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

ECMWFODRD meeting 19-06-2009

DRD meeting, 2 July 2004

Daily Time series of the four Euro-Atlantic weather regimes: analysis and EPS scenarios at t+7days

-1.5

-1.5

1.5

1.5

1.5

1.5

1.5

1.5

ECMWF Mean of 31 Uninitialised Analyses Valid: VT:00UTC 1 December 2011 to 00UTC 31 December 2011 500hPa Geopotential/ Geopotential

-500

-80

-60

-40

-20

20

40

60

80

500

-1.5

-1.5

-1.5

-1.5

1.5

1.5

1.5

ECMWF Mean of 31 Uninitialised Analyses Valid: VT:00UTC 1 January 2012 to 00UTC 31 January 2012 500hPa Geopotential/ Geopotential

-500

-80

-60

-40

-20

20

40

60

80

500

-1.5

-1.5

1.5

1.5

ECMWF Mean of 29 Uninitialised Analyses Valid: VT:00UTC 1 February 2012 to 00UTC 29 February 2012 500hPa Geopotential/ Geopotential

-500

-80

-60

-40

-20

20

40

60

80

500

-3

-1.5

-1.5

-1.5

1.5

1.5

1.51.5

1.5

3

ECMWF Mean of 30 Uninitialised Analyses Valid: VT:00UTC 1 November 2011 to 00UTC 30 November 2011 500hPa Geopotential/ Geopotential

-500

-80

-60

-40

-20

20

40

60

80

500

Nu

mb

er

of s

cen

ario

s

NAO+Blocking

NAO-Atl. Ridge

November 2011 December 2011 January 2012 February 2012

Z500 Monthly mean anomalies from analysis:

Analysis

Wind Storm 2-3 January 2012

ECMWF ANALYSISMslp & Winds 250hPa (kt)

“...this storm was judged as the most severe for 13 years – since 26 December 1998” (south Scotland) MetOffice

SJ

Metosat IR Ch 7 VT: 03Jan 2012 06 UTC

ANALYSIS: System-Relative wind speed & Equiv Pot temperature ~ 850 hPa VT: 03Jan 2012 09 UTC

Analysis: Earth-Relative wind speed (m/s). θ (c. every 2 k) and Q (g/kg)

EPS -Extreme Forecast Index 10fgZ1000 hPa EM

CDFs for the EPS & M-climate (black)

(24-48h)Glasgow airport

VT: 20120103-20120104

31@00 +96h 01@00 +72h

30@00 +120h29@00 +144h

Obs at 0820 UTC

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 5-year return value Probability that Gusts exceed 10-year return value

Monthly forecast performance for DJF 2012

Predictions of the cold wave in February: onset

23-29/01/201216-22/01/2012 30/01-05/02 2012 6-12/02/2012Verifying anomalies

Forecast day12-18

Forecast day19-25

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

IFS forced by observed SST

and sea-ice

2-metre temperature anomalies

Forecast day 26-32

30°N

40°N

50°N

60°N

30°N

40°N

50°N

60°N

0°E20°W40°W 20°E 40°E

0°E20°W40°W 20°E 40°E

SEA-ICE cover (def)

<-10deg -10.. -6 -6.. -3 -3.. -1 -1.. 0 0.. 1 1.. 3 3.. 6 6.. 10 > 10deg

Start date: 05/01

Stratosphere relaxed to analysis

30°N

40°N

50°N

60°N

30°N

40°N

50°N

60°N

0°E 20°E 40°E

0°E 20°E 40°E

SEA-ICE cover (%)

<-10% -10.. -6 -6.. -3 -3.. -1 -1.. 0 0.. 1 1.. 3 3.. 6 6.. 10 > 10%Tropics relaxed to analysis

30°N

40°N

50°N

60°N

30°N

40°N

50°N

60°N

0°E 20°E 40°E

0°E 20°E 40°E

SEA-ICE cover (%)

<-10% -10.. -6 -6.. -3 -3.. -1 -1.. 0 0.. 1 1.. 3 3.. 6 6.. 10 > 10%

30°N

40°N

50°N

60°N

30°N

40°N

50°N

60°N

0°E 20°E 40°E

0°E 20°E 40°E

SEA-ICE cover (%)

