Estimating Avoidable Costs Due to Convective Weather Forecast Inaccuracy

Abstract

We have developed two methods to estimate NAS-wide avoidable costs due to inaccurate convective forecast. The initial, coarser method we have tested was based on the “airspace capacity surplus” concept. We estimated airspace capacity degradation caused by actual and forecast weather; we then compared these estimates to the scheduled demand and actual traffic for the same hours/airspace units. We took the lesser of theoretically possible capacity (given the weather) and scheduled demand in an airspace unit such as a Center, and compared it to the actually achieved occupancy. Any surplus capacity (actual occupancy lower than it could be) indicated avoidable delays, cancellations and, generally, costs. The second, much more refined method is based on our superfast-time simulation model, Dynamic Airspace Rerouting Tool (DART). The model combines airport and airspace operation aspects with rerouting around weather and airspace constraints, and generates a combination of economical reroutes and ground delays for all flights in the NAS in the presence of actual and forecast convective weather. We then apply DART in (1) a “perfect forecast” scenario, using actual (historical) weather only as a proxy for 100% accurate forecast, and (2) an “imperfect forecast” scenario, using a blend of actual weather and convective forecasts with increasing look-ahead horizons. In the latter case, aircraft recheck convective situation at regular intervals while in flight. They may have to hold while airborne; fly extra miles (or conversely, be able to make shortcuts); and be forced to divert. The difference in estimated operating costs incurred in these two scenarios (imperfect vs. perfect forecast) will indicate potential avoidable costs and therefore the benefit pool for NextGen improved-forecast products. It turns out that the annualized avoidable cost estimates computed with both methods are of similar magnitude.