Use of the Convective Weather Avoidance Polygon (CWAP) to Identify Temporally Coherent Convective Storm Boundaries

The Convective Weather Avoidance Polygon (CWAP) is an automatically generated polygon that identifies the storm boundary along which pilots are likely to fly when avoiding the storm. The CWAP takes into account the weather avoidance field (WAF) calculated from the Convective Weather Avoidance Model (CWAM), edges detected in the echo tops field, and winds at the flight altitude. The initial CWAP algorithm successfully identified avoidance boundaries, but forecast CWAP boundaries could change significantly from one forecast to the next – for instance, a large polygon would break into several smaller polygons and then re-combine on successive forecasts. Refinements to the CWAP algorithm have resulted in a marked improvement in the temporal coherence of CWAP from one forecast to the next. As a result, CWAP more reliably identifies the boundaries of operationally significant storms in a region of airspace, and characterizes the forecast weather in the airspace according to CWAP-related metrics such as size, orientation, and severity. Regional weather characteristics based on CWAP provide a foundation for operational weather typing that can be used in the prediction of operational impact on trajectory-based operations and modeling of forecast uncertainty.