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
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