TRENDforecast趋势预测.doc

(3 pages) 272e956344fa4f20e29a49250cd41c13.pdf AERODROME METEOROLOGICAL OBSERVATION AND FORECAST STUDY GROUP (AMOFSG) SEVENTH MEETING Montral, 9 to 12 September 2008 Agenda Item 6: Aerodrome forecasts TREND FORECAST (Presented by Kees Blom) SUMMARY This paper describes a proposal for a new way of issuing a TREND type landing forecast by using the expected prevailing weather parameter values in combination with the temporary variations of the parameter values. 1.INTRODUCTION 1.1In many States use is made of the TREND type landing forecast according to Annex 3 Meteorological Service for International Air Navigation , para 6.3.3: “trend forecast shall consist of a concise statement of the expected significant changes in the meteorological conditions at that aerodrome to be appended to a local routine or local special report, or a METAR or SPECI. The period of validity of a trend forecast shall be 2 hours from the time of the report which forms part of the landing forecast”. 1.2With Amendment 74 to Annex 3 it became possible to issue AUTO METAR during opening hours of aerodromes. Furthermore this has lead to issuing AUTO local reports and AUTO local special reports at some aerodromes as well. AMOFSG/7-SN No. 24 15/8/08 AMOFSG/7-SN No. 24- 2 - 2.DISCUSSION 2.1Automated weather reporting in itself proves to generate more local special reports (and SPECI, when issued), since an automated system will strictly adhere to regulations, where human observers tend to anticipate changes and are able to combine changes which occur shortly after each other into one report. 2.2Preparing TREND forecasts with every new report has always taken a lot of effort from aviation forecasters, even more where they are providing TREND forecasts for several aerodromes from a centralized forecast office. 2.3TREND forecasts according to the present recommendation have to provide the expected significant changes in the meteorological conditions . Especially in weather situations with rapidly changing conditions this results in many different TREND forecasts, while the prevailing weather conditions do hardly change. Examples: METAR EHAM 041425Z 14011KT 4000 SHRA FEW034CB BKN040 05/01 Q1007 BECMG 9999 NSW= SPECI EHAM 041435Z 14011KT 9999 FEW034 BKN040 05/01 Q1007 TEMPO 14017G28KT 4000 SHRA SCT030CB= SPECI EHAM 041435Z 15015G25KT 4000 SHRA FEW032CB BKN040 05/01 Q1007 BECMG 14010KT 9999 NSW= SPECI EHAM 041447Z 15015G25KT 9999 FEW034CB BKN040 05/01 Q1007 BECMG 14010KT TEMPO 4000 SHRA = METAR EHAM 041455Z 13012KT 9999 FEW034CB BKN040 05/01 Q1007 TEMPO 14017G28K 4000 SHRA = (examples provided in METAR/SPECI code, but can also be made for Local/Special reports.) 2.4To reduce the number of different TREND forecasts (and thus workload and costs) it is proposed to change the recommendation for the TREND forecast so that the prevailing conditions in the next 2 hours and the changes in that conditions are forecasted. In the examples of 2.3 only one TREND would according to this proposal have been necessary: METAR EHAM 041425Z 14011KT 4000 SHRA FEW034CB BKN040 05/01 Q1007 14010KT 9999 TEMPO 14017G28K 4000 SHRA SCT030CB= 3.CONCLUSION 3.1Producing TREND forecasts in a centralised forecasting environment is time consuming and leads to high workload, especially in rapidly changing conditions. AMOFSG/7-SN No. 24- 3 - 3.2Changing the existing recommendation on TREND forecasts might reduce workload and costs. 3.3It is proposed to amend the recommendation in Annex 3 para 6.3.3 to a more generic TREND forecast with prevailing conditions followed by expected changes for the next 2 hours, appended as at present to METAR, SPECI, LOCAL repor