1. Heavy Precipitation at the Alpine South Side and Saharan Dust over Central Europe: A Predictability Study using TIGGE Lars Wiegand, Arwen Twitchett, Conny Schwierz & Peter Knippertz 11th EMS Annual Meeting, Berlin, 12–16 Sept. 2011

2. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Outline  Motivation  Upper-Level Development  Forecast performance  Analysis uncertainty  High-Impact Weather  Saharan dust storm  Heavy precipitation at the Alpine south side  Conclusions

3. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Motivation 2008/05/27 10 UTC2008/05/27 13 UTC Motivation

4. Upper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Gorner glacier August 2008 with dust from the May event Motivation

5. Upper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe  flooding on the Alpine south side of Switzerland & Italy  Lago Maggiore rose by 10 cm in 24 hours Motivation 4-day precipitation sum 26–29 May 2008 mm source: ENSEMBLE gridded rain gauge data Motivation

6. Upper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe DATA  Thorpex Interactive Grand Global Ensemble (TIGGE)  10 forecasting centres: Australia, Brazil, China, Canada, ECMWF, France, Japan, Korea, UK, USA  ~500 multi-model ensemble members per day  Exciting new dataset for operational forecasting and research Motivation

7. Upper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-level potential vorticity Upper-Level Development

8. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-Level Development Upper-level potential vorticity

9. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-Level Development Upper-level potential vorticity

10. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-Level Development Upper-level potential vorticity

11. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-Level Development Upper-level potential vorticity

12. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-Level Development Upper-level potential vorticity

13. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Upper-Level Development region of interest (29°-55°N, 15°W-2°E) Upper-level potential vorticity

14. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Root mean square errors (RMSEs) ECMWF_europe BoM_australia CMA_china CMC_canada CPTEC_brazil JMA_japan KMA_korea NCEP_usa UKMO_uk calculated with ECMWF analysis Upper-Level Development

15. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe ECMWF_europe BoM_australia CMA_china CMC_canada CPTEC_brazil JMA_japan KMA_korea NCEP_usa UKMO_uk calculated with every center’s own analysis Upper-Level Development Root mean square errors (RMSEs)

16. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe RMSE/spread comparison Upper-Level Development non-dispersive models

17. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe RMSE/spread comparison Upper-Level Development under dispersive models

18. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Saharan dust outbreak  RGB composite: purple color = dust  from 2008/05/26: 09UTC – 23UTC High Impact Weather

19. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Saharan dust outbreak  RGB composite: purple color = dust  from 2008/05/26: 09UTC – 23UTC High Impact Weather

20. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe 925-hPa wind fields High Impact Weather

21. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Diagnostic approach High Impact Weather for U > U t for U < U t Define “Potential dust uplift” (PDU) Set dust emission threshold: U t = 10 m s –1 at 925hPa

22. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Potential dust uplift forecast High Impact Weather analyses 10 3 m 3 s -3 PDU

23. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe High Impact Weather analyses 10 3 m 3 s -3 PDU Potential dust uplift forecast

24. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe High Impact Weather analyses 10 3 m 3 s -3 PDU Potential dust uplift forecast

25. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe High Impact Weather analyses 10 3 m 3 s -3 PDU Potential dust uplift forecast

26. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Precipitation observation High Impact Weather 4-day precipitation sum 06 UTC 26 – 06 UTC 29 May 2008 mm source: ENSEMBLE (gridded rain gauges data)

27. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Precipitation forecast High Impact Weather observed precipitation (ENSEMBLE data set) mm in 4 days

28. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe High Impact Weather observed precipitation (ENSEMBLE data set) mm in 4 days Precipitation forecast

29. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe High Impact Weather observed precipitation (ENSEMBLE data set) mm in 4 days Precipitation forecast

30. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe High Impact Weather observed precipitation (ENSEMBLE data set) mm in 4 days Precipitation forecast

31. MotivationUpper-Level DevelopmentHigh Impact Weather Conclusions Wiegand et al. – Alpine Precipitation & dust over central Europe Conclusions  TIGGE offers interesting new insight into multi-model ensemble prediction.  Case study of unusual weather event in May 2008.  Forecast performance metrics sensitive to analysis used.  Some TIGGE models with under-dispersive behaviour.  Winds for dust mobilization over Sahara general underpredicted but spread rather large.  Heavy precipitation at Alpine south side fairly well forecast on regional scale.  Multi model approach increases skill!  More in a recently published paper in Weather & Forecasting Conclusions