Federal Aviation Administration 

Research, Engineering and 

Development Advisory Committee 

Report of the 

Weather-ATM Integration 

Working Group 

October 3, 2007 
Executive Summary 

This report provides findings and recommendations of the Weather – ATM 

Integration Working Group (WAIWG) of the National Airspace System Operations 

(NAS OPS) Subcommittee, Federal Aviation Administration (FAA) Research, 

Engineering and Development Advisory Committee (REDAC). 

The objective of this twelve-month study was to examine the potential benefits of 

integrating two highly inexact sciences; weather and air traffic management, and 

to provide research recommendations to the FAA where appropriate. 

The working group members were from airlines, general aviation, NASA, the 

National Weather Service, national research centers and academia. The study 

results are based information gathered during visits to airline operations centers, 

terminal and en route air traffic facilities, and research centers. 

In this report, integration is defined as translating traditional weather information 

into impact measures, such as capacity or flow rates, and automatically or semiautomatically incorporating that data into traffic flow advisory information to 

improve the system capacity and safety in the face of weather hazards. 

 Few instances of integrated tools exist: time-of-flight estimates incorporating 

winds aloft; storm free departure times at one airport, and winter deicing timing. 

All other NAS decision tools use weather manually, as traffic display overlays or 

on separate displays. 

Aviation weather forecasts have much more accuracy in 0-2 hour, tactical time 

frame, than the 2-10 hour, strategic time frame. However, the size and shape of 

the 0-2 hour solution space is much smaller and with increasing congestion, 

more decisions will have to be made in the latter. Conversely the more the 

tactical solution space can be expanded, the more decisions can be delayed 

adaptively and traffic optimized to meet business objectives. 

A key finding, based on an analysis of several 2005-2006 convective events, is 

that as much as two-thirds of the weather related delay is potentially avoidable. 

Another key finding is that a risk management approach with adaptive, 

incremental decision making, based on automatically translating weather 

forecasts into air traffic impacts, presents a major new opportunity for reducing 

weather related delays in the future NAS. 

The key recommendation is that a cross cutting research program, involving 

public and private sector air traffic management and aviation weather experts, is 

needed to exploit these key findings. 

i 
Summary of Recommendations 

Overarching Recommendations

• Initiate a crosscutting research program in ATM/Weather integration 

• Establish Senior Leadership over-sight and REDAC monitoring 

• Revitalize joint FAA-NASA advisory committee reviews of research 

including weather – ATM integration 

• Develop AWRP requirements to support integration efforts 

Research Recommendations: Near Term - IOC 2010

• Identify and quantify avoidable delay. 

• Translate convective weather into ATC impacts 

• Improve AFP by developing a 6-10 hour weather impacts forecast 

• Improve Weather Input into Collaborative Traffic Flow Management 

• Develop guidance on integrated tools for cockpit decision making 

• Integrate airport and terminal area automation with weather 

Research Recommendations: Mid Term - IOC 2015

• Develop adaptive integrated ATM procedures for incremental route 

planning. 

• Develop adaptive integrated ATM procedures for tactical trajectories 

• Develop flexible airspace for weather impacts as a fundamental and initial 

ATM design requirement 

 

Research Recommendations: Far Term - IOC Post 2015

• Replace surrogate weather indicators with true measures of flight hazards 

• Conduct research on probabilistic and deterministic forecasts for multiple 

dynamic flight lanes. 

• Conduct research on gridded and scenario based probabilistic weather 

data for ATM decision tools. 

Human Factors

• Conduct research on the human factors aspects of weather – ATM 

integration 

• Identify best weather practices of air traffic facilities and train these 

practices system wide 

ii 
iii

FAA and NextGen Enterprise Architectures

• Ensure that direct ATM automation-weather integration is a key focus of 

the development of OEP/NAS Enterprise Architecture operational and 

technical views for the transition to NextGen. 

Aviation Weather Research Program 

• Increase support to enable participation in joint weather – ATM integration 

research 

• Restore the National Ceiling and Visibility Program 
Dedication

 

This study was organized by the late Jerry Thompson at a 2006 summer meeting 

in Boulder, Colorado, of the NAS Operations Subcommittee, FAA Research, 

Engineering and Development Committee. That so many contributed to this 

work is a tribute to the importance of this issue and to Jerry. 

iv 
TABLE OF CONTENTS 

 Page 

Executive Summary................................................................................................................... i 

Summary of Recommendations.............................................................................................. ii 

Dedication.................................................................................................................................. iv 

1. Introduction .............................................................................................................................1 

2. Study Description...................................................................................................................3 

3. Background.............................................................................................................................4 

The Weather and Congestion Challenge ......................................................................4 

Aviation Weather ...............................................................................................................4 

Air Traffic Management and Aviation Weather.............................................................5 

Previous Integration Initiatives ........................................................................................6 

Weather in the Cockpit .....................................................................................................7 

4. Avoidable Weather Related Delay ......................................................................................8 

5. Findings and Recommendations - Overarching .............................................................10 

A. Crosscutting Research Program..............................................................................10 

B. Leadership...................................................................................................................10 

C. Requirements Process ..............................................................................................11 

6. Findings and Recommendations: Weather – Air Traffic Management 

Integration.........................................................................................................................12 

A. Assessments of Avoidable Delay ............................................................................12 

B. Translating Weather Data into ATC Impacts .........................................................13 

C. Improve weather input into Collaborative Traffic Flow Management.................16 

D. Weather Information and Pilot Decision Making ...................................................18 

E. Integrating Weather Impacts with Airport Surface and Terminal 

Management Systems...........................................................................................19 

F. Adaptive integrated ATM procedures for incremental route planning................21 

G. Weather Impacts and Tactical Trajectory Management.....................................25 

H. Airspace Designs for Weather Impacts ..................................................................26 

v 
vi

I. Advanced Weather ATM Integration Concepts.......................................................28 

7. Human Factors Considerations for Integrated Tools .....................................................30 

8. Implications on Air Navigation Service Providers...........................................................32 

A. Training on New Integrated Tools............................................................................32 

B. Best Practices in Weather Mitigation ......................................................................32 

9. Implications on Airline and Flight Operations Centers...................................................34 

10. Implications for FAA and NextGen Enterprise Architectures......................................35 

11. Implications for FAA Aviation Weather Research Program........................................36 

12. Summary.............................................................................................................................38

13. Acknowledgements ...........................................................................................................39 

Appendix A. Study Description .............................................................................................40 

Appendix B. Previous Integration Initiatives .......................................................................45 

Appendix C. Glossary of Terms.............................................................................................48 

Appendix D. Avoidable Delay Analysis................................................................................49 

Appendix E. Weather Impact Analysis ................................................................................55 

Appendix F. Route Availability Planning Tool......................................................................68 
1. Introduction 

This report provides findings and recommendations on the integration of weather 

information into air traffic management (ATM) processes and systems. It was 

developed by the Weather/ATM Integration Working Group (WAIWG) under the 

direction of the National Airspace System Operations (NAS OPS) Subcommittee 

and its parent body, the Federal Aviation Administration (FAA) Research, 

Engineering and Development Advisory Committee (REDAC). 

The objectives of the twelve-month study included examining the potential 

benefits associated with a higher degree of integration between two dissimilar 

and fundamentally inexact sciences, namely, weather and air traffic 

management, and with providing specific research recommendations to the FAA 

that were considered most likely to lead to better, more efficient ATM solutions, in 

the face of weather constraints. 

The members of WAIWG believe this report to be complementary to the Next 

Generation Air Transportation System (NextGen) vision as espoused by the Joint 

Planning and Development Office (JPDO). The report is also seen as timely, 

especially when viewed in light of (1) current and projected future increases in 

demand for airspace system capacity, (2) the escalating difficulties associated 

with convective weather constraints in the NAS, and (3) the current state of ATM 

in the NAS. 

With respect to the latter, it is useful to acknowledge that current ATM processes 

and toolsets are only partially automated, and when they are, the underlying 

algorithms are almost always based on nominal (no weather impacts) system 

conditions. Therefore, in the presence of weather constraints in the NAS, most 

ATM personnel discard available automated tools and their solutions and revert 

to the use of manual solutions. Every ATM decision maker has a different level of 

experience and mental capacity. This, combined with the inconsistencies 

naturally associated with human decision making under periods of high mental 

workload and stress, results in ATM solutions in the face of weather constraints 

which are inconsistent, unpredictable and often rigid. 

Additionally, the common coping strategy for the human ATM decision maker is 

to devise solution sets that are applicable to a large number of flights (flow-based 

solutions) instead of tailored to the individual impacted flight (flight-based 

solutions). Unfortunately, a widely applicable solution set is not the best solution 

set for many, if not most, individual flights. Consequently, this strategy results in 

the perception among users of the airspace that NAS resource allocation 

decisions are not equitable. 

A response to the overall ATM decision making problem is to incorporate more 

advanced automation systems that capture the impacts of weather. 

1 
2

As used in this report, integration means that weather information and forecasts 

must be translated from words, pictures or probabilities into quantifiable airspace 

capacity impact values which are then appropriately incorporated into ATM 

processes and technology. One component of this translation will involve gaining 

a better understanding of pilot actions in the face of weather phenomena such as 

thunderstorms and turbulence. These weather-related airspace capacity impact 

values must then be automatically incorporated into aircraft, airline operations 

center (AOC) and ATM toolsets and processes in such a way so as to improve 

system capacity and safety in the face of weather hazards. Many of the study’s 

findings and recommendations are related to this area. 

There are but a few examples of current ATM tools and processes in which 

weather information is integrated. 

• Existing time-of-flight estimators which incorporate winds aloft are used by 

FAA systems today. 

• Certain ATC facilities use a tool which provides storm free departure times 

from a particular airport. 

• Winter deicing times are predicted in certain airports. 

All other NAS ATM decision support tools and traffic management processes use 

weather information manually, as storm depiction overlays or from separate, 

stand-alone displays. 

Aviation weather forecasts have much more accuracy in the zero to two hour 

(“tactical”) time frame, than in the two to ten hour (“strategic”) time frame. 

However, the number of viable solutions in the zero to two hour solution space is 

much less than in the two to ten hour space, and the available solutions 

themselves are also much different. With increasing congestion, it would seem 

that more decisions will have to be made strategically, from two to ten hours 

before departure. If, however, the tactical solution space can be expanded by 

increasing the number of possible solutions, then more decisions can be delayed 

adaptively and more flight trajectories can be optimized against business 

objectives. As will be reported in Section 6, this type of risk management 

approach with adaptive decision making presents a major new opportunity for 

reducing weather related delays and operating costs in the future NAS. 
2. Study Description

This study was organized at a summer, 2006, meeting of the NAS OPS 

Subcommittee with the following terms of reference: 

• Recommend development priorities for integration of Weather and ATM 

covering near (IOC 2010), intermediate (IOC 2015), and long term (IOC 

2025). 

• Consider requirements for the flight deck (weather in the cockpit), Air 

Navigation Service Providers and Flight Operations Centers. 

• Recommend incorporation of the requirements into the FAA Enterprise 

Architecture and the NEXGEN Enterprise Architecture. 

• Recommend changes to the Aviation Weather Research Program’s to 

support study recommendations. 

A study team was formed with representation from the airlines, general aviation, 

the research community, and experts from the weather and air traffic 

management community. 

The year long effort included meetings with the aviation community, FAA facilities 

and committee meetings at various locations. Forty-seven briefings were 

presented including eleven on weather in the cockpit. 

Details on the membership, schedule, relevant literature and briefing sources are 

provided in Appendix A. 

3 
3. Background 

This section provides background information on the evolving challenge of 

weather and congestion, aviation weather products, their use in air traffic 

management, earlier integration initiatives, and issues related to cockpit weather.

The Weather and Congestion Challenge 

Weather has always been a major constraint to air transportation but its impact 

has grown in recent years. The National Airspace System of the United States is 

the most efficient in the world because, unlike other systems, it is allowed to 

operate at full capacity until weather or other constraints require throughput to be 

reduced by traffic management initiatives. Despite a 6% traffic reduction at major 

airports between 2000 and 20061, overall delays have grown due to increased 

enroute traffic volumes and growing enroute congestion. The higher enroute 

volumes result in much more difficult ATM decision making than those in 

response to terminal impacts or constraints. 

