1. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 1 Verification of LEPS products at the DWD - first results Thomas Schumann, Deutscher Wetterdienst, Zentrale Vorhersage D-63067 Offenbach, Germany E-Mail: Thomas.Schumann@dwd.de

2. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 2 Content 1. Introduction 2. A subjective verification method 3. Some case studies 4. Results 5. Conclusions and outlook

3. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 3 1. Introduction A lot of parameters and thresholds available... at time steps H+24... 120 ParameterThresholds (>..., Tn <...) fx10 m/s15 m/s20 m/s25 m/s precip 24h20 mm50 mm100 mm150 mm precip 72h50 mm100 mm150 mm250 mm Tx20°C30°C35°C40°C Tn< 5°C< 0°C< -5°C< -10°C Selection for verification !

4. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 4 2 Examples... Prob fx > 20 m/s May 04, 12 + 24... 48 H Prob Tx > 30°C May 05, 12 + 18... 42 H

5. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 5 2. A subjective verification method Permanent Verification (Excel-Sheet) or Case Studies...

6. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 6 Problem: Lack of severe events (permanent blocking) a few cases only SLP Analysis, May 05, 06 UTC Precipitation Anomaly 2003 Dresden and Duesseldorf (www.cpc.ncep.noaa.gov)

7. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 7 3. Some case studies 3.1. Temperature - late cold outbreaks Date: April 09/10 and 10/11, 2003 ECM April 7, 12 + 72 h, SLP (blue) and T850 (red)ECM April 8, 12 + 72 h L L H H H

8. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 8 Tn forecasts 09/10 April April 08, 12 + 18... 42 H (left top), April 07, 12 + 42... 66 H (left bottom) Tn forecast 10/11 April April 06, 12 + 66... 90 H

9. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 9 EPS ECMWF Prob Tmin < 0°C April 10/11 April 06, 12 + 72... 84 H April 08, 12 + 18... 42 H

10. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 10 Observed Tn April 10, 06 UTC Observed Tn April 11, 06 UTC Late frost over widespread areas

11. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 11... The snow forecast has been performed well... (excerpt Southern Germany) April 07, 12 + 72... 96 H April 11, 06 UTC 24-hr snow amount (cm) April 09, 12 + 24... 48 H

12. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 12 EPS ECMWF prob snow > 1 cm April 09, 12 + 24... 48 H Snow fc from the EPS: No signal !

13. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 13 3.2. Temperature - daily Temperature Maximum ECM March 22, 12 + 72 h, SLP (blue) and T850 (red) Date: March 25, 2003 Tmax exceeding 20°C over Southern Germany is likely H Observed Tmax

14. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 14 March 24, 12 + 18... 42 H (left top), March 23, 12 + 42... 66 H (left bottom) March 21, 12 + 90... 114 H (right) Forecasts perform well, even the effect of large cities (London) is visible ! Useful forecasts also in similar situations !

15. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 15 3.3. Total precipitation, accumulated over 24 hours ECM April 1, 12 + 72 h, SLP (blue) and T850 (red) Case: April 03/04, 2003 large-scale precip at the northern side of the Alps and the Pyrenees mostly convective precip at the Algerian coast and the Croatic and Slowenic mountains L L L H

16. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 16 Obs 24-hr precip values, April 4, 06 UTC (top) and April 5, 06 UTC (right) Gaps caused by countries, doesn´t report 24-hr precip totals a better verification if LEPS could predict 12-hr precip totals at 06 and 18 UTC (synop)

17. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 17 March 31, 12 + 72...96 HApril 1, 12 + 48...72 H April 1, 12 + 72...96 HMarch 31, 12 + 96...120 H LEPS fc valid for April 4 (top) threshold: 20 mm LEPS fc valid for April 5 (bottom) threshold: 50 mm

18. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 18 3.4. Wind gusts Date: April 05/06, 2003 MSLP Analysis April 05, 12 UTC Through situation, in transistion to a cut-off over eastern Europe instable conditions over eastern Germany and Poland ---> gusts April 06, 12 UTC

19. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 19 Max wind gusts (obs) April 05, 18 UTC gusts up to 24 m/s over northeastern parts of Germany and the North Sea coast April 03, 12+24...48 H Threshold: 20 m/s Excellent Forecast

20. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 20 Max wind gusts (obs) April 07, 00 UTC gusts up to 24 m/s near the Baltic Sea coast April 03, 12 + 48...72 H Threshold: 20 m/s Gusts overestimated !

21. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 21 EPS ECMWF prob fx > 20 m/s April 03, 12 + 48... 60 H, valid at April 05, 12... 24 UTC April 04, 12 + 48... 60 H valid at April 06, 12... 24 UTC

22. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 22 April 19, 12 UTC Sat picture (vis) and Geopotential 500hPa ECM 12 + 00 h Small cut-off low over central Germany caused convective precipitation up to 32 mm (10460) 3.5. Convective precipitation events Case study: April 19 - cut-off low

23. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 23 Obs April 19, 18 UTC weather, lightning, radar Obs April 20, 06 UTC 24-hr precip totals

24. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 24 24-hr Precip totals (right) April 19, 00 UTC, GME + 24 h April 18, 12 UTC, ECM + 36 h Both models gave valuable signals ! LEPS April 18, 12 UTC + 24...48 h No signal !

25. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 25 EPS ECMWF prob precip_24hr > 10mm April 18, 12 + 24... 48 H ECMWF T511 precip_24hr April 16, 12 + 66... 90 H (left) April 18, 12 + 18... 42 H (right) valid April 19/20, 06 UTC T511-forecast: event was predicted quite well, but the EPS: No signal

26. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 26 4. Results preliminary status - experiences obtained from several forecasters during semi-operational use Case studies... Subjective verification method takes a lot of time... High expectations to the LEPS well-known problems of the LM- and the ECMWF (EPS- and T511)-forecasts (wind gusts, convective precipitations)

27. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 27 ParameterResultsComments Minimum temperatureNo signalDon´t use the LEPS ! Maximum temperaturefair, usefulrealistic regional assignment of the signals, some skill in med-range Wind gustsfair, usefulgusts sometimes overestimated (LM) realistic presentation of orographic effects, without skill in med-range Snownot very wellrealistic presentation of orographic effects, one case study only precipitation large scalefair, usefulrealistic regional assignment of the signals, rapid lost of predictability by increasing leading time convectivemostly noThe use if LEPS is not signalrecommendable !

28. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 28 5. Conclusions and outlook LEPS wasn´t able to meet our expectations (no skill in med-range) predictions of convective precipitations and gusts, caused by convective events, not useful forecasts of late cold outbreaks: results very poor, no signal Acceptance by forecasters Results of this workshop experiences from other COSMO-LEPS members Further development of the LEPS system Simulation of „historic“ extreme weather events Continuing verification ? Continuous or case-sensitive ? Improvements of the LEPS forecasts in the near future ? Enhanced operational use of the LEPS system by forecaters ?

29. Deutscher Wetterdienst Zentrale Vorhersage DWD Workshop "Use and Verification of LEPS products", Geneve, 26 - 28 May, 2003 29 Thank you for your attention !