1. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 1 Predictability on the Monthly Timescale Frederic Vitart ECMWF, Reading, UK

2. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 2 INDEX  Main sources of predictability in the monthly time scale  The ECMWF monthly forecasting system - Description - Evaluation of the skill - Some examples of forecasts  Future configuration  MJO prediction

3. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 3 Product Tool ECMWF: Weather and Climate Dynamical Forecasts ECMWF: Weather and Climate Dynamical Forecasts Forecasting at ECMWF Medium-Range Forecasts Day 1-10 Medium-Range Forecasts Day 1-10 Atmospheric model Monthly Forecast Day 10-32 Monthly Forecast Day 10-32 Atmospheric model Ocean model Seasonal Forecasts Month 2-6 Seasonal Forecasts Month 2-6 Atmospheric model Ocean model

4. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 4 Monthly forecasting: Bridging the gap between seasonal and medium-range weather forecasting A particularly difficult time range: Is it an atmospheric initial condition problem as medium-range or is it a boundary condition problem? Some source of predictability in the monthly time scale: - Stratospheric initial conditions - The Madden-Julian Oscillation (MJO)

5. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 5 Stratospheric Influence on the Troposphere? (Baldwin 2000) Baldwin and Dunkerton, 2001

6. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 6 Z1000 Response (Weak-CTL) D+1-D+10D+11-D+20 D+21-D+30D+31-D+40 From T. Jung et al 2005

7. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 7 Synoptic Z500 Activity D+21-D+30 From T. Jung et al 2005

8. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 8 Schematic of the MJO From Madden and Julian (1972)

9. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 9 Intraseasonal variability  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. The Madden Julian Oscillation

10. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 10 The Madden Julian Oscillation From http://www.bom.gov.au/bmrc/clf Typical MJO life cycle

11. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 11 An example of MJO: 15/12/92-31/01/93 ERA40 Analysis: U850Velocity Potential 200 hPaOLR

12. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 12 Why is the MJO so important?  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-Nino event. Kessler and McPhaden (1995)  Impact on tropical storms over the eastern North Pacific (Maloney et al, 2000) and Atlantic (Mo, 2000)  Impact on Northern Hemisphere weather

13. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 13 Impact of the MJO on Northern Hemisphere weather Ferranti et al (1990) Relaxation towards analysis Relaxation towards initial conditions Control

14. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 14 Monthly Forecasting System (1) Coupled ocean-atmosphere integrations: a 51-member ensemble is integrated for 32 days every week (every Thursday). Atmospheric component: IFS with the latest operational cycle and with a T159L62 resolution Oceanic component: HOPE (from Max Plank Institute) with a zonal resolution of 1.4 degrees and 29 vertical levels Coupling: OASIS (CERFACS). Coupling every ocean time step (1 hour)

15. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 15 Monthly Forecasting System (2) Atmospheric initial conditions: ERA40 and ECMWF operational analysis Oceanic initial conditions: Last ocean analysis + real time forecast Perturbations: - Atmosphere: Singular vectors + stochastic physics - Ocean: SST perturbations in the initial conditions + wind stress perturbations during data assimilation.

16. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 16

17. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 17 Model Orography and grid at TL159 resolution

18. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 18 Comparison with EPS The monthly forecasting system has a coarser horizontal resolution than EPS (T159 instead of T399) The monthly forecasting system has a longer time step than EPS (1 hour instead of 30 minutes) The monthly forecasting system is an ocean-atmosphere fully coupled system, whereas the EPS is based on atmospheric integrations forced by persisted SSTs

19. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 19 Model Bias

20. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 20 Monthly Forecasting System (3) Background statistics: - 5-member ensemble integrated at the same day and same month as the real-time time forecast over the past 12 years. - This represents a 60-member ensemble. - It is running once every week

21. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 21 Monthly Forecasting products ANOMALIES (2m-tm, mslp, precip..) -

22. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 22 Monthly Forecasting products Terciles (2m-tm, mslp, precip..) -

23. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 23 Monthly Forecasting products -

24. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 24 Summer 2003 heat wave: 2m-tm anomaly 3-9 August 2003 VERIFICATIONForecast 30/07: DAYS 5-11 Forecast 16/07:DAYS 19-25Forecast 23/07: DAYS 12-18

25. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 25 Heat wave of summer 2003 over France

26. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 26 Analysis Day 12-18 30/05-05/0606/06-12/06 13/06-19/06 Day 19-25 Day 26-32 Indian monsoon: precipitation anomaly

27. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 27 Tropical Storms: Monthly Forecast Probability of a tropical storm within 1 degree Day 10-32 Forecast starting on 4 August 2005Model climatology starting on 4 July 1993-2004

28. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 28 Verification. The monthly forecasting system is semi-operational since 27 March 2002 (Products are in www.ecmwf.int/products/forecasts) andwww.ecmwf.int/products/forecasts operational since October 2004.

29. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 29 Impact of ocean-atmosphere coupling N. PACIFIC MOFC/EPS: 20/10 (92% sign) EAST ASIA MOFC/EPS: 24/6 (95% sign) Day 12-18

30. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 30 PROBABILISTIC SCORES: ROC Probability Surface-temperature in upper tercile. N. Extratropics over land WEEK1: DAY 5-11 WEEK2: DAY 12-18 WEEK3: DAY 19-25 WEEK4: DAY 26-32 WEEK3+4: DAY 19-32 ROC SCORES: 0.81 0.71 0.64 0.61 0.63

31. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 31 Comparison with persistence 2-meter temperature in upper tercile - Day 12-18 ROC scoreReliability diagram Persistence of day 5-11 Monthly forecast day 12-18

32. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 32 Comparison with persistence 2-meter temperature in upper tercile - Day 19-32 ROC scoreReliability diagram Persistence of day 5-18 Monthly forecast day 19-32 ROC area=0.6 0.56

33. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 33 ROC Scores DAY 12-18 (WEEK2) 2-meter temperature in upper tercile

34. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 34 ROC Scores DAY 19-32 (WEEK3+4) 2-meter temperature in upper tercile

35. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 35 ROC score

36. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 36 Future plans: VAREPS EPS Integration Initial condition Ocean only integration Heat flux, Wind stress, P-E Coupled forecast at TL255 Day 32 Present system: Initial conditionDay 32 Future system: Coupled forecast at TL159 Day 15

37. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 37 First case of a 3-legs VAREPS (17 July 2002) OPE VAREPS VAriable Resolution EPS (VAREPS) T0T+168T+360 T+768 Ensemble mean High resol. (T511) Control

38. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 38 MJO analysis The method is based on the same method as in Wheeler and Hendon (2004). We use combined EOFs of: - Velocity potential anomalies at 200 hPa - Outgoing Long-Wave Radiations anomalies - Zonal wind at 850 hPa anomalies Anomalies are relative to the past 12 years climate. The fields have been averaged between 10N and 10S and normalized, before computing the combined EOFs. EXPERIMENT: A 5-member ensemble has been run every day from 15 December 1992 to 31st January 1993.

39. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 39 MJO analysis The combined EOFs have been computed on ERA40 daily data from 2002 to 2004.

40. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 40 MJO Experiments: Impact of SSTs CoupledPers. SSTsObserved SSTs. PC1 PC2

41. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 41 Scope for improvement: amplitude of the MJO PHASEAMPLITUDE Velocity potential

42. ECMWF Training course 26/4/2006 DRD meeting, 2 July 2004 Frederic Vitart 42 Conclusion: The monthly forecast skill for the first 10 days is comparable with the skill of the EPS. Beyond forecast day 10, over the Pacific region, the monthly forecast perform better than the EPS. The monthly forecasting system produces forecasts for days 12-18 that are generally better than climatology and persistence of day 5- 11. Beyond 20 days the monthly forecast is marginally skilful. For some applications and some regions, these forecasts could however be of some interest. Model improvements, particularly in simulating the MJO activity are likely to be beneficial for that time range.