A Volume Coverage Pattern (VCP) is the scanning plan a WSR-88D Doppler radar follows: the set of elevation angles the antenna sweeps and how long one full volume scan takes. Operators pick a VCP to balance how often the data updates against how sensitive the radar is to weak echoes and how well it samples storms in the vertical.
How a volume scan works
The antenna turns a full circle at a low angle, then steps up and repeats at higher angles until the volume is complete. Current National Weather Service (NWS) radar training lists patterns that sample from 5 to 15 elevation angles, with full volumes taking roughly 4 to 10 minutes.
The Radar Operations Center (ROC) sums up the choice as sensitivity versus speed. Slower patterns favor weak returns and data quality, while faster ones refresh storms more often.
The current set
NWS training lists two operating modes. Clear Air mode offers VCPs 31, 34 and 35, and Precipitation mode offers VCPs 12, 112, 212 and 215. VCPs 31 and 34 use a long pulse and take about 10 minutes per volume.
The ROC's February 2026 info sheet ranks five patterns from most sensitive to fastest as 35, 215, 112, 212 and 12. It matches 215 to general non-tornadic precipitation, 112 to widespread non-tornadic convection, 212 to all convective modes and 12 to discrete or local convection.
Patterns that have been retired
The set has changed over time. The NWS announced in 2017 that a software build scheduled for 2018 would remove VCPs 11, 21, 211 and 221 and introduce 35 and 215. A 2019 notice announced that VCP 112 would replace VCP 121.
VCP 32, an older clear-air pattern, no longer appears in the current training list, which names VCP 34 instead. Older guides and archived data may still show the retired numbers.
Faster low-level updates, and their limits
Operators can add extra scans near the ground. SAILS (Supplemental Adaptive Intra-Volume Low-Level Scan) inserts one to three extra scans of the lowest angle spread through the volume, and the multi-scan option was first introduced as MESO-SAILS.
A related option, MRLE (Mid-Volume Rescan of Low-Level Elevations), rescans the lowest two to four angles midway through the volume. Each extra low-level scan lengthens the full volume, so the upper tilts update less often, although a 2022 study found statistically significant gains in warning performance with SAILS on.
No pattern removes the radar's geometry limits. The beam still climbs and widens with distance, so distant storms are sampled high above the ground whatever VCP is running.