WORLD AREA FORECAST SYSTEM OPERATIONS GROUP (WAFSOPSG)

Transcription

1 International Civil Aviation Organization WAFSOPSG/7-WP/10 5/7/12 WORKING PAPER WORLD AREA FORECAST SYSTEM OPERATIONS GROUP (WAFSOPSG) SEVENTH MEETING Lima, Peru, 17 to 21 September 2012 Agenda Item 6: Development of the WAFS 6.2: Improved GRIB 2 forecasts for CB clouds, icing and turbulence SIGWX AND UPPER-AIR GRIDDED FORECASTS CONCEPT OF USE (Presented by the WAFC Provider States) SUMMARY SIGWX forecasts and WAFS gridded forecasts of CB cloud, icing and turbulence will both be available for operational use beginning November This paper describes the concept of use for these two different sets of forecasts. 1. INTRODUCTION 1.1 The development of upper-air forecasts of cumulonimbus (CB) clouds, icing, and turbulence in gridded format was at the direction of the World Area Forecast System Operations Group (WAFSOPSG) 1. The development of these gridded forecasts met International Air Transport Association s (IATA s) operational requirements to support the automated integration of forecasts of CB cloud, icing, and turbulence into flight planning systems. Pending final approval by the WAFSOPSG in September 2012, these upper-air forecasts will become operational products beginning November 2013, with Amendment 76 to ICAO Annex 3 Meteorological Service for International Air Navigation. 1.2 At WAFSOPG/4 (2009), the long-term plan for the world area forecast system (WAFS) showed the cessation of the WAFS Significant Weather (SIGWX) forecasts in BUFR code and PNG chart form to occur with Amendment 76 (with effect November 2013). The current long-term plan, endorsed at WAFSOPSG/6 (2011), removed the step to cease provision of SIGWX. Thus, come November 2013, the world area forecast centres (WAFCs) will produce and issue upper-air gridded forecasts of CB cloud, icing and turbulence, as well as SIGWX forecasts that contain forecasts of CB clouds, icing and turbulence. 1 CB cloud and turbulence were from the First Meeting (2003) while icing was added at the Second Meeting (2005). (7 pages) WAFSOPSG.7.WP en.doc

2 WAFSOPSG/7-WP/ A description and discussion of the differences between the content and criteria for the SIGWX and upper-air gridded CB cloud, icing and turbulence is contained in the Appendix to this paper. 1.4 Also the group will recall that Conclusion 5/11, Guidance on the intended use of gridded WAFS forecasts for CB clouds, icing and turbulence in flight documentation was deferred until June 2012 by the Group at its sixth meeting. This working paper (WP) addresses Conclusion 5/11 as well as proposing a concept for the use of both gridded world area forecast system (WAFS) forecasts and WAFS SIGWX forecasts. 2. CONCEPT OF USE 2.1 WAFS upper-air forecasts in grid point format are ideally suited for flight planning systems. Historically, flight planning systems have used upper-air wind forecasts to obtain the optimum (time, distance, or fuel) flight route for their business models. The addition of upper-air icing forecasts provides global icing forecasts for Extended Diversion Time Operations (EDTO) (formally ETOPS). Depending on the user s business model, upper-air forecasts of turbulence and CB clouds can be used for passenger comfort. 2.2 The initial concept for the use of the SIGWX forecasts in support of flight planning has changed. Whereas at one time the SIGWX was used to decide a flight route, there was never an effective means to integrate these forecasts into flight planning systems. Today s flight routes are decided many hours before the SIGWX forecast is produced. In addition, long-haul flights can t effectively use the SIGWX since large portions of their flight occur well after the SIGWX validity time. Thus, the role of the SIGWX chart today is primarily to provide the flight crew with a general overview of the en-route weather for situational awareness. 2.3 The following is an outline of how the SIGWX and the WAFS upper-air gridded CB cloud, icing and turbulence are intended to be used given that both will be available for use in November 2013, and likely continue in use for at least 3 years The WAFCs produce WAFS upper-air gridded data sets for use in flight planning. These data sets include wind, temperature, humidity, CB cloud, icing and turbulence. These data are provided in digital format (i.e., GRIB-2) and are designed to be integrated directly into automatic flight planning systems. The operator may use these data in their flight planning decisions, in accordance with their own business model and safety management systems The WAFCs support the flight documentation requirements of Annex 3 by providing SIGWX forecasts as well as upper-air wind, temperature and humidity forecasts. The WAFCs do not provide visualizations of upper-air gridded CB cloud, icing and turbulence forecasts in support of flight documentation (per Annex 3, Chapter 9) If the operator, State or flight planning service provider has the capability to produce flight route specific visualized output of the upper-air gridded data (including CB cloud, icing and turbulence), as part of their flight documentation, then the operator, State or flight planning service provider should not include the SIGWX in the flight documentation.

