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MEI Analogs


SACRUS

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it looks like 2014 had the highest rise in mei from mar/apr to apr/may period...

year...APR/MAY MEI/ increase

1957...+0.901.....+0.550

1965...+0.521.....+0.419

1972...+0.478.....+0.683

1982...+0.445.....+0.407

1986...+0.488.....+0.322

1993...+1.992.....+0.692

1997...+1.121.....+0.624

2000...+0.188.....+0.709

2002...+0.801.....+0.459

2012...+0.730.....+0.669

2014...+0.932.....+0.780

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MEI Values May/Jun: .878

Closest actuals:

 

2002: .882

1958: .893

1980: .855

2009: .934

1982: .954

 

 

Closest trends based on prior 6 mos;

 

2014 -.318 -.269 -.017 .152 .932 .878

 

2002 -.053 -.213 -.201 .342 .801 .882

1982 -.284 -.15 .086 -.038 .407 .954

2009 -.755 -.72 -.719 -.157 .375 .934

1965 -.522 -.323 -.249 .102 .521 .944

1957 -.948 -.35 .156 .351 .901 .768

1994 .334 .191 .159 .426 .531 .764
 

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  • 4 weeks later...

MEI Values Jun/Jul: .815

Closest actuals:

 

1994: .835
1977: .858

1951: .715

1958: .711

1957: .924
2009: .949
1992: .952
 

 

 

Closest trends based on prior 6 mos;

 

2014 -.318 -.269 -.017 .152 .932 .878 .815

 

2002 -.053 -.213 -.201 .342 .801 .882 .613

2009 -.755 -.72 -.719 -.157 .375 .934 .949

1957 -.948 -.35 .156 .351 .901 .768 .924

1982 -.284 -.15 .086 -.038 .407 .954 1.625

1963 -.701 -.838 -.696 -.814 -.477 -.052 .445 .63

 

 

 

 

 

2002 -.053 -.213 -.201 .342 .801 .882

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  • 5 weeks later...

MEI Values Jul/Aug: .858

Closest actuals:

 

1951: .847

1986: .811

2002: .928

2009: .957

2006: .760

1993: 1.006

1977: .689

 

 

Closest trends based on prior  mos;

 

2014 -.318 -.269 -.017 .152 .932 .878 .816 .858
 

1986 -.309 -.194 .033 -.166 .322 .316 .389 .811

2006 -.474 -.457 -.591 -.686 -.018 .565 .637 .76

2009 -.755 -.72 -.719 -.157 .375 .934 .949 .957

2002 -.053 -.213 -.201 .342 .801 .882 .613 .928

1951 -1.069 -1.193 -1.208 -.439 -.305 .438 .715 .847

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highest mei winters...Highest index and period...Dec/Jan mei...Max oni and period...DJF oni...snowfall and biggest snowfall...average temperature...

.

el nino winters rated by the mei index...2014 last reading was +0.858...

winter.....max mei date D/J mei.....max oni date DJF oni.....snowfall.....big snow ave temp

1982-83...3.038 F/M...2.689..........2.2 NDJ..........2.2..........27.2".....17.6".....37.9

1997-98...3.004 J/A....2.481..........2.4 OND.........2.2...........5.5".......5.0".....39.6

1991-92...2.271 M/A...1.751..........1.6 DJF..........1.6..........12.6".......6.2".....37.2

1986-87...2.131 A/M...1.235..........1.3 JFM..........1.2..........23.1".......8.1".....34.8

1992-93...1.992 A/M...0.700..........0.6 MAM.........0.2..........24.5".....10.6".....35.0

1987-88...1.956 J/A....1.089..........1.6  ASO.........0.8.........19.1".......5.7".....34.7

1972-73...1.944 N/D...1.705..........2.1 OND.........1.8............2.8".......1.8".....35.8

 

2009-10...1.517 J/F....1.148..........1.6 NDJ..........1.6..........51.4".....20.9".....33.8

1965-66...1.477 J/A....1.322..........1.9 OND.........1.4..........21.4".......6.8".....35.9

1957-58...1.474 D/J....1.474..........1.8 NDJ..........1.8..........44.7".....11.8".....33.3

1994-95...1.434 S/O...1.197..........1.2 NDJ..........1.0..........11.8".....10.8".....37.1

2006-07...1.290 O/N...0.970..........1.0 OND.........0.7..........12.4".......5.5".....36.5

2002-03...1.180 D/J....1.180..........1.3 OND.........1.1..........49.3".....19.8".....31.2

1976-77...1.026 A/S...0.517..........0.8 OND.........0.6..........24.5".......5.2".....28.5

 