The FAA S2K (Air Traffic Control System Command Center) home site states: 

“Even under the best weather conditions, overall increases in airspace demand 

and significant increases during peak demand periods routinely leads to 

congestion, which can have a ripple effect throughout the NAS. When areas of 

high demand are impacted by convective weather, the volume and complexity 

issues are extended dramatically requiring a system-wide choreographed effort 

to minimize service disruption.“ 

The challenge is clear: how should Air Traffic Management systems and 

procedures be modernized, and integrated with aviation weather and new 

airspace designs, to minimize disruptions and enable the natural growth of the air 

transportation industry. 

Aviation Weather 

The concerted efforts of FAA, NOAA/NWS, DOD and NASA in the past several 

decades have resulted in the deployment of many new weather sensing systems 

including Geostationary (GOES) and polar (POES) satellites, and NEXRAD, 

ASOS, TDWR and ASR-9 WSP ground systems. 

Using the new sensor data, and advances in computing, image processing and 

weather modeling, the FAA and National Weather Service have made significant 

 

1

 Mitre OPSNET report 

4
improvements to forecasting icing, turbulence, ceiling and visibility, and 

convection events. The integration of NEXRAD sensors enabled the creation of 

new products such as the Collaborative Convective Forecast Product, used for 

strategic traffic planning. The integration of a broad set of terminal area sensors 

to improve the prediction and detection of wind shear led to the Integrated 

Terminal Weather System (ITWS). Similar motivation for en-route or regional 

domains led to the prototype Corridor Integrated Weather System (CIWS). 

The NWS has created a suite of digital weather products on the Aviation Digital 

Data Service (ADDS), which includes a national convective product called the 

National Convection Weather Forecast (NCWF), and a large variety of other 

products. 

Since convection is historically the major reason for delay, especially in the 

summer, an automated 0-1 hour storm motion product (Terminal Convective 

Weather Forecast – TCWF) was developed and, later, a 0-2 hour storm product 

for regional use was created. These tactical products are self scoring, providing 

a metric on their recent performance, which air traffic managers are finding 

useful. Current FAA sponsored research is focused on a developing a single 

integrated convection and wintertime storm product for 2012. 

Additional progress in weather automation has occurred: Preflight briefings of 

icing and turbulence hazards are now automated and can be tailored for specific 

routes and altitudes to simplify go-no-go decisions. An experimental ceiling and 

visibility tool for helicopter medical flights has been deployed. A challenging 

sensor integration and modeling effort was completed at San Francisco to predict 

marine stratus burn off. 

Air Traffic Management and Aviation Weather

With few exceptions the use of the various single and integrated weather 

products by air traffic managers have followed traditional methods and 

procedures: separate displays of weather imagery are examined and air traffic 

flow decisions made by manually estimating the impact of weather based on 

mental models and experience. This may have been adequate in the past, but 

with the growing traffic and greater fragility of the NAS to disruptive weather, 

better means to leverage existing weather products are needed. 

Accordingly, new approaches were developed and have already enjoyed some 

success, evolving ATM toward a more integrated approach with weather impacts. 

The CCFP enabled traffic managers and operators to move beyond arguments 

over convective forecasts. The FEA/FCA process enabled areas of flow, 

impacted by weather, to be isolated from nominally useable airspace. This 

capability was combined with the lessons learned from Ground Delay Programs 

5
and the Flight Schedule Monitor to create the Airspace Flow Program 

capabilities. 

FAA sponsored R&D, the CDM group and others have contributed these and 

other important building blocks in ATM but the following example illustrates an 

opportunity that was identified at New York to take weather integration to the next 

level: 

When the one hour Terminal Convective Weather Forecast (TCWF) product was 

first deployed in 1998, ATC personnel had to mentally extrapolate the forecast 

and calculate the future aircraft locations for each planned departure. This 

proved impractical so a Route Availability Planning Tool, RAPT2

, was developed 

that automates these mentally taxing calculations, making accurate departure 

impact predictions readily available to the supervisors and air traffic flow 

managers. It effectively translated weather information into traffic flow 

constraints. It was subsequently enhanced to account for storm tops, continues 

to be used and refined at New York, is used in associated in air route centers, 

and is being considered for other FAA control facilities. 

RAPT was possible because of the greater accuracy of the 0-1 hour TCWF 

forecast period. Although conceptually simple, it is difficult to extend into enroute 

airspace because of airspace structural rigidity and coordination problems. It also 

highlights the problem of deciding what weather is acceptable to penetrate based 

on radar observations that measure precipitation and not turbulence, and 

variations in pilot reactions. However, it exhibits a key finding of this report which 

cannot be over emphasized: weather can be translated into impact and

converted to an advisory in ATM terms, at least for tactical situations. 

 

Previous Integration Initiatives

Research on weather and ATM Integration has been consistently stifled due to a 

lack of requirements from FAA operations offices. Consequently, atmospheric 

scientists, engineers, and ATM researchers conducted ad hoc efforts to establish 

interest in this area.3

Since May, 2000, groups of weather and air traffic management researchers 

have held five Weather–ATM Integration Workshops, designed to identify 

integration opportunities and stimulate interest within FAA and NASA. The last, 

in October of 2004, identified ten research recommendations which are provided 

in Appendix B. 

 

2

 See Appendix F for description. 

3

 Section 5 of this report will address the requirements problem. 

6
Until recently, neither the FAA nor NASA responded to the recommendations of 

these workshops. A common reaction by FAA air traffic operational offices was 

to insist that weather forecasts be first improved, especially in the 0-6 hour time 

frame before committing to integration efforts. Another reaction was resignation, 

or the suggestion that weather presents an unavoidable disruption to traffic flow. 

However, NASA has recently responded with new research in this area, reported 

in Appendix B. 

As previously stated, with the exception of a departure tool at New York, and a 

winter deicing tool, no existing air traffic management tools are integrated with 

aviation weather beyond providing traditional weather depictions as an overlay 

on traffic displays or flight plans, and using winds for flight time estimates. 4

 

Weather in the Cockpit

The growing use of data-linked weather information in general aviation aircraft 

and, shortly, in air carrier cockpits, presents both challenges and opportunities to 

the aviation community and the FAA. 

There is both government and industry concern about up linked weather 

information, regarding its’ quality, consistency, and use by both general aviation 

and air carrier pilots, especially for storm avoidance. Another concern is that the 

airline cockpit weather demonstrations designed to show how the cockpit 

weather products can lead to better pilot decision making have been conducted 

in situations where congestion was not an issue. When airspace congestion is a 

major concern, pilot decision-making must be done in coordination with the 

current NAS management strategy. 

To identify the key issues associated with the use weather in the cockpit, the 

WAIWG held a special one day session with representatives from the FAA’s 

Aviation Safety (AVS) organization, the airlines, general aviation, ALPA, the 

National Business Aircraft Association (NBAA), and a helicopter medical airlift 

group. 

 

4

 Mitre Survey 

7
4. Avoidable Weather Related Delay

A key issue considered by the committee was the extent to which today’s 

weather delays could be avoided if weather and air traffic management were 

more effectively integrated. Accordingly, the study examined recent convective 

events in view of the higher level of weather related delays in the summer. 

The avoidable delay for actual weather delay cases was determined by a three 

step process: 

(i) The actual weather characteristics (e.g., ceiling/visibility, airport winds, 

and 3 D weather radar reflectivity) were translated into the capacity 

reductions in the associated en route sectors, terminal airspace, and at 

airports5

, 

(ii) The time history of available terminal and en route capacity and the 

traffic demand were input into an fully automatic broad-area ATM 

strategy generator6 to determine reroute strategies or, when 

necessary, minimally disruptive ground or airborne delay programs 

that could have been utilized to minimize overall NAS delay 

(iii) The actual delays and airspace utilization for that date were compared 

to the optimized capacity utilization and its associated delays to 

determine where and when capacity was not fully utilized, and how 

much of the actual delay was “avoidable” where the avoidable delay = 

actual delay – delay for the optimized ATM strategy. 

Since the ATM strategy generator has knowledge of both the current and future 

weather, this is equivalent to assuming the availability of perfect weather 

forecasts as well as the use of optimal ATM responses to that weather. The 

latter, therefore, also assumes that there is perfect coordination between the 

various ATC facilities and between the FAA and airspace users. 

In practice there will always be underutilized airspace capacity in the face of 

weather constraints due to inaccurate forecasts, the suboptimal use of those 

weather forecasts in the development of ATM strategies, flawed coordination 

between various decision makers, communications and infrastructure limitations, 

and/or suboptimal implementation of the strategies (e.g., from delays in 

modifying flight plans, or because a particular aircraft is unable to fly the 

prescribed route due to mechanical issues). 

 

5

 The method by which this was done will be discussed subsequently. 

6

 Bertsimas, D. and S. Stock-Patterson, The Air Traffic Flow Management Problem with En Route 

Capacities, Operations Research, 46, 406-422, 1998 

8
As such, one must carefully look at the circumstances associated with the 

suboptimal use of available capacity in order to judge whether the existence of 

additional usable capacity could have been reasonably anticipated by real-time 

decision makers, given the accuracy of the weather forecasts and other ATM 

decision support then available to the decision makers. Beyond the formation of 

ATM strategies, one must also be aware that the current system infrastructure 

negatively impacts the air traffic manager’s ability to communicate and execute 

an ATM decision once made. 

With those caveats in mind, an analysis was done 7 for several significant 

convective events in 2005 and 2006. Table 1 shows the results. 

Although the magnitude of the avoidable delay was quite high in two of the three 

cases, the fact that much of the actual delay could have been avoided is 

encouraging for weather-ATM integration, since the accuracy of short term (e.g., 

0-2 hour) convective forecasts is much better than the accuracy of longer lead 

time forecasts and, may be easier to improve in the future. 

Details of this analysis are provided in Appendix E. 

Table 1 Preliminary results of determining unavoidable delay for three severe 

weather events in 2005 and 2006.8

 

7

 MIT Lincoln Laboratory 2007 study 

8

 Ibid 

9
5. Findings and Recommendations - Overarching

A. Crosscutting Research Program 

Finding: There is virtually no funded, cross cutting, research taking place in the 

integration of weather information into ATM decision support systems 

automation. 

There is a robust community of researchers and significant funded research 

activity in the ATM DSS automation arena. The same is true of aviation weather 

research, albeit at a much smaller support level. But there is virtually no identified 

or funded research on integrating weather information into ATM decision support 

system automation. Not a single interdisciplinary approach to such research, with 

members of the weather, ATM DSS automation and user communities working 

together as a team to develop an integrated weather/ATM capability, could be 

identified. If considered at all in ATM research, weather is, in effect, an 

afterthought or extension to an ATM tool. 

Recommendation: Initiate and fund a crosscutting research program in Weather/ 

ATM integration and insure that weather aspects are an integral part of all new 

ATM initiatives from the beginning. 

Specific research recommendations are provided Section 6. 

 B. Leadership 

Finding: The support of senior leadership is vital for promoting the development 

of integrated weather – air traffic management capabilities. 

As with any organization, public or private, the clear interest and commitment of 

senior management is needed for the success of a significant new effort such as 

integrating weather information and forecasts and air traffic management 

automation systems. This was emphasized in the REDAC Transitioning 

Research Study and is equally valid for the subject of this study, especially since 

past efforts have not been successful, in part for lack of management support. 

Recommendation: Establish Senior Leadership oversight. 

Senior leadership oversight of all major weather – ATM integration development 

efforts should be established to insure progress and overcome traditional 

resistance that has been resident in the middle management levels of the FAA. 

Recommendation: Establish REDAC monitoring. 

The REDAC should be directed to annually monitor weather/ATM integration 

initiatives to ensure adequate progress. 

10
Finding: Related research at NASA is important to the development of weather – 

ATM integration. 

NASA is currently conducting research directly connected to integrating weather 

and air traffic management processes and automation, although at a modest 

level of effort. This work is informally connected to FAA sponsored research and 

at risk given recent changes in NASA Aeronautics priorities. Additionally, it was 

found that this level of effort is far below the level required to insure the 

necessary cross-disciplinary connection to FAA Weather ATM integration work. 

Recommendation: Revitalize joint advisory committee reviews of FAA and NASA 

joint research such as weather/ATM Integration. 

FAA and NASA should hold joint meetings of their advisory committees and 

include the identification of current and future cross agency research 

opportunities in support of integrating advanced aviation weather and air traffic 

management tools. Furthermore, a Memorandum of Understanding (MOU) or 

Agreement of Understanding (AOU), between FAA and NASA, and 

encompassing weather and ATM research, may be needed to clearly elucidate 

the needed connection between these agencies. 

