# Monday, April 15, 2019
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The following chart compares various climate parameters for warm ENSO episodes that have occurred since 1950. The warm episodes are based on the revised Oceanic Niño Index (ONI) which is calculated using the three month running mean of ERSST.v5 SST anomalies in the Niño 3.4 region with multiple-centered 30 year base periods. Unless noted the warm episodes 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 years prior to 1957, a Nov-Mar GWO phase space plot is included for each warm episode.

Year Jul-Sep
AAM
Nov-Mar
AAM
Peak MEI Peak MEI Season Peak
ONI
Peak ONI Season L.A. Rain GWO
Phase Plot
1951-521 -- -- 0.82 JULAUG 1.2 SON 26.21 --
1952-532 -- -- 0.76 APRMAY 0.8 AMJ-MJJ 9.46 --
1953-542 -- -- 0.48 AUGSEP 0.8 SON-DJF 11.99 --
1957-583,4 -- 0.78 1.47 DECJAN, JANFEB 1.8 DJF 21.13 Click for Nov-Mar GWO Phase Space Plot
1958-594 -0.92 -0.21 0.81 JANFEB 0.6 NDJ, DJF, JFM 5.58 Click for Nov-Mar GWO Phase Space Plot
1963-64 0.01 0.05 0.88 OCTNOV, DECJAN 1.4 OND 7.93 Click for Nov-Mar GWO Phase Space Plot
1965-66 -0.83 -0.75 1.43 JULAUG 2.0 SON, OND 20.44 Click for Nov-Mar GWO Phase Space Plot
1968-69 0.13 0.51 0.85 JANFEB 1.1 DJF, JFM 27.47 Click for Nov-Mar GWO Phase Space Plot
1969-70 0.36 0.41 0.66 OCTNOV 0.9 SON 7.77 Click for Nov-Mar GWO Phase Space Plot
1972-73 -0.10 -0.24 1.83 JUNJUL, JULAUG 2.1 OND, NDJ 21.26 Click for Nov-Mar GWO Phase Space Plot
1976-77 0.29 -0.83 1.02 AUGSEP 0.9 OND 12.31 Click for Nov-Mar GWO Phase Space Plot
1977-78 -0.65 1.01 0.97 SEPOCT, OCTNOV 0.8 OND, NDJ 33.44 Click for Nov-Mar GWO Phase Space Plot
1979-80 0.49 -0.01 0.6 ND, MA, MJ 0.6 NDJ, DJF 26.98 Click for Nov-Mar GWO Phase Space Plot
1982-83 0.94 2.34 2.9 AM 2.2 OND,NDJ, DJF 31.25 Click for Nov-Mar GWO Phase Space Plot
1986-875 0.23 0.02 2.0 MJ87 1.2 NDJ,-JFM 7.66 Click for Nov-Mar GWO Phase Space Plot
1987-885 1.16 1.00 2.0 MJ87 1.7 JAS 12.48 Click for Nov-Mar GWO Phase Space Plot
1991-92 -0.01 0.81 2.0 MA 1.7 DJF 21.00 Click for Nov-Mar GWO Phase Space Plot
1994-95 -0.42 0.77 1.4 SO 1.1 NDJ 24.35 Click for Nov-Mar GWO Phase Space Plot
1997-98 1.82 1.49 2.3, 2.6 MJ97, MA98 2.4 OND, NDJ 31.01 Click for Nov-Mar GWO Phase Space Plot
2002-03 0.05 0.32 1.0, 0.9 JA, ND 1.3 OND 16.49 Click for Nov-Mar GWO Phase Space Plot
2004-05 -0.02 0.75 0.7, 0.8 JA04, FM05 0.7 ASO-NDJ 37.25 Click for Nov-Mar GWO Phase Space Plot
2006-07 0.14 -0.32 0.9 ON 0.9 OND-NDJ 3.21 Click for Nov-Mar GWO Phase Space Plot
2009-10 -0.10 0.30 1.1, 1.3 ON, JF-FM 1.6 NDJ 16.36 Click for Nov-Mar GWO Phase Space Plot
2014-156 -0.52 -0.29 2.2 AS15 1.2 MJJ 8.52 Click for Nov-Mar GWO Phase Space Plot
2015-166 1.34 1.64  2.2 AS15 2.6 NDJ 9.36 Click for Nov-Mar GWO Phase Space Plot
2018-197 -0.43 1.22 0.5, 0.8 AS18, FM19 0.9 OND 17.99 Click for Nov-Mar GWO Phase Space Plot

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. Continuous warm episode from JFM 1953 to JFM 1954.
3. AAM anomaly is average for Jan-Mar 1958.
4. Continuous warm episode from MAM 1957 to JJA 1958 & OND 1958 to FMA 1959.
5. Continuous warm episode from ASO 1986 to JFM 1988.
6. Continuous warm episode from OND 2014 to AMJ 2016.
7. Data as of March 31, 2019.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric angular momentum anomaly for the periods July 1 to September 30 amd November 1 to March 31 of the following year. GWO phase space data is calculated using code from 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). MEI values are v2 starting with 1979-80. MEI v1 values were last updated December 2018.

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 (Multiple centered 30-year base periods.)

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

L.A. Rain: The July-June rainfall year precipitation total in inches for Downtown Los Angeles (USC). Reference WRCC LOS ANGELES DWTN USC CAMPUS, CA. See Precipitation>Quantity>Monthly Precipitation Listings>Monthly Totals.

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 calculated using code from the Global Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann and Berry, 2008.

Monday, April 15, 2019 10:49:50 AM (Pacific Daylight Time, UTC-07:00)  #    Disclaimer  |   |