Publications

Reducing thunderstorm-related air traffic delays in congested airspace has become a major objective of the FAA, especially given the recent growth in convective delays. In 2000 and 2001, the key new initiative for reducing these convective weather delays was "strategic" traffic flow management (TFM). Users were given 2-, 4-, and 6-hour collaborative convective weather forecasts, and collaborative traffic routing plans were established via telecons attended by Air Traffic Control (ATC) and airline traffic managers. This "strategic" approach led to difficulties during a large fraction of the weather events because it was not possible to generate forecasts of convective weather at time horizons between 2 and 6 hours that were accurate enough to assess impacts on routes and capacity, and thereby accomplish effective TFM. During convective weather events, traffic managers tend to focus on tactical TFM [Huberdeau, 2004], yet they had relatively inaccurate current weather information and tactical forecasts. The Corridor Integrated Weather System (CIWS) demonstration began in 2001. The objectives of the demonstration are to provide improved tactical air traffic management (ATM) decision support, via improved real time 3D products and accurate short-term convective weather forecasts, and to determine if this support is an operationally useful complement to "strategic" TFM. The current focus of the CIWS initiative is the highly congested airspace containing the Great Lakes and Northeast corridors, since that region offers the greatest potential for delay reduction benefits. In this paper, we describe the current status of CIWS, including initial operational results of Air Traffic Control (ATC) and airline use of the CIWS weather products. We begin with some CIWS background, describing the motivation for the program, the role of CIWS products in the overall convective weather planning process, and the functional domains in which CIWS products can provide operationally significant benefits. We then review the current CIWS capabilities, spatial coverage, sensors used, products, operational users, and integration with ATM systems. Next the detailed CIWS operational benefits study carried out in 2003 is summarized. Finally, we discuss the FAA plans for CIWS and near term enhancements to the system.

In this paper, we summarize contemporary approaches to quantifying convective weather delay reduction benefits. We outline a program to develop a significantly improved capability that can be used to assess benefits of specific systems. This program may potentially accomplish weather impact normalization for studies of National Airspace System (NAS) performance in handling convective weather. Benefits quantification and NAS performance assessment have become very important topics for the aviation weather community. In an era of significant federal government and airline budget austerity for civil aviation investments, it is essential to quantitatively demonstrate delay reduction benefits of improved weather decision support systems. Major FAA initiatives stress the importance of quantitative system performance metrics that are related to aviation weather. For example, the new FAA Air Traffic Organization (ATO) and the FAA Flight Plan 2004-08 both have quantitative performance metrics that are closely related to reducing convective weather delays. The Flight Plan metrics include: "Improving the percentage of all flights arriving within 15 minutes of schedule at the 35 OEP airports by 7%, as measured from the FY2000-02 baseline, through FY08," and "Maintaining average en route travel times among the eight major metropolitan areas." The ATO metrics include the percentage of on time gate arrivals and the fraction of departures that are delayed greater than 40 minutes. However, these metrics currently do not account for the differences in convective weather severity and changes in the NAS. The dramatic increase in convective season delays in 2004 (Figure 1) due to a combination of severe weather, increases in overall demand, and specific airport issues has demonstrated that one needs to consider these other factors. Approaches to delay reduction quantification that were viewed as successful and valid several years ago are no longer considered to be adequate by either by the FAA investment analysis branch or by the Office of Management and Budget (OMB). The paper proceeds as follows. We first discuss at some length the mechanisms by which convective weather delay occurs in the NAS and highlight challenges in delay reduction assessment. We consider this to be very important since one needs to understand how the system operates if one is to design an effective, accurate performance assessment system. We then consider benefits quantification based on feedback from experienced users of a system. Feedback on "average" benefits from a system at the end of a test period was used to generate delay reduction estimates for the Integrated Terminal Weather System (ITWS) and the Weather and Radar Processor (WARP). This end-of-season interview approach was not viable in highly congested en route airspace. Hence, a new approach was developed for Corridor Integrated Weather System (CIWS) benefits assessment that uses real time observations of product usage during convective weather events coupled with in depth analysis of specific cases. Next, we discuss the problems that arise when one attempts to quantify delay reduction benefits by comparing flight delays before and after the Integrated Terminal Weather System (ITWS) system was deployed at Atlanta Hartsfield International Airport (ATL). This seemingly simple approach has proven very difficult in practice because the convective weather events in the different time periods are virtually never identical and because other aspects of the NAS may also have changed (e.g., user demand, fleet mix, and other systems that impact convective weather delays). It has become clear that one needs a quantitative model for the NAS that would permit adjustment of measured delay data to account at least for the differences in convective weather and changes in user demand (i.e., flight scheduling). The paper concludes with recommendations for measuring near term benefits of various classes of convective weather decision support systems.