2004-05...1.018 F/M...0.296.........0.7 OND.........0.6..........41.0".....13.8".....35.4

1979-80...1.015 N/D...0.694.........0.6 NDJ..........0.5..........12.8".......4.6".....35.4

1977-78...1.007 S/O...0.779.........0.8 NDJ..........0.7..........50.7".....17.7".....30.3

1989-90...0.916 F/M...0.232........-0.1 NDJ.........-0.1..........13.4".......4.7".....35.7

1968-69...0.866 J/F....0.689.........1.1 DJF..........1.1...........30.2".....15.3".....32.9

1963-64...0.856 D/J....0.856.........1.4 OND.........1.1...........44.7".....12.5".....33.3

1951-52...0.847 J/A....0.408.........1.2 SON.........0.6..........19.7".......5.5".....37.0

 

1958-59...0.804 J/F....0.577.........0.6 NDJ..........0.6..........13.0".......5.5".....30.9

1969-70...0.645 O/N...0.357.........0.8 NDJ.........0.6..........25.6".......6.8".....30.5

1978-79...0.598 D/J....0.598........-0.1 NDJ........-0.1..........27.2".....12.7".....32.7

2003-04...0.519 O/N...0.304.........0.3 NDJ.........0.3..........42.6".....14.0".....32.4

1990-91...0.393 F/M...0.308.........0.4 NDJ.........0.3..........24.9".......8.9".....39.2

1952-53...0.382 J/F....0.022.........0.7 MAM........0.5..........15.1".......4.2".....38.1

1993-94...0.334 D/J....0.334.........0.1 NDJ..........0.1..........53.4".....12.8".....31.2

1953-54...0.314 N/D..-0.049.........0.8 OND.........0.7..........15.8".......7.9".....37.4

 

2014-15...0.932 A/M...???.......................................................................

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MEI Values Aug/Sep: .500

Closest actuals:

 

 

1992: .508

1953: .520

2004: .526

2003: .442

1983: .439

 

 

 

 

Closest trends based on prior  mos;

 

2014 -.318 -.269 -.017 .152 .932 .878 .816 .858 .5

 

2009 -.755 -.72 -.719 -.157 .375 .934 .949 .957 .77

2006 -.474 -.457 -.591 -.686 -.018 .565 .637 .76 .802

1963 -.701 -.838 -.696 -.814 -.477 -.052 .445 .626 .764

1953 .022 .382 .263 .711 .83 .227 .395 .248 .52

1992 1.751 1.872 1.992 2.271 2.141 1.74 .953 .536 .508

2004 .304 .327 -.125 .221 .495 .223 .478 .671 .526

1986 -.309 -.194 .033 -.166 .322 .316 .389 .811 1.157
 

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MEI Values Sep/Oct: .360

Closest actuals:

 

 

1952: .304

1968: .425

2004: .476

1990: .247

2003: .515

 

 

 

Closest trends based on prior  mos;

 

2014 -.318 -.269 -.017 .152 .932 .878 .816 .858 .5 .36
 

 

2004 .304 .327 -.125 .221 .495 .223 .478 .671 .526 .476

1992 1.751 1.872 1.992 2.271 2.141 1.74 .953 .536 .508 .672

2006 -.474 -.457 -.591 -.686 -.018 .565 .637 .76 .802 .899

1976 -1.626 -1.399 -1.255 -1.191 -.477 .343 .617 .668 1.024 .947

1953 .022 .382 .263 .711 .83 .227 .395 .248 .52 .091

2009 -.755 -.72 -.719 -.157 .375 .934 .949 .957 .77 1.025

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MEI Values Oct/Nov: .712

Closest actuals:

 

 

1951: .722

1979: .737

1969: .653

2004: .795

1993: .826

 

 

 

 

Closest trends based on prior  mos;

 

2014 -.318 -.269 -.017 .152 .932 .878 .816 .858 .5 .36 .712

 

2004 .304 .327 -.125 .221 .495 .223 .478 .671 .526 .476 .795

1969 .689 .866 .445 .617 .697 .799 .426 .158 .161 .504 .653

1951 -1.069 -1.193 -1.208 -.439 -.305 .438 .715 .847 .769 .743 .722

1979 .598 .361 -.011 .289 .384 .389 .355 .644 .769 .64 .737

1986 -.309 -.194 .033 -.166 .322 .316 .389 .811 1.157 .994 .867

 

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MEI Values Nov/Dec:  0.578

Closest actuals:

 

1993: 0.565

1976 : 0.552

1992: 0.642

2004: 0.647

1951: 0.466

 

 

Closest trends based on prior  mos;

 

2014   -0.318  -0.269  -0.017   0.152   0.932   0.878   0.816   0.858     0.5    0.36   0.712   0.578

 

2004    0.304   0.327  -0.125   0.221   0.495   0.223   0.478   0.671   0.526   0.476   0.795   0.647

1951   -1.069  -1.193  -1.208  -0.439  -0.305   0.438   0.715   0.847   0.769   0.743   0.722   0.466

