1. © Crown copyright Met Office Met Office seasonal forecasting for winter 2010-11 Jeff Knight (with thanks to many colleagues)

2. © Crown copyright Met Office The main event: December

3. © Crown copyright Met Office December 2010 Month Mean Temp (degC) Feb-47 -2.0 Jan-63-1.8 Feb-86-1.2 Jan-40 -1.1 Feb-63-1.1 Dec-10 Courtesy of Mike Kendon (NCIC) Snow at Land’s End

4. © Crown copyright Met Office December 2010: Central England Temperature series 3 voyages of Captain Cook 1768 - 1779 The coldest December since 1890 The second coldest December in a series from 1659 Queen Victoria’s coronation 1838 World War 1 1914-1918 December 2010 Public execution of Charles 1 st 1649 (only 10 years before series starts) Courtesy of Mike Kendon (NCIC)

5. © Crown copyright Met Office UK Temperatures: recent winters

6. © Crown copyright Met Office Christmas Eve 2010 Satellite Receiving Station, Dundee University 1150 GMT 7 January 2010 Photo: NASA/GSFC, MODIS Rapid Response. 2009-10 and 2010-11

7. © Crown copyright Met Office Met Office Winter Forecast 2010-11

8. © Crown copyright Met Office DJF Met Office Seasonal Forecast for UK Government Outlook for December 2010 – February 2011 For the period December 2010-February 2011, there is a 25% chance of mild conditions, a 30% chance of near-average and a 45% chance of cold conditions over northern Europe. For precipitation, there is a 25% chance of wet conditions, a 35% chance of near-average and a 40% chance of dry conditions over northern Europe.

9. © Crown copyright Met Office GloSea4 ‘November’ ensemble GloSea4 L85DJF

10. © Crown copyright Met Office Temperature terciles from Nov L85 GloSea (1996-2009 climate)

11. © Crown copyright Met Office Precipitation terciles from Nov (1996-2009 climatology) L85 GloSea (1996-2009 Climate)

12. © Crown copyright Met Office Nino3.4 plumes: GloSea4-EC-EUROSIP Charts courtesy of ECMWF

13. © Crown copyright Met Office Cluster analysis Fereday et al. (2008), J. Climate 6 two month seasons, 10 clusters per season North Atlantic / Europe region Clusters from observed 1850-2003 daily mean MSLP dataset For 2004 onwards use NCEP reanalysis Remove seasonal mean from NCEP MSLP Assign each field to closest cluster

14. © Crown copyright Met Office ND 2010 cluster frequencies Highest number of days for ~100 and ~50 years respectively

15. © Crown copyright Met Office ND 2010 Clusters

16. © Crown copyright Met Office Oct-Nov North Atlantic SST October 201114-21 Nov 2011

17. © Crown copyright Met Office North Atlantic Sub-Surface temperature May October Rodwell and Folland (2002), Q. J. R. Meteorol. Soc.

18. © Crown copyright Met Office Quasi-Biennial Oscillation W phase of QBO → stronger polar vortex, less chance of a stratospheric warming event So perhaps switch to zonal at end of winter? This is also the signal from La Niña

19. © Crown copyright Met Office ‘Canonical’ JF La Niña clusters

20. © Crown copyright Met Office Later Forecasts

21. © Crown copyright Met Office JFM, FMA from preceding month FMA JFM D-J-F

22. © Crown copyright Met Office Stratosphere?

23. © Crown copyright Met Office JF 2011 cluster frequencies

24. © Crown copyright Met Office JF 2011 Clusters

25. © Crown copyright Met Office Worldwide

26. © Crown copyright Met Office La Niña Teleconnections During La Niña the rainfall that normally falls out over the Pacific shifts westDuring La Niña the rainfall that normally falls out over the Pacific shifts west

27. © Crown copyright Met Office Global precipitation

28. © Crown copyright Met Office Queensland

29. © Crown copyright Met Office Conclusions GloSea4 did a reasonable job in predicting the likelihood of a cold winter In later forecasts, however, it wanted to retain the cold for too long Consistency with EuroSIP and other models Other factors such as La Niña, Atlantic SSTs and the QBO were considered alongside models Potential additional influences were the continuing low solar activity (Ineson et al., 2011), low sea-ice,...

30. © Crown copyright Met Office Advertisement For various long-range forecasts including decadal global temperature forecasts and seasonal tropical storm forecasts: http://www.metoffice.gov.uk/science/specialist/long-range For the seasonal probability maps, ENSO forecast and skill scores: http://www.metoffice.gov.uk/science/specialist/seasonal

31. © Crown copyright Met Office Questions and answers

32. © Crown copyright Met Office Title