3.1
Where is my thunderstorm forecast? The shifting paradigms of NextGen weather information

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Tuesday, 25 January 2011: 1:30 PM
Where is my thunderstorm forecast? The shifting paradigms of NextGen weather information
310 (Washington State Convention Center)
Jack May, AvMet Applications International, Inc., Reston, VA; and C. G. Souders, R. C. Showalter, J. Tauss, C. Miner, and T. Kays
Manuscript (521.2 kB)

The Next Generation Air Transportation System (NextGen) weather requirements for full operating capability (FOC) have been developed over the last three years. This measured, team-based process has produced drafts of functional requirements distributed for comment in Jan 2008, the performance requirements for super-density airports distributed for comment in fall of 2009 and the performance requirements for remaining airspaces available Sep 2010. The Joint Planning and Development Office (JPDO) study team performed the functional analysis and developed the functional requirements. The FAA led NextGen Weather Performance Requirements Team (NWPRT) developed the performance requirements using a multi-agency team. This paper will help explain the reasoning and assumptions that were used to create these requirements.

Because the teams were focused on the NextGen Concept of Operation, all proposed weather requirements were based on the needs of fight planning, trajectory based operations, NAS management, and airport operations in a highly integrated and highly automated environment. Use of weather information was not envisioned as it is today where it is independently considered and evaluated by decisionmakers. Instead, weather information needs in 2025 were envisioned as highly granular, frequently probabilistic, and used by automated tools to develop weather impact assessments. These impact assessments will allow decision support tools to help decisionmakers effectively manage the amount of risk due to weather enabling them to maximize efficiency and safety. The weather requirements are focused on the needs of the 4-D Weather Single Authoritative Source for observed and forecast weather parameters.

FOC weather requirements were drafted in an idealized sense so as to not confuse today's technological solutions with true weather requirements (e.g., solution independent). For example, today's convective technological solution uses a two-dimensional depiction of radar reflectivity to represent a volume of convective weather hazards. In an effort to disassemble the true components of convective weather hazards, the team identified as requirements each weather hazard caused by convection, including those hazards which often exist outside regions of high reflectivity such as turbulence, gust fronts, even tornadoes.

The Next Gen forecast weather requirements include only those elements considered primary components. Forecast weather information was not considered primary if it could be calculated or derived using primary information. Examples of non-primary information not included in the requirements are density altitude, altimeter setting, and relative humidity. The team envisioned net-available tools that users and user systems could access to make calculations when needed.

The NextGen forecast weather requirements also did not include three-dimensional objects that could be constructed from primary weather components. Examples of 3-D objects not included are freezing level, cloud layers, and thunderstorms. Because of the high spatial and temporal resolution of weather information requirements, derivable information such as storm top, storm movement, vertically integrated liquid, and composite reflectivity are not a part of the FOC requirements. The NWPRT assumed these constructions and value-added information, if needed for human use at FOC, would be created by user systems (such as displays).

Using concepts suggested by the NextGen Concept of Operations (ConOps), the NextGen Weather ConOps and FAA's NextGen Concept of Use, some requirements are simple expressions of both forecast and probabilistic elements. For example, in order to avoid a complicated series of requirement statements regarding various cloud ceilings, tops, layers, and coverage, the requirements provide high temporal and spatial resolution forecasts for “cloud” and “probability of cloud.” It is envisioned navigation tools will assess the impact of the high resolution 4-D cloud (and cloud probability) forecasts according to user risk preferences and will select the most efficient and safest trajectory.

The NWPRT also assumed new, unanticipated ways will be found to mitigate the impact of unusual or impacting weather expected on a monthly or seasonal basis. The team wanted to support with valid information open-ended statements such as “Thunderstorms will be above average in the Northeast this summer, therefore…,” or “Winter weather will have a higher than normal impact on the Front Range this spring, therefore…”.

Both teams took on the challenge to develop weather requirements for operations that do not yet exist and that are not limited to the context of today's use of weather information. The result is stated within the context of NextGen operations and with a concerted effort to identify the true nature of aviation weather needs. These requirements will properly steer the research community toward their eventual fulfillment.