1963   -0.701  -0.838  -0.696  -0.814  -0.477  -0.052   0.445   0.626   0.764   0.832   0.859   0.748
1976   -1.626  -1.399  -1.255  -1.191  -0.477   0.343   0.617   0.668   1.024   0.947    0.48   0.552

1992 1.751 1.872 1.992 2.271 2.141 1.74 .953 .536 .508 .672 .603 .642
1969    0.689   0.866   0.445   0.617   0.697   0.799   0.426   0.158   0.161   0.504   0.653   0.383


 

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MEI Values Dec/Jan: .406

Closest actuals:

 

 

1952: .403

1970: .361

1994: .340

1991: .312

2004:  .310

1977: .518

 

 

Closest trends based on prior  mos;

 

Year      JUNJUL  JULAUG  AUGSEP  SEPOCT  OCTNOV  NOVDEC DECJAN

 

2014   .816 .858 .500 .360 .712 .578 .406

 

 

1951 .715 .847 .769 .743 .722 .466
1952 .403 .

 

1990 ..43 .093 .126 .376 .247 .378 .339
1991 .312

 

1969 .426 .158 .161 .504 .653 .383
1970 .361

 

2003 .048 .093 .246 .442 .515 .528 .319
2004 .31

 

1978  -.407 -.193 -.386 -.023 .197 .399
1979 .596

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MEI Values Jan/Feb: .468

Closest actuals:

 

1964: .439

1990 : .524

1970: .410

1953: .375

1979: .354

1980: .611

 

 

 

 

Closest trends based on prior  mos;

 

Year     AUGSEP  SEPOCT  OCTNOV  NOVDEC DECJAN JANFEB

 

2014   .500 .360 .712 .578 .406  .468

 

2003    .442    .515    .528    .319
2004    .31    .333

 

1990     .376    .247    .378    .339
1991    .312    .32    

 

1993    .987    1.06    .826    .565
1994    .34    .194   

 

1951    .769    .743    .722    .466

1952    .403    .120    

 

1978    -.386    -.023    .197    .399
1979    .596    .354

  

1969    .161    .504    .653    .383
1970    .361    .410

 

1963    .764    .832    .859    .748
1964    .855    .439    

 

1976    1.024    .947    .48    .552
1977    .518    .258  

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MEI Value

Feb/mar: .650

closest actuals

 

1966: .687

1980: .685

2005: .562

1959: .501

1973: .829

1981: .453

1969: .447

 

 

Cloest trends

 

2014    .152    .932    .878    .816    .858    .5    .36    .712    .578
2015    .406    .468    .65

 

1991    .312    .32    .409    

1959    .578    .807    .501

1980    .698    .611    .685

1969    .69    .867    .447    

1970    .361    .41    .215

1994    .34    .194    .168 

 

 

 

 

 

 

 

 

 

2011 -1.654 -1.552 -1.548 -1.495

 

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  • 4 weeks later...

MEI Value

Mar/Apr: .953

 

Closest Actuals (value);

 

 

1980: .914

2010: .894

1958: 1.038

1953: .707

1981: .646

 

 

Cloest trends

 

2015    .406    .468    .65    .953

 

1980    .698    .611    .685    .914    

1953    .016    .375    .244    .707    

1991    .312    .32    .409    .471

1981    -.243    -.153    .453    .646    

1993    .701    1.005    .994    1.408    

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http://www.esrl.noaa.gov/psd/enso/mei/index.html


"In the context of intermittent weak El Niño conditions over the last year, this section features a comparison figure with similar weak events, excluding prolonged "Year-2" El Niño conditions. It appears that the situation will become more clear-cut by mid-2015, so that a larger sample of comparable events can be chosen.


The updated (March-April) MEI has risen by 0.30 standard deviations to +0.95, for a strongly increased ranking, now crossing over the 'strong' El Niño threshold (upper 10%ile). Something similar happened last year when the MEI peaked in April-May 2014 with +0.93, only to drop back in subsequent months. Just two years earlier, it also ramped up to similar rankings with a +1.14 reading in June-July 2012 only to revert to neutral just two months later. Therefore, I am a bit hesitant to call this a 'strong El Niño' just yet. Looking at the nearest 12 rankings (+/-6) in this season, and excluding cases with declining values in the wake of previous El Niño events gives us six 'analogues' to ponder: 1953, 1980, and 1981 (all followed by ENSO-neutral conditions later that year), as well as 1987, 1992, and 1993 which continued with El Niño conditions for much of remainder of those years. Not exactly a 'ringing endorsement', but healthy 50/50 odds for El Niño (higher than last month).


Positive SST anomalies have intensified over much of the equatorial Pacific, all the way to the South American coast, as seen in the latest weekly SST map.


