1. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 1 Monthly Forecasting at ECMWF Frédéric Vitart European Centre for Medium-Range Weather Forecasts

2. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 2 Product ECMWF: Weather and Climate Dynamical Forecasts ECMWF: Weather and Climate Dynamical Forecasts Medium-Range Forecasts Day 1-10(15) Medium-Range Forecasts Day 1-10(15) Monthly Forecast Day 10-32 Monthly Forecast Day 10-32 Seasonal Forecasts Month 2-7 Seasonal Forecasts Month 2-7 Forecasting systems at ECMWF

3. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 3 Index Main sources of predictability on the monthly time-scale Madden Julian Oscillation Soil Moisture Stratospheric Initial conditions The ECMWF monthly forecast system Description Some examples of forecasts Skill

4. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 4 A particularly difficult time range: Is it an atmospheric initial condition problem as medium-range forecasting or is it a boundary condition problem as seasonal forecasting? Some sources of predictability : Sea surface temperatures Land surface conditions: snow-soil moisture The Madden Julian Oscillation Stratospheric variability Atmospheric dynamical processes (Rossby wave propagations, weather regimes…) Sea ice cover –thickness ? Bridging the gap between Climate and weather prediction

5. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 5 5 Koster et al, GRL 2011 Impact of soil moisture

6. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 6 Stratospheric Sudden Warmings Chui and Kunz, 2009

7. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 7 Baldwin and Dunkerton, 2001 Stratospheric influence on the troposphere?

8. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 8 Z1000 Response (Weak vortex-CTL) D+1-D+10D+11-D+20 D+21-D+30D+31-D+40 From T. Jung et al 2005 Stratospheric influence on the troposphere?

9. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 9 Synoptic Z500 Activity D+21-D+30 From T. Jung et al 2005 Stratospheric influence on the troposphere?

10. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 10 From Madden and Julian (1972) The Madden-Julian Oscillation (MJO)

11. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 11 The Madden Julian Oscillation (MJO) From http://www.bom.gov.au/bmrc/clf MJO life cycle (From NASA)

12. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 12 The Madden Julian Oscillation (MJO) The MJO is a 40-50-day oscillation The MJO is a near-global scale, quasi-periodic eastward moving disturbance in the surface pressure, tropospheric temperature and zonal winds over the equatorial belt. The Madden-Julian Oscillation (MJO) is the dominant mode of variability in the tropics in time scales in excess of 1 week but less than 1 season. The MJO has its peak activity during Northern winter and spring.

13. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 13 The Madden Julian Oscillation (MJO) Impact on the Indian and Australian summer monsoons (Yasunari 1979), Hendon and Liebman (1990) Impact on ENSO. Westerly wind bursts produce equatorial trapped Kelvin waves, which have a significant impact on the onset and development of an El-Niňo event. Kessler and McPhaden (1995) Impact on tropical storms (Maloney et al, 2000; Mo, 2000) Impact on Northern Hemisphere weather Why is the MJO so important?

14. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 14 Lin et al, MWR 2010 See also Simmons et al JAS 1983 Ting and Sardeshmukh JAS 1993 Impact of the MJO on Extratropics

15. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 15 MJO Prediction Combined EOF1 Combined EOF2 From Wheeler and Hendon, BMRC

16. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 16 MJO FORECAST

17. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 17 Impact on Europe Cassou (2008)

18. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 18 Experiments setting: -46 day forecasts at T255L62 coupled to HOPE -15 members -Starting dates: 15 Nov/Dec/Jan/Feb/Mar/Apr 1989-2008 -Model Cycle 32R3 (operational cycle from 11/07 to 06/08) MJO prediction

19. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 19 Perfect Model Ensemble mean/ reanalysis MJO Skill scores Bivariate Correlation Bivariate RMS error Ensemble Spread Ensemble mean/ reanalysis Climatology

20. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 20 Impact on Precipitation anomalies (Summer)

21. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 21 Impact on Tropical Cyclone Density (Summer) Vitart, GRL 2009

22. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 22 Impact on the Extratropics- Z500 anomalies

23. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 23 Phase3+10 days Impact on weather regimes in hindcasts NAO- NAO+ Atlantic ridge Scandinavian blocking Phase6+10 days

24. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 24 T850 anomalies – NDJFM 1989-2008 Phase 3 + 10 days Phase 6 + 10 days ERA MODEL Degree C

25. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 25 0.04 Probabilistic skill scores – NDJFMA 1989-2008 Reliability Diagram Probability of 2-m temperature in the upper tercile Day 19-25 Europe 0.03 -0.09 MJO in IC NO MJO in IC N. Extratropics -0.06

26. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 26 The ECMWF monthly forecasting system A 51-member ensemble is integrated for 32 days twice a week (Mondays and Thursdays at 00Z) Atmospheric component: IFS with the latest operational cycle and with a T639L62 resolution till day 10 and T319L62 after day 10. Persisted SST anomalies till day 10 and ocean-atmosphere coupling from day 10 till day 32. Oceanic component: HOPE (from Max Plank Institute) with a zonal resolution of 1.4 degrees and 29 vertical levels Coupling: OASIS (CERFACS). Coupling every 3 hours.

27. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 27 Ocean only integration Coupled forecast at TL319 Day 32 EPS Integration at T639 Initial condition Heat flux, Wind stress, P-E Day 10 The ECMWF VarEPS-monthly forecasting system

28. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 28 The ECMWF monthly forecasting system Atmospheric initial conditions: ECMWF operational analysis Oceanic initial conditions: Accelerated ocean analysis Perturbations: Atmosphere: Singular vectors + stochastic physics Ocean: Wind stress perturbations during the data assimilation Background statistics: 5-member ensemble integrated at the same day and same month as the real-time time forecast over the past 20 years (a total of 100 member ensemble). Initial conditions: ERA Interim. Produced once a week.

29. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 29 The ECMWF monthly forecasting system Anomalies (temperature, precipitation..) -

30. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 30 The ECMWF monthly forecasting system Probabilities (temperature, precipitation..) -

31. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 31 The ECMWF monthly forecasting system

32. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 32 Experimental product: Tropical cyclone activity The ECMWF monthly forecasting system

33. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 33 MJO Forecasts

34. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 34 34 Precip anomalies : 26 July 2010 – 01 August 2010

35. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 35 Skill of the ECMWF Monthly Forecasting System ROC score: 2-meter temperature in the upper tercile Day 19-25Day 26-32 Day 5-11Day 12-18

36. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 36 Skill of the ECMWF Monthly Forecasting System 2-meter temperature in upper tercile - Day 12-18 ROC scoreReliability diagram Persistence of day 5-11 Monthly forecast day 12-18 Day 12-18 Day 19-25 Persistence of day 5-18 Monthly forecast day 19-32

37. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 37 OLR anomalies - Forecast range: day 15

38. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 38 MJO skill scores

39. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 39 Impact of the MJO on the N. Extratropics 2002 MOFC hindcasts 2012 MOFC hindcasts ERA Interim

40. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 40 NAO skill scores – Day 19-25

41. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 41 Performance of the monthly Forecasts Day 12-18 Day 19-25 Day 26-32 2-metre temperature ROC area over Northern Extratropics

42. Training Course 2013– NWP-PR: The Monthly Forecast System at ECMWF 42 Conclusion SSTs, Soil moisture, stratospheric initial conditions and MJO are source of predictability at the intra-seasonal time scale. In particular the MJO has a significant impact on the forecast skill scores beyond day 20. The monthly forecasting system produces forecasts for days 12-18 that are generally better than climatology and persistence of day 5- 11. Beyond day 20, the monthly forecast is marginally skilful. For some applications and some regions, these forecasts could however be of some interest. There has been a clear improvement in the monthly forecast skill scores over the past 10 years. This improvement is likely to be related to improved prediction in the Tropics and most especially improved MJO prediction.