Long Range Forecast 2011 Southwest Monsoon Rainfall

1. UPDATE LONG RANGE FORECAST
FOR
2011 SOUTHWEST MONSOON RAINFALL
21st June, 2011

2. Long Range Forecasts Issued For
All India Season Rainfall
All India
All India
June – September Rainfall
April
Update for All India
June – September Rainfall June
2
22-Jun-11

3. Forecast for the 2011 South-west monsoon
rainfall issued on 19th April, 2011
South-west monsoon season (June
to September) rainfall for the country
as a whole most likely to be Normal
(96-104% of Long Period Average
(LPA)).
Quantitatively, it is likely to be 98% of
the LPA with a model error of ± 5%.
22-Jun-11

4. Monsoon So Far
Advancement of  IMD had forecasted that the
monsoon will set over Kerala on
Monsoon 2011 31st May with a model error of
±4 days.
 Southwest monsoon over
Andaman Sea was delayed by
about 10 days.
 Set over Kerala on 29th May
2011. 3 days before its normal
date of 1st June.
 As on 20th June 2011, the
northern limit of monsoon (NLM)
passes through 22.0°N/60.0°E,
Porbandar, Veraval, Dahanu,
Nasik, Adilabad, Nagpur,
Jabalpur, Khajuraho, Kanpur,
Shahjahanpur, Mukteshwar and
Lat 31.0°N/ Long. 80.0°E.
4
29th June, 2010

5. Monsoon So Far:
Cumulative Rainfall till 20th June, 2011
Cumulative
(1-20 June)
Regions
Rainfall
(% of LPA)
Country as a
111
whole
Northwest India 126
Central India 124
South Peninsula 123
North East India 91
5
29th June, 2010

6. Second Stage Forecasts to be issued….
All India
Update for All India
June – September Rainfall
All India Monthly
(July & August) Rainfall
4 Geographical Regions
June – September Rainfall for
Four Geographical Regions
6
22-Jun-11

7. Second Stage Forecasts: Method….
a) Forecast update for the southwest monsoon
season (June-September) rainfall over the country
as a whole using a 6-parameter ensemble
statistical model with a model error of ± 4%.
b) Forecast for the monthly rainfall over the country
as a whole for the months of July & August using
separate principle component regression models
with a model error of ± 9%.
c) Forecasts for the southwest monsoon season
(June-September) rainfall for the following four
broad geographical regions of India using separate
multiple linear regression models with a model
error of ± 8%.
7
29th June, 2010

8. Predictors Used for the Update Forecast for the
Season (Jun-Sept) Rainfall over the Country as a Whole
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 February + March Neutral
Pressure
4 North Atlantic Mean Sea Level May Unfavorable
Pressure
5 Nino 3.4 SST Tendency (March to May) – Unfavorable
(December to February)
6 North Central Pacific wind at 1.5 May Neutral
Km above sea level
8
29th June, 2010

9. Geographical Locations
of the 6 Predictors
9
29th June, 2010

10. Ensemble Forecasting System for
Seasonal Rainfall over Country as a whole:
Linear Models
ALL POSSIBLE ENSEMBLE
MR MODEL MODELS AVERAGE OF
(63) BEST MODELS
PREDICTORS MEAN
(6) FORECAST
PPR ALL POSSIBLE ENSEMBLE
MODEL MODELS AVERAGE OF
(63) BEST MODELS
Non-Linear Models
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.
10
29th June, 2010

11. RAINFALL (% DEP. FROM LPA)
-25
-20
-15
-10
-5
0
5
10
15
20
1981 25
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
YEAR
1997
1998
1999
(1981-2010): JUNE
2000
ACTUAL
2001
2002
2003
2004
2005
2006
2007
AVE_EMR+EPPR
2008
2009
2010
ERFORMANCE OF ENSEMBLE FORECAST SYSTEM

12. 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%
22-Jun-11

13. IMD SFM Experimental Forecast: JJAS 2011
Rainfall over country as a whole Close to Normal
13
29th June, 2010

14. 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.
22-Jun-11

15. International Climate Research Centers
That Provide Experimental LRF
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
22-Jun-11

16. 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.

18. Climatological Probabilities Normal to Above Normal
Normal Below Normal

19. ENSO- Neutral Conditions over Pacific
oAs of Now, ENSO-Neutral
conditions prevails.
22-Jun-11

20. Forecast of ENSO- Neutral Conditions
oHigh probability of
ENSO- Neutral
Conditions likely to
prevail during the
monsoon season
and rest of the this
year.

21. 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

22. Years Subsequent to La Nina and Monsoon ?
La Nina +1 Year ISMR
1955 110.1 Two (1964 & 1971) of the 11 La Nina
1956 113.6 years prior to 2010 was immediately
1957 97.6 followed by El Nino years and the
1965 81.8
nation-wide season rainfall during
both of these years was deficient
1971 104.0
(below 90%).
1972 76.1
1974 88.0
1976 102.5 The remaining 9 La Nina years were
followed by ENSO-neutral conditions.
1989 100.9
1999 95.6
2008 98.3 During 8 of these ENSO-neutral
2011 ? years, nation-wide monsoon season
EXC(>+10) 2
rainfall was normal (6 years) or excess
(2 years) and during the remaining one
NOR (±10) 6
ENSO-neutral year (1974) it was
DEF (<-10) 3 deficient.
Total Years 11
22-Jun-11

23. Natural Variability of Indian Summer Monsoon
Rainfall: Epochal Variation
31-YEAR MOVING AVERAGE OF SEASONAL
4
MONSOON RAINFALL
3
RAINFALL ANOMALY
(% DEP. FROM LPA)
2
1
0
-1
-2
-3 y = 2E-08x 5 - 5E-06x 4 + 0.0004x 3 - 0.0085x 2 + 0.0044x
2
R = 0.7663
-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
Presently Rainfall in the Below Normal Epoch of its Natural Variability

24. 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 the
month of July 2011 is likely to be 93% of its
LPA and that in the month of August is likely
to be 94% of LPA both with a model error of
± 9 %.
24
25th June, 2010

25. Summary of the Update Forecasts for 2011
Southwest Monsoon Rainfall
iii)Rainfall over Broad Geographical
Regions
Over the four broad geographical
regions of the country, rainfall for
the 2011 Southwest Monsoon
Season is likely to be 97% of its LPA
over North-West India, 95% of its
LPA over North-East India, 95% of
its LPA over Central India and 94%
of its LPA over South Peninsula, all
with a model error of ± 8 %.
25
29th June, 2010

26. Thank you