The Corridor Integrated Weather System (CIWS) seeks to improve safety and reduce delay by providing accurate, automated, rapidly updated information on storm locations and echo tops along with two-hour high-resolution animated growth and decay convective storm forecasts. An operational benefits assessment was conducted using on-site observations of CIWS usage at major en route control centers in the Northeast and Great Lakes corridors and the Air Traffic Control Systems Command Center (ATCSCC) during six multi-day periods in 2003. (Not complete).

The Corridor Integrated Weather System (CIWS) seeks to improve safety and reduce delay by providing accurate, automated, rapidly updated information on storm locations and echo tops along with two-hour high-resolution animated growth and decay convective storm forecasts. An operational benefits assessment was conducted using on-site observations of CIWS usage at major en route control centers in the Northeast and Great Lakes corridors and the Air Traffic Control Systems Command Center (ATCSCC) during six multi-day periods in 2003. This first phase of the benefit assessment characterizes major safety and delay reduction benefits and quantifies the delay reduction benefits for two key Traffic Flow Management (TFM) user benefits: "keeping air routes open longer/reopening closed routes soon" and "proactive, efficient reroutes of traffic around storm cells." The overall CIWS delay reduction for these two benefits is 40,000 to 69,000 hours annually with an equivalent monetary value ot $127M to $26M annually. Convective weather delays at most of the major airports in the test domain, normalized by thunderstorm frequency, decreased after new CIWS echo tops and forecast products were introduced. Recommendations are made for near-term, low-cost improvements to the CIWS demonstration system to further increase the operational benefits.

Reducing congested airspace delays due to thunderstorms has become a major objective of the FAA due to the recent growth in convective delays. In 2000 and 2001 the key new initiative for reducing these convective weather delays was "strategic" traffic flow management (TFM) at time scales between 2 and 6 hours in advance using collaborative weather forecasts and routing strategy development. This "strategic" approach experienced difficulties in a large fraction of the weather events because it was not possible to forecast convective storm impacts on routes and capacities accurately enough to accomplish effective traffic flow management. Hence, we proposed in 2001 that there needed to be much greater emphasis on tactical air traffic management at time scales where it would be possible to generate much more accurate convective weather forecasts. In this paper, we describe initial operational results in the very highly congested Great Lakes and Northeast Corridors using weather products from the ongoing Corridor Integrated Weather System (CIWS) concept exploration. Key new capabilities provided by this system include very high update rates (to support tactical air traffic control), much improved echo-tops information, and fully automatic 2-hour convective forecasts using the latest "scale separation" storm tracking technologies. Displays were provided at major terminal areas, en route centers in the corridors, and the FAA Command Center. Substantial reduction in delays has been achieved mostly through weather product usage at the shorter time scales. Quantifying the achieved benefits for this class of products have raised major questions about the conceptual framework for traffic flow management in these congested corridors that must be addressed in the development of air traffic management systems to utilize the weather products.

It is demonstrated in this paper that weather depictions in an operational environment based upon VIL provide more meaningful information for en route traffic routing than a BREF product. VIL precipitation proves advantageous in limiting contamination from Anomalous Propagation (AP) ground clutter, biological targets (e.g., birds and insects), and radar artifacts. The extended vertical coverage of VIL sampling also better depicts storm cells as they first develop, further assisting traffic managers achieve more efficient use of tactical airspace when weather occurs unexpectedly.