The THORPEX Interactive Global Ensemble (TIGGE) and development of a future

1. The THORPEX Interactive Global Ensemble (TIGGE) and development of a future Global Interactive Forecast System (GIFS) GIFS-TIGGE WG report for WWRP JSC4 Richard Swinbank, with thanks to Zoltan Toth, the GIFS-TIGGE working group, THORPEX IPO and other colleagues

2. TIGGE and GIFS • TIGGE • Objectives • TIGGE archive status • TIGGE-LAM • Research using TIGGE data • Publications • Calibration & combination of ensemble forecasts • Predictability & dynamical processes • GIFS developments • Developing links with CBS/SWFDP • Examples of tropical cyclone forecast products

3. TIGGETHORPEX Interactive Grand Global Ensemble • A major component of THORPEX: a World Weather Research Programme to accelerate the improvements in the accuracy of 1-day to 2-week high-impact weather forecasts • GEO task WE-06-03 – “TIGGE and the Development of a Global Interactive Forecast System for Weather” Objectives: • Enhance collaboration on ensemble prediction, both internationally and between operational centres & universities. • Facilitate research on ensemble prediction methods, especially methods to combine ensembles and to correct systematic errors • Enable evolution towards a prototype operational system, the “Global Interactive Forecast System”

4. TIGGE data • Ten of the leading global forecast centres are providing regular ensemble predictions to support research on predictability, dynamical processes and development of probabilistic forecasting methods. • TIGGE data is made available for research after a 48-hour delay. Near real-time access may be granted for specific projects through the THORPEX International Project Office.

5. Summary of TIGGE database (late 2010) * Delivery of KMA & BoM data currently suspended

6. TIGGE Archive Usage (NCAR + ECMWF)

7. TIGGE-LAM: TIGGE for limited-area models The TIGGE-LAM panel, chaired by Tiziana Paccagnella (ARPA-SIM), supports the coordinated development of the Limited Area Model Ensemble Prediction System component of TIGGE. This Panel works in close coordination with the GIFS-TIGGE WG, in liaison with pre-existing LAM EPS initiatives and in coordination with the THORPEX regional committees. The panel facilitates the interoperability of the different modelling systems contributing to TIGGE and coordinates the archiving of limited-area ensemble forecasts – the three TIGGE archive centres have agreed to host a sub-set of high priority data Highlights: • The TIGGE LAM Panel is being restructured in Regional sub-groups to give more emphasis to the regional component of TIGGE LAM and to facilitate the focus on regional activities. European, North America and Asia sub-groups have already been formed. • The TIGGE-LAM plan is close to being finalised, and the draft version is available from the TIGGE-LAM website http://www.smr.arpa.emr.it/tiggelam/. See Tiziana’s talk for more details

8. Publicising TIGGE • Major Article in BAMS • New leaflet to publicise TIGGE to researchers • Contribution to GEO book “Crafting Geoinformation” • Tropical cyclone case study in WMO Bulletin • Update of TIGGE website

9. TIGGE Research Following the successful establishment of the TIGGE dataset, the main focus of the GIFS-TIGGE working group has shifted towards research on ensemble forecasting. Particular topics of interest include: • a posteriori calibration of ensemble forecasts (bias correction, downscaling, etc.); • combination of ensembles produced by multiple models; • research on and development of probabilistic forecast products. TIGGE data is also invaluable as a resource for a wide range of research projects, for example on dynamical processes and predictability. Up to the end of 2010, 43 articles related to TIGGE have been published in the scientific literature

10. Multi-model ensemble forecasts of T850 Demonstrates benefit of multi-model ensemble, provided that the most skilful models are used. Renate Hagedorn, ECMWF

11. Multi-model ensemble compared with reforecast calibration • Reforecast calibration gives comparable benefit to multi-model ensemble • Choice of verification data set (in this case, ERA-Interim) could have subtle but significant effect on relative benefits • Calibration could further enhance benefit of multi-model ensemble Renate Hagedorn

12. Uncalibrated precipitation forecasts Probabilistic verification • Based on ECMWF, UKMO, NCEP, 12 hour accumulations, 2 years data (autumn 2007 - autumn 2009) for UK region. • Verified against UKPP composite data; thresholds taken from one-month 5x5 gridpoint ukpp climatologies • Multimodel (pfconcat) has consistent slight advantage over single model ensembles in resolution (solid) and reliability penalty (dotted) • The overall Brier Skill Score (resolution-reliability) is negative for long lead times and high thresholds Single model ensembles Multimodel ensemble Jonathan Flowerdew, Met Office

