What does NEXRAD stand for?

NEXRAD stands for Next Generation Weather Radar. The network is the WSR-88D (Weather Surveillance Radar – 1988 Doppler): about 160 S-band radars (~10 cm wavelength) operated jointly by the National Weather Service, the FAA, and the Department of Defense.

What do the colors on weather radar mean?

Radar colors show reflectivity in dBZ (decibels of reflectivity, a logarithmic scale). Greens are light rain, yellow and orange are heavy rain or a developing thunderstorm, and red and magenta are the most intense cores — hail becomes increasingly likely above about 55 dBZ. Radar measures the energy returned, not rainfall directly, so a very high dBZ core often means hail.

What is the difference between reflectivity and velocity on radar?

Reflectivity shows how much precipitation is falling. Velocity (Doppler) shows how it is moving: green is motion toward the radar and red is motion away. A small patch of bright green right beside bright red at the same range — a "couplet" — means the air is rotating, a possible mesocyclone and the signature forecasters watch for ahead of a tornado.

Why does radar miss storms that are far away?

The radar beam rises and widens with distance. About 100 miles from a radar, even the lowest tilt is roughly 12,000 ft above the ground, so the beam overshoots low clouds and light rain near the surface. The picture is most reliable close to a radar site.

What is dual-polarization radar?

Since around 2012, NEXRAD radars pulse both horizontally and vertically, adding products that reveal target shape and uniformity: Differential Reflectivity (ZDR), Correlation Coefficient (CC), and Specific Differential Phase (KDP). A Tornado Debris Signature — high reflectivity plus a tight velocity couplet plus a co-located drop in CC at low levels — is treated as confirmation that a tornado is lofting debris on the ground.

How to Read NEXRAD Weather Radar — Reflectivity, Velocity & Dual-Pol

How to Read NEXRAD Weather Radar — Reflectivity, Velocity & Dual-PolReading NEXRAD radar — reflectivity colors and dBZ, Doppler velocity and rotation couplets, dual-pol products, alert polygons, and the limitations of the beam.The NEXRAD composite is the live, mosaiced view from multiple Doppler radar sites. The colors show reflectivity, which roughly indicates precipitation intensity. Your county is outlined in blue.Reflectivity colors

Light green: Light rain (drizzle to light shower).

Green: Moderate rain.

Yellow: Heavy rain / start of thunderstorm intensity.

Orange: Heavy thunderstorm, possibly small hail.

Red: Intense storm, likely hail.

Magenta/Pink: Extreme — large hail almost certain.

Light blue: Snow (different intensity scale).

Colored polygonsActive NWS warnings, watches, and advisories shaded by event type — red for tornado warnings, orange for severe thunderstorm, etc.Pinned iconsLocal Storm Reports from the last 24 hours: red triangles = tornadoes, blue circles with numbers = hail (size in inches), green diamonds = wind (speed in mph), teal squares = flooding.LimitationsNEXRAD beams curve up with distance. Beyond ~150 miles, the beam is high enough that low-level features (light rain, snow at the surface) get missed. The composite has small seams between contributing radars and lower resolution at long range.Honest note: this is a free radar feedBloomWX renders a free composite NEXRAD layer (Iowa Environmental Mesonet / RainViewer tiles). It updates roughly every 5 minutes, which is fine for situational awareness and SKYWARN spotting from a fixed location. It is *not* the right tool if you're driving toward a storm.For active storm chasing — making intercept decisions on rotation, debris signatures, or velocity couplets — pay for a real radar app:

RadarScope (dtn.com/radarscope): what every spotter and chaser I know runs. Single-site Level 2/3, velocity, dual-pol products, storm tracks. ~$10/yr basic, ~$100/yr Pro Tier 2 with MRMS and lightning.

RadarOmega (radaromega.com): modern competitor with a slick UI and good MRMS / TDS overlays.

GR2Analyst / GRLevel3 (grlevelx.com): desktop, used by media meteorologists and serious chasers. Steeper learning curve but unmatched product depth.

BloomWX has no affiliate relationship with any of these — they're recommended on merit. Use the free dashboard radar to monitor the broader picture; switch to a paid single-site app the moment you're inside the warning polygon or moving toward one.

Frequently asked questions

What does NEXRAD stand for?: NEXRAD stands for Next Generation Weather Radar. The network is the WSR-88D (Weather Surveillance Radar – 1988 Doppler): about 160 S-band radars (~10 cm wavelength) operated jointly by the National Weather Service, the FAA, and the Department of Defense.
What do the colors on weather radar mean?: Radar colors show reflectivity in dBZ (decibels of reflectivity, a logarithmic scale). Greens are light rain, yellow and orange are heavy rain or a developing thunderstorm, and red and magenta are the most intense cores — hail becomes increasingly likely above about 55 dBZ. Radar measures the energy returned, not rainfall directly, so a very high dBZ core often means hail.
What is the difference between reflectivity and velocity on radar?: Reflectivity shows how much precipitation is falling. Velocity (Doppler) shows how it is moving: green is motion toward the radar and red is motion away. A small patch of bright green right beside bright red at the same range — a "couplet" — means the air is rotating, a possible mesocyclone and the signature forecasters watch for ahead of a tornado.
Why does radar miss storms that are far away?: The radar beam rises and widens with distance. About 100 miles from a radar, even the lowest tilt is roughly 12,000 ft above the ground, so the beam overshoots low clouds and light rain near the surface. The picture is most reliable close to a radar site.
What is dual-polarization radar?: Since around 2012, NEXRAD radars pulse both horizontally and vertically, adding products that reveal target shape and uniformity: Differential Reflectivity (ZDR), Correlation Coefficient (CC), and Specific Differential Phase (KDP). A Tornado Debris Signature — high reflectivity plus a tight velocity couplet plus a co-located drop in CC at low levels — is treated as confirmation that a tornado is lofting debris on the ground.

Part of the BloomWX learn library — beginner-friendly explainers covering every surface of the BloomWX weather dashboard. Open BloomWX to see live data for any U.S. county.