<-10% -10.. -6 -6.. -3 -3.. -1 -1.. 0 0.. 1 1.. 3 3.. 6 6.. 10 > 10%

30/01-05/02 2012Verifying anomalies

NW Iberian PeninsulaPPN time series ( normal )

12-18/12/201105-11/12/2011 19-25/12/2011 26/12-01/01/2012

Verifying anomalies

Forecast day12-18

Forecast day19-25

09-15/01/201202-08/01/2012 16-22/01/2012 23-29/01/2012

Verifying anomalies

Forecast day12-18

Forecast day19-25

06-12/02/201230/01-05/02/2012 13-19/02/2012 20-26/02/2012

Verifying anomalies

Forecast day12-18

Forecast day19-25

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.



Seasonal forecast performance for DJF 2012



NINO 3.4 past predictions



2mt predictions for DJF 2012: init.date:1Nov2011

-2

-2

-2-2

-1

-1

-1 -0.5

-0.5 -0.5

-0.5

-0.5

-0.5

-0.2

-0.2

0.2

0.2

0.2

0.5

1

1 12

2

70°S70°S

60°S 60°S

50°S50°S

40°S 40°S

30°S30°S

20°S 20°S

10°S10°S

0° 0°

10°N10°N

20°N 20°N

30°N30°N

40°N 40°N

50°N50°N

60°N 60°N

70°N70°N

160°W

160°W 140°W

140°W 120°W

120°W 100°W

100°W 80°W

80°W 60°W

60°W 40°W

40°W 20°W

20°W 0°

0° 20°E

20°E 40°E

40°E 60°E

60°E 80°E

80°E 100°E

100°E 120°E

120°E 140°E

140°E 160°E

160°E

ECMWF Mean of 31 Uninitialised Analyses Valid: VT:00UTC 1 December 2011 to 00UTC 31 December 2011 Surface: 2 metre temperature/Surf: 2 metre temp

-20

-2

-1

-0.5

-0.2

0.2

0.5

1

2

20

Verifying anomaliesECMWF Ens. Mean anomalies

EUROSIP Ens. Mean anomaliesAGCM forced by SST (S3)



-1. 5

-1.5

-1.5

-1.5

-1.5

-1.5

-1.5

1.5

1.5

1.5

1.5

1.5

1.5

3


-500

-80

-60

-40

-20

20

40

60

80

500

Verifying anomalies DJF 2012

Z500 Predictions for DJF 2012:

Init.date:1Nov2011ECMWF Ens. Mean Anom.

EUROSIP Ens. Mean Anom.



Z500 Predictions for DJF 2012 Init.date:1Nov2011

Ensemble size = 51, climate size = 450Forecast start reference is 01/11/11Mean Z500 anomalyECMWF Seasonal Forecast

Solid contour at 1% significance levelNOV 2011System 4

60°N

60°W

90°W

120°W 120°E

90°E

60°E

0°E 150°E150°W

0°E30°W 30°E

<- 40m

- 40..- 20

- 20..- 10

- 10..- 5

- 5 .. 5

5 .. 10

10.. 20

20.. 40

> 40m


Solid contour at 1% significance levelDJ 2011/12

System 4

60°N

60°W

90°W

120°W 120°E

90°E

60°E

0°E 150°E150°W

0°E30°W 30°E

<- 40m

- 40..- 20

- 20..- 10

- 10..- 5

- 5 .. 5

5 .. 10

10.. 20

20.. 40

> 40m


Solid contour at 1% significance levelJF 2012

System 4

60°N

60°W

90°W

120°W 120°E

90°E

60°E

0°E 150°E150°W

0°E30°W 30°E

<- 40m

- 40..- 20

- 20..- 10

- 10..- 5

- 5 .. 5

5 .. 10

10.. 20

20.. 40

> 40m

Nov 2011 Dec 2011- Jan 2012 Jan –Feb 2012

-3

-1.5

-1.5

-1.5

1.5

1.5

1.51.5

1.5

3

ECMWF Mean of 30 Uninitialised Analyses Valid: VT:00UTC 1 November 2011 to 00UTC 30 November 2011 500hPa Geopotential/ Geopotential

