How to Read Weather Radar — Australian Guide
Weather radar is one of the most powerful tools for tracking precipitation and severe weather in real-time. Understanding how to read radar displays can help you make better decisions about when to shelter, travel, or plan outdoor activities. This guide will teach you to interpret radar like a meteorologist.
How Weather Radar Works
Weather radar sends out pulses of microwave energy and measures what bounces back. When these pulses hit precipitation (rain, snow, hail), some energy reflects back to the radar antenna. By measuring the strength and timing of these returns, radar can determine:
- Location - Where precipitation is occurring
- Intensity - How heavy the precipitation is
- Movement - Which direction the storm is traveling
- Height - How tall the storm is (with 3D scanning)
Understanding the Color Scale
The colors on radar represent reflectivity, measured in dBZ (decibels relative to Z). Higher dBZ values mean more intense precipitation.
Clear air or very light precipitation
Light rain or drizzle
Light to moderate rain
Moderate rain
Heavy rain, possible small hail
Very heavy rain, hail likely
Severe storms, large hail possible
Types of Radar Products
Reflectivity
The most common radar view, showing precipitation intensity using color-coded returns. This is what most people think of as "weather radar." Higher values indicate heavier precipitation.
Doppler Velocity
Shows the motion of precipitation toward (usually green) or away from (usually red) the radar. Used to detect rotation in storms and identify wind patterns that could indicate tornado development.
Composite/Mosaic
Combines data from multiple radar sites into a single view, covering large areas like entire states or the country. Great for seeing the big picture but may have gaps or seams between radar coverage areas.
Accumulated Rainfall
Estimates total rainfall over a period (1 hour, 9 hours, etc.) based on radar returns. Useful for flood forecasting but should be verified with actual rain gauge measurements.
Identifying Severe Storm Signatures
Supercell Structure
Supercells are rotating thunderstorms capable of producing large hail, damaging winds, and tornadoes. On radar, look for:
- Hook echo - A hook-shaped appendage on the storm, often indicating rotation
- Bounded weak echo region (BWER) - An area of weak or no returns surrounded by intense returns, indicating powerful updrafts
- V-notch - A V-shaped notch on the downwind side, indicating a strong updraft deflecting surrounding air
Velocity Couplet
On Doppler velocity radar, a "couplet" is where red (away from radar) and green (toward radar) returns are adjacent to each other. This indicates rotation and is a key signature for tornado detection. The tighter and more intense the couplet, the stronger the rotation.
Bow Echo
A bow-shaped line of storms often indicates damaging straight-line winds. These can produce wind gusts exceeding 100 km/h and should be taken as seriously as tornado warnings.
Practical Radar Reading Tips
Use Animation
Always watch the radar loop, not just a single frame. Storm motion, development, and decay are much easier to see when you can see how the pattern has evolved.
Check Multiple Sites
Different radars may show different perspectives of the same storm. If you're between radars, check both for the most complete picture.
Account for Delay
Remember radar images are typically 6-10 minutes old. Fast-moving storms may have already moved past the position shown on the most recent image.
Know the Limitations
Radar has blind spots, and not all hazards are detectable. Small tornadoes, dry microbursts, and flash flooding can occur without strong radar signatures.
Practice Reading Radar
View live Australian weather radar on our Weather Charts page or explore the Rainfall Forecast to see radar in action.
Frequently Asked Questions
What do the different colors on weather radar mean?
On reflectivity radar, colors represent precipitation intensity. Light blue/green indicates light rain, yellow/orange shows moderate rain, red indicates heavy rain, and purple/white typically shows extremely heavy precipitation or hail. Each radar system may have slightly different color scales.
What is Doppler radar and how is it different?
Doppler radar measures not just the location and intensity of precipitation, but also its movement toward or away from the radar. This helps meteorologists detect rotation in storms (potential tornadoes), wind shear, and storm motion.
Why does radar sometimes show rain when it's dry outside?
Radar beams travel in straight lines while the Earth curves away, so at long distances the beam may be looking at clouds or precipitation high in the atmosphere that evaporates before reaching the ground (called virga). Ground clutter, insects, and anomalous propagation can also cause false returns.
How often does weather radar update?
BOM radar images typically update every 6-10 minutes, depending on the radar site. This means the most recent image you see could be several minutes old. During severe weather, some radars can operate in faster modes with more frequent updates.