Recent challenges and opportunities for operational radar algorithms afforded by the NEXRAD radar network

For nearly 23 years, the NEXRAD radar network has continually incorporated state-of-the-science enhancements through refreshes of radar technology. The past few years have seen several substantial modifications ranging from a dual-polarization upgrade to implementation of dynamic scanning strategies. These modifications have already produced significant changes to operational radar products and will continue to do so for years to come.

Weather Decision Technologies (WDT) has utilized WSR-88D Level II data since it became publicly available in real-time in 2004. Data from 155 radars are ingested, quality-controlled, mosaicked into 3-dimensional grids from which a suite of derived 2-dimensional products are produced for clients. Low latency and high quality are paramount. Polarimetric data has provided opportunities for immediate improvement in WDT products through quality control, improved hail detection and more accurate quantitative precipitation estimates (QPE). But, experience with operational polarimetric data over the past three years has shown it can present its own set of challenges, including false precipitation detections during spring and fall and differential reflectivity calibration issues.

Beyond the polarimetric upgrade, new dynamic scanning techniques have been instituted within NEXRAD radars allowing for faster scanning update times especially for the lowest elevation angle. Automated Volume Scan Evaluation and Termination (AVSET), Supplemental Adaptive Intra-Volume Low-Level Scan (SAILS) and now Multiple Elevation Scan Option for SAILS (MESOSAILS) can provide low level scan updates approaching just one minute. In response to the increased temporal resolution, WDT has implemented a new mosaicking method which reduces the update time of its products from 5 to 2.5 minutes, with 1-minute update frequency a possibility in the near future. This increase has already positively impacted hail swath detections and promises to improve other products such as rotation tracks, severe storm attribute identification and tracking as well as QPE. Increasing mosaic spatial resolution is more problematic and a new, customized technique is currently being explored that would produce 250-m mosaics efficiently designed to take advantage of a cloud computing environment.

Examples of enhanced products made possible with recent NEXRAD network upgrades will be shown along with new challenges that have to be addressed. A look forward to very high resolution real-time radar products suitable for production within a cloud computing environment will be presented.