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Predicting severe weather by EPS tools - current results

NOAA12, 03 June 2005, 15:33 UTC (University of Bern). Predicting severe weather by EPS tools - current results. Thomas Schumann, Deutscher Wetterdienst, Zentrale Vorhersage D-63067 Offenbach, Germany E-Mail: Thomas.Schumann@dwd.de. Outline 1. Introduction - current situation

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Predicting severe weather by EPS tools - current results

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  1. NOAA12, 03 June 2005, 15:33 UTC (University of Bern) Predicting severe weather by EPS tools - current results Thomas Schumann, Deutscher Wetterdienst, Zentrale Vorhersage D-63067 Offenbach, Germany E-Mail: Thomas.Schumann@dwd.de ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  2. Outline 1. Introduction - current situation 2. EPS products used for severe weather prediction 3. Case studies 4. Preliminary verification results 5. Conclusions ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  3. 1. Introduction - current situation Forecaster: a great variety of products ECMWF EPS and derived productswww.ecmwf.int ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  4. PEPS Udos model market (DWD Intranet, in future included into NinJo) Decision, which EPS tool will be used, depends from • Purpose of my forecast (overview, • detailled view, ... severe weather) • lead time • expected scale of the event SRNWP PEPS Plots for global models: Available parameters: Z500 T850 MSLP • ECMWF • GME • GFS • UKMO • LFPW • CMC (still not used) COSMO-LEPS ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  5. Problems (or advantages?): Forecaster has to keep in mind: • Clustering always provides a compromise. Different clustering • methods could lead to different results. • The EPS mean / the best populated cluster / the majority of global • models not always shows the szenario that finally will happen. • No model is perfect, models more or less inconsistent („jumping“, • caused from changes in initial and boundary conditions). • selection of available modelsallows to create a EPS as well • from global models as fromLAMs (different model physics, • parametrisation scheme and resolution, ...) ---> SRNWP EPS ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  6. 2. EPS Products used for severe weather prediction ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  7. 3. Case studies A) Late frost - 20/21/22 April 2005 B) Heavy precipitation - 14 May 2005 C) „Hot day“ .... 03 June 2005 D) Thunderstorm - Squall line 03/04 June2005 • How did COSMO-LEPS and SRNWP-PEPS perform • against observations ? • against probabilities of the „pure“ (uncalibrated) ECMWF EPS? SRNWP-PEPS (PEPS): http://www.dwd.de/en/FundE/Projekte/ PEPS/index.htm (forecasts password-protected) ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  8. A) Late frost - 20/21/22 April 2005 Tmin Observations, 20 April, 06 UTC (NE-Part of Germany) MSLP analysis, 20 April, 06 UTC ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  9. COSMO-LEPS, 17 April 05, 12 + 42 ... 66 H COSMO-LEPS, 18 April 05, 12 + 18 ... 42 H PEPS forecast, 19 Apr 05, 12 + 18 ... 30 H (EPS-mean) SRNWP-PEPS: Temp below 3C in the N-part of Germany likely, frost 2 m above sfc not ! COSMO-LEPS: Frost in the NE-part of Germany likely ! ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  10. ECMWF EPS probabilities for Tmin > 0 C 19 April, 00 + 24 H Frost in the NE-part of Germany likely ! ECMWF EPS probabilities for Tmin > 0 C 18 April, 12 + 36 H ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  11. Two days later... The climax of the cold outbreak Tmin Observations, 22 April, 06 UTC MSLP analysis, 22 April, 06 UTC ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  12. COSMO-LEPS, 17 April 05, 12 + 90 ... 114 H ECMWF EPS, 17 April 05, 12 + 96 ... 120 H COSMO-LEPS, 18 April 05, 12 + 66 ... 90 H 18 April 05, 12 + 72 ... 96 H Probabilities Tmin < 0 C 22 April, 06 UTC Event well predicted by COSMO-LEPS as well as by the ECMWF EPS even in the early medium-range ! ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  13. B) Heavy precipitation - 14 May 2005 Precip (obs, 24 hr-accumulated), 15 May 2005, 06 UTC Precip locally above 50 mm / 24 h in the W-part above 30 mm MSLP analysis, 14 May, 18 UTC ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  14. PEPS, 14 May, 00 + 06 ... 30 H 24 hr-acc precip probab > 50 mm PEPS, 14 May, 00 + 06 ... 30 H 24 hr-acc precip probab > 20 mm PEPS, 14 May, 00 + 06 ... 30 H EPS mean ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  15. COSMO-LEPS forecasts: probab´s > 50 mm / 24 h (top) and > 20 mm / 24 h (bottom) 11 May 12 + 66 ... 90 H 12 May 12 + 42 ... 66 H 13 May 12 + 18 ... 42 H ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  16. 12 May 00 + 60 ... 84 H 11 May 12 + 72 ... 96 H 12 May 12 + 48 ... 