 C. Requirements Process 

Finding: Current Weather Research Requirements do not include weather – ATM 

Integration. 

Finding: ATM research only considers weather as an extension or afterthought, 

and that a new approach where weather is considered up front is needed. 

 While many of the existing aviation weather research efforts are important, they 

do not include work on weather integration with ATM, because the AWRP 

leadership does not have requirements from ATO to move in that direction. 

Additionally, the working group was not made aware of ATM requirements for 

weather integration, and could not find examples in the operational or research 

offices of the FAA where integration was considered a requirement. 

Recommendation: Develop requirements for weather ATM Integration 

participation within the AWRP. 

11
6. Findings and Recommendations: Weather – Air Traffic 

Management Integration 

This section provides findings and recommendations regarding weather – air 

traffic management in nine areas: 

Near Term: IOC 2010 

 A. Assessments of Avoidable Delay 

 B. Translating Weather Data into ATC Impacts 

 C. Improve weather input into Collaborative Traffic Flow Management 

 D. Weather Information and Pilot Decision Making 

 E. Integrating Weather Impacts with Airport and Terminal TFM 

Mid Term: IOC 2015 

 F. Adaptive integrated ATM procedures for incremental route planning 

 G. Weather Impacts and Tactical Trajectory Management Systems 

 H. Design Airspace for Weather Impacts 

Far Term: IOC Post 2015 

 I. Advanced Integrated ATM Approaches 

It is important to recognize that the research elements for each epoch must start 

now, in order to meet the Initial Operating Capability dates indicated. 

While certain key human factors issues are highlighted for these different time 

frames, because many of those issues cut across near-, mid- and far-term 

epochs, most of the human factors considerations are documented in a separate 

section (Section 7). 

 

Near Term: IOC 2010 

A. Assessments of Avoidable Delay 

Finding: Weather related delay may be significantly reduced through improved 

integrated decision tools. 

As described in Section 4 and Appendix E, an analysis of recent convective 

events indicates that opportunities exist to significantly reduce weather related 

delay if weather and ATM functions are integrated and provided to decision 

makers. 

12
 It is important that research continue to improve understandings of the 

characteristics of avoidable delay and support the development of integrated 

methods to exploit these phenomena. 

The analysis process cited provides explicit flight profiles for each aircraft (that 

could be provided to traffic flow management play back facilities) operational 

facility domain experts could provide useful feedback on the practicality of the 

automatically generated ATM strategies. 

Recommendation: Research is needed to identify and quantify avoidable delay. 

Quantitative research studies of “avoidable” delay, should be conducted each 

year, based on significant summer or winter storm events, to identify 

opportunities to reduce delay and to evaluate the performance of weather – ATM 

integration capabilities as they are developed and fielded. 

Recommendation: ATM/TFM/AOC/FOC Involvement is needed. 

Operational user feedback on the feasibility of the ATM strategies developed by 

the automatic planner described in Section 4 should be provided. 

B. Translating Weather Data into ATC Impacts 

Finding: Initial efforts on translating weather data into ATC impacts have shown 

some success, but additional research is needed. 

A key research question is the translation of current weather data and weather 

forecasts into ATC impacts, i.e., airspace that pilots will seek to avoid and the 

associated airspace capacity impacts. Since this is an important topic, an 

example is provided here; a more detailed description is provided in Appendix E. 

For this analysis, the integration of weather and ATM is shown architecturally in 

Figure 1. The process begins with descriptions of pilot behavior and weather, 

translates them into capacity impacts, using airspace and operational 

descriptions, and provides the results to algorithms that incorporate user 

demands and response strategies to develop decision advisories. 

A pilot weather deviation model, shown in detail in Figure 2, was developed from 

over 500 flight-storm encounters in the Midwest. 

The pilot weather deviation (avoidance) model can be combined with real time 

weather radar data and convective weather forecasts to generate graphical 

depiction of the regions that pilots will seek to avoid. These regions of high 

13
likelihood of pilot deviation can used to forecast which routes will be blocked and 

hence the reduction in en route sector capacity. 

The pilot weather deviation (avoidance) model can be combined with real-time 

weather radar data and convective weather forecasts to generate graphical 

depictions of the regions that pilots will seek to avoid. These regions of high 

likelihood of pilot deviation can used to forecast which routes will be blocked and 

model the associated reduction in enroute sector capacity. 

To this point, a very limited amount of validation of the pilot weather avoidance 

region models and sector capacity models, as supported by NASA “foundational 

research” funding, has taken place. However, good agreement has been shown 

for many cases of level flight in en route airspace, but there are a number of 

situations where the models clearly are not adequate. 

Fig. 1 Weather – ATM Integration Architecture. Shows the translation 

from weather impact and pilot preferences to capacity impact (dark blue 

boxes), and then to ATM decision support. 

14
There are significant research questions, such as whether the architecture in 

Figure 1 is the best model, how to characterize the turbulence associated with 

storms, and pilot human factors questions such as the impact of information 

provided to the cockpit via data link on pilot decision making. Pilots flying for 

different airlines or with different equipment may make different decisions in the 

same weather situations. But of more concern, the same pilot may make different 

decisions when placed in two identical weather situations. 

Figure 2. Pilot Deviation Model. Typical results for pilot avoidance of storms 

as a function of the flight path coverage of high reflectivity storms and the aircraft 

altitude relative to the storm radar echo tops. The plot shows the probability that 

a plane will deviate around a storm as a function of the fractional VIP level 3 or 

high reflectivity coverage and the difference between the flight altitude and the 

highest radar echo tops within the box. 

Recommendation: Expand research on the translation of convective weather 

impacts into ATC impacts so that this information can be used to effectively 

support decision making. 

Research should be conducted to address the following elements: 

15
 a. Improve the models for convective weather impacts, e.g. route blockage 

and airspace capacity. 

 b. Determine if pilot thresholds for weather conditions that lead to 

deviations can be reduced, since unexpected deviations around storm regions in 

high density airspace can lead to prolonged, unnecessary route closures 

 c. Determine if the data link transfer of ground derived weather and ATC 

domain information (spatial boundaries acceptable for maneuvering) to the pilot 

achieve a more consistent pilot response to convective weather 

 d. Determine if the airspace usage differs between various en route 

facilities [e.g., the Jacksonville Center (ZJX) appears to have very different 

procedures for convective weather ATM than many of the ARTCCs in the 

northeast]. 

 e. Develop models for storm impacts on arrival and departure flows in both 

en route and terminal airspace. 

C. Improved weather input into Collaborative Traffic Flow 

Management 

 

Collaborative Decision Making is a Government - Industry Partnership, which has 

been advocated by the White House Commission on Aviation Safety and 

Security. It has been successful in making procedural and cultural changes in 

Traffic Flow Management during disruptive congestion and weather events in the 

NAS. 

Finding: The collaborative use of the Airspace Flow Programs (AFP) and other 

Traffic Management Initiatives (TMI) in response to thunderstorm related 

airspace constraints, requires a strategic convective weather forecast that 

provides a translation of those constraints into flow impacts. 

The AFP has improved the FAA’s response to weather impacts but is limited by 

the existing aviation weather forecasts for decisions on the timing, scope and 

duration of AFP traffic metering and other TMI’s. The need for more consistent 

and accurate forecast information remains. Even with better forecasts, this 

information would be far more useful if automatically translated into flow or 

capacity impacts. 

When traffic flow managers have high-quality integrated weather information they 

can execute very effective tactical adjustments to airspace and traffic. However, 

effective strategic planning requires traffic management decisions to be made 

under high levels of uncertainty. The approach needs to be adaptive and control 

actions need to be limited and distributed across the multiple facilities and 

16
operators. More consistent interpretation and control actions can be expected if 

weather impacts are automatically provided. 

Recommendation: Develop a six-eight-ten hour convective forecast for strategic 

flow management decisions with automatically generated and updated forecasts 

of flow impacts. 

This should be a joint program between the AWRP and the TFM R & D programs 

with involvement by representatives of the CDM Weather Team. 

Finding: Probabilistic TFM research ongoing at NASA and MITRE could be 

leveraged during weather impacts to shift route/trajectory responsibilities back to 

the operator community and free traffic managers to focus on their core 

business: managing capacity and throughput within their airspace. 

Finding; Traffic managers today are often too preoccupied rerouting aircraft to 

focus on fine tuning their airspace and maximizing throughput in spite of 

convective weather and other weather impacts. 

Recommendation: Improve the Traffic Management interaction with AOC/FOC’s 

during weather impacts. 

Develop collaborative TFM systems that allow operators to better manage risks 

in meeting their own business objectives. Specifically, collaborative TFM systems 

should be developed that give operators the following capabilities: 

• Enable visibility into probabilistic TFM weather mitigation strategies 

through robust TFM data feeds for integration into their own internal 

systems via CDMnet and eventually System Wide Information 

Management (SWIM). 

• Electronically pre-negotiate multiple trajectory options with Traffic 

Managers. 

• Select viable route/altitude/delay options during severe weather impacts. 

• Integrate and ingest ATC-approved trajectories onto the flight deck for 

execution consistent with their own corporate infrastructure, business 

objectives and regulatory requirements. 

• Expand collaboration to include flight deck capabilities and decision 

making tools consistent with NextGen and within the corporate 

infrastructure, business objectives and regulatory requirements of the 

operator. 

17
D. Weather Information and Pilot Decision Making 

This section addresses the use of weather information, including data linked 

weather, on pilot decision making. This is a very important aspect of integrating 

weather and air traffic management decision support tools. 

Finding: Pilots’ response to weather situations can be inconsistent. Pilots flying 

for different airlines or with different equipment may make different decisions in 

the same weather situations. But of more concern, the same pilot may make 

different decisions when placed in two identical weather situations. 

Finding: FAA, AOC/FOCs, and flight crews often make decisions using different 

weather information. Today, automation in the FAA, AOC/FOCs, and the cockpit 

is seldom effectively linked. Furthermore, consistent weather information is not 

shared across these communities for joint decision making. An example is 

turbulence, which is validated via subjective pilot reports (PIREPs) or aircraftspecific automated turbulence observations, and as such may provide 

inconsistent information from different classes of aircraft or from different pilots.

Finding: Decision processes do not provide for the joint determination of 

appropriate weather mitigations. 

The pilot, dispatcher and air traffic control decision making process, one of the 

cornerstones of the CDM concept, does not automatically or easily take into 

account flight limitations and preferences, aircraft capabilities, operator routing 

preferences and delay tradeoffs, in conjunction with mitigating disruptive 

weather. 

Finding: Pilots may not understand the aviation system consequences if an 

aircraft significantly deviates from its current flight plan in congested airspace. 

For example, deviations into airspace being used by a stream of traffic going in a 

different direction can result in major routes being closed by ATC which in turn 

results in major delays for many flights. 

Recommendation: Initiate a research program to develop procedures and 

guidance on the integration of weather and airspace congestion information for 

preflight and in-flight decision making tools. 

The program should include the following objectives: 

Develop appropriate rule sets for weather avoidance decision making in both non 

congested and, highly congested airspace. 

18
Develop ways to incorporate the same rule set into preflight, cockpit, AOC/FOC, 

and ATM decision support tools. 

Develop methods to integrate and/or display current and forecast weather impact 

to flight profile, airspace congestion information, and weather decision support 

information in preflight and cockpit systems to enable greater shared situational 

awareness and improved collaborative decision making. 

Conduct research on the direct, machine to machine, information transfer among 

cockpit, FOC, and ATM computing systems and determine whether this will 

facilitate consistent and expeditious decision making. This will place the users 

more “over the loop” than “in the loop” with respect to weather decision making. 

 E. Integrating Weather Impacts with Airport Surface and 

Terminal Management Systems 

Decision support systems for the airport surface and terminal air space domains 

are not effectively integrated with weather information. With the exception of the 

Route Availability and Planning Tool (RAPT), weather information for terminal 

and surface operations is provided by a separate display or an overlay on ATC 

and ATM displays. 

Utilizing all available capacity at major airports during bad weather is very 

challenging and failing to do so results in schedule disruptions, passenger 

frustrations, and economic losses to airlines and affiliated business. 

To ensure each arrival and departure slot is used, extensive coordination and the 

utilization of multiple and separate weather sources is required. But manually 

estimating the impact of a departure or arrival decision, with in the face of 

dynamically changing weather in real time is impractical and results in unused 

capacity. 

