We present a method for quantifying the impact of forecast convective weather – specifically, as reflected in the Collaborative Convective Forecast Product (CCFP) - on the National Airspace System (NAS). Data generated by a convective forecast product (broad areas, percentage coverage and confidence level) is converted to a gridded format similar to the actual convective weather data (detailed reports on a NAS-wide hexagonal grid). From this, we build a NAS Weather Impacted Traffic Index (WITI) showing how the forecast and actual weather might have impacted the air traffic. Rather than using instantaneous CCFP snapshots two hours apart as a basis for direct CCFP-to-NCWD verification, we use interpolation and CCFP conversion to quasi-NCWD format in 1-hour increments, which may be a better reflection of the NAS operators' perception and use of convective forecast products. The WITI metric for both actual and forecast en-route convective impact can be computed for the NAS as a whole and also can be apportioned to individual airports by hour of the day, just as delays, for instance, originate and eventuate at airports. This drill-down ability allows us to compare weather impact with delays, with both metrics normalized against their respective multi-year NAS averages.

The method we have developed shows relatively high correlation between actual and forecast weather impact over an entire convective season. At the same time, significant over- or under-prediction can occur on specific days, and even wider disparities can occasionally be observed for specific regions/airports and times of the day.

The aim of the project is to better understand how the accuracy of the weather impact forecast (not just the weather forecast in itself) affects NAS operational response strategies. We therefore compare the forecast-vs.-actual WITI “deltas” with NAS operational outcome metrics such as delays; other metrics, e.g. excess miles flown, can be considered also. Future extensions of the current methodology are also discussed, especially the extension to terminal area forecasts.

We also describe and present advanced visualization techniques used in our analysis. By combining innovative weather impact information presentation (NAS-at-a-Glance charts, WITI and its “deltas”, Delays) with weather/traffic animation, a more useful toolset can be provided to the air traffic management specialists and aviation weather experts.