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ECMWF Forecasts Laura Ferranti, Frederic Vitart and Fernando Prates

ECMWF Forecasts Laura Ferranti, Frederic Vitart and Fernando Prates . Predictability of Atlantic weather regimes for medium forecast ranges. Daily Time series of the four Euro-Atlantic weather regimes: analysis and EPS scenarios at t+7days. NAO+. NAO-. Blocking. Atl. Ridge.

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ECMWF Forecasts Laura Ferranti, Frederic Vitart and Fernando Prates

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  1. ECMWF ForecastsLaura Ferranti, Frederic Vitart and Fernando Prates

  2. Predictability of Atlantic weather regimes for medium forecast ranges

  3. Daily Time series of the four Euro-Atlantic weather regimes: analysis and EPS scenarios at t+7days NAO+ NAO- Blocking Atl. Ridge Analysis Number of scenarios Z500 Monthly mean anomalies from analysis: November 2011 December 2011 January 2012 February 2012

  4. Wind Storm 2-3 January 2012 ECMWF ANALYSIS Mslp & Winds 250hPa (kt) “...this storm was judged as the most severe for 13 years – since 26 December 1998” (south Scotland) MetOffice

  5. Metosat IR Ch 7 VT: 03Jan 2012 06 UTC Analysis: Earth-Relative wind speed (m/s). θ (c. every 2 k) and Q (g/kg) SJ ANALYSIS: System-Relative wind speed & Equiv Pot temperature ~ 850 hPa VT: 03Jan 2012 09 UTC

  6. EPS -Extreme Forecast Index 10fgZ1000 hPa EM 29@00 +144h 30@00 +120h CDFs for the EPS & M-climate (black) (24-48h)Glasgow airport VT: 20120103-20120104 Obs at 0820 UTC 31@00 +96h 01@00 +72h

  7. 01@00 +72 VT: 04 Jan 00 UTC Probability that gusts exceed 5-year return value 02@00 +48 VT: 04 Jan 00 UTC 02@00 +48 VT: 04 Jan 00 UTC Probability that Gusts exceed 10-year return value Probability that gusts exceed 5-year return value

  8. Monthly forecast performance for DJF 2012

  9. Predictions of the cold wave in February: onset 16-22/01/2012 23-29/01/2012 30/01-05/02 2012 6-12/02/2012 Verifying anomalies Forecast day12-18 Forecast day19-25

  10. Predictability of the Cold event in Feb 2012 Sensitivity experiments to investigate the sources of predictability of the cold event in February: 51 member 32-day T255L91 coupled from day 0 for 2 starting dates 5th and 9th Jan 2012 : - Control experiment - IFS forced by observed SST/Sea Ice - Stratosphere relaxed to operational analysis - Tropics (20N-20S) relaxed to operational analysis

  11. 2-metre temperature anomalies IFS forced by observed SST and sea-ice 30/01-05/02 2012 Verifying anomalies Start date: 05/01 Forecast day 26-32 Stratosphere relaxed to analysis Tropics relaxed to analysis

  12. NW Iberian PeninsulaPPN time series ( normal )

  13. 05-11/12/2011 12-18/12/2011 19-25/12/2011 26/12-01/01/2012 Verifying anomalies Forecast day12-18 Forecast day19-25

  14. 02-08/01/2012 09-15/01/2012 16-22/01/2012 23-29/01/2012 Verifying anomalies Forecast day12-18 Forecast day19-25

  15. 30/01-05/02/2012 06-12/02/2012 13-19/02/2012 20-26/02/2012 Verifying anomalies Forecast day12-18 Forecast day19-25

  16. Conclusions: “The most severe storm for 13 years” in Scotland was well predicted 3-2 days in advance by the EPS. The Extreme Forecast Index (EFI) and probabilities for very unusual wind gusts thresholds provided reliable information at this forecast time range. The onset of the cold event in February was well predicted at day 12-18 while its demise was persisted for a further week. Sensitivity experiments indicate that the larger contribution to the cold Feb conditions over Western Europe is associated with tropical variability. The persistence of dry-than-normal conditions was well predicted at day 12-19 in SW Europe for December and January but poor during late January and February.

  17. Seasonal forecast performance for DJF 2012

  18. NINO 3.4 past predictions

  19. 2mt predictions for DJF 2012:init.date:1Nov2011 Verifying anomalies ECMWF Ens. Mean anomalies AGCM forced by SST (S3) EUROSIP Ens. Mean anomalies

  20. Z500 Predictions for DJF 2012:Init.date:1Nov2011 ECMWF Ens. Mean Anom. Verifying anomalies DJF 2012 EUROSIP Ens. Mean Anom.

  21. Z500 Predictions for DJF 2012 Init.date:1Nov2011 Nov 2011 Dec 2011- Jan 2012 Jan –Feb 2012 Verifying anomalies: ECMWF Ens. M. anom :

  22. Z500 Predictions for DJF 2012 Init. date: 1 Dec 2011 Dec 2011 JF 2012 Verifying anomalies: ECMWF Ens. M. anom :

  23. Anomaly correlations of forecasts initiated withfour Atlantic regimes: All forecast in the seasons Nov- April 2008-2011 + Nov-March 2012 Thanks to Martin Janousek

  24. RMSE/sda Persistence distribution 1-4 5-8 9-12 13-16 >17days Thanks to Martin Janousek

  25. Predictive skill of the Euro-Atlantic regimes in the monthly forecastBrier Skill Scores : Red values are the BSS from the persisting the preceding week Blue values are the BSS from System 3 [ From Susanna Corti]

  26. Conclusions: Overall the temperature anomalies for DJF were well predicted by the seasonal forecast. ECMWF and Eurosip systems overestimated the teleconnections associated with La Niña. The onset of the cold event in February was well predicted at day 12-18 while its demise was persisted for a further week. Sensitivity experiments indicate that the larger contribution to the cold Feb conditions over Western Europe is associated with tropical variability. An experiment with an ocean mixed layer show a further cooling in SST and 2m temp for the cold event in Feb. .

  27. Conclusions: There is skill in predicting the Euro-Atlantic weather regimes up to day 15-21 in the monthly forecast and up to month 1 in the seasonal forecast. Sys4 skill is improved with respect to Sys3 for all the regimes. Flow dependent scores indicate that forecast initiated in blocking conditions have less skill than the forecast initiated in NAO- conditions. Further assessment is in progress.

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