13. Probability verification- idealised calibration • Use model climatology for forecast thresholds • Provides upper bound on benefit from calibration • Increases BSS resolution and reduces reliability penalty • Multi-model ensemble remains superior Single model ensembles Multimodel ensemble Jonathan Flowerdew, Met Office

14. Precipitation forecasts over USA • 24 hour accumulations, data from 1 July 2010 to 31 October 2010. • 20 members each from ECMWF, NCEP, UK Met Office, Canadian Meteorological Centre. • 80-member, equally weighted, multi-model ensemble verified as well. • Verification follows Hamill and Juras (QJ, Oct 2006) to avoid over-estimating skill due to variations in climatology. • Conclusions: • ECMWF generally most skillful. • Multi-model beats all. Tom Hamill

15. Forecasts of cyclone tracks Jana Čampa, Heini Wernli

16. North Atlantic eddy-driven jet “regimes” • North Atlantic eddy-driven jet profile is taken as vertically/zonally averaged low-level zonal wind in North Atlantic sector (15-75N, 300-360E) • Split into three clusters S, M, N using K-means clustering • Transition probability defined: Tom Frame, John Methven, U. Reading

17. Brier Skill Score: regime transition probabilities 3years of TIGGE data for ONDJF (2007-2010), ECMWF, UKMO, MSC

18. Blocking frequency comparison (DJF) +5 days +9 days +15 days Matsueda (2009) The state-of-the-art NWP models simulate the blocking frequency well. But models still underestimate the (extreme) blocking frequency.

19. MJO Forecast comparison - ECMWF and UKMO have a superior performance in simulating MJO. - Predicted phase speed tends to be slower than observed one. • Predicted amplitude tends to belarger than observed one. Matsueda and Endo (2011, in prep.)

20. Tropical cyclone forecasts – ensemble spread contradictions ECMWF (50 members) NCEP (20 members) Sinlaku initiated at 12UTC 10 Sep. 2008 Japan Black line: Best track Grey lines: Ensemble member Munehiko Yamaguchi Philippines Taiwan Dolphin initiated at 00UTC 13 Dec. 2008

21. ECMWF NCEP Steering vector T+0h Asymmetric propagation vector Spread grows with time Does not spread with time T+48h • SV-based perturbations better capture: • Baroclinic energy conversion within a vortex • Baroclinic energy conversion associated with mid-latitude waves • Barotropic energy conversion within a vortex • Munehiko Yamaguchi

22. Comparisons of TC track forecasts • NOAA developing EnKF for eventual operational use in hybrid EnKF/variational data assimilation system. • Early June 2010 through end of October 2010; verification against “best track” information. • Out-performs NCEP operational - differences are statistically significant. • Also compares well with ECMWF (not shown) 23 Tom Hamill

23. Towards the Global Interactive Forecast System (GIFS) • Many weather forecast situations are low probability but high risk – unlikely but potentially catastrophic. Probabilistic forecasting is a powerful tool to improve early warning of high-impact events. • The objective of the GIFS is to realise the benefits of THORPEX research by developing and evaluating probabilistic products to deliver improved forecasts of high-impact weather. • As a first step, the GIFS-TIGGE working group set up a pilot project for the exchange of real-time tropical cyclone predictions using “Cyclone XML” format.

24. GIFS concept • GIFS will use global-regional-national cascade pioneered by the WMO Severe Weather Forecast Demonstration Project (SWFDP). No single “GIFS centre”. • Further development and evaluation of products will be done in conjunction with SWFDP and other regional pilot projects. • Use of web-enabled technology for generation and distribution of products.

25. GIFS development • GIFS-TIGGE WG has initiated a GIFS development project • Develop products, based on TIGGE ensembles, focused on forecasts of • Tropical cyclones • Heavy precipitation • Strong winds • Collaborate with WMO Severe Weather Forecast Demonstration Project (SWFDP) and other FDPs and RDPs to provide an environment for the evaluation of prototype products, and to ensure that products address needs of operational forecasters and end users.

26. GIFS development project interactions

27. Tropical cyclone productsfrom MRI/JMA http://tparc.mri-jma.go.jp/cyclone/

28. New tropical cyclone product:Strike probability time-series at a city Tetsuo Nakazawa

29. Summary • Since October 2006, the TIGGE archive has been accumulating regular ensemble forecasts from leading global NWP centres. • The archive is a tremendous resource for the research community at large, and in particular the science working groups of THORPEX. • Both multi-model combination of ensemble forecasts and calibration techniques can be used to enhance probabilistic forecast skill. • As the basis of the development of the future Global Interactive Forecast System, products are being developed to enhance the prediction of high-impact weather, starting with tropical cyclones. • GIFS products will be developed & evaluated in conjunction with SWFDP and other regional projects. TIGGE website: http://tigge.ecmwf.int