For an alternate interpretation of the current situation, I recommend reading the NOAA ENSO Advisory which represents the official and most recent Climate Prediction Center opinion on this subject. In its latest update (April 9th, 2015), El Niño conditions were diagnosed, and expected to continue through boreal summer and even autumn with a greater than 60% chance. This month's assessment will probably be similar if not stronger.


There are a number of ENSO indices that are kept up-to-date on the web. Several of these are tracked at the NCEP website that is usually updated around the same time as the MEI, in time for this go-around. In early 2014, Niño regions 3 and 3.4 dropped to around -0.5C for both indices, followed by a steady warm-up from March through June, reaching +0.9C for Niño 3, and just shy of +0.5C for Niño 3.4. In July 2014, both indices dropped by more than 0.2C, still above +0.5C for Niño 3, but only +0.2C for Niño 3.4. This continued during the month of August. Since then, monthly values rose to +0.9C for Niño 3 and +0.85C for Niño 3.4 in November, their highest values since July 2012 and March 2010 for Niño 3 and 3.4, respectively. Since then, Niño 3.4 weakened to just above +0.5C in January through March, but rose to +0.8C in April, while Niño 3 dropped all the way to +0.15C in March, but rebounded to +0.7C in April.


For extended Tahiti-Darwin SOI data back to 1876, and timely monthly updates, check the Australian Bureau of Meteorology website. This index has often been out of sync with other ENSO indices in the last decade, including a jump to +10 (+1 sigma) in April 2010 that was ahead of any other ENSO index in announcing La Niña conditions. In 2014, its value has varied from +12 in January (moderate La Niña conditions) to -13 in March and -11 in August (full-blown El Niño conditions). April and May were positive, indicating mild La Niña conditions in opposition to all other ENSO indices, but between August and November negative SOI values between -8 and -11 indicated at least weak El Niño conditions. Since December, it rose all the way to +1 in February 2015, only to drop back to -11 in March, and up again to -4 in April. While the SOI remains a noisy ENSO index, it was more clearly in the El Niño 'camp' than others from August 2014 through March 2015 with an eight-month average of almost -8.


An even longer Tahiti-Darwin SOI (back to 1866) is maintained at the Climate Research Unit of the University of East Anglia website, however with less frequent updates, although the last one was just completed to include data through 2014. Extended SST-based ENSO data can be found at the University of Washington-JISAO website, which is now a full four years behind schedule (through January 2011). El Niño already went through a four-month 'dress rehearsal' last boreal summer, disappeared for two months, returned for two months, went back to an El Niño-flavored neutral status in January, only to cross back over that threshold in February and grow further in March and April (for the MEI). Will the event take hold and grow further over the next six months, as is advertized by most models, or will it disappear again? It appears that the overall situation is more favorable in 2015 than in 2014 (or 2012). For the time being, at least some typical El Niño impacts may be anchored by positive PDO conditions that have prevailed for all of 2014, reaching record levels at or above +2 since December 2014. Meanwhile, the westerly wind burst mentioned in March may have found a worthy replacement in early May."


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  • 4 weeks later...

\MEI Value

 
Apr/May: 1.567
 
Closest Actuals (value);
 
1997: 1.17
1993: 1.994
1987: 2.14
1992: 2.148
2014:  .967
 
 
 
Cloest trends
 
2015 .406 .468 .65 .953 1.567
 
 
1997 -.485 -.602 -.244 .537 1.17
1993 .701 1.005 .994 1.408 1.994
1987 1.237 1.184 1.727 1.867 2.14
1980 .698 .611 .685 .914 .95
1992 1.749 1.87 1.987 2.269 2.148 
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In the context of rapidly strengthening El Niño conditions over the last few months, this section features a comparison figure with analogous events since 1950.

The updated (April-May) MEI has risen by 0.61 standard deviations in one month to +1.57, for a high ranking above the 'strong' El Niño threshold (upper 10%ile). This is the highest MEI value in 17 years, surpassing the peak of the 2009-10 El Niño by a few 1/100. The current El Niño has ranked above the weak El Niño threshold for four months in a row, and above the strong threshold for two months running. If it were to remain above the strong threshold for just one more month, it would be the first strong El Niño event since 1997-98 with at least three months registering in the upper 10%ile. By this definition, six other El Niño events occurred since 1950: 1957-58, '65-66, '72-73, '82-83, '86-87, and '91-92, or just over once a decade.

Looking at the nearest 12 rankings (+5/-7) in this season, and excluding cases with declining April-May values compared to earlier in the year gives us six 'analogues' to ponder: 1957, 1987, 1993, 1997, 2002, and 2014 (all but 2014 are included in the MEI comparison figure of this section). Except for 2002-03, peak values of the remaining four events reached the strong threshold and maintained it from three months (1993) to 13 months (1997-98). None of the comparison figure cases dropped back to ENSO-neutral rankings before the end of the calendar year. Thus, if it were not for last year's unusual evolution, it would be safe to state that El Niño conditions are virtually guaranteed through 2015. Nevertheless, the odds for a substantial El Niño during the next six months appear better than since at least 2009.

