Storm Processes Depicted by the WSR-88D and KOUN Sector Scans during Severe Pulse Thunderstorms

Recently new scanning techniques designed to improve the temporal resolution of storms sampled by the Weather Surveillance Radar – 1988 Doppler (WSR-88D) network became operational. These techniques include 1) automated volume scan and termination (AVSET) and 2) supplemental adaptive intra-volume low-level scan (SAILS). AVSET is designed to minimize volume scan time (based on range), whereas SAILS is designed to provide more frequent updates at the lowest elevation. Concurrently, the NOAA National Severe Storms Laboratory has run KOUN using sector scans as a proxy for rapid-scanning polarimetric phased array radar. These sector scans provide shorter volume updates compared to SAILS (about 2 min vs 5.5 min) but similar updates at 0.5 degrees.

The use of these scanning techniques during severe weather events in central Oklahoma provides the opportunity to analyse and compare the storm evolution depicted by the WSR-88D to those depicted by KOUN. This study examines severe pulse thunderstorms that occurred on 8 July 2014 along a quasi-stationary cold front within a highly unstable environment. Storm Data reports indicate that these storms produced hail up to 1.5 inches in diameter and severe wind speeds (e.g., 52 kts) in Wayne, Oklahoma. Tree damage was also observed by the second author and local flooding unofficially reported. Given these severe weather observations, the analysis and presentation focuses on the evolution in the vertical of radar signatures key to assessing 1) severe hail and wind precursors (e.g., ZDR columns, ZDR holes/troughs, ρ_HV magnitude, and mid-altitude convergence) and 2) the occurrence of hail and wind near the ground (e.g., radial divergence). Operational implications of the WSR-88D and KOUN scanning techniques will also be discussed.