Finding: Integrating Airport Surface and Terminal Area Weather and ATM Tools 

could improve system performance and capacity. 

Surface and terminal airspace operations could be improved if weather and traffic 

information were combined into a single system that computes the impact of the 

weather on potential traffic management decisions and provides the results in 

simple, easily understood display of decision options. 

The Route Availability and Planning Tool (RAPT) successfully integrates weather 

and ATM for departures, but has only been deployed in a single region and is not 

integrated with automated surface movement systems, or the FAA’s Departure 

Flow Management (DFM) initiative. In addition, the provisions of a similar 

19
capability in TMA has not been explored. 

Surface surveillance systems are gaining acceptance among NAS operators, but 

the deployment and use of systems such as ASDE-X lags behind industry

versions. Furthermore, operators report that air traffic decisions makers are often 

under-informed on actual surface and terminal conditions. 

Coordination with airline and other operations centers is critical to successful 

optimization of terminal operations. 

Current TAF forecasts are inadequate for efficient surface and terminal decisionmaking during anticipated and actual weather impacts. ITWS is an outstanding 

terminal and surface tool but is not integrated with other decision support tools. 

Recommendations: Expand the use of route availability tools to integrate airport 

and terminal area weather data and ATM Tools. 

Expand the deployment of integrated tools, such as route availability, to 

additional airports and terminal regions to improve NAS performance at the 

largest airports impacted by convective activity. 

Conduct research on enhancing the Traffic Management Advisor (TMA) to 

achieve a weather sensitive arrival planning tool. 

Integrate RAPT, ITWS, DFM and TMA with surface management systems to 

provide a singular terminal management tool spanning departures, arrivals and 

surface movement. Consider common use by air traffic and operators for 

collaborative decisions. 

Support CDM and other efforts to provide meaningful and integrated terminal and 

TRACON specific weather forecast information. 

 

20
Mid Term: IOC 2015 

F. Adaptive Integrated ATM procedures for Incremental Route 

Planning 

Uncertainty about weather, traffic and infrastructure constraints present major 

challenges to air traffic management. A new approach, to take better advantage 

of available airspace and airport capacity, is to manage traffic adaptively. This is 

motivated by the relationship, over time, between the effectiveness of alternative 

control actions for individual flights and the predictability (level of uncertainty) of 

events (both traffic and weather) that are causing the need for control. 

Ideally control decision points should be delayed as late as possible to allow the 

accuracy of the prediction to improve. However, delaying the decision may 

reduce the control options and their effectiveness. While this may be straight 

forward for one aircraft, it can become vastly more complex as multiple flights 

with varying decision points are considered. 

E

F

F

E

C

T

I

V

E

N

E

S

S

T I M E

THEORETICAL RELATIONSHIP

Figure 3. The relative relationship between the accuracy of predictions 

(weather, flight movement) and control effectiveness over time. 

21
An example of today’s approach to "flow level" traffic management is 

demonstrated in the figures below, captured from Flight Explorer. The current 

solution to a traffic overload of the southeast arrival corner post at Chicago 

O’Hare (ORD) is to reroute all ORD-bound flights which originate in the Miami 

(ZMA) and Jacksonville (ZJX) ARTCCs westward via St. Louis (STL) to the 

southwest arrival corner post. The associated reroute advisory is disseminated 

well before most of the affected flights are dispatched, without taking into 

consideration any circumstances that may have, in the meantime, affected the 

ability of an individual flight to fly the new route. 

A “flight level” traffic management solution would delay this type of rerouting 

decision until it was time to dispatch the affected flight, and it would do so while 

taking into consideration whether that flight has already been delayed because of 

involvement in some other TMI due to, for example, an enroute weather 

constraint or a technical (communications outage) constraint. Instead of 

negatively impacting such a flight with two TMIs, that flight could be given priority 

to be one of the flights using the southeast ORD corner post, allowing it to fly on 

the normal route, and reducing its flying time by about 10%. In this manner, by 

delaying decisions until they need to be made, and by making them at a flightspecific level, adaptive traffic flow management can make decisions that are 

better informed. 

 

Figure 4. ORD OXI-ROYKO Playbook Route. Moving flights to the 

Southwest ORD arrival fix. 

22
 

Figure 5. The normal preferential (required) route for flights from south 

Florida to ORD. 

Another situation arises when weather is forecast to block a section of a planned 

route resulting in a “no routes available” response from the air traffic control 

authorities. An alternative is to offer the operator the option of departing with a 

partial flight plan, and enough fuel to accept some level of deviation, based on 

the presumption that the weather will be better known as the aircraft proceeds 

towards its’ destination, and can select the mid and final routes as their 

availability becomes more certain. This incremental route planning and filing 

approach is not unlike what was in common practice in the past, and requires 

more agility by the operator and air traffic control facilities, but will reduce the 

impact of weather on capacity. 

Finding: The use of adaptive ATM decision-making offers opportunities to reduce 

delays. 

Uncertainty is a critical characteristic of weather and traffic forecasts. 

Furthermore, the level of uncertainty changes over time. For example, while 

there may be a great deal of uncertainty about whether thunderstorms will delay 

the departure of a particular flight out of EWR 3 hours before its scheduled 

departure time, that uncertainty is likely to be significantly reduced at 20 minutes 

before its scheduled departure time. We therefore need to refine existing TFM 

procedures, as well as develop new TFM procedures, that are flexible, making it 

possible to adapt plans as uncertainty is reduced. 

23
Some of following findings and recommendations reinforce several cross-cutting 

recommendations elsewhere in this document. In particular, in order to develop 

an effective adaptive TFM system, it is critical to pursue those general findings 

regarding the representation of uncertainty in weather and traffic forecasts and 

concerned with translating such information into meaningful decision parameters. 

Finding: The inequitable approaches to the allocation of scarce NAS resources is 

a major impediment to Adaptive TFM and other Traffic Management Initiatives. 

While NAS resources are far from a completely equitable allocation on fair 

weather days, weather impacts create major dislocations of NAS resources and 

tend to highlight equity issues among the diverse NAS operators. 

Ideally, the equity issues should be addressed in the automation and not distract 

the traffic manager or operators from working together to address the weather 

impacts themselves. 

Recommendation: Develop Weather Impact Forecasts versus Time. 

Develop weather forecasting capabilities that incorporate representations of the 

uncertainties associated with different weather phenomenon for different 

planning horizons. This should be included in the research recommended in 

Section 6 B, translating weather into ATM impacts.

Recommendation: Develop Adaptive ATM/TFM Procedures. 

Develop TFM procedures that are adaptive, and that take advantage of changes 

in uncertainty over time. These procedures should incorporate distributed work 

strategies that match the locus of control for a specific decision with the person 

or group that has access to the knowledge, data, motivation and tools necessary 

to effectively make that decision. Such adaptive procedures require an 

integrated approach to strategic planning and tactical adaptation. 

Recommendation: Manage at the Flight Level. 

Take advantage of trajectory-based management so that control actions and 

their impacts can be more directly and precisely localized at the points in the 

system where they are required to deal with a given scenario. In particular, this 

means that tools and procedures need to be developed to adaptively manage at 

the flight level instead of traffic flows, and that the air traffic management user 

does not need detailed meteorology experience. 

Recommendation: Translate weather information and forecasts to parameters 

relevant to decision support tools. 

24
Develop decision support tools that translate the implications of probabilistic 

weather forecasts into the decision parameters that are relevant to the 

application of particular TFM procedures and in a way that the air traffic 

management user does not require significant meteorological training. 

Recommendation: Develop human-centered designs. 

Develop human-centered designs for these decision support tools that enable 

their users to understand the current state of the relevant parts of the NAS, and 

that support these users in understanding the basis and implications of 

recommendations generated by their decision support tools that automatically 

generate options for users to consider. 

Recommendation: Develop tools and automation enabling operations and 

implementation. 

Develop computer-supported communication tools and automated decision 

support tools that enable effective coordination and collaboration in this 

distributed work system, and that enable timely implementation of the decisions 

that are made. 

 G. Weather Impacts and Tactical Trajectory Management 

Finding: There are few examples of seamless integration of weather information 

into ATM DSS Automation. 

The objective of ATM/Weather Integration is a seamless and transparent system 

that accounts for weather effects in all of the ATM algorithms. This objective is far 

from satisfied. 

A good example of the seamless integration of weather information involves the 

forecast grid winds which are embedded in a variety of operator and ATC 

automation systems and which are a key component of the aircraft trajectory 

computation algorithms of these systems. The trajectories are used by pilots, 

aircraft dispatchers and controllers, and by algorithms such as conflict detection, 

without the users explicitly being necessarily aware of the exact wind component 

forecast that was included in the calculation. However, other useful weather 

information such as the probability of a thunderstorm hazard, turbulence or icing 

is not directly incorporated into automation tools

Recommendation: Implement Tactical Trajectory Management with integrated 

weather information. 

25
Develop a highly automated advanced Tactical Trajectory Management (TTM) 

decision support capability integrated with convective weather and turbulence to 

decrease controller and pilot workload, and increase safety. This would be a 

mostly automated system. This capability would assist the controller in a shared 

severe weather separation responsibility with the pilot. 

Recommendation: Investigate the human factors issues (communication, 

information display, safety nets, cognitive complexity, and mental workload) 

associated with new paradigms for tactical trajectory management. 

 H. Airspace Designs for Weather Impacts

 The current NAS Airspace and infrastructure were designed to maximize 

throughput under ideal conditions. Weather considerations have yet to be fully 

incorporated into current airspace design and ATM control systems. As a result, 

the NAS airspace is mostly structured around rigid, stratified, and directional 

routes. The ATC automation that supports tracking and flight data processing 

operates as a carbon copy of the airspace, was designed to operate under 

perfect conditions, and has its own set of rigid processing logic developed in the 

early 1970’s. Both the airspace and supporting automation systems are 

inherently inefficient during a weather event. The ERAM effort, while essential to 

future progress, will begin with a replication of the existing NAS structure and 

automation. 

 

Finding: Existing Airspace Design profoundly influences and contributes to 

weather related delays. 

The development of airspace designs, such as the dynamic reconfiguration of 

airspace, must allow flexible and efficient routing during adverse weather 

conditions, and not just when conditions are nominal. 

Airspace design tends to bind the ATM solution space. Rigid airspace, 

procedures, and antiquated infrastructures contribute to system inefficiencies 

during weather events. The resultant delay is proportional to traffic density and 

the complexity of an impacted area. 

Service providers and users have an array of decision support capabilities that 

support flight planning and execution decisions; however, these sophisticated 

tools are of marginal value in weather situations because weather information is 

not sufficiently integrated and utilized at the service delivery points. Further, 

these decision support capabilities are not developed in a congruent approach 

with airspace design. 

26
This lack of integration forces ATM decision-making and solutions in the face of 

weather to be overly conservative and does not scale to predicted traffic volumes 

in the future. 

The impact of adverse weather on the airspace system is inherently non-linear. 

As a result, if localized decisions are made without consideration of the impact on 

the local or national airspace system, local inefficiencies can be greatly magnified 

at the system level. Conversely there are artificial limitations on the ability of 

operators and local facilities to allow regional approaches to help achieve system 

benefits. The working group was quite alarmed about this finding, because 

without an integrated approach early on, it could preclude the use of weather as 

a more advanced system develops, just when the criticality of weather integration 

is known to be vital to capacity enhancements of NextGen. The lack of weather 

integration will severely hamper effective decision-making using increased levels 

of automation required by larger traffic volumes. 

 

It is critical that weather information and functionalities be incorporated in the 

development of airspace structural design and decision support systems in the 

initial stages of development. Addressing these goals as an afterthought has 

been historically ineffective. These capabilities must be considered in the design 

of the airspace itself. NexGen air traffic control systems and airspace must be 

designed from the beginning with capabilities that support Traffic Flow 

Management in making flexible and efficient responses to common weather 

impacts. 

Recommendation: Airspace designs should enable route flexibility during 

adverse weather conditions. 

If the vision of 4D trajectories is to become a reality, the airspace must be 

designed to support seamless adjustments of the route of flight in all four 

dimensions, as required by weather impacts. 

The development of ATM decision support tools must be done jointly with the 

weather research community so that decisions will adequately address impacts 

of adverse weather. Foundational efforts that reach across the disciplines of 

airspace design, weather translation into ATM impact and ATM decision support 

are required to achieve effective integration. 