-500

-80

-60

-40

-20

20

40

60

80

500

-1.5

-1.5

-1.5

1.5

1.5

1.5

1.5

1.5


-500

-80

-60

-40

-20

20

40

60

80

500

-1.5

-1.5

-1.5

-1.5

-1.5

1.5

1.5

1.5

1.5


-500

-80

-60

-40

-20

20

40

60

80

500

ECMWF Ens. M. anom :

Verifying anomalies:




Solid contour at 1% significance levelDEC 2011System 4

60°N

60°W

90°W

120°W 120°E

90°E

60°E

0°E 150°E150°W

0°E30°W 30°E

<- 40m

- 40..- 20

- 20..- 10

- 10..- 5

- 5 .. 5

5 .. 10

10.. 20

20.. 40

> 40m


Solid contour at 1% significance levelJF 2012

System 4

60°N

60°W

90°W

120°W 120°E

90°E

60°E

0°E 150°E150°W

0°E30°W 30°E

<- 40m

- 40..- 20

- 20..- 10

- 10..- 5

- 5 .. 5

5 .. 10

10.. 20

20.. 40

> 40m

Dec 2011

-1.5

-1.5

1.5

1.5

1.5

1.5

1.5

1.5


-500

-80

-60

-40

-20

20

40

60

80

500

-1.5

-1.5

-1.5

-1.5

-1.5

1.5

1.5

1.5

1.5


-500

-80

-60

-40

-20

20

40

60

80

500

JF 2012

Z500 Predictions for DJF 2012 Init. date: 1 Dec 2011

Verifying anomalies:

ECMWF Ens. M. anom :



Anomaly correlations of forecasts initiated withfour Atlantic regimes:

Thanks to Martin Janousek

All forecast in the seasons Nov- April 2008-2011 + Nov-March 2012



RMSE/sda

Thanks to Martin Janousek

1-4 5-8 9-12 13-16 >17days

Persistence distribution



Predictive skill of the Euro-Atlantic regimes in the monthly forecast

Brier Skill Scores :Forecast Range

All regimes NAO+ Blocking NAO- Atl.Ridge

1-7 days 0.88 0.92 0.91 0.85 0.82

5-11 days 0.35 -0.05 0.25 -0.23 0.42 0.19 0.20 -0.35 0.39 -0.08

12-18 days 0.09 -0.06 0.21 0.03 0.0 0.13 0.15 -0.17 -0.11 -0.51

15-21 days 0.07 -0.02 0.04 0.05 0.05 0.01 0.09 -0.10 -0.04 -0.12

22-28 days -0.02 -0.04 -0.06 -0.02 -0.10

19-25 days -0.03 -0.03 -0.16 -0.11 0.0

26-32 days 0.0 -0.04 -0.04 -0.04 -0.20

1-30 days 0.23 0.13 0.32 0.26 0.17 0.05 0.35 0.25 0.05 -0.07

31-60 days -0.07 -0.05 -0.11 -0.03 -0.16

Red values are the BSS from the persisting the preceding weekBlue values are the BSS from System 3 [ From Susanna Corti]

Forecast Range

All regimes NAO+ Blocking NAO- Atl.Ridge

1-7 days 0.88 0.92 0.91 0.85 0.82

5-11 days 0.35 -0.05 0.25 -0.23 0.42 0.19 0.20 -0.35 0.39 -0.08

12-18 days 0.09 -0.06 0.21 0.03 0.0 0.13 0.15 -0.17 -0.11 -0.51

15-21 days 0.07 -0.02 0.04 0.05 0.05 0.01 0.09 -0.10 -0.04 -0.12

22-28 days -0.02 -0.04 -0.06 -0.02 -0.10

19-25 days -0.03 -0.03 -0.16 -0.11 0.0

26-32 days 0.0 -0.04 -0.04 -0.04 -0.20

1-30 days 0.23 0.13 0.32 0.26 0.17 0.05 0.35 0.25 0.05 -0.07

31-60 days -0.07 -0.05 -0.11 -0.03 -0.16



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.

.



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.

Documents

ECMWF Forecasts Laura Ferranti, Frederic Vitart and Fernando Prates