Microburst events observed with the National Weather Radar Testbed phased array radar

Microbursts are small-scale (< 4 km diameter) outflows induced by strong downdrafts in thunderstorms that frequently cause damage to property and are a hazard to aviators. Many severe microbursts originate from storm cells that form in regions of moderate-to-high Convective Available Potential Energy (CAPE), weak environmental shear, and environments that are highly unstable to downdraft formation. These storm cells typically have a life cycle of 20-40 minutes, which makes them very difficult to predict.

Automated algorithms that analyze radar data and make short-term predictions for microburst events, as well as detecting low-altitude divergence signatures associated with their outflows, have been implemented for WSR-88D and TDWR systems. These applications rely on microburst “precursors” that may be observed at the higher altitudes of a storm shortly preceding the outflow at the surface to make short-lead-time forecasts of a microburst event. However, microburst events evolve rapidly, and because these radars typically only sample the upper portions of a storm once every 4 to 6 minutes (depending on scanning strategy), they may not sample key precursor features aloft or the near-surface outflow.

This presentation examines damage-producing severe microburst events that occurred in Central Oklahoma during July 2006 that were observed with the National Weather Radar Testbed (NWRT) Multifunction Phased Array Radar (MPAR). These storms formed within 50 km of the PAR site and were sampled with a temporal resolution of 15 to 30 seconds. We will compare the PAR observations of the storms with the KTLX WSR-88D, OKC TDWR, and multi-radar, multi-sensor information from the Warning Decision Support System – Integrated Information. Additional cases of microbursts collected during Spring 2007 may also be described.