Recommendation: Investigate the human factors issues associated with the 

dynamic reconfiguration of airspace, including issues associated with information 

display, training and cognitive complexity. 

27
FAR TERM: IOC Post 20159

I. Advanced Weather ATM Integration Concepts 

 The NAS can be considered a network of airports, waypoints and fixes. This 

network can be disrupted due to weather constraints such as convective activity, 

resulting in a loss of capacity in an airspace region. Thunderstorms contributes 

the most to delays in the NAS so a method needs to be created to estimate the 

loss of capacity in an airspace region using both deterministic and probabilistic 

weather forecasts for short and longer range planning. 

Finding: Modern, risk management methods are being applied to address 

uncertainty and guide the integration of weather and ATM tools.10

 Recent NASA sponsored research11 which employed a Maxflow / Mincut theory 

used for network flow problems, showed that the maximum amount of flow is 

equal to the capacity of a minimum cut, e.g., the bottleneck of a system defines 

the maximum flow. Applying this to ATM, the number and widths of flight lanes 

can be computed in the presence of weather constrained regions using this 

theory. The capacity of those regions can be estimated by adding assumptions 

of aircraft navigational performance and the permeability of convective regions 

using a convective weather translation model. Navigational performance will 

determine the number of available flight lanes with narrower flight lanes being 

reserved for aircraft with higher navigational performance. 

The Maxflow/Mincut theory can be applied using either deterministic or 

probabilistic weather information. Deterministic information is most appropriate 

for short look-ahead times and probabilistic for longer look-ahead times beyond 

about one hour. Probabilistic forecasts for look-ahead times beyond two hours 

may require the use of scenario-based probabilistic forecasts which are being

developed. An enhancement to this work can include changing altitude to 

traverse weather constrained regions allowing the development of flight tubes 

instead of 2D flight lanes and including crossing-flows in the determination of 

capacity. 

Recommendation: Develop methods which combine the use of both probabilistic 

and deterministic forecasts, and observations, to maximize throughput using 

multiple dynamic flight lanes or “tubes” in weather impacted areas. 

 

9

 The Study Group felt that a far term defined as post 2015 was preferred. 

10 Initial versions of some of these capabilities can be implemented by 2015 11 METRON analysis presented at WAIWG meeting 

28
Recommendation: Develop methods to transition from a probabilistic trajectory or 

flight envelope to a 4D trajectory which is useable for separation and safety 

assurance. 

Recommendation: Establish an independent bi-annual review of this work to 

determine the potential benefits and costs to aviation. 

Finding: Current weather sensing often relies on surrogate measure of hazard 

versus actual hazard detection. This sometimes causes an overly conservative 

approach to weather avoidance and results in the quarantine of much more 

airspace than necessary. At other times, it may cause the routing of an aircraft 

through a real hazard not adequately represented by the surrogate measure. 

Recommendation: Conduct research into replacement of surrogate weather 

indicators such as radar reflectivity with reflectivity with actual indicators such as 

turbulence, icing, lightning, or wind shear, and an estimate of ATM impact. For 

example, radar reflectivity can be translated to ATM impact by estimated 

airspace pilots will avoid and the associated airspace capacity loss. 

Finding: Gridded and scenario based weather forecasts each have potential for 

integration with ATM decision making tools and processes. 

There are probabilistic weather forecast products available today for convection 

and stratus which estimate the probability of a specific outcome at a specific 

location that are often referred to as gridded probability forecasts. ATM decision 

algorithms that use these products typically threshold the probability values to 

use them deterministically for decision making. Other types of probabilistic data, 

such as scenario based probability forecasts, and more sophisticated uses of 

probabilistic data are being developed. Scenario based forecasts shows several 

potential weather outcomes and associated uncertainty for each outcome. More 

sophisticated decisions can then be based on the likelihood that each outcome 

will actually occur. 

Recommendation: Develop methods to use gridded and scenario based 

probabilistic weather data for ATM decision making. 

Develop methods to translate deterministic and probabilistic convective forecasts 

to ATM impact for use in network based capacity estimate models. 

Determine the reduction in capacity of an airspace region due to convective 

weather using a network model. 

Recommendation: Investigate the human factors issues associated with the 

integration of such probabilistic modeling into decision-support tools. 

29
7. Human Factors Considerations for Integrated Tools 

Human factors issues are a pervasive consideration in developing a more 

integrated approach to dealing with the impacts of weather on ATM. As 

technologies are developed to provide access to probabilistic weather 

information, and to help translate it into critical decision parameters, a key 

challenge is the need to understand the strengths and weaknesses of these 

technologies, and to develop a resilient, cost-effective design that integrates 

human expertise with such advanced technological support. 

Finding: Need to balance human and technology roles. 

The complexities associated with representing uncertainty in the weather and 

reasoning about its implications on ATM decision making indicate a need for 

decision support tools that help the human user process such information. 

However, these very same complexities mean that such technologies must be 

assumed to be brittle, as it will be very difficult for designers to anticipate all of 

the scenarios that could arise and to encode effective responses. Thus, it is 

necessary to balance the strengths and weaknesses of the operators who are 

dealing with situations in real time, with the strengths and weaknesses of the 

technology developers, who must try to anticipate all of the situations that could 

develop, and support effective responses through their technologies. (To err is 

human, and both system operators and system designers are human.) 

Recommendation: Develop advanced information sharing and display concepts 

for the design of integrated decision-support tools. 

Develop strategies for information representation and display that enable people 

to maintain situation awareness regarding weather and traffic impacts, develop 

shared mental models, and evaluate inputs to the decision process provided by 

technology. 

Of particular importance is the need to conduct research on strategies for 

representing, integrating and displaying probabilistic information about 

uncertainty regarding weather and traffic constraints and its predicted impacts as 

a function of look-ahead time. Equally important is the need to research new 

strategies for risk management that make use of such information. Research on 

the effective use of probabilistic information by ATC, TFM and FOCs is a major 

challenge that needs to commence in the near term in order to obtain short term 

benefits and to enable more powerful solutions in the longer term. This research 

needs to consider human factors as well as technology development challenges. 

Recommendation: Develop new approaches and strategies for effective 

distributed decision making and cooperative problem solving. 

30
Develop effective strategies and technologies (decision support and 

communication tools) to enable distributed decision making to address the 

interaction of weather and traffic constraints, and to adaptively respond to 

situations as they evolve. This requires consideration of cognitive complexity, 

workload, and the ability of people to develop and maintain necessary levels of 

skill and expertise. It requires consideration of the need to design a resilient 

system that provides effective safety nets. And it requires system engineering 

decisions concerning when to design the system to provide coordination as a 

result of the completion of independent subtasks and when to design the system 

to support collaboration in order to ensure that important interactions occur. 

Develop technologies that support cooperative problem solving environments 

that allow people to work interactively with decision support technologies and 

with each other to assess situations as they develop, and to interactively 

generate and evaluate potential solutions. 

Recommendation: Develop methods for implementing human-centered designs 

for decision-support tools. 

Develop effective procedures and technologies to ensure effective 

communication and coordination in the implementation and adaptation of plans in 

this widely distributed work system that includes meteorologists, traffic 

managers, controllers, dispatchers, ramp controllers and pilots. 

31
8. Implications on Air Navigation Service Providers

A. Training on New Integrated Tools 

Finding: New integrated tools will bring changes to all aviation segments. 

As weather information is integrated into the decision tools used by TFM’s, 

FOC’s, ATC facilities, and flight decks, the procedures, responsibilities, and 

supporting technologies for each group will change. It is vital that each group, at 

every level, have a clear understanding of their new capabilities and 

responsibilities, and their relationships with other groups and stake holders to 

enable a shared common situational awareness. 

Recommendation. Proactively enable new training on integrated tools. 

 

The FAA and aviation industry should proactively develop training curricula for 

controllers, traffic managers, pilots, dispatchers, and weather personnel which 

cover 

• The new roles and responsibilities in the use of supporting technologies 

• The roles, responsibilities and expectations of other decision makers with 

whom each group must interface 

• The training doctrine, developed in concert with the integrated tools 

development, leveraging that real-world experience to maximize early 

benefits and refinements. 

• The training cadre, deployed to all major new facilities as the tools are 

deployed to both assist in training and to maximize early benefits and 

identify problems. 

The resulting procedures and rules must be translated into controlling documents 

such as the Federal Air Regulations (FARs), the Airman Information Manual 

(AIM), Air Traffic Manuals, Flight Manuals, and Aircraft Manuals. 

B. Best Practices in Weather Mitigation 

Finding: Some FAA facilities have very effective ATM methods during weather 

impacts while others do not. 

Operators maintain that there are significant differences in the performance of air 

traffic facilities during severe weather events. Although differences in geography, 

special use airspace, and regional weather do exist, some facilities are 

consistently recognized for their innovative and proactive responses to weather 

events. The successful facilities approach bad weather events through flexible 

32
airspace and route utilization coupled with pragmatic flow management 

techniques. These informal “best practices” provide significant gains in efficiency 

and delay reductions. 

Other facilities are less successful. They are limited to practices which include 

an insistence upon pre established practices, the refusal to cross flows, an 

inability to mix operations, and the inability to dynamically modify airspace when 

there are clear benefits. Also, the inherent risks of convection result in 

tendencies to avoid engagement, citing workload, airspace rigidity, and 

procedural reasons. 

An examination of, the performance of the more successful facilities reveals an 

integrated approach to weather impacts, where the careful selection and 

application of initiatives appropriate to the developing conditions minimizes 

disruptions. 

 

Recommendation: Identify best weather practices of air traffic facilities and train 

these practices system wide. 

Identify facilities with superior performance and develop best practices guidance 

for use by other facilities. Do not limit benchmarking to NAS facilities only. Seek 

global examples and new visions of innovative weather management techniques. 

Develop and train ARTCC and TRACON ATC and TFM staff on “best practices” 

during the introduction and first five years of all new weather and weather-ATM 

integrated tools 

Establish metrics which compare alternative processes. 

33
9. Implications on Airline and Flight Operations Centers 

Finding: The integration of weather into ATM operations, consistent with 

NextGen Concept of Operations and the Operational Evolution Partnership 

(OEP), offers all classes of network operators in the NAS a significant opportunity 

to improve their operational performance. 

NextGen is expected to provide Network operators, including large airlines and 

charter operators, greatly expanded opportunities to optimize the operation of 

their fleets at the system level. These opportunities will include not only greater 

route freedom and metering options for individual flights, but also, with better 

forecasts of weather impacts, a greater ability to reduce system risks across 

groups of interdependent flights, subject to multiple TMI’s. 

This enhanced visibility into the risks associated with weather impacts implies a 

greater responsibility for the consideration of multiple trajectory options, and the 

supporting technology and infrastructure to communicate with the service 

provider, in advance trajectory negotiations, rather than today’s singular 

expression of intent (e.g., the filed ATC Flight plan). 

While the service provider can enable shared situational awareness through the 

development of open systems, large network operators are in the best position to 

integrate weather and ATM information into their internal systems and to use that 

information to develop system strategies and tactics on tradeoff of multiple 

trajectory options and TMI’s during periods of uncertain weather impacts. These 

tactics and strategies will likely include the manipulation of flights in all four 

dimensions. 

 

Recommendation: Ensure strong industry participation in CDM and NextGen 

concept development and implementation and consider expanding industry 

participation on review boards. 

 

Industry must have voice and buy-in to future developments to ensure that 

internal corporate infrastructure and business systems can support, blend with 

and interact effectively with the NAS service provider systems. 

Joint development of these systems is possibly the key component of a 

successful future capability 

34
10. Implications for FAA and NextGen Enterprise Architectures 

Finding: The integration of weather into ATM operations, including directly into 

advanced automation tools, is a fundamental component of NextGen and must 

be a focus of the Concept of Operations, the Operational Evolution Partnership 

(OEP) and NAS Enterprise Architecture (EA) development. 

The NextGen Concept of Operations establishes the mitigation of weather as a 

major focus for enhancing capacity and improving safety. The concept specifies 

the need for direct integration of “common” weather information into air 

transportation decisions making, with emphasis on direct integration of weather 

into advanced decision support tools. Other NextGen products (e.g. R&D Plan, 

Integrated Work Plan, and EA) further define these concepts and specify multiagency actions to develop and implement the needed capabilities. 