Positive SST anomalies have consolidated over the equatorial Pacific, all the way from the dateline to the South American coast, as seen in the latest weekly SST map. While most of these anomalies reach +1 to +2C, one can find anomalies in excess of +3C near Galapagos.

For an alternate interpretation of the current situation, I recommend reading the NOAA ENSO Advisory which represents the official and most recent Climate Prediction Center opinion on this subject. In its latest update (May 14th, 2015), El Niño conditions were diagnosed, and expected to continue through the rest of 2015 with a greater than 80% chance. I see no reason to disagree with this assessment.

There are a number of ENSO indices that are kept up-to-date on the web. Several of these are tracked at the NCEP website that is usually updated around the same time as the MEI, in time for this go-around. In early 2014, Niño regions 3 and 3.4 rose from around -0.5C for both indices to +0.9C for Niño 3, and just shy of +0.5C for Niño 3.4 by June. This first stage of El Niño-like conditions was interrupted in July and August with barely positive values, only to rise again to +0.9C for Niño 3 and +0.85C for Niño 3.4 in November 2014. The following four months saw Niño 3 values as low as +0.2C, and Niño 3.4 hanging in around +0.5C. The Niño 3 anomaly rose by a full degree Celsius since then, reaching +1.2C in May, while Niño 3.4 rose to +1.0C in May. Weekly SST anomalies show a continual rise thru last month, reaching +1.4C and 1.3C by the end of May, respectively.

For extended Tahiti-Darwin SOI data back to 1876, and timely monthly updates, check the Australian Bureau of Meteorology website. This index has often been out of sync with other ENSO indices in the last decade, including a jump to +10 (+1 sigma) in April 2010 that was ahead of any other ENSO index in announcing La Niña conditions. In 2014, its value has varied from +12 in January (moderate La Niña conditions) to -13 in March and -11 in August (full-blown El Niño conditions). April and May were positive, indicating mild La Niña conditions in opposition to all other ENSO indices, but between August and November negative SOI values between -8 and -11 indicated at least weak El Niño conditions. Since December, it rose all the way to +1 in February 2015, only to drop back to -11 in March, up again to -4 in April, and back down to its lowest value so far in May: -14. While the SOI remains a noisy ENSO index, it was more clearly in the El Niño 'camp' than others from August 2014 through March 2015 with an eight-month average of almost -8.

An even longer Tahiti-Darwin SOI (back to 1866) is maintained at the Climate Research Unit of the University of East Anglia website, however with less frequent updates, although the last one was just completed to include data through 2014. Extended SST-based ENSO data can be found at the University of Washington-JISAO website, which is now a full four years behind schedule (through January 2011).

Stay tuned for the next update by July 12th (travel, sorry!) to see where the MEI will be heading next. El Niño went through a four-month 'dress rehearsal' last boreal summer, disappeared for two months, returned for two months, went back to an El Niño-flavored neutral status in January, but has steadily grown to its highest value in 17 years as of April-May 2015. If it stays above +1.2 for just one more month, it will have exceeded the upper decile threshold for three months running, thus joining the somewhat exclusive 'club' of strong events according to the MEI. Meanwhile, typical El Niño impacts will be supported by positive PDO conditions that have endured since January 2014, reaching record levels from December through February 2015. Daily updates of the ENSO status can be found at the TAO/TRITON website

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  • 1 month later...

MEI Value


 

May/Jun: 2.06

 

Closest Actuals (value);

 

1987: 1.954

1983: 2.201

1997: 2.339

1992: 1.762

1998: 1.239

 

 

Closest trends:

 

2015    .406    .468    .65    .953    1.567    2.06

 

1987    1.237    1.184    1.727    1.867    2.14    1.954

1997    -.485    -.602    -.244    .537    1.17    2.339    

1983    2.687    2.903    3.024    2.835    2.537    2.201

1992    1.749    1.87    1.987    2.269    2.148    1.762    
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  • 4 weeks later...

