MEI Index (last update: 3 February 2010)
Bimonthly MEI values (in 1/1000 of standard deviations), starting with Dec1949/Jan1950, thru last
month. More information on the MEI can be found on the MEI homepage.
Missing values are left blank. Note that values can still change with each monthly update, even
though such changes are typically smaller than +/-0.1. All values are normalized for each bimonthly
season so that the 44 values from 1950 to 1993 have an average of zero and a standard deviation of "1".
Responses to 'FAQs' can be found below this table:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT OCTNOV NOVDEC
1950 -1.052 -1.145 -1.278 -1.037 -1.42 -1.371 -1.326 -1.107 -.609 -.381 -1.18 -1.254
1951 -1.078 -1.213 -1.218 -.457 -.266 .401 .745 .856 .819 .75 .716 .465
1952 .412 .135 .094 .22 -.308 -.685 -.285 -.194 .349 .3 -.346 -.154
1953 .011 .388 .225 .68 .825 .24 .421 .248 .553 .091 .055 .3
1954 -.047 -.039 .125 -.599 -1.465 -1.596 -1.414 -1.46 -1.174 -1.381 -1.134 -1.113
1955 -.782 -.7 -1.2 -1.652 -1.651 -2.27 -1.923 -2.022 -1.797 -1.756 -1.844 -1.865
1956 -1.429 -1.286 -1.367 -1.185 -1.362 -1.521 -1.251 -1.148 -1.381 -1.463 -1.059 -1.044
1957 -.966 -.406 .13 .389 .882 .754 .941 1.141 1.149 1.095 1.114 1.237
1958 1.478 1.47 1.34 .925 .751 .882 .687 .453 .193 .167 .466 .691
1959 .541 .804 .487 .182 .027 .006 -.179 .062 .007 -.092 -.165 -.256
1960 -.306 -.259 -.076 -.019 -.34 -.24 -.32 -.246 -.494 -.365 -.33 -.435
1961 -.175 -.238 -.038 .043 -.291 -.113 -.267 -.341 -.304 -.558 -.418 -.624
1962 -1.062 -.994 -.755 -1.034 -.92 -.829 -.721 -.53 -.522 -.664 -.614 -.502
1963 -.729 -.853 -.677 -.763 -.431 -.069 .382 .606 .753 .815 .852 .748
1964 .853 .469 -.338 -.673 -1.27 -1.094 -1.417 -1.528 -1.288 -1.215 -1.244 -.938
1965 -.571 -.309 -.216 .119 .524 .93 1.377 1.485 1.424 1.213 1.362 1.249
1966 1.303 1.183 .674 .474 -.141 -.147 -.127 .15 -.122 -.047 .027 -.172
1967 -.465 -.921 -1.071 -1.03 -.408 -.307 -.621 -.496 -.702 -.727 -.421 -.388
1968 -.622 -.758 -.624 -.968 -1.066 -.739 -.528 -.139 .186 .41 .582 .362
1969 .673 .834 .397 .584 .71 .8 .441 .215 .18 .508 .672 .381
1970 .378 .384 .181 -.077 -.153 -.687 -1.092 -1.03 -1.242 -1.095 -1.079 -1.215
1971 -1.208 -1.497 -1.793 -1.851 -1.452 -1.481 -1.226 -1.243 -1.466 -1.415 -1.33 -1.012
1972 -.6 -.373 -.212 -.125 .538 1.155 1.804 1.776 1.538 1.638 1.744 1.763
1973 1.746 1.513 .827 .495 -.124 -.79 -1.05 -1.311 -1.693 -1.667 -1.489 -1.844
1974 -1.906 -1.792 -1.706 -1.582 -1.007 -.629 -.774 -.695 -.636 -1.041 -1.256 -.934
1975 -.555 -.579 -.904 -.98 -.881 -1.173 -1.505 -1.692 -1.836 -1.976 -1.771 -1.747
1976 -1.604 -1.384 -1.266 -1.195 -.505 .292 .589 .677 1.046 .952 .459 .546
1977 .517 .285 .147 .56 .371 .491 .854 .696 .786 1.007 .981 .87
1978 .776 .898 .974 .18 -.352 -.527 -.424 -.237 -.405 -.013 .198 .407
1979 .589 .373 .009 .308 .426 .452 .389 .627 .78 .655 .741 1.006
1980 .69 .567 .699 .891 .912 .862 .821 .39 .283 .209 .249 .113
1981 -.251 -.205 .417 .635 .072 -.013 -.03 -.113 .176 .118 -.036 -.146
1982 -.263 -.175 .084 -.056 .455 .993 1.6 1.765 1.794 2.017 2.448 2.432
1983 2.703 2.962 3.109 2.994 2.555 2.203 1.781 1.229 .517 .052 -.148 -.166
1984 -.34 -.529 .17 .387 .106 -.134 -.122 -.196 -.087 .013 -.325 -.6
1985 -.561 -.6 -.732 -.477 -.738 -.122 -.181 -.416 -.554 -.151 -.071 -.306
1986 -.306 -.204 .066 -.107 .328 .308 .386 .727 1.107 1.007 .857 1.181
1987 1.253 1.174 1.714 1.878 2.128 1.92 1.855 2.013 1.886 1.637 1.254 1.267
1988 1.129 .671 .458 .288 .088 -.661 -1.115 -1.276 -1.537 -1.327 -1.46 -1.319
1989 -1.128 -1.266 -1.024 -.75 -.497 -.283 -.437 -.488 -.271 -.319 -.059 .143
1990 .233 .529 .852 .411 .572 .424 .1 .122 .389 .274 .389 .342
1991 .322 .296 .375 .35 .686 1.048 1.018 1.028 .713 1.012 1.199 1.312
