wind profile shows the low-level jet and veering winds
Lessons In This Unit
- 12.1How Weather Radar WorksWeather radar sends out short, powerful pulses of microwave energy and listens for echoes bouncing off rain, snow, hail and other targets. The time an echo takes to return...Intermediate · 9 min
- 12.2Reading Reflectivity (dBZ)Radar colors show reflectivity, measured in dBZ: how much energy bounces back from targets. Greens are light rain around 20 to 30 dBZ, yellows moderate, reds very heavy rain...Intermediate · 9 min
- 12.3Reading Velocity: Wind Toward And AwayOn Doppler velocity radar, green shows motion toward the radar and red shows motion away, with brighter shades meaning faster speeds. Only motion along the beam is measured....Advanced · 10 min
- 12.4Beam Height, Range And The Cone Of SilenceRadar can miss rain because its beam rises with distance while the Earth curves away. At 100 miles the lowest beam is about 10,000 feet up, so shallow rain, drizzle or...Intermediate · 9 min
- 12.5Dual-Polarization: ZDR, CC And KDPDual-pol radar sends and receives both horizontal and vertical pulses. Comparing them tells forecasters about the shape, size and variety of targets, not just how much energy...Advanced · 9 min
- 12.6What's Falling: Hydrometeor ClassificationRadar uses a hydrometeor classification algorithm that combines reflectivity, ZDR, correlation coefficient, KDP, field texture and the estimated melting layer. Fuzzy logic...Advanced · 9 min
- 12.7VIL, Hail Size, Spin Strength And Echo TopsVIL, or vertically integrated liquid, estimates the total liquid water in the column above each point, in kilograms per square meter. It turns reflectivity at every height into...Advanced · 9 min
- 12.8The VAD Wind ProfileA VAD wind profile (VWP) is a radar product that estimates wind speed and direction at many heights above a Doppler radar every few minutes. As the dish spins, radial velocity...Advanced · 8 min
Questions People Ask
Is LightningWX an official warning source?
No. LightningWX shows live NEXRAD radar and NWS warnings for learning and awareness. For warnings and safety decisions, always follow the National Weather Service.
Do I need a meteorology background for this unit?
No, but it is rated intermediate to advanced. Each lesson builds on the one before it, so start with how radar works.
What is the difference between reflectivity and velocity?
Reflectivity shows how much energy returns, which relates to how hard it is raining or hailing. Velocity shows motion toward or away from the radar.
By the end of this unit you will read radar better than most people who post screenshots of it. Use that power kindly. - Jen — Jen
