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METWSG/2-SN No. 11
/ METWSG/2-SN No. 11
20/3/09

METEOROLOGICAL WARNINGS STUDY GROUP (METWSG)

SECOND MEETING

Montréal, 19 to 21 May 2009

Agenda Item / 5: / Content and issuance of SIGMET
5.1: / Improved issuance of SIGMET

CONCERNS ABOUT THE PROPOSAL FOR THE ISSUANCE OF SIGMET

TO BE TAKEN UP BY REGIONAL CENTRES

(Presented by Zhang Zhongfeng)

SUMMARY
This study note discusses the concerns about the proposal for the issuance of SIGMET to be taken up by regional centres. The views presented in this paper represent the consensus of Chinese aviation meteorologists.

1.INTRODUCTION

1.1At the first International Civil Aviation Organization (ICAO) Meteorological WarningStudy Group (METWSG) meeting in November 2007, a group of experts discussed ways to improve theissuance of Significant Meteorological Information (SIGMET) by the existing Meteorological Watch Offices (MWO). It has been recognized for some time by the Air Navigation Commission (ANC) that there is a need toimprove MWOs’ capabilities to issue SIGMET. In accordance with METWSG Action 1/2, an ad hocworking group was established to further review this issue. The group was requested to study ways ofimproving the situation by establishing dedicated regional centres in support of improved SIGMETavailability. In addition, the group was also tasked to consider the improvement of the existing MWObased framework and to consider developing proposals to improve training related to SIGMET, regulartesting and real-time monitoring and extend successful measures to all ICAO regions.

1.2The ad hocworking group has undergone a lot of discussions on this issue and study notes with different views were prepared. Considering aviation safety, it is difficult for us to accept the proposal for the creation of regional centres to replace the existing Meteorological Watch Offices (MWOs) for issuing SIGMET. The following key issues will be considered inthis paper:

a)Status of MWOs;

b)Safety aspect of SIGMET issuance;

c)Timeliness aspect of SIGMET issuance;

d)Verification of gridded forecast from numerical model; and

e)Sovereignty of Contracting States.

2.DISCUSSION

2.1MWOs are the building blocks of the ICAO SIGMET issuance system. They cannot be replaced by any other mechanisms without properly addressing the feasibility and other technical and non-technical issues of the proposed mechanisms and agreement by the Contracting States. It is our view that irrespective of the stage of development of the numerical weather prediction (NWP) method, it cannot completely replace the observation, detection and forecasting processes in the SIGMET issuance.

2.2The information in SIGMET not only includes large-scale systems such as volcanic ash and tropical cyclones, but alsoincludes significant weather of convection, turbulence, icing, etc., which have strong impacts on aviation safety. From the perspective of weather watch, severe convective weather monitoring requires information from local weather radars that regional centres do not currently have access. From the perspective of prediction, as we know, global-scale or regional-scale numerical weather forecast models possess a certain skill to predict large-scale atmospheric circulation patterns and weather with resolution of the order of several tens of kilometers, but still have very limited ability to predict meso-scale and micro-scale weather such as severe squall lines and clear-air turbulence which require NWP models with extremely high spatial resolution of the order of 1 km or less. For China, we have a vast area of 9,600,000 square kilometers with 10 MWOs. Each MWO can obtain information from several weather radars in its area of responsibility. Even so, there may still be gaps in space and time in the weather watch, due to transient and sporadic nature of the smaller scale events such as turbulence, which is also not detectable by the weather radar. Therefore, it is hard to imagine that only several regional centres around the world could provide adequate weather watch, detection and prediction of global hazardous weather in a timely manner, not to mention that the NWP forecasts in many cases cannot meet the performance requirements and that the availability of essential meteorological information particularly weather radar data at the regional centres cannot be ensured. Apart from the availability of weather radar information, the provision of special air-reports, i.e. aircraft reports, by the local ATC for the immediate attention of the associated MWO for SIGMET issuance could not be achieved in a timely manner by regional centres.

2.3It is also not feasible in terms of the timeliness in issuing the safety critical SIGMET information if MWOs issue SIGMET only after receiving the advisory messages issued by regional centres. The MWOs, suitably equipped and manned by qualified and trained aeronautical meteorological forecasters, should be able to issue the SIGMET information in a timely manner (e.g. in terms of minutes) based on real-time weather and aircraft observations (e.g. weather radar, wind profiler, AMDAR), weather detection methods, and special air-reports. On the other hand, global NWP models typically provide forecast outputs once every 6 hours, with time resolution of 3 to 6 hours, and available only many hours after the observation time. It is not realistic to expect that NWP model forecasts are able to accurately capture the small-scale hazardous weather events such as turbulence, severe squall lines, and other mesoscale convective systems.

2.4Another key issue is that the gridded forecasts of hazardous weather phenomena, such as icing, turbulence and convection of the global models, have yet to be verified.There has a high risk for aviation flight to use this type of products. Giving a wrong message is worse than giving nothing.

2.5ICAO has determined the rights for Contracting States in section 2.1 of the Standards and Recommended Practices (SARP) of ICAO Annex 3 — Meteorological Service for International Air Navigation, so the discussions on the SIGMET provision issues should be based on this. The issuance of SIGMET for aviation safety to meet the needs of international air navigation shall be determined by each ContractingState according to the situation.

3.recommendation

3.1From the above discussions which query the feasibility of regional centres taking up the role of issuing safety-critical SIGMET information, the METWSG should not focus on establishing the regionalcentres, but on how to further improve the ability of the existing MWOs. There is a need for ICAO to ascertain the reasons and the circumstance of those MWOs who could not currently issue SIGMET in accordance with the Standards and Recommended Practices (SARP) of ICAO Annex 3 and to take appropriate actions based on such findings. Targeted assistance should be provided to these MWOs by ICAO and WMO, e.g. Special Implementation Project (SIP) or Voluntary Cooperation Programme (VCP), so that the specific shortcomings and deficiencies could be rectified and the capabilities of the MWOs concerned could be re-established.

3.2It is also recommended to strengthen the promulgation of educational material (e.g. SIGMET posters and other guidance materials). Additional training on the issuance of SIGMET, especially for the LDC States, could be provided by States in a position to do so, in coordination with WMO and ICAO, in a more cost-effective manner, e.g. utilization of web-based platform and training material.

3.3More attention should be paid on verification of gridded numerical weather prediction model forecasts output, especially for icing, turbulence, cumulonimbus clouds. More work should be done in this area. Because numerical model has different performance in different regions, experts from different regions should involve in the model output verification.

3.4For some LDCs, if they are willing to designate other country (e.g., neighboring States) to fulfill their obligations to issue SIGMET, the issuance can be done by bilateral arrangement. To ensure the accuracy of the SIGMET, ICAO should evaluate the capabilities of the designated State, such as the technological strength and whether or not they understand the weather characteristics of the country concerned. In the meantime, the above-mentioned capacity building efforts could in time enable the LDC States to re-establish their capabilities in issuing SIGMET. At the time of preparation of this paper, such a bilateral arrangement is being established in the Asia/Pacific Region.

4.action by the metwsg

4.1The METWSG is invited to:

a)note the information in this paper; and

b)consider the recommendation provided.

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