The OEP is the FAA’s response to transitioning the NAS to NextGen, and 

weather impact mitigation is a key focus area and defined by the “Reduce 

Weather Impact” solution set. The OEP is an evolving operational view, and a 

companion technical view (systems, algorithms, performance requirements, 

evolution strategy, concepts of use, etc) is needed to be embodied in the NAS 

Enterprise Architecture. Both the operational and technical views are necessary 

to driving investment decisions within the FAA, and to enabling continuing 

dialogue with the NextGen stakeholders on plans and progress related to ATMweather integration. 

Recommendation: Ensure that direct ATM automation-weather integration is a 

key focus of the development of OEP/NAS EA operational and technical views 

for NAS transition to NextGen. 

To achieve the capacity and safety goals for NextGen, weather and ATM 

automation developments must become aligned and focused to define the 

operational and system views for the evolution to highly automated weather 

impact analysis and solution-generation system, where the human operators are 

no longer the “glue” for trajectory level decisions. This is a necessary and 

fundamental shift from today where weather display and human interpretation is 

the norm. The resultant operational and technical views must be reflected in the 

OEP and companion NAS EA in order to enable timely investment decision on 

deploying these needed integrated automation-weather capabilities. This 

information must also be (constantly) coordinated with NextGen concept and EA 

development to ensure consistency. 

35
11. Implications for FAA Aviation Weather Research Program 

Finding: The Aviation Weather Research Program continues to be very important 

to efforts to improve the capacity and safety of the National Airspace System, but 

support has declined. 

The FAA Aviation Weather Research Program (AWRP), in collaboration with the 

NOAA National Weather Service, has been very successful in sponsoring and 

implementing weather research capabilities focused on the real world needs of 

aviation. 

While the progress in forecasting, especially in the tactical, 0-2 hour period, has 

been significant, aviation continues to need increased accuracy for longer time 

periods, in convection, turbulence, icing and ceiling/visibility products. 

The current effort to develop a single convective forecast tool, that incorporates 

the best techniques from the several existing products, for the 0-8 hour forecast 

period, is an important effort and will help efforts to integrate weather with air 

traffic management on a national level. 

Support for the AWRP has declined in recent years, causing the reduction or 

cancellation of programs and an overall concern about its’ future by the various 

research organizations affiliated with this area. 

The major reduction in the National Ceiling and Visibility Program has caused an 

important flight advisory product, designed to help helicopter emergency medical 

evaluation flights, to be initiated with no forecasting component. Other programs 

such as Oceanic Weather have been eliminated. 

Recommendations: Support for the AWRP should be increased beyond previous 

levels. 

Support for the AWRP should be increased to enable further improvements in the 

0-8 hour forecast time frame, and to allow the weather research community to 

enter into joint collaborations with the automation research community in 

integration of weather information into ATM DSS. Additionally, the FAA ATO-P 

organization should reexamine the R&D goals for AWRP in light of the needs of 

NextGen. 

Support for the National Ceiling and Visibility Program should be restored. 

Related efforts to support and benefit individual sectors of the industry should be 

prioritized and addressed. For example: 

 1. Development of the Helicopter Emergency Medical Evacuation 

System (HEMS) tool. 

36
 2. Rewriting FAR 121 limitations regarding Ceiling and Visibility such as 

FAR 121.619 (also know as the “1, 2, 3 Rule” for alternate fuel specifications 

Finding: Common metrics for the most significant aviation en route weather 

hazards should be expeditiously adopted by all systems measuring, reporting 

and/or forecasting the hazard. The following are listed in priority order: 

1. Turbulence (convection induced) 

2. Turbulence (clear air and mountain wave) 

3. Lightning 

4. Icing and Hail 

Recommendation: Conduct research to develop improved methods of sensing 

turbulence taking advantage of a multi-sensor approach using radar, profilers, 

anemometers, satellite imagery, GPS, and instrumented aircraft to 

improve the forecasting and now casting of convective and non-convective 

turbulence. 

37
12. Summary 

This study examined the proposition of integrating weather and air traffic 

management to determine potential benefits and where appropriate recommend 

FAA research and development activities. 

In this report, integration is defined as translating traditional weather information 

into weather impact measures, such as capacity or flow rates, and automatically 

or semi-automatically incorporating that data into both individual aircraft and 

traffic flow advisory information to improve the system capacity and safety in the 

face of weather hazards. 

Aviation weather has much more forecast accuracy in 0-2 hour, tactical time 

frame, than the 2-10 hour, strategic time frame. However, the size and shape of 

the 0-2 hour solution space is much smaller than 2-10 hour space, and with 

increasing congestion, more decisions will have to be made in the latter. 

Conversely the more the tactical solution space can be expanded, the more 

decisions can be delayed adaptively and traffic optimized to meet business 

objectives. 

It was found that opportunities exist to reduce the current weather related delay 

for both tactical 0-2 hours and strategic 2-10 hour planning horizons. 

The study also found that a risk management approach with adaptive decision 

making and incremental route planning, presents a major opportunity to reduce 

weather related delay. 

An integrated, cross disciplinary research program involving both aviation 

weather and air traffic management researchers will be needed for research on 

these initiatives to be successful. 

Finally, this research will take place and succeed only with the enthusiastic 

support of senior leadership. 

38
13. Acknowledgements 

The study group is very grateful for the support provided many individuals and 

organizations that served on the study and hosted meetings. 

The FAA ATO and AVS offices 

The National Weather Service 

Northwest, American, and Delta Airlines 

NASA Ames Research Center 

The Dallas-Fort Worth and New York ATC Facilities 

NCAR, Lincoln Laboratory and Mitre, who also provided a document web site. 

Ohio State University 

National Business Aircraft Association 

Aviation Weather Associates, Inc. 

Jerry Thompson Associates 

John Rekstad and Richard Heuwinkel, for being the designated FAA Federal 

Officials for the study. 

Gloria Dunderman for administrative support at all of the meetings 

Denise Davis for travel support 

We appreciate those who provided the briefings listed in Appendix A 

39
Appendix A. Study Description 

Working Group Membership 

NAME AFFILIATION WAIWG ROLE 

Bill Leber Northwest Airlines Chair 

Ray LaFrey Retired MIT - LL Co-Chair 

Richard Heuwinkel 

John Rekstad 

FAA 

FAA 

DFO 

Deputy DFO 

Roger Beatty American Airlines Member 

Steve Brown NBAA Member 

Bruce Carmichael NCAR Member 

Gloria Dunderman FAA Member 

Jim Evans MIT LL Member 

David Frame JTA Member 

Matt Fronzak Delta Air Lines Member 

Kevin Johnston NOAA/NWS Member 

John McCarthy Aviation Weather Associates, Inc. Member 

Philip Smith OSU Member 

Eugene Wilhelm MITRE CAASD Member 

Steve Green NASA Ames Member 

40
Study Schedule 

2006 2007

Plan 

Data Collection 

Analysis

Initial F&Rs

Final Report

REDAC 

Initial Briefing 

REDAC Briefings

MSP Wash DFW N90 Wash ATL Ames 

41
Literature List - Partial 

• ““Next Generation Air Transportation System – Integrated Plan”, Joint 

Planning & Development Office, December 2004 

• “Next Generation Air Transportation System, Weather Concept of 

Operations”, Version 1.0, May 13, 2006 

• “An Operational Systems Vision for Aviation Weather-in-the-Cockpit Data 

Link”, FAA AVS Office, 2006 

• “Weather in the Cockpit Concept of Operations” DRAFT 10/7/2006, Tenny 

Lindholm, NCAR 

• “FAA Flight Plan” 2007-2011, FAA 

• “Implications of a Successful Benefits Demonstrations for Integrated 

Weather/Air Traffic Management (WX/ATM) System Development and 

Testing”, Conference Paper J3.3, 12th Conference on Aviation, Range, 

and Aerospace Meteorology, AMS, Atlanta, GA, Jan 2006 , J. Evans, MIT 

Lincoln Laboratory, January 2006 

• “TRACON Weather Forecast Requirements Recommendations”, 

Collaborative Decision Making (CDM), Weather Evaluation Team (WET), 

Version 14, December 20, 2006 

• “Tactical Weather Decision Support to Complement ‘Strategic’ Traffic”, 

The Fourth 

International Air Traffic Management R&D Seminar ATM-2001 J. Evans, 

MIT Lincoln Laboratory 2001 

• “Recommended HEMS Current and Future FAA/NWS Aviation Weather 

Product Development”, Air Evac EMS, Inc., Association of Air Medical 

Services, January 21, 2007 

42
Briefings to Study Group 

Gene Wilhelm, et al Mitre CAASD TFM Weather Mitigation, 

 Probabilistic Weather, Cockpit 

 Weather 

Harry Swenson, et al NASA Ames. Technical briefings of weather 

integration efforts in technical 

elements of NASA’s Airspace 

and Airportal Projects 

Bruce Carmichael NCAR Weather ATM Integration Issues 

J. Wetherly, D. Sims FAA ATO Views on Wx-ATM Integration 

M. Sammatino FAA ATO Views on Tactical Wx mitigation 

M. Klopfenstein Metron Wx and TFM Strategies 

M. Ball U of Md Equity of NAS Delays 

S. Green NASA ARC Delay Banking 

M. Andrews JPDO WxIPT Process for Wx RE&D 

 Management 

T. Fahey Northwest Airlines Airline Weather Issues 

L. Sherrtz NOAA Weather Information Decision 

 Aide 

R. Beatty American Airlines Airline Weather Issues 

L. Pruzak, N90 N90 Operations, RAPT, 

 CIWS, ITWS 

R. Tamburro N90 TMO Tour N90 TFM 

C. Gallo 

R. Klarmann Continental Airlines EWR Hub Tower Operations in 

 Wx 

43
M. Weber,et al MIT Lincoln Lab. Integrated Systems 

 Decision Support, RAPT, 

 Rapid Prototyping, 

 CIWS Re-engineering 

Weather in the Cockpit Briefings 

T. Lindholm NCAR Weather In the Cockpit 

Capt. J. Burns United Airlines Electronic Flight Bag 

S. Young NASA Langley Integrated Intelligent Flight Deck 

Robert Ruiz FAA AVS Processes for Approval of WIC 

S. VanTrees FAA AVS AVS Vision for WIC 

Cathy Bigelow FAA AVS Air-Ground Certification 

Capt.T. McVenes ALPA ALPA Views 

Matt Fronzak Delta Airlines WIC Views 

S. Brown NBAA NBAA Views 

Eric Lugger Air Evac LifeTeam Helicopter Medical Flight Issues 

E. Dash Raytheon R&D for WIC 

44
Appendix B. Previous Integration Initiatives 

Five ATM/Weather Integration Workshops were held to encourage better use of 

aviation weather in air traffic management: 

Workshop #1 – May 2000 

Workshop #2 – July 2002 

Workshop #3 – January 2003 

Workshop #4 – June 2003 

Workshop #5 – October 2004 

The following recommendations were developed during the October 2004 

Workshop. Instances where NASA has responded to the recommendations are 

noted. 

ATM/Wx Integration Workshops 

“10 Key Research Recommendations”

• Define Convective Impact and Constrained Areas for Evaluating 

Convective Forecast Products and Developing Air Traffic DecisionSupport Tools 

– Provide observation field definitions to represent convective activity 

and its effects in support of TFM and Air Traffic Control (ATC) DS 

tools; forecast guidance products; and verification methodologies 

that provide operationally-relevant information 

Note: NASA is co-authoring an ATIO paper to verify 

Convective Weather Avoidance Model (aka Convective 

Storm Flight Deviation Model). 

• Integrate Departure Management System for Severe Convective Weather 

– Provide route availability guidance for individual flights based on 

the filed flight plans, explicitly identify pathfinders, and present the 

salient decision information for alternative routes when the filed 

path is blocked by severe convective weather 

• Develop Convective Storm Flight Deviation (CSFD) Model & Incorporating 

Algorithms into Multiple ATM Decision Support Capabilities 

– Develop an advanced model of CSFD that correlates (predicts) 

traffic flow deviations from convective forecast products, and 

integrate the model into research prototypes of DS tool capabilities 

45
Note: NASA is supporting research to develop CWAM2 and 

integrated CWAM into a research version of FACET for 

automated routing studies (not an overlay and in early 

stages of maturity). NASA is also investing efforts to use 

CWAM in ATM decision-making and improving this model 

using human factors information. 