MEI Value


 

Jun/Jul: 1.972

 

Closest Actuals (value);

 

1987: 1.855

1972: 1.826

1983: 1.767

1982: 1.614

1993/2012:  1.168

1997:  2.826

 

 

 

Closest trends:

 

2015    .406    .468    .65    .953    1.567    2.06    1.972

 

1987    1.237    1.184    1.727    1.867    2.14    1.954    1.855    

1997    -.485    -.602    -.244    .537    1.17    2.339    2.826

1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    

1993    .701    1.005    .994    1.408    1.994    1.556    1.168

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MEI Value

 
Jun/Jul: 1.972
 
Closest Actuals (value);
 
1987: 1.855
1972: 1.826
1983: 1.767
1982: 1.614
1993/2012:  1.168
1997:  2.826
 
 
 
Closest trends:
 
2015    .406    .468    .65    .953    1.567    2.06    1.972
 
1987    1.237    1.184    1.727    1.867    2.14    1.954    1.855    
1997    -.485    -.602    -.244    .537    1.17    2.339    2.826
1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    
1993    .701    1.005    .994    1.408    1.994    1.556    1.168

 

Something else to point out... 1997 is the only other year where the streak of MEI values >2 started in June. (yes, July technically broke this streak but the difference is negligible)

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  • 5 weeks later...

MEI Value

 
Jul/Aug: 2.367
 
Closest Actuals (value);
 
1987: 1.982
1972: 1.827
1982: 1.817
1997: 3.038
1965: 1.436
 
 
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG 
2015    .406    .468    .65    .953    1.567    2.06    1.972    2.367
 
1987    1.237    1.184    1.727    1.867    2.14    1.954    1.855    1.982    
1982    -.278    -.138    .102    -.013    .432    .965    1.614    1.817
1997    -.485    -.602    -.244    .537    1.17    2.339    2.826    3.038
1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    1.827
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http://www.esrl.noaa.gov/psd/enso/mei/index.html 

The six loading fields show the correlations between the local anomalies and the MEI time series. Land areas as well as the Atlantic are excluded and flagged in green, while typically noisy regions with no coherent structures and/or lack of data are shown in grey. Each field is denoted by a single capitalized letter and the explained variance for the same field in the Australian corner.

The sea level pressure (P) loadings show the familiar signature of the Southern Oscillation: high pressure anomalies in the west and low pressure anomalies in the east correspond to positive MEI values, or El Niño-like conditions. Consistent with P, U has positive loadings centered along the Equator, corresponding to westerly anomalies mostly west of the dateline. In contrast, significant negative loadings cover the easternmost Pacific off the Central American coast, denoting easterly anomalies during El Niño at this time ofyear. The meridional wind field (V) features its biggest negative loadings north of the Equator across the eastern Pacific basin, flagging the southward shift of the ITCZ that is common during El Niño-like conditions, juxtaposed with large positive loadings northeast of Australia (southerly anomalies during El Niño).

Both sea (S) and air (A) surface temperature fields exhibit the typical ENSO signature of a wedge of positive loadings stretching from the Central and South American coast to just east of the dateline, or warm anomalies during an El Niño event. At the same time, total cloudiness © tends to be increased over the central and western equatorial Pacific (mainly east of Indonesia), while the easternmost Pacific is often less cloudy than normal east of Galapagos.

The MEI now stands for 23.8% of the explained variance of all six fields in the tropical Pacific from 30N to 30S, having regained about 6% since May-June. Seventeen years ago, right after the MEI was introduced to the internet, the explained variance of the MEI for July-August 1950-1997 amounted to 26.5%. This drop-off by almost 3% reflects the diminished coherence and importance of ENSO events in much of the recent 17 years, although it has regained 1.0% compared to last year's minimum. The loading patterns shown here resemble the seasonal composite anomaly fields of Year 0 in Rasmusson and Carpenter (1982).

With the MEI indicating even stronger El Niño conditions, one can find a long list of key anomalies in the MEI component fields that exceed or equal one standard deviation, or one sigma (compare to loadings figure). Every one of them flags El Niño rather than La Niña conditions.

Significant positive anomalies (coinciding with high positive loadings) indicate very high sea level pressure anomalies (P) northwest of Australia, strong westerly wind anomalies (U) along the Equator, especially close to the dateline, southerly wind anomalies (V) northeast of Australia, and very high sea surface (S) and air temperatures (A) over the central and eastern equatorial Pacific. Significant negative anomalies (coinciding with high negative loadings) have become reestablished over the eastern equatorial Pacific as well as near Hawai'i for sea level pressure (P). They also flag increased easterlies (U) off the Central American coast, strongly increased northerlies (V) over the same region, anomalously cold air temperatures (A) east of Australia, and decreased cloudiness © near Galapagos. Compared to last month, both SLP and SST anomalies over the eastern Pacific have grown in the normalized sense.

In the context of strong El Niño conditions since March-April 2015, this section features a comparison figure with the classic set of strong El Niño events during the MEI period of record.

Compared to last month, the updated (July-August) MEI has increased significantly by 0.39 standard deviations to +2.37, or the 2nd highest ranking, surpassed only in 1997 at this time of year. This new peak value of the current event ranks third highest overall at any time of year since 1950, with 1982-83 and 1997-98 remaining in a 'Super El Niño' club of their own (for now), with peak values around +3 standard deviations.

