NEXRAD Radar Basics: Understanding How Storm Radar Works

By StormAuditor Editorial Team · Published 2026-07-16 · Updated 2026-08-11

Based on public NOAA and National Weather Service records, published under StormAuditor's methodology and data-source standards. Radar-derived hail sizes are estimates unless attributed to a ground report.

NEXRAD (Next-Generation Radar) is the backbone of severe weather detection, providing crucial data on approaching storms. Understanding how this advanced Doppler radar works can help property owners, contractors, and adjusters interpret storm reports and historical weather data more effectively.

NEXRAD Radar Basics: How Storm Radar Works

NEXRAD radar (Next-Generation Radar) plays a key role in finding and tracking severe weather, including hail and high winds. If you research past storm damage for a property, learning how this technology works gives you useful context. It helps you interpret historical weather records and services like StormAuditor.

What is NEXRAD Radar and How Does It Work?

NEXRAD is a network of 160 high-resolution Doppler weather radars. The National Weather Service (NWS) operates them across the United States. These radars send pulses of electromagnetic energy into the atmosphere. When the pulses hit precipitation (rain, snow, hail) or other targets like insects or dust, some energy scatters back to the radar antenna. This 'echo' gives meteorologists critical information about the storm.

Doppler weather radar gathers two main types of information:

1. Reflectivity: This measures the intensity of the returned signal. It reflects the size, shape, and concentration of precipitation within a storm. Higher reflectivity values usually mean more intense precipitation. That can signal heavy rain or, importantly for property damage, larger hail. For example, a very high reflectivity core might suggest hail that could exceed the severe threshold of 1.00" (quarter-size).

2. Velocity: This measures how precipitation particles move directly toward or away from the radar antenna. From these Doppler shifts, meteorologists can determine wind speeds and directions within a storm. They can spot rotation that hints at potential tornadoes (EF0 tornado range 65-85 mph, severe wind threshold 58 mph). They can also detect damaging straight-line winds.

Modern NEXRAD radars are also Dual-Polarization capable. They transmit and receive both horizontal and vertical radar pulses. That yields more detail about hydrometeor type (rain, hail, snow), size, and shape. This capability helps tell heavy rain from large hail. It improves the accuracy of hail size estimates like those used in StormAuditor's methodology.

How StormAuditor Utilizes NEXRAD Data

StormAuditor uses NEXRAD data to provide property-specific historical weather insights. For hail analysis, StormAuditor's SAHE-2 (Storm Auditor Hail Estimate v2) primarily uses MRMS MESH (Maximum Estimated Size of Hail) from Hail Explorer. MESH is a sophisticated product derived from NEXRAD radar data. It gives per-pixel estimates of hail size across a storm's path. These swaths are critical for checking whether a property saw hail at or above the severe threshold of 1.00" (quarter size), or even the significant severe threshold of 2.00" (hen egg).

For wind, NEXRAD velocity data is crucial for severe thunderstorm and tornado warnings. But StormAuditor's SAWE-2 (Storm Auditor Wind Estimate) methodology focuses on NOAA ASOS/AWOS station peak-gust archives and model-derived background winds. It cross-references these with SPC storm reports of measured wind gusts. This gives a robust estimate of damaging wind conditions. We acknowledge that peak gust between stations can exceed reported values, and that station-based observations can under-sample microbursts. The NWS and NOAA issue severe thunderstorm warnings (for winds >= 58 mph or hail >= 1.00") and tornado warnings using real-time NEXRAD data. StormAuditor tracks these as an authoritative record for a property's warning history through IEM (Iowa Environmental Mesonet) archives.

When you use our /address-lookup tool, StormAuditor processes historical NEXRAD-derived data. It checks whether your property fell within estimated hail swaths or severe warning polygons. Remember: NEXRAD provides ESTIMATES of severe weather conditions, not direct measurements at every single point. StormAuditor combines this information with other reliable sources to give you the most complete picture possible.

Practical Guidance for Property Owners, Contractors, and Adjusters

Understanding NEXRAD radar helps you make sense of historical weather reports, especially for date-of-loss research [/date-of-loss-weather-research].

  • Property Owners: Suppose a StormAuditor report shows your property inside a NEXRAD-derived hail swath of, say, 1.25" (half-dollar size) or 1.75" (golf ball size). That suggests a high likelihood of functional hail damage, especially to asphalt shingles. Knowing this can inform your talks with contractors and adjusters. Remember: asphalt shingles typically begin showing functional hail damage around 1.00"–1.25" impacts. Window/skylight breakage becomes common at ~1.75"+.
  • Contractors: Radar data from StormAuditor's /hail and /wind explorers can help you prioritize inspections. It also helps you check observed damage against the storm's expected severity. For example, a 2.00" (hen egg) hail swath over an area greatly raises the probability of severe roof and property damage.
  • Adjusters: NEXRAD-derived data, combined with SPC storm reports, provides a strong evidence base for evaluating claims. Our reports can help confirm whether severe hail (1.00"+) or damaging winds (58 mph+) were present at a specific location and time. That supports efficient claim processing. The data can substantiate conditions that could cause uplift to asphalt shingles (55–70 mph) or widespread blow-off (75–85 mph).

Limitations

NEXRAD radar is highly advanced, but it has limits. Radar systems can sometimes under-estimate hail size, especially wet hail. They can over-estimate it in scenarios with very high reflectivity cores. The beam spreads with distance, so data farther from the radar is less precise. Ground clutter and atmospheric conditions can also affect data quality. StormAuditor reduces these limits by combining multiple data sources and providing estimates, not direct measurements. We never claim to 'prove' damage causation. Our goal is accurate historical weather intelligence. For more details on what StormAuditor provides, see our /limitations page.

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FAQ

Q: What is NEXRAD radar, and what does it detect?

A: NEXRAD (Next-Generation Radar) is a network of Doppler weather radars operated by the NWS. It detects precipitation, measures its intensity (reflectivity), and tracks its movement (velocity). That lets meteorologists follow storms and identify severe weather like hail (1.00" or larger) and damaging winds (58 mph or higher).

Q: How does StormAuditor use radar data for hail?

A: StormAuditor's SAHE-2 uses NEXRAD-derived products like MRMS MESH to estimate the Maximum Estimated Size of Hail (MESH) at a property's location. This helps show whether a property saw hail meeting severe thresholds, such as 1.00" (quarter-size) or 2.00" (hen egg).

Q: Can NEXRAD radar tell me if my roof was damaged?

A: NEXRAD radar data can tell you whether severe weather, such as hail of a certain size or strong winds, likely occurred at your location. It provides crucial environmental context. It cannot directly assess property damage. That requires a qualified inspector, who can use a StormAuditor report as part of their assessment.

Q: Are radar hail size estimates always accurate?

A: NEXRAD radar provides highly useful estimates, but they are not always perfectly accurate. Wet hail or complex storm structures can lead to under- or over-estimation. StormAuditor addresses this by combining radar data with other sources, like SPC storm reports, to offer the most reliable estimates possible.

Q: What is 'dual-polarization' radar?

A: Dual-polarization is an enhancement to NEXRAD radar. It sends and receives both horizontal and vertical radar pulses. This yields more detail about precipitation type (rain, hail, snow), size, and shape. It greatly improves the ability to tell large hail from heavy rain.