Measurement of Hazardous Winter Storm Phenomena at the Portland OR International Airport

Wind shear and lightning strikes to aircraft are classically associated with summer convective weather. However, a recent study of West Coast airports found that severe wind shear and lightning strikes can occur during winter storms in the Portland Oregon terminal area. These unexpected phenomena arise from the local topography (especially surface cold air outflows from the Columbia River gorge) and, the weakly electrified nature of the fall/winter/early spring convective storms in the Portland area.

This paper describes initial results of measurements with a transportable pencil beam C-band Doppler weather radar at the Portland Oregon International airport (PDX). The radar will be used to collect data on winter and early spring storms and wind shear events. It is believed that the vertical wind shear events, experienced by aircraft arriving and departing PDX, could have similar headwind changes as summer convective wind shear phenomena (e.g., > 30 knot losses or gains in airspeed).

Both PPI and RHI Doppler radar scans were utilized so as to determine the vertical shear of the wind shear events and to characterize the 3D structure. A second, but equally important, objective of this study is to determine whether the baseline ASR-9 Weather System Processor (WSP), which is planned for PDX, will adequately detect the vertical wind shear. The C-band Doppler radar data will be used to create synthetic ASR-9 reflectivity and Doppler radial velocity data. This synthesized ASR-9 data will be analyzed to evaluate the ability of the ASR-9 to detect the vertical wind shear.

The paper will characterize key meteorological features of the wind shear and lightning storms observed and then discuss the viability of various options (e.g., an unmodified ASR-9 WSP, a modified WSP, and a WSP augmented with data from other sensors such as vertical profilers) for providing timely warning on hazardous phenomena.

* This work was sponsored by the Federal Aviation Administration. The views expressed are those of the authors and do not reflect the official policy or position of the U.S. Government. ^ Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the FAA or the U.S. Air Force.