Met Office seasonal forecasting for winter 2010-11

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Met Office seasonal forecasting for winter 2010-11 Jeff Knight (with thanks to many colleagues)


The main event: December


December2010

MonthMean Temp (degC)

Feb-47 -2.0

Jan-63 -1.8

Feb-86 -1.2

Jan-40 -1.1

Feb-63 -1.1

Dec-10 -1.0

Courtesy of Mike Kendon (NCIC)

Snow at

Land’s End


December 2010: Central England Temperature series

3 voyages of Captain Cook 1768 - 1779

Monthly Mean Central England Temperature - December

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

1650 1700 1750 1800 1850 1900 1950 2000 2050

Year

Mea

n D

ecem

ber

CE

T (

deg

C)

The coldest December since 1890

The second coldest December in a series from 1659

Queen Victoria’s coronation 1838

World War 11914-1918 December 2010

Public execution of Charles 1st 1649 (only 10 years before series

starts)

Courtesy of Mike Kendon (NCIC)


UK Temperatures: recent winters


Christmas Eve 2010 Satellite Receiving Station, Dundee University

1150 GMT 7 January 2010Photo: NASA/GSFC, MODIS Rapid Response.

2009-10 and 2010-11


Met Office Winter Forecast 2010-11


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.


GloSea4 ‘November’ ensemble

GloSea4 L85DJF


Temperature terciles from Nov

L85 GloSea (1996-2009 climate)


Precipitation terciles from Nov(1996-2009 climatology)

L85 GloSea (1996-2009 Climate)


Nino3.4 plumes: GloSea4-EC-EUROSIP

Charts courtesy of ECMWF


Cluster analysisFereday 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


ND 2010 cluster frequencies

Highest number of days for ~100 and ~50 years respectively


ND 2010 Clusters


Oct-Nov North Atlantic SST

October 2011 14-21 Nov 2011


North Atlantic Sub-Surface temperature

May October

Rodwell and Folland (2002), Q. J. R. Meteorol. Soc.


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


‘Canonical’ JF La Niña clusters


Later Forecasts


JFM, FMA from preceding month

FMA

JFM

D-J-F


Stratosphere?


JF 2011 cluster frequencies


JF 2011 Clusters


Worldwide


La Niña Teleconnections• During La Niña the rainfall that normally falls out o

ver the Pacific shifts west


Global precipitation


Queensland


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, ...


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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


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Met Office seasonal forecasting for winter 2010-11

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