• Develop Probabilistic Scenarios-Based Event Forecasting with TFM 

– Integrate the uncertainty in weather forecasts with strategic TFM 

planning 

Note: NASA is supporting research to develop these 

forecasts and to use these data in TFM decisions.

• Develop Fast-Time Simulation Tool Integrated with the Corridor Integrated 

Weather System (CIWS)/National Convective Weather Forecast (NCWF) 

Products 

– Study the impact of weather on air traffic using an integrated fast 

time simulation tool 

• Incorporate Convective Weather Forecast Products for Use by ATM DS 

Capabilities 

– Integrate and evaluate convective forecast products into DS 

capabilities for en route/departure/arrival operations (e.g., timebased metering and 4D trajectory negotiation) 

• Integrate TFM and Probabilistic Weather Forecasts 

– Continue and extend initial research efforts, concentrating on 

developing concepts for using probabilistic weather forecasts to 

predict the impact of weather on National Airspace System (NAS) 

capacity 

Note: NASA has proposed funding an external group to use 

these forecasts in TFM decisions.

• Develop En Route Weather Integration and Resolution Capabilities 

– Continue and extend current research efforts to provide sector 

controllers with integrated tools to support the pilot in the 

identification and avoidance of severe weather areas 

• Integrate CIWS into an En-route Analysis Platform 

– Develop an operational concept for using advanced weather 

forecast technology (e.g., CIWS) in conjunction with aircraft 

46
trajectories and traffic demand to identify and mitigate the impact of 

hazardous convective weather during high traffic demand periods 

• Develop a Fast-time Simulation Analysis of TFM/Collaborative Decision 

Making (CDM) Integrated with Probabilistic Convective Forecast 

– Fast-time simulation analysis of traffic scenarios to determine the 

sensitivity of flight/flow deviation decisions through convectivelyconstrained airspace using a probabilistic forecast of convective 

strength 

47
Appendix C. Glossary of Terms

AIRMET Airman's Meteorological Information 

ARSR Air Route Surveillance Radar 

ASOS Automated Surface Observing System 

ATOP Advanced Technology and Oceanic Procedures 

AVN Aviation Forecast 

CIP Current Icing Potential Product 

CCFP Collaborative Convective Forecast Product 

CIWS Corridor Integrated Weather System 

DOTS Dynamic Ocean Track System 

DSP Departure Spacing Program 

DSR Display System Replacement 

DUAT Direct User Access Terminal 

DUATS Direct User Access Terminal Service 

ERAM En Route Automation Modernization 

ETMS Enhanced Traffic Management System 

FIP Forecast Icing Potential 

GTG Graphical Turbulence Guidance 

pFAST Passive Final Approach Spacing Tool 

METAR Meteorological Aviation Report 

NCWF National Convective Weather Forecast 

NEXRAD Next generation weather Radar 

OASIS Operational and Supportability Implementation System 

RAPT Route Availability Planning Tool 

RUC Rapid Update Cycle 

RVR Runway Visual Range 

SIGMET Significant Meteorological Information 

STARS Standard Terminal Automation Replacement System 

TAF Terminal Area Forecast 

TFM-M Traffic Flow Management Modernization 

TMA Traffic Management Advisor 

URET User Request Evaluation Tool 

WSDM Weather Support to Decision Making 

48
Appendix D. Avoidable Delay Analysis 

A key issue considered by the committee was the extent to which today’s 

weather delays could be avoided if weather and air traffic management were 

more effectively integrated. 

Avoidable delay has been recently examined quantitatively using Resource 

Utilization, one of three proposed metrics currently under study by the FAA and 

airlines. Resource Utilization is defined by the S2K/RTCA Customer Metrics 

Working Group as “the safe and efficient use of available airport or airspace 

capacity.” 

The focus of the initial analysis was on convective events in view of the higher 

level of weather related delays in the summer and predictions by FAA analyses 

that convective delays could result in the loss of airline profits by 2014 unless the 

overall NAS capability to manage convective weather was improved. 

Measurement of capacity utilization and, the extent to which incomplete capacity 

utilization resulted in avoidable delays, is particularly difficult during convective 

weather since storms reduce capacity in both en route and terminal areas. In 

particular, en route capacity loss results in network congestion that must be 

addressed by a combination of aircraft altitude adjustments, route adjustments 

and metering delays on the ground and air. Determining the appropriate mix of 

trajectory adjustments and delays is a very difficult computational challenge. 

The avoidable delay for an actual weather delay case was determined by a three 

step process: 

1. The actual weather characteristics (e.g., ceiling/visibility, airport 

winds, and 3 D weather radar reflectivity) were translated into the 

capacity reductions in affected en route sectors, terminal airspace, 

and airports12, 

2. The time history of available terminal and en route capacity 

together with the traffic demand were input into an fully automatic 

broad-area ATM strategy generator13 to determine reroute 

strategies or, when necessary, minimally disruptive ground or 

airborne delay programs that could have been utilized to minimize 

overall NAS delay 

3. The actual delays and airspace utilization for that date were 

compared to the optimized capacity utilization and its associated 

delays to determine where and when capacity was not fully utilized, 

 

12 The method by which this was done will be discussed subsequently. 

13 Bertsimas, D. and S. Stock-Patterson, The Air Traffic Flow Management Problem with En Route 

Capacities, Operations Research, 46, 406-422, 1998 

49
and how much of the actual delay was “avoidable” where the 

avoidable delay = actual delay – delay for the optimized ATM 

strategy. 

Since the ATM strategy generator has knowledge of both the current and future 

weather in its strategy development, this is equivalent to assuming both perfect 

weather forecasts as well as optimal ATM responses (including perfect 

coordination between the various ATC facilities and, between the FAA and 

airlines). 

In practice there will be underutilized capacity due to inaccurate weather 

forecasts as well as non optimal use of the weather forecasts to develop ATM 

strategies, flawed coordination between various decision makers, 

communications and infrastructure limitations, and/or non optimal implementation 

of the strategies (e.g., from delays in modifying flight plans). 

Hence, one must carefully look at the circumstances associated with non optimal 

use of available capacity to understand whether the existence of usable capacity 

could have been reasonably anticipated by real time decision makers given the 

forecasts and other ATM decision support then available to the decision makers. 

Beyond the formation of ATM strategies one must also examine the infrastructure 

limitations to communicate and execute an ATM decision once made. 

Computations of “avoidable” delay together with analysis of circumstances 

associated with non optimal use of available capacity have been carried out 14 for 

several significant convective events from 2005. Table 1 shows the results of 

these computations. 

Comparison of the flight tracks determined with the optimized ATM strategy 

generation algorithm with the flight tracks for the same aircraft on the actual 

weather event (figures 1-3) showed that much of the avoidable delay arose from 

the inability of the decision makers during the real time operations to utilize 

capacity that had become available after weather impacts ended. Although the 

magnitude of the avoidable delay was quite high in two of the three cases, the 

fact that much of the current delay could have been avoided by relative short 

lead time ATM actions is quite encouraging for weather-ATM integration since 

the accuracy of short term (e.g., 0-2 hour) convective forecasts is much better 

than the accuracy longer lead time forecasts and, may be easier to improve in 

the near term. 

The post event analysis tool described above could also be used to quantitatively 

assess the performance improvement provided by integrated ATM-weather 

system under test. Since an integrated ATM-weather decision support system 

should help the decision maker better utilize available capacity, one could use as 

 

14 MIT Lincoln Laboratory 2007 study to be published in 2007 

50
a metric the degree to which capacity was fully utilized when needed before and 

after an integrated ATM-weather decision support system was deployed15. 

Table 1 Preliminary results of determining unavoidable delay for three severe 

weather events in 2005 and 2006. 16

 

15 An alternative metric – comparison of delays before and after an integrated ATM-weather decision 

support system was installed- is very difficult to use in practice since the “unavoidable” delay is an 

uncontrolled variable that depends on the exact time-space distribution of storms as well as the demand. 16 MIT Lincoln Laboratory Study; to be published in 2007 

51
Fig. 1 Example of comparing capacity utilization in real time with optimized use of 

available capacity by post event analysis tool for a severe weather event on 

7/27/2005. 

 The left hand large plots show flight trajectories (in white) overlaid on CIWS 

precipitation product; the right side large plots show flight trajectories (in white) 

overlaid on CIWS echo tops product. The small insert on the left hand side 

shows the fractional loss in sector capacity based on blockage of principal routes 

through the various sectors as determined from the CIWS reflectivity and echo 

tops products. The purple boxes show a region where there was a significant 

difference in airspace usage. 

52
Fig.2. Verification of the validity of the assumed airspace availability in the post 

event analysis. 

 The upper plots show flight trajectories (in white) overlaid on CIWS precipitation 

product; the two lower plots shows the fractional loss in sector capacity based on 

blockage of principal routes through the various sectors as determined from the 

CIWS reflectivity and echo tops products. The purple boxes show a region 

where there had been a significant difference in airspace usage at 1945Z. The 

weather in purple box region was more severe and the fractional capacity loss 

was greater at 2015Z than at 1945Z. The conclusion is that the ATC system was 

at least 30 minutes late in utilizing available capacity near J36/J95 after 1945Z. 

53
Fig. 3 Additional example of comparing capacity utilization in real time with 

optimized use of available capacity by post event analysis tool for a severe 

weather event on 7/27/2005. 

 The left hand large plots show flight trajectories (in white) overlaid on CIWS 

precipitation product; the right side large plots show flight trajectories (in white) 

overlaid on CIWS echo tops product. The small insert on the left hand side 

shows the fractional loss in sector capacity based on blockage of principal routes 

through the various sectors as determined from the CIWS reflectivity and echo 

tops products. The purple boxes show a region where there was a significant 

difference in airspace usage. 

54
Appendix E. Weather Impact Analysis 

A key element of an integrated ATM/weather decision support system (figure 1) 

is the translation of current weather data and weather forecasts into ATC 

impacts, i.e., airspace that pilots will seek to avoid and the associated airspace 

capacity impacts. 

Fig. 1 Relationship of the translation from weather impact to capacity 

impact (dark blue boxes) to the overall use of weather information for ATM 

decision support 

The principal focus for the committee study was on translation for convective 

weather given the high level of delays associated with convective weather and, 

the current state of knowledge on the relationship of convective weather 

characteristics to capacity impacts. In view of the importance of this topic for the 

practical utilization of integrated weather-ATM decision support tools and the lack 

of previous FAA funded research in this area, this section will include a relatively 

detailed summary of the status of knowledge to date before discussing the 

recommended research program. 

55
Current state of technology in translation from weather impacts to ATC impacts 

It is clear from figure 1 that determining the regions of airspace which pilots 

will/should avoid is a critical first step. The FAA Aeronautical Information Manual 

(AIM) suggests that pilots avoid thunderstorms characterized by “intense radar 

echo” in en route airspace by at least 20 nautical miles (40 km). 

However, an initial study (Rhoda, et. al., 1999) of pilot convective weather 

avoidance decision making at Dallas-Ft. Worth showed that many air carrier 

arrivals would penetrate high reflectivity cells when within 10 nm of the airport. A 

follow up study (Rhoda, et. al., 2002) of pilot behavior in both terminal and en 

route airspace near Memphis, TN confirmed that arrivals often penetrate high 

reflectivity storms when near the airport and, that pilots fly over high reflectivity 

cells in en route airspace and penetrate lower cells whose reflectivity is less than 

VIP level 3. 

NASA has funded some initial “foundational” research to develop a quantitative 

model that would predict when a pilot will deviate around convective weather in 

en route airspace as well as estimating the storm-aircraft separation associated 

with deviations. These models were determined from analysis of several 

hundred air carrier flight – convective storm encounters in the Midwest of the 

type shown in figure 2 

Fig. 2 Example of plane encounters with convective weather in the Indianapolis 

ARTCC (ZID). Blue trace is an aircraft that deviated; pink track is an aircraft that 

penetrated (or, over flew) the storm. Left hand side background is color coded 

CIWS echo tops (yellow is 30 Kft.); right hand side plot background is CIWS 

radar reflectivity (yellow is VIP level 3 equivalent). Blue crosses on right hand 

side plot are lightning strokes. The white box indicates the weather characteristic 

analysis box. 

56
The results from over 500 encounters of the type illustrated in figure 2 were put 

into a statistical classifier package to determine which combination of radar 

reflectivity, echo tops and lightning data best explained whether a plane would 

penetrate or, deviate around a storm. Typical results of the statistical 

classification are shown in figure 3. 

