Strategic Forecasts of TRACON Airspace Capacity during Convective Weather Impacts

Weather accounts for a majority of the delay in the US National Airspace System (NAS) and convective weather accounts for much of the weather delay.  To try and mitigate these delays, forecasts of convective weather are used by traffic flow managers to attempt to match traffic demand to capacity constraints of specific air traffic resources such as en route flows or departure fixes via a strategic management plan.  Traffic demand for impacted resources is managed through the application of traffic management initiatives (TMI) that either remove demand from an impacted airspace or reduce demand by delaying the departure of flights filed through the impacted airspace.  Typical strategic TMI programs used by the Air Traffic Managers of today are mandatory playbook reroutes, Ground Delay Programs (GDP) and Airspace Flow Programs (AFP).  Since these TMIs require the pre-departure management of demand, the lead time for such decisions may be several hours in advance of the event onset to ensure that the TMI is in place soon enough to capture demand prior to departure.  This also allows airline operators to plan for the schedule and fueling consequences of the TMI.

For successful planning of TMIs, decision makers require weather forecasts of the impacted airspace between 2 and 8 hours in advance of the event to set the critical parameters of the TMI such as start time, duration and maximum flow reduction.  Weather-only convective forecasts are available to the traffic planner in the strategic time domain such as the Consolidated Storm Prediction for Aviation (CoSPA).   However, these forecasts provide little guidance about aviation impact on the air traffic resources and the precise location, severity, scale, and timing of operationally significant storms and the human response to those storms can be notoriously difficult to predict.   Therefore, the decision maker is left to make critical TMI decisions based on a subjective assessment of potentially conflicting weather forecast information.

The lack of an explicit translation of weather forecasts into resource constraints is a shortfall in the current weather information available to air traffic managers for strategic traffic flow management.  There are several consequences of this shortfall.  First, without an explicit translation there is a lack of an operationally relevant methodology to assess weather forecast resource impact and overall forecast performance.  Each participant (e.g., Air Traffic Control System Command Center (ATCSCC), Air Routes Traffic Control Center (ARTCC) Traffic Manager Unit (TMU) and Airline Operations Center (AOC)) comes into the collaborative strategic planning process with their own set of operational objectives, favorite forecast information, risk tolerance, etc.  This wide and often divergent range of opinions and goals must somehow be melded into a plan of action.  Without shared objective forecasts of weather impacts and estimates of decision risk, there is little common ground on which to base discussions about the best plan of action that addresses the different legitimate concerns of stakeholders.  Second, the utility of convective weather forecasts is directly related to the quality of decisions and NAS performance outcomes that the forecasts can support.  The definition of explicit, validated weather translations provides an objective and operationally relevant measure of truth against which forecasts can be compared.  Without translation-based forecast evaluations, it is difficult to determine how much of an operational shortfall in convective weather mitigation is due to poor weather forecasts and how much is the result of poor interpretation and application of forecast information.

This paper will present ongoing research of the Strategic TRACON Capacity Forecast (STCF) which will provide the TFM planner with a forecast of estimated capacity of arrival, departure, and transition traffic flows in the TRACON and near enroute airspace for major metroplexes.  The concept closely follows the Traffic Flow Impact (TFI) concept developed for enroute airspace and presented last year at the Fifth Aviation, Range and Aerospace Meteorology Special Symposium in New Orleans [1].

The STCF requires adaptation to address operational and mitigation strategies in the TRACON airspace, including:                                                                                  

1. Corner post impacts for TRACONs like Chicago or Atlanta, where there is considerable flexibility in the use of airspace,
2. Arrival / departure corridor impacts for highly structured TRACONs like NY and Philadelphia, where complex airspace may demand higher precision forecasts of airspace impacts on smaller spatial scales,
3. On-airport impacts that may result in degradation of all arrival and departure capacity, and
4. Mitigation strategies to account for the forecast uncertainty that arises in long horizon forecasts of impacts on a limited spatial scale of a TRACON corner post.

The STCF will address a similar set of TMI planning decisions as those addressed by TFI.  The integration of forecasts of TRACON impacts with enroute impact forecasts from the TFI forecast will ensure that there will be sufficient TRACON capacity to accommodate arrival demand that successfully negotiates enroute impacts.  The STCF will help planners maintain a sustainable balance between arrival and departure demand and avoid excessive departure delays or gridlock due to over-delivery of arrivals into impacted TRACON airspace.

Ref. 1: M. Matthews, J. Venuti and R DeLaura, “Translating Convective Weather Forecasts into Strategic Traffic Management Decision Aids”, 5^th Aviation, Range and Aerospace Meteorology Special Symposium, New Orleans, LA, January 2016.