1957-58(Moderate El Nino) and 1958-59(Warm Neutral)
SST anomalies from 1957-58 on the right and 1958-59 on the left
1976-77(Weak/Moderate El Nino) and 1977-78(Moderate El Nino)
SST anomalies from 1976-77 on the left and 1977-78 on the right
1986-87(Moderate El Nino) and 1987-88(Moderate El Nino)
1986-87 on the left and 1987-88 on the right
2002-03(Moderate El Nino) and 2003-04(Warm Neutral)
1918-19(Moderate El Nino) and 1919-20(Weak El Nino)
1911-12(Moderate El Nino) and 1912-13(Cool ENSO Neutral Conditions)
As you can see, all of these setup's have a secondary el nino(sometimes considered warm neutral) that is weaker in terms of anomalies when compared to the first nino. The 1911-12 and 1912-13 couplet is the only exception, with ENSO neutral conditions occurring in the second winter(1912-13).
Now comes the question whether the current pattern we are in is considered a period of 3+ years with cooler then normal ENSO conditions. Unlike most negative ONI periods including 1 or more la nina events, trimonthly ONI managed to spike at or above +0.5c for two trimonthly period's in the fall of 2012. Although by official standards this is not considered an el nino, it can significantly alter the global climate system. The question for me was if I could find a good analog to see if it made a difference to the ENSO state following a long cool ENSO period with an el nino year afterwords. After some research, the mid 1930's matched up pretty well. Below are the ONI values in this period courtesy of Bob Tisdale. Note the long period of negative ONI values from late 1932 through mid 1939. This period included several spikes into warm neutral conditions(similar to the 2012 period) although official nino status was never met. Coming out of this period was not only a double nino, but a triple nino.
So what would be some potential effects of a double el nino if analogs hints verify?
1) A temporary spike in global temperatures.
2) Longer lasting temporary +PDO regime within a multidecadal -PDO phase. This means a relief from drought conditions that currently exist over the SW and southern plains states.
3) Strength of ENSO in the 2015-16 winter could dictate the H5 pattern across the eastern U.S(stronger events correlate to very cold temperatures east of the rockies e.g 77-78 and 69-70 while warm neutral events correlate to warmth e.g 03-04).
4) Continued below normal ACE/tornadic activity over the next 2 years with a significant spike to follow.
Questions and comments are encouraged in the section below. You can tweet me with your questions, @blizzardof96.