3 -3- WAFSOPSG/6-WP/10 3. CONCLUSION 3.1 The WAFS upper-air gridded forecasts of CB cloud, icing and turbulence are intended to be integrated into flight planning systems. WAFS SIGWX forecasts are intended for flight documentation and situational awareness. 3.2 The WAFS upper-air gridded forecasts of CB cloud, icing and turbulence will not be made into visualized products by the WAFCs (refer to Decision 6/17 in Appendix A). As such, flight crews will only have the SIGWX in their flight documentation and not the WAFS gridded forecasts of CB cloud, icing and turbulence. If an operator, State or flight planning service provider has the capability to produce flight route specific visualized output of the upper-air gridded data (including CB cloud, icing and turbulence), as part of their flight documentation, then the operator, State or flight planning service provider should not include the SIGWX in the flight documentation. 3.3 In regard to the information provided in this paper, the group is invited to endorse the following conclusion: Conclusion 7/xx Use of SIGWX and WAFS upper-air forecasts of CB cloud, icing and turbulence That, following the approval by the WAFSOPSG in September 2012, the intended use of SIGWX charts for flight documentation, and WAFS upper-air forecasts of CB cloud, icing and turbulence for use in flight planning systems, be documented in the next update to Doc 8896, Manual of Aeronautical Meteorological Practice. Specifically, a) the WAFCs produce WAFS upper-air gridded data sets for use in flight planning. These data sets include wind, temperature, humidity, CB cloud, icing and turbulence. These data are provided in digital format and are designed to be integrated directly into automatic flight planning systems. The operator may use these data in their flight planning decisions, in accordance with their own business model and safety management systems. b) the WAFCs support the flight documentation requirements of Annex 3 by providing SIGWX forecasts as well as upper-air wind, temperature and humidity forecasts. The WAFCs do not provide visualizations of upper-air gridded CB cloud, icing and turbulence forecasts in support of flight documentation. c) if the operator, State or flight planning service provider has the capability to produce flight route specific visualized output of the upper-air gridded data (including CB cloud, icing and turbulence), as

4 WAFSOPSG/7-WP/10-4- part of their flight documentation, then the operator, State or flight planning service provider should not include the SIGWX in the flight documentation. 4. ACTION BY THE WAFSOPSG 4.1 The WAFSOPSG is invited to: a) note the information contained in this working paper; and b) decide on the draft decision for this group s consideration.

5 APPENDIX DIFFERENCES BETWEEN WAFS UPPER-AIR GRIDDED DATA SETS AND WAFS SIGWX FORECASTS 4.2 WAFS upper-air forecasts of icing, turbulence and CB cloud, in grid point format, are provided with valid times at 3 hour intervals, from T+6, 9, 12, 15, 18, 21, 24, 27, 30, 33 and 36 hours from model initialization time (T). They provide the user with grid point forecasts valid at 3 hourly increments from 6 hours through 36 hours, which is enough to satisfy the needs of both short-haul and long-haul flight operations. These forecasts are produced by computer algorithms run on numerical prediction models. They are not edited by an aviation meteorologist, nor are they visualized by the WAFCs SIGWX forecasts are produced by an aviation meteorologist, and are only provided for one time step, T+24 hours. The aviation meteorologist uses the output from numerical prediction models as well as other meteorological information to produce the SIGWX forecasts. The SIGWX forecasts are not amended or updated when newer numerical prediction models are produced, rather a new SIGWX is issued for a later validity time. 4.4 WAFS upper-air gridded data sets have different element criteria from the WAFS SIGWX charts. To highlight this fact the following information is presented, which is taken from Annex 3, Appendix 2, Technical Specifications Related to the WAFS. CB Clouds: Gridded CB Cloud forecasts shall be as described in Annex 3 Meteorological Service for International Air Navigation App 2, e) horizontal extent and flight levels of base and top of cumulonimbus clouds Whereas the SIGWX forecasts shall include CB according to the regulations: App 2, a) cumulonimbus clouds associated with thunderstorms and with tropical cyclone; b) severe squall lines; c) moderate or severe turbulence; d) moderate of severe icing; and e) widespread sandstorm/duststorm. Also for the SIGWX App 2, b) The abbreviation CB shall only be included when it refers to the occurrence or expected occurrence of cumulonimbus clouds: 1) affecting an area with a maximum spatial coverage of 50 per cent or more of the area concerned; 2) along a line with little or no space between individual clouds; or 3) embedded in cloud layers or concealed by haze As such, the WAFS gridded CB Cloud data are forecasts of all cumulonimbus clouds, whereas WAFS SIGWX contains a subset of CB clouds that must meet strict criteria. Thus users of the SIGWX typically

