Severe Weather 101

Hail Detection

Hail can be detected using radar. On Doppler radar, hail generally sends a return signal that looks like extremely heavy rainfall.

Dual-polarization radar technology, used by the NWS, can help tell the difference between hail, ice pellets and rain, and even determine hail size.

What we do: NSSL's Hydrometeor Classification Algorithm (HCA) uses dual-polarization technology to automatically sort between ten types of radar echoes including big raindrops and hail. This helps the forecaster quickly assess the precipitation event and better forecast how much will fall.

NSSL’s Multi-Radar, Multi-Sensor (MRMS) system produces a Maximum Estimated Hail Size product, or MESH. This product is accumulated over several time periods (e.g., 1-hr, 1-day) and can help in both issuing warnings and verification of incidences of hail after the fact.

NSSL researchers developed the Hail Detection Algorithm, or HDA, which was the first operational hail sizing algorithm for the WSR-88D radars. Deployed in the late 1990s, the HDA produced a single hail size estimate per storm and provided information to forecasters on the probabilities of hail and severe hail within an approaching thunderstorm.

NSSL collaborates with research organizations to help the insurance industry anticipate and react to hail and other storm damage, saving time and money. Under the terms of multi-year joint research projects, NSSL provides data to partnering companies, which in turn provide critical insurance industry feedback and quality control assessments to improve NSSL's algorithms.