Over the last week, we have seen a continuation of the ongoing warming trend in the equatorial Pacific. Notably, the eastern Pacific is shouldering the trend, with a notable jump in the Niño 1+2 regions (from 0.9 C to 1.3), the Niño 3 region (from 0.5 C to 0.8 C) and the Niño 3.4 region (from 0.7 C to 0.9 C.) The Niño 3.4 region is now at its warmest anomaly since December, but also, the distribution here is more indicative of a classic El Niño than we have seen in months, given that the eastern Pacific is showing anomalously warm water. The Niño 4 region, which I'll note is now at its strongest anomaly since January 2010, is still generally leading the other regions. This in itself suggests to me that the the western warm pool has plenty more heat to spill eastward and feed the EKW that is starting to surface. Normally, as we set up towards a classical/canonical El Niño formation, the Niño 4 region would cool relative to the eastern Pacific regions, giving the equatorial Pacific a fairly even distribution of nominal temperatures. This need not always happen, but it was a prominent feature during the peak of the 1997-1998 El Niño. Bottom line though, the ocean temperature profile is highly supportive of a classical El Niño. See also the attached SST anomaly chart from OSPO at NOAA for April 20, 2015.
Nino1+2 Nino3 Nino34 Nino4
Week SST SSTA SST SSTA SST SSTA SST SSTA
11MAR2015 26.1-0.3 26.8-0.2 27.6 0.5 29.2 1.0
18MAR2015 26.5 0.0 27.3 0.2 27.8 0.6 29.4 1.2
25MAR2015 27.4 1.2 27.8 0.6 28.0 0.6 29.3 1.1
01APR2015 27.4 1.4 27.9 0.6 28.2 0.7 29.5 1.1
08APR2015 26.7 0.9 27.9 0.5 28.4 0.7 29.6 1.2
15APR2015 26.8 1.3 28.3 0.8 28.7 0.9 29.7 1.3