UPDATE LONG RANGE FORECAST

FOR

2011 SOUTHWEST MONSOON RAINFALL

21st June, 2011

22-Jun-112

April

June

All India June – September Rainfall

Update for All India June – September Rainfall

All India

Long Range Forecasts Issued For

All India Season Rainfall

22-Jun-11

Forecast for the 2011 South-west monsoon

rainfall issued on 19th April, 2011

South-west monsoon season (Juneto September) rainfall for the countryas a whole most likely to be Normal(96-104% of Long Period Average(LPA)).

Quantitatively, it is likely to be 98% ofthe LPA with a model error of± 5%.

4

29th June, 2010

Monsoon So Far

IMD had forecasted that themonsoon will set over Kerala on31st May with a model error of±4 days.

Southwest monsoon overAndaman Sea was delayed byabout 10 days.

Set over Kerala on 29th May2011. 3 days before its normaldate of 1st June.

As on 20th June 2011, thenorthern limit of monsoon (NLM)passes through 22.0°N/60.0°E,Porbandar, Veraval, Dahanu,Nasik, Adilabad, Nagpur,Jabalpur, Khajuraho, Kanpur,Shahjahanpur, Mukteshwar andLat 31.0°N/ Long. 80.0°E.

Advancement of

Monsoon 2011

5

29th June, 2010

Monsoon So Far:

Cumulative Rainfall till 20th June, 2011

Regions

Cumulative

(1-20 June)

Rainfall

(% of LPA)

Country as a

whole 111

Northwest India 126

Central India 124

South Peninsula 123

North East India 91

22-Jun-116

Update for All India June – September Rainfall

All India Monthly(July & August) Rainfall

June – September Rainfall for Four Geographical Regions

All India

4 Geographical Regions

Second Stage Forecasts to be issued….

7

29th June, 2010

Second Stage Forecasts: Method….

a) Forecast update for the southwest monsoonseason (June-September) rainfall over the countryas a whole using a 6-parameter ensemblestatistical model with a model error of± 4%.

b) Forecast for the monthly rainfall over the countryas a whole for the months of July & August usingseparate principle component regression modelswith a model error of± 9%.

c) Forecasts for the southwest monsoon season(June-September) rainfall for the following fourbroad geographical regions of India using separatemultiple linear regression models with a modelerror of± 8%.

8

29th June, 2010

S.No Predictor Period F/N/U

1 North Atlantic SST December + January Favorable

2 Equatorial SE Indian Ocean SST February + March Neutral

3 East Asia Mean Sea Level

Pressure

February + March Neutral

4 North Atlantic Mean Sea Level

Pressure

May Unfavorable

5 Nino 3.4 SST Tendency (March to May) –

(December to February)Unfavorable

6 North Central Pacific wind at 1.5

Km above sea level

May Neutral

Predictors Used for the Update Forecast for the

Season (Jun-Sept) Rainfall over the Country as a Whole

9

29th June, 2010

Geographical Locations

of the 6 Predictors

10

29th June, 2010

PREDICTORS

(6)

MR MODEL

PPR

MODEL

ENSEMBLE

AVERAGE OF

BEST MODELS

ENSEMBLE

AVERAGE OF

BEST MODELS

MEAN

FORECAST

ALL POSSIBLE

MODELS

(63)

ALL POSSIBLE

MODELS

(63)

Ensemble Forecasting System for

Seasonal Rainfall over Country as a whole:

The average of the ensemble forecasts from best out of all

possible MR (multiple regression) models and that from PPR

(projection pursuit regression) models gives the final forecast.

Linear Models

Non-Linear Models

ERFORMANCE OF ENSEMBLE FORECAST SYSTEM

(1981-2010): JUNE

-25

-20

-15

-10

-5

0

5

10

15

20

251981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

YEAR

RA

INF

AL

L (

% D

EP

. F

RO

M L

PA

)

ACTUAL AVE_EMR+EPPR

22-Jun-11

Probabilistic Forecast Based on

5- Parameter Ensemble Forecasting system:

Predefined Rainfall Categories

Category Category

Deficient Less than 90%

Below Normal 90%-96%

Normal 96%-104%

Above Normal 104%-110%

Excess more than 110%

13

29th June, 2010

IMD SFM Experimental Forecast: JJAS 2011

Rainfall over country as a whole Close to Normal

22-Jun-11

National Climate Research Centers

That Provide Experimental LRF

Indian Institute of Tropical Meteorology (IITM),

Pune,

Indian Institute of Science (IISc), Bangalore,

Space Applications Centre (SAC), Ahmedabad,

National Aerospace Laboratories (NAL),

Bangalore,

Centre for Mathematical Modelling and Computer

Simulation (CMMACS), Bangalore,

National Centre for Medium Range Weather

Forecasting (NCMRWF), Noida and

Center for Development of Advanced Computing

(C-DAC), Pune.

