Convective weather delays have been the principal cause of the dramatic delay growth in the US aviation system over the past 3 years. In 2000, the key new initiative for reducing these delays was "strategic" traffic flow management (TFM) coordination through the Collaborative Convective Forecast Product (CCFP), the Strategic Planning Team, and Collaborative Routing (CR).

One of the major challenges in convective weather management is the need to predict route availability and sector/airport capacity for highly congested airspace. This problem is particularly acute near major airport complexes such as the New York City area and highly congested en route corridors such as the Great Lakes Corridor from Chicago to New York.

Analysis of operations in congested airspace has shown that changes in storm locations as little as 2-4 miles can make a major difference in the impact of the weather on the ATC system operations. Accurate forecasting of the spatial extent and severity of convective weather (e.g., spatial extent to within 5 km) two or more hours in the future has proven very difficult with the result being that the strategic plans have often be of limited use.

As a result of this difficulty in accurately forecasting convective weather several hours in advance, tactical weather decision support is an essential complement to the "strategic" approach to handling severe weather. This consists of:

a. terminal and en route weather prediction systems [e.g., Integrated Terminal Weather System (ITWS)], the Corridor Integrated Weather System (CIWS)], and

b. traffic flow management and automation decision support tools to facilitate effective use of the tactical weather information.

Recent operational experience at reducing weather delays at the New York terminal area and in the Great Lakes Corridor using experimental ITWS and CIWS systems will be discussed in detail. Real time products are provided to towers, TRACONs, ARTCCs, the Command Center and airlines to facilitate collaborative decision making. We show these tactical weather decision support systems provide very high delay reductions (e.g., over 2 million minutes per year for the NY terminal area alone). However, these weather information systems alone cannot fully address the operational needs of the air traffic control and airline dispatcher.

Air traffic management tools that can utilize the tactical weather decision support products and permit "what if" examination of solutions to the predicted weather situation are critical to handling convective weather in congested airspace. Key issues include reducing controller workload, unambiguously identifying regions of airspace that pilots will seek to avoid and addressing the traffic flow management consequences of tactical handling of convective weather. We discuss how contemporary traffic automation and traffic flow management tools under development by MITRE and NASA are an essential complement to the tactical weather information systems such as ITWS and CIWS.

The paper concludes with a summary of the many very difficult meteorological, air traffic management, and concept of operations problems that must be addressed to significantly improve the aviation system handling of significant convective weather.

*This work was sponsored by the Federal Aviation Administration under Air Force Contract No. F19628-00-C-0002. The views expressed are those of the authors and do not reflect the official policy or position of the U.S. Government. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the US Government.