This climate highlight deals with the change in values of Southern Oscillation Index (SOI) and Pacific North American Index (PNA) from May to October for the past 52 years. These values were found courtesy of the Climate Diagnostics Center.
In the table below, the PNA and SOI values are not the actual data values. These values represent a difference between the two indices pertaining to the May and October values for that particular year. The numbers listed in the column entitled “Rank” are the rankings of the following winters. The values were then plotted with the appropriate ranking.
| May-Oct
|
PNA |
SOI |
Rank | May-Oct
|
PNA |
SOI | Rank | |
|
1951 |
-0.9 |
-0.6 |
44 |
1976 |
-1.6 |
0.6 |
1 |
|
|
1952 |
2.1 |
-0.7 |
51 |
1977 |
0.1 |
-0.6 |
2 |
|
|
1953 |
0.8 |
1.9 |
49 |
1978 |
2.1 |
-0.1 |
9 |
|
|
1954 |
-2.1 |
0.4 |
27 |
1979 |
1.6 |
1.8 |
27 |
|
|
1955 |
-2.7 |
1.2 |
24 |
1980 |
1 |
0.4 |
14 |
|
|
1956 |
0.9 |
2 |
37 |
1981 |
-0.9 |
-2 |
10 |
|
|
1957 |
-1.9 |
-0.2 |
32 |
1982 |
-1.7 |
-0.7 |
48 |
|
|
1958 |
-0.6 |
1.4 |
5 |
1983 |
-0.6 |
-0.5 |
26 |
|
|
1959 |
-0.7 |
0 |
45 |
1984 |
-2.4 |
0.3 |
35 |
|
|
1960 |
2.2 |
-1.4 |
8 |
1985 |
-0.6 |
-1 |
16 |
|
|
1961 |
-0.6 |
0.1 |
16 |
1986 |
-1.7 |
1 |
24 |
|
|
1962 |
-0.2 |
-1.1 |
3 |
1987 |
3.8 |
0.1 |
27 |
|
|
1963 |
0.2 |
-1.7 |
13 |
1988 |
-1.3 |
1.5 |
33 |
|
|
1964 |
0 |
-0.4 |
18 |
1989 |
-0.6 |
0.8 |
22 |
|
|
1965 |
0.7 |
-0.6 |
33 |
1990 |
1.2 |
-1.1 |
46 |
|
|
1966 |
1.4 |
-0.4 |
30 |
1991 |
-1.6 |
1.2 |
38 |
|
|
1967 |
0 |
-0.3 |
11 |
1992 |
-1.8 |
1 |
21 |
|
|
1968 |
0.9 |
-1.4 |
20 |
1993 |
2.2 |
-0.7 |
3 |
|
|
1969 |
-1.3 |
-0.1 |
6 |
1994 |
0.2 |
-0.8 |
42 |
|
|
1970 |
0.4 |
0.7 |
12 |
1995 |
2.2 |
-2.1 |
15 |
|
|
1971 |
0.6 |
1.6 |
31 |
1996 |
-0.1 |
0.5 |
47 |
|
|
1972 |
1.2 |
-0.4 |
36 |
1997 |
-1.6 |
0.9 |
52 |
|
|
1973 |
0 |
-0.4 |
38 |
1998 |
3.3 |
0 |
50 |
|
|
1974 |
2 |
-0.2 |
43 |
1999 |
-0.5 |
0.3 |
40 |
|
|
1975 |
-0.7 |
-0.6 |
22 |
2000 |
1.2 |
0.3 |
19 |
|
|
|
|
|
|
2001 |
1.3 |
0.8 |
53 |
|
|
|
|
|
|
2002 |
1.6 |
-2.1 |
7 |
|
|
|
|
|
|
2003 |
-0.5 |
0.6 |
|
In the following image, PNA differences from May to October are on the x-axis and SOI differences are on the y-axis. The years when the PNA and SOI differences were positve tended to be mild and the years when the values were negative tended to be cold. In 2003, the SOI difference was positive while the change in PNA was negative, and therefore is predicted to be slightly on the cold side. 2003 is marked on the graph with the year above the data point.