• Identifying weather information needs to support TFM operational decision-making
• Having decision-makers validate the needed accuracy for that weather information
The first and most important challenge is to determine “What weather information is needed.” This was performed using prior work (e.g., Mission Need Statement 339 and Mid-Term Concepts of Operation) and updated TFM decision documentation. However, simply identifying the required weather information alone is not enough. In order for the weather information to provide value-added support to the operational decision-maker in improving their decisions, the 'goodness' of the weather information must also be determined. The 'goodness' of that information must be determined by the decision-makers and is usually evaluated in terms of its accuracy. This includes how precise the observation is measured or how well the forecast matches the verifying observation. In addition, the decision-maker places high value on other attributes including latency, spatial and temporal resolution, and the magnitude accuracies of the various forecast weather elements. Once the decision-makers have validated these required accuracy values, the associated performance requirements were developed. These performance requirements drive the selection of solutions developed as part of the FAA's Acquisition Management System for the various capabilities of the NAS weather architecture, i.e., observing, forecasting, and dissemination.
To begin this process, representatives from the FAA NextGen Weather Performance Requirements Team (NWPRT) and the National Weather Service (NWS) began working with TFM specialists to determine their Mid-Term weather information needs. A joint FAA and NWS TFM Weather Requirements Working Group (TRWG) formed in August 2010 with the following objectives:
• Develop requirements for weather information services for Mid-Term Operational Capability (MOC)
• Establish a plan to implement solutions meeting those requirements
• Baseline current NWS weather forecast support capability
As the NWPRT worked with the TRWG, it became clear that for TFM, the emphasis was two-fold--mitigate current shortfalls in weather support, as well as move toward the Mid-Term. As a result, the TRWG asked NWS to baseline their current forecast performance capability for weather information out to eight hours in terms of time of onset, time of cessation, Probability of Detection, False Alarm Rate, timing error and location error.
The NWPRT was asked to develop the Near-Term requirements using these performance criteria for TFM to facilitate the determination of when the current shortfalls might be mitigated. However, to perform a gap analysis between the NWS' baseline forecast performance values, based on the above criteria, and the Mid-Term requirements, it was necessary for the NWPRT to develop additional mid-term requirements with the same performance criteria as the near-term requirements, which are very different from the MOC and Far-Term requirements previously developed by the NWPRT. Examples of the functional requirements are listed below. Of these criteria, the NWPRT had previously only written requirements for location error.
Some examples of TFM Mid-Term functional requirements are listed below:
• The Mid-Term NAS shall forecast the time of the onset of thunderstorms with a probability greater than or equal to 50 percent and with tops over 30,000 feet expected to intersect jet routes that cut across the Flight Constrained Areas for areas greater than 20 miles in diameter.
• The Mid-Term NAS shall determine the probability of detection for the forecast of the time of the onset thunderstorms with a probability greater than 50 percent and with tops over 30,000 feet in Flight Constrained Areas.
• The Mid-Term NAS shall determine the false alarm rate for forecast of the time of the onset of thunderstorms with a probability greater than 50 percent and with tops over 30,000 feet in Flight Constrained Areas.
• The Mid-Term NAS shall determine the timing error for the forecast the time of the onset of thunderstorms with a probability greater than 50 percent and with tops over 30,000 feet in Flight Constrained Areas.
• The Mid-Term NAS shall determine the location error for the forecast location of the onset of thunderstorms with a probability greater than 50 percent and with tops over 30,000 feet in Flight Constrained Areas.
To establish a weather performance baseline for TFM, the NWS is identifying the current weather forecast performance capabilities. When NWS has completed their baselined weather performance requirements, the FAA will perform a gap analysis to determine how much improvement in forecasting weather is required to meet the TFM Mid-Term aviation weather needs. Additionally, the FAA will develop a transition plan specifying how to mitigate the gaps in weather services to meet Mid-Term operational needs, when the gaps will be mitigated, and who is responsible for the gap mitigation.
Once performance requirements are validated, the FAA will start writing the translation requirements for converting state of the atmosphere information into potential NAS weather-related constraints. At this time, the FAA is moving forward with convective weather translation, which will be available in 2015. Over the next year, the FAA will determine which additional state of the atmosphere weather information will be translated into NAS constraints.