HIGHLIGHT: The seasonal mean NINO3.4 anomaly was positive at 0.57 C for JFM2015, almost unchanged from DJF, and the fifth running 3-month mean > = 0.5C.

The CA method, acting on global JFM2015 seasonal means as latest input, but using a string of global SST going back one year, has all of its members, with exception of one, staying positive until the end of 2015. By MAM most of its members will have fallen slightly below 0.5C, but then rise again. By SON 2015 at least half of the members are >0.50 and one member is above 1.0. By OND the ensemble mean is above 0.5. No members indicate La Nina.

Weights were stable from last month. There are 5 (5) large +ve (-ve) weights in excess of abs(0.10). Four years in the 1957-1966 decade have unusually high weights (like 1959 +0.17 and 1965 -0.17) – this old decade has only recently become so important in constructing the analogue. Moreover, 1958, 1959 and 1960 are ALL strongly positive and 1964-1967 all strongly -ve, so in addition to interannual, the interdecadal plays a big role here. Noteworthy is also the high weight for 2014. Last year is used in only 6 of the 12 construction so 0.17 is doubly impressive. In the 6 constructions 2014 was used in the weight was an unheard of 0.35. The forecast should thus be considered a warning, namely that the warm event currently shaping up has a good chance evolving the same way as last year (and stay weak).

Announcement: As of last month the covariance matrix has been upped by one. This could lead, potentially, to rather big changes to weights assigned to individual years. But that did not happen. If weights were unchanged they moved forward into the next year, given conventions etc.

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 FMA2014 thru JFM2015). Years in the table are labeled by the year of the middle month of the most recent predictor season. Weights for 1956 and 2014 are less (by 50%) because only half the members use these years ("early" members use 1956, "late" members 2014). Data currently thru Mar 2015. This month the year 2014 has, for the first time, a weight in this table.

Year	IP	Wgt	Year	IP	Wgt	Year	IP	Wgt	Year	IP	Wgt	Year	IP	Wgt	Year	IP	Weigt
1956	xx	-6	1966	xx	-13	1976	Xx	-3	1986	xx	7	1996	xx	3	2006	xx	0
1957	xx	-1	1967	xx	-4	1977	Xx	2	1987	xx	-1	1997	xx	8	2007	xx	-5
1958	xx	15	1968	xx	1	1978	Xx	7	1988	xx	-10	1998	xx	-5	2008	xx	-2
1959	xx	17	1969	xx	-9	1979	Xx	-12	1989	xx	-7	1999	xx	-2	2009	xx	1
1960	xx	8	1970	xx	-3	1980	Xx	9	1990	xx	-2	2000	xx	-16	2010	xx	6
1961	xx	-2	1971	xx	1	1981	Xx	1	1991	xx	8	2001	xx	-4	2011	xx	0
1962	xx	4	1972	xx	-8	1982	Xx	-4	1992	xx	3	2002	xx	1	2012	xx	12
1963	xx	4	1973	xx	4	1983	xx	-4	1993	xx	0	2003	xx	17	2013	xx	1
1964	xx	-9	1974	xx	0	1984	Xx	2	1994	xx	8	2004	xx	0	2014	xx	17
1965	xx	-17	1975	xx	7	1985	Xx	-7	1995	xx	2	2005	xx	3	2015	xx	NA

Weights are high +ve (>+0.10) for 2014,2012,2003,1959,1958

Weights are high -ve (< - 0.10) for 2000,1988,1979,1966,1965

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

0.57	0.51	0.42	0.34	0.36	0.32	0.22	0.24	0.38	0.56	0.61	0.57	0.5	0.49	0.43	0.29	0.14	0.06	0.14	0.17	0.17
JFM15		MAM		MJJ		JAS		SON		NDJ		JFM16		MAM		MJJ		JAS		SON

One month ago:

0.62	0.58	0.46	0.35	0.33	0.34	0.3	0.2	0.18	0.26	0.35	0.35	0.25	0.27	0.25	0.25	0.24	0.19	0.17	0.24	0.27
	JFM15		MAM		MJJ		JAS		SON15		NDJ		JFM16		MAM		MJJ		JAS

Two months ago:

0.76	0.72	0.59	0.34	0.28	0.23	0.22	0.19	0.12	0.09	0.14	0.19	0.17	0.05	-0.04	0	0.08	0.12	0.12	0.11	0.18
NDJ		JFM15		MAM		MJJ		JAS		SON15		NDJ		JFM16		MAM		MJJ		JAS

Three months ago:

0.75	0.77	0.68	0.5	0.32	0.25	0.19	0.19	0.17	0.15	0.13	0.21	0.25	0.14	-0.01	-0.06	0.01	0.11	0.14	0.11	0.05
	NDJ		JFM15		MAM		MJJ		JAS		SON15		NDJ		JFM16		MAM		MJJ

Four months ago

0.6	0.66	0.78	0.76	0.63	0.46	0.38	0.29	0.25	0.17	0.17	0.18	0.25	0.25	0.19	0.07	0.02	0.09	0.16	0.12	-0.02
SON		NDJ		JFM15		MAM		MJJ		JAS		SON15		NDJ		JFM16		MAM		MJJ

Anomalies relative to 1981-2010 climo.