Figure 3 Typical results for statistical classification. The left hand plot shows the 

probability that a plane will deviate around a storm as a function of the fractional 

VIP level 3 or high reflectivity coverage of the weather analysis box shown in 

figure 3 and the difference between the flight altitude and the highest radar echo 

tops within the box. The right hand plots show a best fit delineation of the 

tradeoff between coverage by high reflectivity weather and flight altitude relative 

to echo tops. 

We see that aircraft whose altitude is less than the echo tops altitude will 

generally deviate at relatively low fractional coverage. However, aircraft whose 

flight altitude is at least 5 Kft. above the echo tops typically will not deviate 

around the storm region. 

The best fit models of pilot deviation as a function of the convective weather 

characteristics can be used to generate spatial fields of the likelihood of pilot 

deviation as a function of location as shown in figure 4. 

57
Figure 4 Translation of CIWS reflectivity and echo tops spatial fields into 

fields of regions where pilots are likely to deviate (middle plots) and fields 

of the probability of pilot deviation (right hand plots) as a function of the 

aircraft altitude. Note that the region of likely deviations is much smaller 

for aircraft at 39 Kft. than for aircraft at 31 Kft. The deviation spatial fields 

have been termed “weather avoidance fields” (WAF). Results from a 

conference paper by DeLaura (2007) 

The WAF can be validated by seeing if flights do in fact deviate around the high 

WAF regions that were computed from radar and lightning data alone. Figure 5 

shows an example of the data used to validate the deviation fields. 

58
Figure 5 Example of a weather avoidance field (WAF) validation test. Tracks of 

aircraft are overlaid on the WAF determined from weather radar and lightning 

data alone to see if aircraft are deviating around storms as predicted. The region 

with the orange oval contains a number of tracks that did not deviate around an 

area where the echo tops was well above the flight altitude. 

It is evident from figures 3 and 5 that there were flights that deviated around 

weather they could have over flown and aircraft that penetrated regions of storms 

at flight altitudes lower than the radar echo tops. In figure 5, we see that the 

unexpected storm penetrations occurred principally in one region as opposed to 

being randomly distributed over the regions of high values of deviation 

probability. 

A major objective of the future research in this area should be to reduce the 

spread in pilot thresholds for weather conditions that lead to deviations 

(especially the ones where a pilot seems very conservative) since unexpected 

deviations around storm regions in high density airspace can lead to prolonged, 

unnecessary route closures. 

59
There are two known sources of variability in pilot decisions to deviate around 

storm regions: 

1. We may not currently be considering the best set of weather predictors, 

and 

2. One pilot may be deviating for a smoother ride and then others will 

follow that pilot’s track. 

For the case shown in figure 5, meteorological analysis found that the region in 

the orange oval was a region of storm decay. It is well known meteorologically 

that decaying storms tend to have mainly weak downdrafts aloft with relatively 

low turbulence. Hence, research is currently underway to see if the inclusion of 

storm growth/decay information might improve the performance of the deviation 

prediction model. 

Another apparent anomaly in pilot decision making was noted in testing of the 

Route Availability Planning Tool (RAPT) in the summer of 2007 as shown in 

figure 6. 

Figure 6 Example of a significant difference in storm deviation behavior between 

arrivals (white tracks) and departures (blue tracks observed at New York on 20 

June 2007 at around 0000Z (8 pm local time). Arrivals penetrated regions of 

high reflectivity and storms tops over an extended time period during which 

departures would not penetrated the same storm. Differences in pilot behavior 

cannot be explained by aircraft altitude differences. 

60
There are various possible explanations for the differences in deviation behavior 

shown in figure 6. ATC personnel have suggested that an important factor may 

be the difference in the visual depiction of the storms between having the storms 

back lit by the sun (departures) versus the storm depiction with the sun behind 

the pilot (arrivals). 

Unexpected deviations around storms are a major concern for convective 

weather ATM in general and particularly for integrated ATM-weather decision 

support systems. If deviations around storm regions in congested airspace of the 

type shown in figure 6 result in the deviating aircraft interfering with other 

aircraft, ATC will often shut down the use of the route that was being used by the 

deviating aircraft. Reopening such route after weather impacts have ended can 

be very time consuming and result in a significant loss of usable capacity. 

A concern here is that a pilot deviating simply to get a somewhat smoother ride 

may not understand the implications of an unexpected deviation on route usage 

by other aircraft. Alternatively, a pilot may attempt to penetrate a severe storm 

without fully understanding the hazard in such a storm and then request 

significant deviations in an effort to avoid additional difficulties in flight 

management. 

Data link transfer of weather and ATC domain information to the pilot could be 

very useful in achieving a much more consistent pilot response to convective 

weather: 

(1) ground derived weather characteristics (e.g., storm growth or decay, 

likelihood of hail) that should be of concern to the pilot 

(2) a visual depiction of spatial boundaries that would be acceptable to ATC 

as a "normal" maneuvering region 

Since traffic flow management (TFM) decision support tools typically require as 

an input an estimate of future capacity, one must translate the WAF information 

into estimates of loss of en route and terminal capacity. 

(Song, et. al., 2007) state that “Sector capacity can be defined in terms of the 

number of aircraft which may enter a sector within the given time period, without 

causing excessive sector controller workload; that is, the maximum number of 

aircraft that can be safely handled by the controller. Controller workload reflects 

the overall level of demand for controller’s perceptual and cognitive resources.” 

The translation from WAF to sector capacity requires assumptions on use of the 

airspace including the relationship of the structural flows in the sector when 

convective weather occurs. Estimates of the sector capacity with convective 

weather have been made with two rather different models: 

61
(1) (Martin, et. al., 2007) estimate the effective sector capacity by determining 

the fraction of routes that are not blocked by convective weather 

(including consideration the fair weather demand on those routes). The 

basis for that assumption is that the complexity/workload for sectors is 

well understood only if the normal structural flow is maintained. If the flow 

spatial structure is quite different from the normal structure, controllers 

typically cannot not manage the normal number of aircraft in their sector 

due to lack of experience with the flow pattern. 

(2) (Mitchell, et. al., 2006) estimate the throughput of aircraft flying in a single 

direction (e.g., west to east) through a sector which contains convective 

weather assuming that the planes can fly along undulating parallel “tubes” 

through the weather. An implicit assumption is that aircraft separation is 

provided by a fully automatic algorithm and, no results are shown for the 

situation where there are crossing and/or merging routes within a sector. 

The sector throughput of the (Mitchell, et. al.) “tube” model for airspace usage is 

clearly much higher for a given spatial distribution of weather than the estimate 

based on blockage of the normal routes. However, since the assumptions 

(Mitchell, et. al) make regarding separation of aircraft from other aircraft do not 

seem applicable to today’s human based plane separation system, it is not 

possible to validate their estimates of capacity by comparison with today’s flight 

usage. 

Figure 7 shows a typical result for en route sector capacity during convective 

weather determined by the method discussed in (Martin, et. al., 2007). 

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Fig. 7. Fractional capacity loss for a number of the en route sectors in the 

northeast portion of the US on 16 July 2005. The capacity loss was estimated 

using the CIWS reflectivity and echo tops data for 1845Z together with the pilot 

weather avoidance and RAPT route blockage models. 

Some limited comparisons have been made between the actual uses of en route 

sectors during convective weather with the predicted use based the route 

blockage sector capacity model described above. An initial result is shown below 

in fig. 8 

63
Fig. 8 Comparison of aircraft counts over a 15 minute periods for a 

number of convective weather events in the sectors shown in figure 7 with 

the aircraft counts predicted from CIWS weather data alone as a function 

of the predicted fractional route blockage (RA). 

The mode of the distributions is zero (no error). However, for higher fractional 

blockages, the number of observed aircraft is often less than the predicted 

number of aircraft. This result is expected for the reason shown in figure 9. 

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Fig. 9. A major cause of differences between predicted number of aircraft in a 

sector during convective weather and the observed number of aircraft in the 

sector is the impact of convective weather in adjacent sectors. The top 3 plots 

show that on fair weather, the observed number of aircraft in the Cleveland en 

route sector 66 at a given time of day (2218 Z) was very consistent. The bottom 

figure shows the (fair weather traffic normalized) fractional route blockage for 

sector 66 and its surrounding sectors on 16 July 2005 when there was extensive 

route blockage by convective weather. We see that although there is essentially 

no route blockage in sector 66, many of the surrounding sectors have very 

significant route blockage. Hence, it is not surprising that the number of aircraft 

actually observed in sector 66 on 16 July was much less than would be expected 

by considering only the characteristics of the weather within sector 66. 

We see from figure 9 that experimental validation of sector capacity estimates in 

convective weather needs to consider the constraints on usage of a sector under 

examination by convective (and, non convective) weather elsewhere in the NAS. 

Hence, validation of the models for sector capacity in convective weather can 

necessitate a very detailed understanding of NAS dynamics. 

The above discussion has provided a short summary of the current state of 

knowledge in this very important area of translation of weather information into 

ATC impacts. We view the validation results shown above as fairly promising 

given the very low level of funded research in this area to date. However, there 

clearly are major research needs that we will now briefly discuss. 

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Recommended research on translation of convective weather impacts into ATC 

impacts 

The development and validation of models for pilot weather avoidance is clearly 

critical to both ATC impact determination and decision support tool development. 

As was noted above, there are a number of convective weather factors (e.g., 

storm growth / decay, how to best characterize the turbulence associated with 

storms, and visual cues) that need to be considered. Also, there are pilot human 

factors issues that also need consideration (e.g., whether the flight is delayed, 

alternatives to penetration of a storm, airframe differences, airline, etc) as well as 

the possible impact of information provided to the cockpit via data link on pilot 

decision making. 

To date, WAF modeling have only considered en route level flight. Clearly, there 

needs to be consideration of ascending and descending aircraft as well as 

terminal area pilot decision making including landing and takeoff operations. 

The models for airspace usage (including models for route blockage and, the 

importance of use of normal routes) are in a very preliminary state. Only en 

route sectors have been considered to date with the aircraft principally in level 

flight. Additional ARTCCs need to be studied to determine if the airspace usage 

is differs between various en route facilities [e.g., the Jacksonville Center (ZJX) 

appears to have very different procedures than many of the ARTCCs in the 

northeast]. 

 Also, it is necessary to study the management of arrival and departure flows in 

both en route and terminal airspace. It appears that terminal areas have a much 

higher propensity to routinely operate in convective weather with routing that is 

very different from the normal fair weather routes. Hence, determining the 

effective capacity for various different storm spatial distributions within a terminal 

area will be a significant undertaking. 

One of the important questions in the research is how accurate the translation 

modeling needs to be to support the successful utilization of integrated 

convective weather-ATM decision support tools (i.e., the right hand side of figure 

1). The required accuracy will clearly depend on the specific DST and its 

intended function. 

At this point, there are a very limited number of such tools in experimental 

operational use. It will be important for the FAA to take advantage of the ongoing 

operational testing of DSTs such as RAPT to get insights into the required 

accuracy for translation process so that the DST output quality is high enough to 

achieve operational user acceptance. 

66
It will also be important to start identifying the additional model accuracy 

requirements that may be generated through innovative longer lead time 

approaches to ATM such as discussed by (Mitchell, et. al.) 

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Appendix F. Route Availability Planning Tool 

Current departure decisions in the presence of convective weather require ATC 

to estimate whether the aircraft will have a storm free flight. 

Weather Traffic 

Mental model 

for typical 4 D 

departure 

trajectories 

 

“ If I depart NWA 123 will 

 it encounter weather?” 

Figure 1. Existing Decision Process 

The Route Availability Planning Tool uses the Terminal Convective Weather 

Product storm motion forecasts and typical departure flights along defined 

Standard Instrument Departure (SID) Routes to determine if an aircraft would 

encounter a storm for departure times in the next thirty minutes. The information 

68
is color coded in a display, one row for each SID, where red indicates a likely 

encounter with a storm and green a safe departure. 

Since its’ first deployment, the tool has incorporated storm echo tops as well and 

is continuing to be refined as experience is gained. 

Storm SIDs & 

Motion Aircraft Models Computer

69

 

Figure 2. Route Availability Planning Tool 

The RAPT display indicates, by color coding, if an aircraft departing at some time 

in the next 30 minutes will encounter a storm during the first 30 minutes of flight. 

RAPT 

900 910 920 930 940 950 1000 

SID R13

Display 

“Depart NWA 123 

At 9:20 on R13”