International Climate Research Centers

That Provide Experimental LRF

22-Jun-11

World Meteorological Organization (WMO)’s Lead

Centre for Long Range Forecasting - Multi-Model

Ensemble (LRFMME), Korea

National Centers for Environmental Prediction (NCEP),

USA

International Research Institute for Climate and

Society (IRI), USA

Meteorological Office, UK, the European Center for

Medium Range Weather Forecasts (ECMWF), UK

Meteo France

The Experimental Climate Prediction Center (ECPC),

USA, and

Asian-Pacific Economic Cooperation (APEC) Climate

Centre, Korea

Experimental Forecasts from

Statistical and Dynamical Models

The experimental forecasts show

large divergence (from deficient to

excess rainfall) with dynamical

models particularly coupled models

indicating normal to excess rainfall.

Climatological Probabilities

Below NormalNormal

Normal to Above Normal

22-Jun-11

ENSO- Neutral Conditions over Pacific

oAs of Now, ENSO-Neutral

conditions prevails.

Forecast of ENSO- Neutral Conditions

oHigh probability of

ENSO- Neutral

Conditions likely to

prevail during the

monsoon season

and rest of the this

year.

22-Jun-11

Indian Ocean Dipole

Latest forecasts do not

suggest development of

either a positive or a

negative Indian Ocean

Dipole event during the

2011 monsoon season.

In the absence of strong

monsoon forcings from both

Pacific and Indian Oceans,

intraseasonal variation may

become more crucial during

this southwest monsoon

season and lead to increased

uncertainty in the monsoon

forecasts.

22-Jun-11

Years Subsequent to La Nina and Monsoon ?La Nina +1 Year ISMR

1955 110.1

1956 113.6

1957 97.6

1965 81.8

1971 104.0

1972 76.1

1974 88.0

1976 102.5

1989 100.9

1999 95.6

2008 98.3

2011 ?

EXC(>+10) 2

NOR (±10) 6

DEF (<-10) 3

Total Years 11

Two (1964 & 1971) of the 11 La Nina

years prior to 2010 was immediately

followed by El Nino years and the

nation-wide season rainfall during

both of these years was deficient

(below 90%).

The remaining 9 La Nina years were

followed by ENSO-neutral conditions.

During 8 of these ENSO-neutral

years, nation-wide monsoon season

rainfall was normal (6 years) or excess

(2 years) and during the remaining one

ENSO-neutral year (1974) it was

deficient.

31-YEAR MOVING AVERAGE OF SEASONAL

MONSOON RAINFALL

y = 2E-08x5 - 5E-06x

4 + 0.0004x

3 - 0.0085x

2 + 0.0044x

R2 = 0.7663

-4

-3

-2

-1

0

1

2

3

4

1905

1910

1915

1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

YEAR ENDING 31-YEAR SLIDING WINDOW

RA

INF

AL

L A

NO

MA

LY

(% D

EP

. F

RO

M L

PA

)

Natural Variability of Indian Summer Monsoon

Rainfall: Epochal Variation

Presently Rainfall in the Below Normal Epoch of its Natural Variability

24

25th June, 2010

Summary of the Update Forecasts for

2011 Southwest Monsoon Rainfall

i) Southwest Monsoon Season Rainfall

Rainfall over the country as a whole for the 2011 southwest monsoon season (June to September) is most likely to be below normal (90-96% of LPA).

Quantitatively, monsoon season rainfall for the country as a whole is likely to be 95% of the long period average with a model error of ±4%.

ii) Monthly (July & August) Rainfall

Rainfall over the country as a whole in themonth of July 2011 is likely to be 93% of itsLPA and that in the month of August is likelyto be 94% of LPA both with a model error of± 9 %.

25

29th June, 2010

Summary of the Update Forecasts for 2011

Southwest Monsoon Rainfall

iii)Rainfall over Broad GeographicalRegions

Over the four broad geographicalregions of the country, rainfall forthe 2011 Southwest MonsoonSeason is likely to be 97% of its LPAover North-West India, 95% of itsLPA over North-East India, 95% ofits LPA over Central India and 94%of its LPA over South Peninsula, allwith a model error of± 8 %.

Thank you