Looking at the nearest 6 rankings (+1/-5) in this season, and excluding cases with declining July-August values compared to earlier in the year gives us the same five 'analogues' as last month: 1965, 1972, 1982, 1987, and 1997. All five maintained strong El Niño status through at least December of their respective calendar years. However, three of them ('65, '72, and '97) peaked already in July-August (the current season), followed by minor declines by the end of the year. Only 1982 showed continued growth right into the following year, while 1987 had already peaked back in May of that year.

Positive SST anomalies cover the eastern equatorial Pacific, all the way from just west of the dateline to the South American coast, as seen in the latest weekly SST map. This includes anomalies above +2C from about 90W to 170W, with a few peak values in excess of +3C.

For an alternate interpretation of the current situation, I recommend reading the NOAA ENSO Advisory which represents the official and most recent Climate Prediction Center opinion on this subject. In its latest update (August 13th, 2015), El Niño conditions were diagnosed, and are expected to continue through the rest of 2015 with a greater than 90% chance. I see no reason to disagree with this assessment.

There are a number of ENSO indices that are kept up-to-date on the web. Several of these are tracked at the NCEP website that is usually updated around the same time as the MEI, just in time for this go-around. Since October 2014, Niño region 3.4 first hovered around +0.5C, but rose steadily from April onwards, reaching +1.3C in June, +1.6C, and +2.1C in August. Niño region 3 dropped out of weak El Niño conditions from January through March 2015, but quickly rose from +0.7C in April to +2.3C in August 2015.

For extended Tahiti-Darwin SOI data back to 1876, and timely monthly updates, check the Australian Bureau of Meteorology website. This index has often been out of sync with other ENSO indices in the last decade, including a jump to +10 (+1 sigma) in April 2010 that was ahead of any other ENSO index in announcing La Niña conditions. In 2015, its value varied from +1 in February (neutral ENSO conditions) down to -11 in March, up again to -4 in April, and back down below -10 since May, reaching -20 in August, its lowest value since February 2005, and its first four-month run below -10 since early 1998.

An even longer Tahiti-Darwin SOI (back to 1866) is maintained at the Climate Research Unit of the University of East Anglia website, however with less frequent updates, with the last one to include data through 2014. Extended SST-based ENSO data can be found at the University of Washington-JISAO website, which is now more than four years behind current conditions.

Stay tuned for the next update by October 5th (probably earlier) to see where the MEI will be heading next. El Niño conditions are guaranteed to persist into the upcoming boreal winter season, most likely at strong levels for much of that period. Whether it will reach the elusive 'Super El Niño' level remains to be seen. In addition, typical El Niño impacts will be supported by positive PDO conditions that have endured since January 2014, reaching record levels from December 2014 through February 2015. Daily updates of the ENSO status can be found at the TAO/TRITON website, showing a renewed westerly wind surge near the dateline as of the beginning of September.

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  • 2 months later...

A bit late but wanted to add for reference

 

MEI Value

 
Aug/Sep: 2.527
 
Closest Actuals (value);
 
1997: 3.049
1987: 1.888
1982: 1.808
1972: 1.547
1965: 1.399
 
 
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP
2015    .406    .468    .65    .953    1.567    2.06    1.972    2.367    2.527
 
1997    -.485    -.602    -.244    .537    1.17    2.339    2.826    3.038    3.049    
1987    1.237    1.184    1.727    1.867    2.14    1.954    1.855    1.982    1.888    
1982    -.278    -.138    .102    -.013    .432    .965    1.614    1.817    1.808
1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    1.827    1.547
1965    -.526    -.324    -.254    .083    .51    .919    1.356    1.436    1.399
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MEI Value

 
Sep/Oct: 2.225
 
Closest Actuals (value);
 
1997: 2.417
1982: 2.019
1987: 1.643
1972: 1.651
1965:  1.399
 
 
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT
2015    .406    .468    .65    .953    1.567    2.06    1.972    2.367    2.527    2.225
 
1997    -.485    -.602    -.244    .537    1.17    2.339    2.826    3.038    3.049    2.417
1987    1.237    1.184    1.727    1.867    2.14    1.954    1.855    1.982    1.888    1.643
1982    -.278    -.138    .102    -.013    .432    .965    1.614    1.817    1.808    2.019    
1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    1.827    1.547    1.651    
1965    -.526    -.324    -.254    .083    .51    .919    1.356    1.436    1.399    1.217 
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  • 5 weeks later...

