1. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Limited-Area Ensemble Prediction: the ARPA-SMR LEPS system Stefano Tibaldi, Tiziana Paccagnella, Chiara Marsigli, Fabrizio Nerozzi, Andrea Montani ARPA-SMR With contributions from F.Molteni, R.Buizza and H.Hersbach, all at ECMWF, at some time Limited-Area Ensemble Prediction: the ARPA-SMR LEPS system Stefano Tibaldi, Tiziana Paccagnella, Chiara Marsigli, Fabrizio Nerozzi, Andrea Montani ARPA-SMR With contributions from F.Molteni, R.Buizza and H.Hersbach, all at ECMWF, at some time

2. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 The need for the regionalisation of scenarios The LEPS approach –Methodology –Some case studies –Statistical evaluation COSMO-LEPS Concluding remarks OUTLINE

3. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 THE NEED FOR REGIONALISATION OF SCENARIOS (1) Despite the recent increase of computer power resources, which have allowed the development of more and more sophisticated NWP models, the accurate forecast of extreme weather conditions, especially when related to intense and localised precipitation structures, is still difficult. This limitation is due, among other reasons, to the inherent low degree of deterministic predictability associated to this kind of phenomena.

4. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 THE NEED FOR REGIONALISATION OF SCENARIOS (2) Global-model ensemble systems have been shown to be important tools to tackle the predictability problem beyond day 3. Operational ensemble systems are usually run at a coarser resolution with respect to single deterministic model integrations for obvious economy reasons. The EPS skill in producing quantitative forecasts of intense and localised events in the short- and early- medium-range is still limited, although growing.

5. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 THE LEPS APPROACH The main purpose of the LEPS project is to produce a system capable of providing the forecaster some probabilistic guidance to identify the possible occurrence of severe weather conditions in the time range: “late-short-range (>48h) up to early-medium-range (120h)”.

6. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 THE LEPS APPROACH LEPS is designed to combine in a single system the (supposed) ability of a global ensemble prediction system to generate an exhaustive set of large-scale evolution scenarios (through an adequate sampling of the phase-space in the neighbourhood of the best available initial conditions) With the (supposed) capability of a LAM of detailing atmospheric phenomena on the local scales, particularly the precipitation field, in regions with complex orography

7. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 The obvious solution: one LAM integration for each global EPS member All the information from the global EPS is retained BUT it is hardly feasible on an operational basis (at least at ARPA-SMR) The B.F. (Brute Force) APPROACH

8. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 For each LAM run: Computer time: +120 hours of LAM integration 306 x 258 x 32 grid points  13 hours cpu on vpp5000 Data volume (IC and BCs):  0.9 GB for each member B.F.: REQUIRED RESOURCES (evaluated on COSMO-LEPS configuration) B.F.: REQUIRED RESOURCES (evaluated on COSMO-LEPS configuration) 51 runs 663 hours cpu! 46 GB!

9. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 The LAM is nested in only a limited number of members selected from the global EPS, the Representative Members Some of the information from global EPS is lost BUT the operation becomes feasible on an operational basis THE LEPS APPROACH

10. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Most Representative Member  one per cluster  choice is based on selected 3D fields: has to be: the closest to the mean of its own cluster AND the most distant to the other clusters’ means  5 runs instead of 51, 102 or 153!!

11. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Dim 2 Initial conditions Dim 1 LEPS – Limited area Ensemble Prediction System Dim 2 Possible evolution scenarios Dim 1 Initial conditions EPS and ensemble size reduction Cluster members chosen as representative members (RMs) LAM integrations driven by RMs LAM scenario

12. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 LEPS – Limited area Ensemble Prediction System Dim 2 Initial conditions Dim 1 LAM scenario PROBABILITY MAPS: WEIGHTING?????? precipitation scenarios

13. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 The basic idea was to leave the task of exploring the phase space to the global EPS, while the LAM has to zoom in the forecast, producing adequately intense local phenomena (e.g. precipitation maxima), but….

14. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Precip outliers 91 ECMWF EPS DJF 1999/2000

15. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 QUESTIONS: Are we adequately sampling the space of possibilities (i. e. the phase space around the initial conditions)?

16. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 The same 700hPa isoline plotted for the 51 Members at + 72 The same 700hPa isoline plotted for the 51 Members at + 120 Spread: EPS started at 14 May 1999, 00 UTC

17. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Spread vs error Mean square error/mean square spread

18. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 How can we improve our exploration of the phase space, increasing the available number of EPS forecasts? By resurrecting the old concept of time-lagged ensemble forecast! The Super-Ensemble!

19. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Precip outliers 91 ECMWF EPS DJF 1999/2000

20. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 LEPS super-ensemble start of integrations 102 members Day n EPS Day n Day n-2 EPS Day n-2 clustering time Verification period

21. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 102 members (50 + 1)*2 5 representative members (RMs) Summary of the LEPS methodology 5 LAMBO integrations nested on 5 RMs: LEPS - Limited-area (High Resolution) Ensemble Prediction System 5 clusters Hierarchical Cluster Analysis method: Complete Linkage area: Southern Europe fields: 4 variables at 4 levels (3D cluster) number of clusters: fixed to 5 Representative Member Selection  one per cluster  base on the nearest (3D fields) to the mean of its own cluster AND the most distant to the other clusters’ means Super ensemble : 2 global ensembles starting 5/3 days before the verification time

22. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 LEPS: SOME CASE STUDIES

23. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Soverato: 8, 9, 10 - Sep - 2000

24. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

25. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

26. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

27. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

28. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

29. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

30. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Soverato flood

31. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Soverato (Calabria) flood ECMWF proxy of 24h cumulated precipitation 10/09/2000 at 00Z 91

32. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Between 9 and 10 September, rainfall peaks above 300 mm in 24 hours were recorded close to the village of Soverato this causing landslides, great disruption and losses of life. 8 9 10

33. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 ECMWF probability maps for 24h cumulated precipitation exceeding P threshold at +60h P > 20 mm/ 24 hP > 50 mm/ 24 hP > 100 mm/ 24 h Ensemble T255 Soverato (Calabria) flood 30 100

34. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 P > 20 mm/ 24 hP > 50 mm/ 24 hP > 100 mm/ 24 h LEPS probability maps for 24h cumulated precipitation exceeding P threshold at +60h LEPS – 5 LAMBO runs driven by the 5 RMs selected from 153 members of the Super- Ensemble TL255 Soverato (Calabria) flood 47 75 58 42

35. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Probability maps for 24h cumulated precipitation exceeding threshold at +60h Brute-force approach 51 LAMBO runs on ensemble EPS T L 255L40 (51 members ) P > 50 mm / 24 h 33 23 Soverato (Calabria) flood: BF vs LEPS 25 54 LEPS: 5 weighted LAMBO runs on ensemble EPS T L 255L40 P > 50 mm / 24 h

36. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 MAP IOP2b: 19, 20 - Sep - 1999

37. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

38. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

39. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

40. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002

41. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 24 hours observed precipitation from 06 to 06 UTC MAP IOP 2B, 20-21 September 1999

42. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 ECMWF probability maps for 24h cumulated precipitation exceeding threshold at +66 hours ECMWF EPS forecasts 51 members P > 20mm/24h MAP IOP 2B P > 50mm/24h 98%

43. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 LEPS probability maps for 24h cumulated precipitation exceeding threshold at +66 hours LEPS: 5 LAMBO runs at 20 km on Super-Ensemble TEPS T L 159 P > 20mm/24h MAP IOP 2B P > 50mm/24h

44. WORKSHOP ON SHORT-RANGE ENSEMBLE PREDICTION USING LIMITED-AREA MODELS Instituto National de Meteorologia, Madrid, 3-4 October 2002 Probability maps for 24h cumulated precipitation exceeding threshold at +66 hours P > 50mm/24h Brute-force approach 51 LAMBO runs on TEPS T L 159 (51 members) MAP IOP 2b BF vs LEPS LEPS: 5 weighted LAMBO runs at 20 km on ensemble EPS T L 159