May 22 - July 31
Comparing Downburst and Tornado Signatures in Mesoscale Convective Systems between NEXRAD and Phased Array Radar
Sean Phipps, Kristofer S. Tuftedal, Charles M. Kuster, and Vivek N. Mahale
What is already known:
- Single and dual-polarization radar signatures such as mesovortices, rear inflow jet(s), and KDP cores, are used to forecast perils in short timescales.
- KDP cores and subsequent collapses are used as downburst precursor and identification signatures respectively due to the negative buoyancy generation of melting hailstones and precipitation loading
- Phased array radar (PAR) is a rapid-update radar that can capture transient signatures earlier and more reliably than a non-rapid-update radar such as the ones used in the current NEXRAD network
What this study adds:
- Supported previous research pertaining to faster and more reliable detection of downburst precursor signatures. PAR KDP maxima usually meets KDP core thresholds a few minutes sooner than NEXRAD. PAR also detected transient KDP core development and collapse where NEXRAD did not.
- Contributed to the ongoing investigation of downburst signature manifestation and downburst augmentation of mesovortices by using PAR data. In one cold-season QLCS case, KDP core development and subsequent collapse preceded mesovortex genesis.
Abstract:
Dual-polarization (dual-pol) phased array radar (PAR) is being considered as a potential replacement to the current Weather Surveillance Radar-1988 Doppler (WSR-88D) network (NEXRAD) because of its high cost-benefits, better polarimetric data quality, and finer temporal resolution. Research on the utility of using dual-pol PAR to identify downburst signatures in mesoscale convective systems (MCSs) is limited; therefore, this study uses KTLX and KOUN NEXRAD radars and the National Severe Storms Laboratory’s (NSSL’s) Advanced Technology Demonstrator (ATD) S-band dual-pol PAR to compare temporal evolutions of specific differential phase (KDP) core maxima in seven cores. Sampled KDP cores are obtained from three MCSs; a warm season mesoscale convective complex (MCC) transition into a bow echo, a warm season bow echo, and a cold season quasi-linear convective system (QLCS). The QLCS case provided mesovortices for further analysis, in which this study uses quantifications of downdraft and circulation strength with ATD to identify correlations between storm characteristics. This analysis revealed that: 1) the KDP genesis threshold was met earlier in ATD in all cases where it was measured; 2) KDP and mesovortex sampling is incomplete with WSR-88D and sometimes misses transient KDP cores; 3) one downburst indicated by a KDP core and subsequent collapse augmented mesovortexgenesis in a cold-season QLCS case. These results support the conclusion that PAR enables the earlier detection of downburst precursor signatures and illuminates details of KDP cores, collapses, and columns not captured by the current WSR-88D network.