Estimating the likelihood of success in departure management strategies during convective weather

The presence of convective weather (thunderstorms) in terminal and nearby en route airspace of major metroplex areas can have significant impacts on departure operations. Traffic on departure routes impacted by convective weather may be constrained by miles-in-trail (MIT) restrictions, to allow controllers the time needed to maneuver individual flights around thunderstorms that pilots wish to avoid. When the workload required to manage traffic flows becomes too great, departure routes may be closed. Departures still on the ground that are filed on closed or restricted routes may face significant delays as they wait for clearance on their filed route, or for a viable reroute to be implemented. The solution proposed in concepts such as the Integrated Departure Route Planning tool (IDRP) [1] is the use of weather and departure demand forecasts to plan and implement reroutes to avoid weather and volume congestion proactively, well in advance of route restrictions or closures. As traffic management concepts propose longer forecast horizons for proactive planning, they must account for the considerable uncertainty inherent in air traffic management during convective weather. The Route Availability Planning Tool (RAPT) [2], a departure management decision support tool that forecasts convective weather impacts on departure routes, has been used in both New York and Chicago to proactively plan reroutes of pending departures to avoid weather impacts. However, even with RAPT, there is uncertainty in predicting convective weather impacts, wheels-off times for pending departures, and demand for different departure resources, particularly when schedules are disrupted by weather impacts. These uncertainties can limit the planning horizon and reduce the effectiveness of proactive rerouting. Air traffic managers with the primary responsibility for departure route management at current RAPT prototype sites (the traffic management units (TMU) in ZNY in New York and ZAU in Chicago) employ many tactics (including, but not restricted to, proactive rerouting) to mitigate convective weather impacts while accounting for the limits of forecast certainly. This paper presents convective weather impact mitigation tactics observed in departure management during RAPT field evaluations in New York [3, 4] and Chicago [5], proposes objective characteristics that may be used to define success and failure in reroute decisions, examines the probabilities of different outcomes based on weather-avoiding reroute strategies, and explores the factors that affect the choice of departure management tactics and outcomes.