Seasonal forecasts

Laura Ferrantiand the Seasonal Forecast Section

User meeting 15-17 June 2005

Outline:- Performance 2004-2005

- Drought conditions over the Iberian peninsula

- Progress with the multi-model system

- Some results from the experimentation done to test the next system (S3).

2004-2005 Performance

• Monsoon 2004

• Tropical storm activity

• Anomalously cold Feb 2005

SST SST predictions predictions for the JJA for the JJA

20042004i.c. 01/05/2004i.c. 01/05/2004

-0.5

0.5

0.5

0.51

-3

-2

-2-2

-1 -1-1

-1

-1

-1-1

1

1

1

1

1

1

1

2

60°S60°S

30°S 30°S

0°0°

30°N 30°N

60°N60°N

150°W

150°W 120°W

120°W 90°W

90°W 60°W

60°W 30°W

30°W 0°

0° 30°E

30°E 60°E

60°E 90°E

90°E 120°E

120°E 150°E

150°E 180°

180°

-8

-7

-6

-5

-4

-3

-2

-1

-1.5

-0.5

0.5

1

1.5

2

3

4

5

6

7

8JJA 2004 SST anomalyJJA 2004 SST anomalyOp. anal-era40 (1987-2001)Op. anal-era40 (1987-2001)

PrecipitationJJA 2004

-2

-1

-1

-1

-1

-1

-0.5

-0.5

-0.5

-0.5

-0.5

-0.5

-0.5

-0.5

-0.2

-0.2

-0.2

-0.2

-0.2

-0.2

-0.2

-0.2-0.2

-0.2

-0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.5

0.5

0.5

0.5

1

1

1

2

-1

-1

-1

-1

-1

-1

-1

-1-1

-1

-1

-1-1 -1

-1

-1

1

1

1

1

1

1

1

1

1

1

1

2

2

2

30°S 30°S

0°0°

30°N 30°N

0°

0° 30°E

30°E 60°E

60°E 90°E

90°E

-4

-3

-2

-1

-0.5

-0.2

0.2

0.5

1

2

3

4

GPCP anomalies (1987-2001)

Prob. for the below normal category Ensemble mean anomaly

Tropical storm activity:

Climate2004

June July August September October November

Month

0

1

2

3

4

5

6

7

8

Tro

pica

l sto

rm F

requ

ency

20041992-2003

Observed tropical storm frequency over the Atlantic:

May June July AugustMonth

0

1

2

3

4

5

6

7

8

Tro

pica

l sto

rm F

requ

ency

Over Western North Pacific:

2mt anomalies JFM 2005

January February March 2005

Seasonal forecast

performance JFM 2005

-9-6

-6

-6

-3

-3

-3

-3

-3

-3

-3

3

3

3

3

3

3

3

3

3

3

6

6

6

6

69

9

9 9

12

12

15

15

-2

-2

-1

-1

-1

-1

-1

-1

- 1

-1

1

1

1

11

1

1

1

1

2

2

30°N

60°N

180°150°W

120°W

90°W

60°W

30°W 0° 30°E

60°E

90°E

120°E

150°E

ECMWF Mean of 28 Uninitialised Analyses Valid: VT:00UTC 1 February 2005 to 00UTC 28 February 2005 500hPa geopotential height/ geopotential heig

-100

-15

-12

-9

-6

-3

3

6

9

12

15

100

Z 500 Feb 2005

Accumulated precip 1 Sept 2004 – 10 June 2005

Accumulated precip 1 Oct 2004 – 31 May 2005

% of normal

Instituto da Água, Portugal

Precipitation, Centre/South Portugal

Instituto da Água, Portugal Monthly precipitation

Accumulated

Accumulated, climate

Southern Iberian Peninsula 40-37N 9E-0W:

1 2 3 4 5 6 7 8 9 10 11 120

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10 11 120.15

0.3

0.45

0.6

0.75

0.9

1.05

1.2

s.m

.i.

Soil MoisturePrecipitation (GPCP)

20052004

200320022001

months months

Seasonal predictions of precipitations:

summer 2005 versus summer 2003

1 2 3 4 5 6 7 8 9 10 11 120

1

2

3

4

5

6

7

1 2 3 4 5 6 7 8 9 10 11 120.15

0.3

0.45

0.6

0.75

0.9

1.05

1.2

s.m

.i.

Precipitation (GPCP) Soil Moisture

20052004

200320022001

40-50N 0-15E

Probability of 2m Temp > upper tercile of the model climate

JJA 2005

JJA 2003

Ensemble size = 41, climate size = 60Forecast start reference is 01/05/05Prob(upper tercile) - 2m temperatureMétéo-France Seasonal Forecast

No significance test appliedJJA 2005System 2

30°N 30°N

45°N45°N

60°N 60°N

30°W

30°W 0°

0° 30°E

30°E

Forecast issue date: 15/05/2005

0..10% 10..20% 20..40% 40..50% 50..60% 60..70% 70..100%

Ensemble size = 41, climate size = 225Forecast start reference is 01/05/05Prob(upper tercile) - 2m temperatureUKMO Seasonal Forecast

No significance test appliedJJA 2005System 2

30°N 30°N

45°N45°N

60°N 60°N

30°W

30°W 0°

0° 30°E

30°E

Forecast issue date: 15/05/2005

0..10% 10..20% 20..40% 40..50% 50..60% 60..70% 70..100%

Probability of 2m Temp > upper tercile of the model climate for JJA 2005

Forecasts start 1 May 2005

Met Office

ECMWF

Météo France

Conclusions-Predictions of the monsoon precipitation for JJA 2004 verified well.

-Over the West Pacific basin the forecast predicted successfully higher tropical storm activity than the climatology. Over the Atlantic the forecast has not been as good.

-Beyond the first month the skill of the seasonal forecast for a single month can be limited by the chaotic nature of the atmosphere.

-Dry conditions over the Iberian Peninsula were consistently predicted since November 2004.

-For the next summer warm anomalies are predicted over the South-western Europe.

Multi-model :

• Verification of the individual multi-model component is completed this includes the original and revised Météo France system.

• Multi-model products as well as their verification is in progress.

• What issues are involved for reaching the operational status:

- A suitable hind-cast ensemble size covering the same period.

- Some coordination on how to display the products on the web.

Météo France S2

Météo France S1

Météo France S2Météo France S1

System 3 experimentation:

System 3 experimentation:

Too weak easterlies

System 3 experimentation

:

Experimentation for System 3:

• Results from coupled integrations with a more recent version of the atmospheric model (CY29R1) indicate generally a higher skill except for a specific season and location.

•This seems to be related with the mean state of the atmospheric model that tends to underestimate the easterlies over the central tropical Pacific.

•One possible solution to this problem may be a correction term during the model integration.

• Further experimentation is in progress including the testing of the latest atmospheric cycle.