1992 1.734 1.849 1.986 2.246 2.109 1.791 1.002 .589 .492 .634 .571 .62
1993 .667 .941 .956 1.38 1.983 1.531 1.142 1.054 1.001 1.081 .846 .597
1994 .38 .191 .126 .449 .618 .612 .876 .632 .649 1.346 1.245 1.189
1995 1.19 .883 .805 .342 .456 .481 .291 .065 -.361 -.442 -.492 -.502
1996 -.591 -.62 -.263 -.524 -.234 -.026 -.151 -.233 -.318 -.378 -.091 -.36
1997 -.403 -.488 -.195 .479 1.107 2.314 2.673 2.882 2.831 2.184 2.327 2.24
1998 2.424 2.663 2.635 2.553 1.964 1.11 .4 -.172 -.577 -.807 -1.1 -.967
1999 -1.05 -1.11 -.997 -.978 -.67 -.384 -.518 -.737 -.893 -.947 -1.048 -1.205
2000 -1.129 -1.186 -1.04 -.435 .016 -.267 -.211 -.145 -.229 -.324 -.725 -.625
2001 -.525 -.682 -.61 -.154 .151 -.005 .194 .321 -.21 -.33 -.248 -.048
2002 -.015 -.175 -.135 .378 .885 .838 .588 .886 .782 .901 .984 1.152
2003 1.253 .909 .794 .356 .037 .009 .028 .277 .47 .562 .536 .361
2004 .336 .361 -.131 .243 .44 .24 .471 .622 .568 .52 .816 .684
2005 .325 .742 .924 .538 .708 .46 .429 .432 .206 -.254 -.397 -.532
2006 -.383 -.464 -.611 -.646 -.02 .496 .648 .752 .868 1.014 1.288 .963
2007 .986 .491 .097 .041 .165 -.307 -.264 -.411 -1.106 -1.119 -1.134 -1.144
2008 -.965 -1.359 -1.566 -.903 -.389 .069 .041 -.174 -.554 -.728 -.547 -.626
2009 -.703 -.725 -.737 -.191 .344 .855 .897 .978 .754 .999 1.039 1.084
2010 1.157
(1) If you are trying to relate the MEI to monthly values of, say, precipitation, it may be
expedient to use the MEI value of month(i-1) and month(i) as if it were the value for
month(i) only. Since it takes a week or so for the global atmosphere to respond to tropical
SST anomalies, the resulting lag is thus built into the analysis (I have verified this for
southwest U.S. precipitation).
(2) Next update: 6 March 2010 (possibly earlier)
(3) Are there MEI values available prior to 1950? YES (I have some), and NO (I do not deem them
fit for distribution yet). However, we just submitted a paper on our extended MEI (MEI.ext)
that uses Hadley Centre reconstructed SLP and SST data back to 1871. If it gets accepted/
published, we will have a 'sister' website to the MEI that will have the MEI.ext data,
various comparison figures, and a discussion online. This paper has been tentatively
accepted, so I hope to be able to hoist the sister website in 2010.
(4) Why do I believe that the MEI is better for monitoring ENSO than the SOI or various SST
indices? In brief, the MEI integrates more information than other indices, it reflects
the nature of the coupled ocean-atmosphere system better than either component, and it is
less vulnerable to occasional data glitches in the monthly update cycles. Now, if you are
interested in ENSO impacts in a very specific part of the world, I would suggest that you
obtain other ENSO indices as well and establish which one best fits your needs.
For instance, in Australia, Darwin sea level pressure and/or the SOI may be more appropriate
than the MEI. My claim here is that the MEI does a better job than other indices for the
overall monitoring of the ENSO phenomenon, including, for instance, world-wide correlations
with surface temperatures and rainfall.
(5) I have been asked about MEI-like indices for the Indian Ocean, and at present I have no such
project under way, nor do I know of any such data.
(6) Given the integrative approach of the MEI, I am very hesitant to give out subsets of the data
that make up the MEI (for instance, its SST or SLP components alone). Therefore, I will not
honor requests of that nature.
(7) If you are interested in MEI predictions, please contact me directly under my e-mail address:
Klaus Wolter (klaus.wolter@noaa.gov).
Link to ranked MEI values is here.
Go back to MEI homepage.