6 WAFSOPSG/7-WP/10 A-2 find that the WAFC Provider States denote areas of isolated or occasional embedded CB or frequent CB cloud coverage on the SIGWX. Turbulence: Gridded turbulence data shall be clear-air turbulence for layers centered at flight levels 240, 270, 300, 340, 390 and 450 ; and in-cloud turbulence for layers centered at flight levels 100, 140, 180, 240 and 300. SIGWX forecasts shall be moderate or severe turbulence (in cloud or clear air). Note that Annex 3 does not state that the gridded turbulence are to provide intensities of moderate or severe. Icing: Gridded icing data shall be icing for layers centered at flight levels 60, 100, 140, 180, 240 and 300. SIGWX shall be moderate or severe icing. Note that Annex 3 does not state that the gridded icing are to provide intensities of moderate of severe. As such the WAFS gridded icing are forecasts of all icing, in the form of potential, for the entire globe. ICAO Annex 3, Appendix 2, paragraph 1.3.3, requires SIGWX to contain forecasts of moderate or severe icing. It should be noted that SIGWX Medium Level forecasts are not global, with forecasts provided for portions of the North Atlantic, Europe, Middle East and South Asia. 4.5 A summary of the differences is presented in the table below: Production WAFS SIGWX forecasts Generated by a meteorologist using a computer tablet (or workstation) using various computer models and datasets. The two WAFC s SIGWX forecasts are not harmonized. WAFS Upper-Air Gridded data sets of CB Clouds, Icing and Turbulence Produced directly from numerical weather prediction models. Harmonization The two WAFC s harmonize their gridded data sets to produce consistent forecasts of CB clouds, icing and turbulence. Validity time T+24 hours T+6, 9, 12, 15, 18, 21, 24, 27, 30, 33 and Updates Cumulonimbus (CB) Clouds None. The 24 hour SIGWX forecast is not updated (or amended). A subset of CB clouds. That subset is: 1) CBs affecting an area with a maximum spatial coverage of 50 per cent or more of the area concerned; 2) CBs along a line with little or no space between individual clouds; or 3) CBs embedded in cloud layers or concealed by haze 36 hours Updated every 6 hours. E.g., the 24 hour forecast would be updated with a new 18 hour forecast; then that 18 hour forecast would be updated with a new 12 hour forecast, etc. All CB clouds. Turbulence Moderate or severe turbulence Clear-air turbulence for layers centered at flight levels 240, 270, 300, 340, 390 and 450; and in-cloud turbulence for layers centered at flight levels 100, 140, 180, 240 and 300. Icing Moderate or severe icing Icing for layers centered at flight levels 60, 100, 140, 180, 240 and 300.

7 A-3 WAFSOPSG/7-WP/10 5. DECISION BY THE WAFSOPSG 5.1 The WAFSOPSG noted at their sixth meeting the differences mentioned above, as well as the concerns regarding visualization, and endorsed the following decision (bold emphasis added for this WP only). Decision 6/17 - Visualization of the WAFS gridded data sets for CB clouds, icing and turbulence That, a) the visualization of the first generation of WAFS upper-air gridded forecasts can not be expected to duplicate or harmonize with the current SIGWX forecasts as the criteria for the icing, turbulence and CB cloud elements differ; and b) States or commercial vendors are best suited as the developers and providers of visualised products derived from the WAFS gridded forecast data sets, including concatenated charts or time-height flight profiles for individual flights; and c) WAFS SIGWX forecasts should continue to be provided by the WAFC Provider States in their current formats until such time as the WAFSOPSG finds a suitable alternative, or when the requirement for provision by the WAFC Provider States ceases. END