# Sunday, January 10, 2010
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Following is a chart comparing the 2009-10 El Niño to other warm ENSO episodes that have occurred since 1950. The warm episodes are based on the Oceanic Niño Index (ONI) and are those specified in the CPC's tabulation of Cold & Warm Episodes by Season. A description of the parameters follows the chart. With the exception of 1951-52, a GWO phase space plot is included for each warm episode. Data for 2009-10 will be updated periodically.

Year Nov-Mar
AAM
Peak MEI Peak MEI Season Peak
ONI
Peak ONI Season L.A. Rain GWO
Phase Plot
1951-521 -- 0.856 JULAUG 0.8 SON 26.21 --
1957-582 0.773 1.470 DECJAN, JANFEB 1.7 DJF 21.13 Click for Nov-Mar GWO Phase Space Plot
1963-64 0.046 0.858 OCTNOV, DECJAN 1.0 OND, NDJ 7.93 Click for Nov-Mar GWO Phase Space Plot
1965-66 -0.748 1.485 JULAUG 1.6 OND, NDJ 20.44 Click for Nov-Mar GWO Phase Space Plot
1968-69 0.513 0.834 JANFEB 1.0 DJF, JFM 27.47 Click for Nov-Mar GWO Phase Space Plot
1972-733 -0.239 1.804 JUNJUL 2.1 NDJ 21.26 Click for Nov-Mar GWO Phase Space Plot
1976-77 -0.828 1.046 AUGSEP 0.8 OND 12.31 Click for Nov-Mar GWO Phase Space Plot
1977-78 1.008 1.007 SEPOCT, OCTNOV 0.7 OND, NDJ, DJF 33.44 Click for Nov-Mar GWO Phase Space Plot
1982-83 2.337 3.109 FEBMAR 2.3 NDJ, DJF 31.25 Click for Nov-Mar GWO Phase Space Plot
1986-874 0.019 2.128 APRMAY 1.3 JFM 7.66 Click for Nov-Mar GWO Phase Space Plot
1987-884 1.000 2.013 JULAUG 1.6 JAS, ASO 12.48 Click for Nov-Mar GWO Phase Space Plot
1991-92 0.808 2.246 MARAPR 1.8 DJF 21.00 Click for Nov-Mar GWO Phase Space Plot
1994-95 0.764 1.346 SEPOCT 1.3 NDJ 24.35 Click for Nov-Mar GWO Phase Space Plot
1997-98 1.481 2.882 JULAUG 2.5 OND, NDJ 31.01 Click for Nov-Mar GWO Phase Space Plot
2002-03 0.324 1.230 DECJAN 1.5 OND 16.49 Click for Nov-Mar GWO Phase Space Plot
2004-05 0.747 0.924 FEBMAR 0.9 ASO 37.96 Click for Nov-Mar GWO Phase Space Plot
2006-07 -0.322 1.288 OCTNOV 1.1 OND, NDJ 3.21 Click for Nov-Mar GWO Phase Space Plot
2009-105 0.304 1.502 JANFEB 1.8 NDJ 16.36 Click for Nov-Mar GWO Phase Space Plot
1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. AAM anomaly is average for Jan-Mar 1958.
3. Several MEI values were near 1.8 during 1972-73.
4. Continuous episode from JAS 1986 to JFM 1988.
5. Data as of June 30, 2010.

Nov-Mar AAM: The mean of the global relative atmospheric angular momentum anomaly for the period November 1 to March 31 of the following year. Data is from the GWO phase space data file linked on the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Peak MEI: The peak seasonal value of the Multivariate ENSO Index (MEI). Reference Wolter and Timlin, 1993, 1998.

Peak MEI Season: The peak bi-monthly season(s) for which the MEI is computed.

Peak ONI: The peak Oceanic Niño Index (ONI) based on SST anomalies in the Niño 3.4 region. Reference Climate Prediction Center Cold & Warm Episodes by Season (1971-2000 climatology).

Peak ONI Season: The peak tri-monthly season(s) for which the ONI is computed.

L.A. Rain: The water year precipitation total in inches for Downtown Los Angeles (USC). Reference NWS Los Angeles/Oxnard Downtown Los Angeles Climate Page, 1921-2006 Water Year Rainfall.

GWO Phase Space Plot: Plot of global relative atmospheric angular momentum anomaly vs. global relative atmospheric angular momentum tendency anomaly for the period November 1 to March 31 of the following year. Data is from the GWO phase space data file linked on the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.