Using Wind Profilers to Examine Non-Convective Low-Level Wind Shear in North Carolina

Low-level wind shear (LLWS) events are difficult to observe, forecast, and verify due to the high vertical and temporal resolution required to properly observe the phenomenon. Pilot Reports (PIREPs) are unreliable while conventional observational and forecast data within the boundary layer are often too sparse to properly sample LLWS. Wind profilers can observe the boundary layer with enough vertical sampling to capture LLWS and be used for forecast verification. In this study, data from wind profilers were used to calculate low-level wind shear below at or below 2000 feet as defined in NOAA Technical Memorandum NWS FCST-23 which states,

“Non-convective wind shear is defined as a change in horizontal wind speed and/or direction, and/or vertical wind speed with distance, measured in a horizontal and/or vertical direction…. A sufficient difference in wind speed, wind direction, or both, can severely impact airplanes, especially within 2,000 ft AGL because of limited airspace for recovery.”

Wind profiler data used in this study spans the time frame of November 2013 to April 2016. Terminal Aerodrome Forecasts (TAFs) were evaluated for the presence of LLWS and compared to observations from the wind profiler data to determine the accuracy of the TAF forecast. False alarm rates as well as the number of non-forecasted LLWS events were evaluated. Wind profilers were also used to analyze the characteristics of typical LLWS events over central North Carolina. A local climatology is presented along with typical patterns that result in LLWS over central North Carolina in order to improve pattern recognition techniques used by forecasters to better anticipate low-level wind shear events.