>One of the indicators that many El Nino watchers keep tabs on is the animated cross-sectional view of subsurface temperature anomalies of the equatorial Pacific that’s available from the NOAA Climate Prediction Center (CPC):
Figure 1 is a copy of the most recent .gif animation of the equatorial Pacific temperature anomalies. It ends with the November 9, 2009 pentad. The magnitude of the subsurface anomalies (up to 6 deg C plus) have some bloggers concerned that the 2009/10 El Nino will reach super El Nino levels, comparable to the 1982/83 and 1997/98 El Nino events. This leads to an obvious question…
HOW DO THE CURRENT SUBSURFACE ANOMALIES COMPARE TO PAST EL NINO EVENTS?
I have not found an archive of the subsurface equatorial Pacific temperature graphics at the CPC website, but the European Centre for Medium-Range Weather Forecasts (ECMWF) website has the equatorial subsurface temperature anomaly cross-sections archived here:
The graphics also include the Indian and Atlantic Ocean cross-sections. The archive starts in January 1959, and the most current month is October 2009. Unfortunately, it’s the recent elevated subsurface anomalies that concern some, and they rise significantly over the past few weeks, so the October monthly graphic really does not capture that recent surge. But ECMWF also presents daily “real time” views that start in February 2007.
So for this visual comparison of current conditions to past major El Nino events I’ll use the recent daily view and the historic monthly views.
I’ve provided a graph of NINO3.4 SST anomalies since 1970 as a reference, Figure 2.
To put the recent subsurface anomalies into perspective, here are .gif animations of the daily view for November 13, 2009 compared to the November graphics of major El Nino events since 1970. Again, keep in mind that these .gif animations compare monthly values for November to a daily value near to the middle of November 2009.
Also, this is only a visual comparison, nothing more. You’ll also note that the monthly graphics of the earlier El Nino events appear to be more mature. That is, their warm anomalies reach as far east as the continental land mass, but the current warm anomalies are still a significant distance away. Is the current El Nino late to develop or is that difference in apparent development a function of the daily versus monthly views? Dunno.
The comparison of the current graphic to November 1997 (near the peak of the El Nino of the Century) is shown in Figure 3. The current anomalies are nowhere close to it.
The SST anomalies of the 1982/83 El Nino peaked near to the NINO3.4 SST anomalies of the 1997/98 El Nino. The current subsurface anomalies appear lower than the November 1982 values, Figure 4.
Third on the list of major El Nino events was the 1972/73 El Nino, and the current subsurface anomalies appear to fall short of its November 1972 values, as shown in Figure 5.
The peak SST anomalies of the 1991/92 El Nino are next, and the current anomalies appear higher. Refer to Figure 6.
Next for your viewing pleasure is November 1986 (part way into the 1986/87/88 El Nino). The current values also appear a little stronger than it, too, Figure 7.
THE BIG IF
So if these comparisons of subsurface anomalies can be used as a predictor of the peak SST anomalies, the current El Nino would peak somewhere between the 1991/92 El Nino and the 1972/73 El Nino. Will it? Dunno. I don’t make predictions. The current El Nino may have some surprises in store.
Time will tell.