An Investigation of Radar Signatures and Challenges Associated with Tornadic Storms in Pennsylvania at Distant Radar Ranges for Warning Criteria Improvements

In an operational lens, the decision to warn on tornadic storms is dependent on radar characteristics and storm-scale features outlined in national guidance. The distinctive topographic features and severe weather regimes of Pennsylvania, coupled with portions of County Warning Areas (CWA) in spots of poor radar coverage, can cause warning decisions to be rather difficult, especially at far radar ranges. As a radar beam travels to a target, its width increases and thus the resolution is decreased. This, in conjunction with the fact that the radar beam height with respect to Earth’s surface increases with range, can obscure features typically utilized as warning decision confidence builders. This project assesses the radar signatures of all confirmed tornadoes greater than 50 nautical miles from a radar site across the state of Pennsylvania from 2012-2022. A thorough analysis of variables such as rotational velocity, azimuthal shear, and gate to gate shear aims to produce threshold values that can be used by forecasters during severe weather operations. In addition to radar analysis, Rapid Refresh (RAP) model archive data is examined for each case across various storm mode classifications including quasi-linear convective systems, linear hybrids, supercells, marginal cells, and disorganized convection. The refinement of baseline guidance values according to observations unique to Pennsylvania tornadoes are in an effort to increase the probability of detection and ensure CWA constituents receive adequate lead time to protect themselves from life-threatening adverse weather.