MEI Value

 
Oct/Nov: 2.308
 
Closest Actuals (value);
1982: 2.433    
1997: 2.575
1972: 1.747
1965: 1.355    
2006: 1.322    
1987: 1.271
1994: 1.29
 
 
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT NOVDEC
2015    .406    .468    .65    .953    1.567    2.06    1.972    2.367    2.527    2.225    2.308
 
1997    -.485    -.602    -.244    .537    1.17    2.339    2.826    3.038    3.049    2.417    2.575    2.326

1982    -.278    -.138    .102    -.013    .432    .965    1.614    1.817    1.808    2.019    2.433    2.411

1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    1.827    1.547    1.651    1.747    1.745

1987    1.237    1.184    1.727    1.867    2.14    1.954    1.855    1.982    1.888    1.643    1.271    1.253
1965    -.526    -.324    -.254    .083    .51    .919    1.356    1.436    1.399    1.217    1.355    1.256
 
 
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  • 1 month later...

MEI Value

 
Nov/Dec: 2.308
 
Closest Actuals (value);
 
1997: 2.368
1982:  2.418
1972: 1.761
1991: 1.325
1987: 1.284
1965: 1.253
1994: 1.229
   
 
 
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT NOVDEC
2015    .406    .468    .65    .953    1.567    2.06    1.972    2.367    2.527    2.225    2.308    2.123
 
1997    -.485    -.602    -.244    .537    1.17    2.339    2.826    3.038    3.049    2.417    2.575    2.368
1982    -.278    -.138    .102    -.013    .432    .965    1.614    1.817    1.808    2.019    2.433    2.418
1972    -.594    -.417    -.251    -.195    .5    1.106    1.826    1.827    1.547    1.651    1.747    1.761
1965    -.526    -.324    -.254    .083    .51    .919    1.356    1.436    1.399    1.217    1.355    1.253
 
 
 
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  • 2 months later...

Feb MEI Value

 
Dec/Jan: 2.202
 
Closest Actuals (value);
 
1998: 2.503
1992: 1.749
1973: 1.720
1983:  2.691
1958:  1.474
   
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT NOVDEC
2015    .419    .468    .65    .953    1.567    2.06    1.972    2.367    2.527    2.225    2.308    2.123
2016    2.202    
 
 
1982    -.268    -.138    .102    -.013    .432    .965    1.614    1.817    1.808    2.019    2.433    2.418
1983    2.691
 
1997    -.489    -.595    -.244    .537    1.17    2.339    2.826    3.038    3.049    2.417    2.575    2.368
1998    2.503
 
1972    -.595    -.422    -.251    -.195    .5    1.106    1.826    1.827    1.547    1.651    1.747    1.761
1973    1.72
 
1987    1.243    1.192    1.727    1.867    2.14    1.954    1.855    1.982    1.888    1.643    1.271    1.284
1988    1.116    
 
----------------------------------------------------------------------------------------------------------------------------------------------------------

 

 

March MEI Value

 
Jan/Feb : 2.121
 
Closest Actuals (value);
 
1992: 1.864    
2010: 1.521
1998: 2.792
1973: 1.497
1958: 1.442
   
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT NOVDEC
2015    .419    .468    .65    .953    1.567    2.06    1.972    2.367    2.527    2.225    2.308    2.123
2016    2.202    2.121  
 
 
1982    -.268    -.138    .102    -.013    .432    .965    1.614    1.817    1.808    2.019    2.433    2.418
1983    2.691    2.909
 
1997    -.489    -.595    -.244    .537    1.17    2.339    2.826    3.038    3.049    2.417    2.575    2.368
1998    2.503    2.792
 
1972    -.595    -.422    -.251    -.195    .5    1.106    1.826    1.827    1.547    1.651    1.747    1.761
1973    1.72    1.497
 
2010    1.152    1.521   
 
1992    1.749    1.864
 
1987    1.243    1.192    1.727    1.867    2.14    1.954    1.855    1.982    1.888    1.643    1.271    1.284
1988    1.116    .697
 
 
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  • 1 month later...

March MEI Value

 
Feb/Mar : 1.96
 
Closest Actuals (value);
 
1992: 1.993
1987: 1.719
2010: 1.427        
1958: 1.32
1998: 2.768
 
   
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT NOVDEC

2016    2.202    2.121    1.96
 
1998    2.503    2.792    2.768
2010    1.152    1.521    1.427
1973    1.72    1.497    .845
1958    1.474    1.442    1.32
1988    1.116    .697    .487
 
 
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  • 3 weeks later...

March MEI Value

 
Mar/Apr : 2.070
 
Closest Actuals (value);
 
1992: 2.275
1987: 1.866
1998: 2.685
1993: 1.409
1983: 2.824
 
   
Closest trends:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT NOVDEC

2016    2.202    2.121    1.96    2.07
 
1992    1.749    1.864    1.993    2.275     
1987    1.243    1.192    1.719    1.866
1998    2.503    2.792    2.768    2.685   
2010    1.152    1.521    1.427    .95
1958    1.474    1.442    1.32    1.013
 
 
 
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