72 H 13 May 00 + 36 ... 60 H 13 May 12 + 24 ... 48 H 14 May 00 + 12 ... 36 H ECMWF-EPS forecasts 15 May 12 UTC (24 hr accum precip: probab´s > 20 mm / 24 h Signal became weaker with decreasing lead time and approaching of the event ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  17. C) „Hot day“ .... 03 June 2005 Tmax (Obs), 03 June, 18 UTC Few stations in SW-Germany > 30°C ! MSLP analysis, 03 June, 15 UTC ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  18. PEPSmean, 02 June, 12 + 06 ... 30 H 03 June, 00 + 06 ... 30 H Probabilities not available ! PEPS forecasts based on 02 June, 12 UTC and 03 June, 00 UTC didn´t show Tmax above 30 C over SW Germany (EPSmean) ! ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  19. COSMO-LEPS probabilities T > 30 C 30 May 12 + 90 ... 114 H 31 May 12 + 66 ... 90 H 01 June 12 + 42 ... 66 H 02 June 12 + 18 ... 42 H Tmax above 30 C over SW-Germany very likely ! Persistent signal EPS (ECMWF) without of any signal ! ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  20. ECMWF EPS probab´s Tx > 30 C (03 June, 18 UTC) ECMWF EPS probab´s Tx > 25 C (03 June, 18 UTC) Tmax underestimated caused from the „lower“ resolution of the EPS 02 June, 00 + 36 ... 42 H 02 June, 12 + 24 ... 30 H ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  21. D) Thunderstorm - Squall line 03/04 June2005 Observed gusts (m/s), 03 June, 18 UTC 04 June, 00 UTC ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  22. Hail in Northern Germany (picture by Matthias Jaenicke) Damages by the storm in the forests near Offenbach (picture by Klaus Paetzold) ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  23. prob fx > 20 m/s 03 June, 00 + 18 ... 30 H PEPS, prob fx > 20 m/s 03 June, 00 + 06 ... 18 H PEPS, prob fx > 20 m/s, 03 June, 12 + 06 ... 18 H Most severe gusts over NW and N-Part of Germany ? ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  24. COSMO-LEPS fx > 20 m/s 30 May 12 + 96 ... 120 H 31 May 12 + 72 ... 96 H 01 June 12 + 48 ... 72 H 02 June 12 + 24 ... 48 H Weak signals for gusts over the W- and S-part of Germany Signal over N-Germany for lead time > 48 h only ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  25. Signal over N-part of Germany not consistent 01 June, 00 + 66 ... 72 H 01 June, 12 + 54 ... 60 H Increased prob´s later... No indications over the central part of Germany ! 02 June, 00 + 42 ... 48 H 02 June, 12 + 30 ... 36 H ECMWF EPS probabilities for gusts > 20 m/s (03 June, 18 ... 24 UTC) ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  26. 4. Preliminary verification results • COSMO-LEPS: • still subjective verification, carried out by the medium-range • shift meteorologist • Tables: Verification against observations • Main results: • Tmin, Tmax: useful, able to add value to forecasts (improved) • Wind gusts: good, orographic effects overestimated • Conv wind gusts: signals mostly too weak (Improvement ?) • Large-scale precip: good, orographic effects overestimated • Convective precip: not useful • CAPE: still under evaluation • Snow: good, orographic effects overestimated ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  27. PEPS: • operational experimental suite since beginning of this year • Forecaster collecting experience • Set of forecasts (weather parameter, leading time) will be increased Parameter: 24h-accumutated precipitation (00 UTC +06...+30h) Observations: Max. 217 synoptical stationens of the DWD (06...06 UTC) N: Sample size POD: Probability of Detection (hit rate). Perfect score: 1 FAR: False Alarm Ratio. Perfect score: 0 HSS: Heidke Skill Score. Perfect score: 1 TS: Threat Score. Perfect score: 1 HSS=100*(a+d-R)/(a+b+c+d-R) . Obs yes Obs no fc yes a b fx no c d R=((a+b)(a+c)+(c+d)(b+d))/(a+b+c+d) TS=100*a/(a+b+c) ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  28. ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  29. ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  30. 5. Conclusions • Forecaster hat to deal with and to check a great collection of • products in a limited time frame before making a decision • EPS-products: more and more accepted by the forecaster • - content has to be condensed and compressed - products valid for different temporal and spatial scales -tailored products predicting severe weather in the meso-scale -----> COSMO - LEPS, SRNWP PEPS • preliminary verification results of COSMO - LEPS and SRNWP PEPS • encouraging (daily use by the forecaster, case studies) - COSMO - LEPS: quasi-operational use, improvements to be seen - SRNWP PEPS: experimental, first results promisingly Problem presenting EPS forecast customer-friendly not been solved ECMWF Forecast Product Users Meeting 15 - 17 June 2005

  31. That´s it ! Thank you for your attention! Headquarter of the DWD in Offenbach Central Forecasting ECMWF Forecast Product Users Meeting 15 - 17 June 2005

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