Over the year of the study, three main types of weather were found to lead to high delays at Newark. These were, in order of frequency: low ceilings and visibility (C&V), thunderstorms, and strong gusty surface and low-level winds; in order of severity (for a single day): thunderstorms, low C&V, and winds. While thunderstorms have the most severe impact per event (a 4:3:2 delay ratio among the three events), the annual delay impact of C&V is actually greater (by a small margin) due to their higher frequency. Furthermore, the impact of reduced capacity due to low ceilings and visibility were generally more predictable. High surface winds had the potential for delays depending on runway configuration (and hence the direction of the wind).
When studying delays and delay reduction, it is critical to understand what delays are avoidable versus those that are unavoidable. The initial goal of this study was to quantify what types of weather delays at Newark could be mitigated by ITWS/TCWF. Given that C&V had the greatest overall impact, we focused our study on these cases to determine if available capacity was being efficiently utilized. While several cases showed that traffic management did well matching demand to available capacity, there were cases which showed room for at least some improvement. Through the use of an established model for aircraft queuing, it is shown that even a small improvement could result in significant cost benefits.
Improvement in this area will require highly accurate one-hour forecasts for use in traffic flow management decision making. Several research efforts are ongoing to improve the forecasts and the traffic flow managers and airline dispatchers access to these forecasts. One effort is the aforementioned TCWF, which has been shown in many cases to accurately predict the start and end to stratiform precipitation events. Another effort is underway to more accurately predict all low ceiling and visibility events, including those caused by fog and low clouds not associated with precipitation.
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