HIGHLIGHT: Normals have been changed to 1981-2010, note substantial changes in the weights!!!. The Nino34 climos have gone up by about 0.1K

The seasonal mean NINO3.4 anomaly was -1.02 for FMA2011, down from JFM.  La Nina has weakened, not unusual for the season of course.

The CA method, acting on global FMA2011 seasonal means as latest input, has 100% of its members in La Nina territory only thru AMJ.  La Nina conditions, but weaker and many members not making -.5, are expected by CA for rest of 2011, with a slight increase in coolness towards the end of the year. Thus there could a weak La Nina next winter. Some members crawl into positive territory by early spring 2012.

Weights have changed because a) two months ago the matrix size has increased by one, from 53 to 54, and this resets the weights given co-linearity among years, and b) we have changed normals as of this forecast to the 1981-2010 base period. There are seven years with high +ve weight!, and six high -ve weight. OCN flavor is much reduced, with more +ve weight given to older years than before.

Table 1. Inner products (IP; scaled such that the sum of absolute values is 100; not shown) and weights (Wgt multiplied by 100.) of each of the years to construct an analogue to the sequence of 12 consecutive overlapping 3-month periods defined as the base (currently the 12 overlapping seasons string MAM2010 thru FMA2011). Years in the table are labeled by the year of the middle month of the most recent predictor season. Weights for 1956 and 2010 are less (by 50%) because only half the members use these years ("early" members use 1956, "late" members 2010). Data currently thru Apr 2011.

Year

IP

Wgt

Year

IP

Wgt

Year

IP

Wgt

Year

IP

Wgt

Year

IP

Wgt

Year

IP

Weigt

1956

xx

1

1966

xx

-12

1976

xx

 6

1986

xx

-9

1996

xx

17

2006

xx

-1

1957

xx

-5

1967

xx

-2

1977

xx

-10

1987

xx

-9

1997

xx

 9

2007

xx

-1

1958

xx

-8

1968

xx

-8

1978

xx

 2

1988

xx

-5

1998

xx

-3

2008

xx

 17

1959

xx

-4

1969

xx

11

1979

xx

 1

1989

xx

 6

1999

xx

 1

2009

xx

  5

1960

xx

-17

1970

xx

11

1980

xx

-1

1990

xx

-5

2000

xx

 9

2010

xx

10

1961

xx

-2

1971

xx

 2

1981

xx

 3

1991

xx

-1

2001

xx

-10

2011

xx

NA

1962

xx

 8

1972

xx

 1

1982

xx

 1

1992

xx

-8

2002

xx

 8

xx

Xx

1963

xx

 15

1973

xx

 1

1983

xx

-1

1993

xx

-8

2003

xx

-9

xx

Xx

1964

xx

-5

1974

xx

21

1984

xx

 0

1994

xx

-14

2004

xx

 0

xx

Xx

1965

xx

-6

1975

xx

-3

1985

xx

-11

1995

xx

-5

2005

xx

-1

xx

Xx

 

Weights are high +ve (>+0.10) for 2010,2008,1996,1974,1971,1970,1963. Weights are high -ve (< - 0.10) for 2001,1994,1985,1977,1966,1960.

Ens ave Nino34 anomaly forecasts, for leads -3, -2, -1, 0 etc: in plain numbers (ensemble mean):

-1.02

-0.97

-0.74

-0.45

-0.33

-0.25

-0.26

-0.33

-0.45

-0.48

-0.47

-0.4

-0.34

-0.26

-0.25

-0.18

-0.13

-0.01

0.06

0.11

0.12

MAM11

MJJ

JAS

SON

NDJ

JFM

MAM12

MJJ

JAS

SON

One month ago:

-1.26

-1.23

-1.01

-0.64

-0.49

-0.41

-0.36

-0.38

-0.43

-0.54

-0.54

-0.49

-0.36

-0.18

-0.06

-0.02

0.03

0.06

0.18

0.25

0.32

JFM11

MAM

MJJ

JAS

SON11

NDJ

JFM12

MAM

MJJ

JAS

Two months ago:

-1.46

-1.49

-1.33

-0.99

-0.78

-0.69

-0.67

-0.65

-0.66

-0.71

-0.79

-0.77

-0.67

-0.47

-0.27

-0.05

0.03

0.09

0.08

0.15

0.2

JFM11

MAM

MJJ

JAS

SON11

NDJ

JFM12

MAM

MJJ

JAS12

Three months ago:

-1.54

-1.62

-1.66

-1.39

-1.07

-0.83

-0.67

-0.6

-0.57

-0.59

-0.62

-0.69

-0.68

-0.5

-0.36

-0.21

-0.02

0.08

0.17

0.2

0.27

NDJ

JFM

MAM11

MJJ

JAS

SON

NDJ

JFM12

MAM

MJJ

JAS

 

Four months ago:

 

-1.54

-1.67

-1.86

-1.88

-1.47

-1.07

-0.78

-0.54

-0.38

-0.24

-0.19

-0.14

-0.16

-0.07

-0.07

-0.06

-0.02

0.11

0.23

0.33

0.36

NDJ

JFM11

MAM

MJJ

JAS

SON11

NDJ

JFM12

MAM

MJJ

 

Anomalies relative to 1981-2010 climo, as of this release. Older forecasts (1-4 months ago) are relative to 71-2000