NEXRAD Radar Basics: Understanding How Storm Radar Works

Published 2026-07-16 · Updated 2026-07-16

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) is instrumental in identifying and tracking severe weather events, including hail and high winds. For anyone researching past storm damage for a property, understanding the basics of how this technology operates provides valuable context for interpreting 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 operated by the National Weather Service (NWS) across the United States. These radars send out pulses of electromagnetic energy into the atmosphere. When these pulses encounter precipitation (rain, snow, hail) or other atmospheric targets like insects or dust, a portion of the energy is scattered back to the radar antenna. This 'echo' provides meteorologists with critical information about the storm.

There are two primary types of information gathered by Doppler weather radar:

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

2. Velocity: This measures the movement of precipitation particles directly towards or away from the radar antenna. By analyzing these Doppler shifts, meteorologists can determine wind speeds and directions within a storm, identify rotation indicative of potential tornadoes (EF0 tornado range 65-85 mph, severe wind threshold 58 mph), and detect damaging straight-line winds.

Modern NEXRAD radars are also Dual-Polarization capable. This means they transmit and receive both horizontal and vertical radar pulses, providing even more detailed information about hydrometeor type (rain, hail, snow), size, and shape. This enhanced capability helps distinguish between heavy rain and large hail, improving the accuracy of hail size estimates like those used in StormAuditor's methodology.

How StormAuditor Utilizes NEXRAD Data

StormAuditor leverages the power of 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, providing per-pixel estimates of hail size across a storm's path. These swaths are critical for determining if a property was impacted by hail meeting or exceeding the severe threshold of 1.00" (quarter size) or even significant severe thresholds of 2.00" (hen egg).

For wind analysis, while NEXRAD velocity data is crucial for severe thunderstorm and tornado warnings, StormAuditor's SAWE-2.9 (Storm Auditor Wind Estimate v2.9) methodology focuses on NOAA ASOS/AWOS station peak-gust archives and model-derived background winds, cross-referenced with SPC storm reports of measured wind gusts. This provides a robust estimate of damaging wind conditions, acknowledging that peak gust between stations can exceed reported values and that station-based observations can under-sample microbursts. However, the NWS and NOAA issue severe thunderstorm warnings (for winds >= 58 mph or hail >= 1.00") and tornado warnings using real-time NEXRAD data, which StormAuditor tracks 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 to determine if your property was within estimated hail swaths or severe warning polygons. It's important to remember that NEXRAD provides ESTIMATES of severe weather conditions, not direct measurements at every single point. StormAuditor synthesizes this information with other reliable sources to give you the most comprehensive picture possible.

Practical Guidance for Property Owners, Contractors, and Adjusters

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

  • Property Owners: If a StormAuditor report indicates your property was within a NEXRAD-derived hail swath of, say, 1.25" (half-dollar size) or 1.75" (golf ball size), this suggests a high likelihood of functional hail damage, particularly to asphalt shingles. Knowing this can inform your discussions with contractors and adjusters. Remember, asphalt shingles typically begin showing functional hail damage around 1.00"–1.25" impacts, while window/skylight breakage becomes common at ~1.75"+.
  • Contractors: When assessing properties, radar data from StormAuditor's /hail and /wind explorers can help prioritize inspections and validate observed damage against the expected severity of the storm. For example, knowing a 2.00" (hen egg) hail swath passed over an area significantly increases 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 if severe hail (1.00"+) or damaging winds (58 mph+) were present at a specific location and time, facilitating efficient claim processing. This data can substantiate the presence of conditions that could cause uplift to asphalt shingles (55–70 mph) or widespread blow-off (75–85 mph).

Limitations

While NEXRAD radar is highly advanced, it has limitations. Radar systems can sometimes under-estimate hail size, especially wet hail, or over-estimate it in scenarios with very high reflectivity cores. The beam spreads with distance, leading to less precise data further from the radar. Additionally, ground clutter and atmospheric conditions can affect data quality. StormAuditor mitigates these limitations by combining multiple data sources and providing estimates, not direct measurements. We never claim to 'prove' damage causation; our goal is to provide 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 determines its movement (velocity), allowing meteorologists to track 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 utilizes NEXRAD-derived products like MRMS MESH to estimate the Maximum Estimated Size of Hail (MESH) that occurred at a property's location. This helps identify if a property was impacted by 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 if severe weather, such as hail of a certain size or strong winds, likely occurred at your location. It provides crucial environmental context but cannot directly assess property damage. For that, a qualified inspector is needed, 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. Factors like wet hail or complex storm structures can lead to under- or over-estimation. StormAuditor addresses this by integrating 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 that sends and receives both horizontal and vertical radar pulses. This capability provides more detailed information about precipitation type (rain, hail, snow), size, and shape, significantly improving the ability to distinguish large hail from heavy rain.