December El Niño update: phenomenal cosmic powers!

The effects of El Nino in the US during spring and summer are not as strong or reliable as they are in the winter. As far as severe weather in spring is concerned, if you are talking about tornados and severe thunderstorms mainly in the central and even eastern US, there has been found a slight tendency for enhanced activity for La Nina rather than El Nino. But remember that during the severe weather season (April - June), ENSO is often weak, because it is typically a transition season. However, some years there is a marked ENSO signal then, such as April - June 2015, when El Nino conditions were definitely present. There is a SLIGHT tendency for warmer than average summers following an El Nino the previous winter, due to the lingering warming effects on the global temperature. The upper air heights are often above normal in the subtropics during that following summer, and sometimes that can extend into the interior of large continents like North America. But again, it is not nearly as reliable as the winter climate effects in the US. Those effects are in action right now, and should tilt the odds toward above-average temperatures in the northern tier of the US, including New England (especially north of Massachusetts).

Do I detect a note of cynicism and distrust about how NOAA develops and maintains its ENSO-related SST data sets? Hmmm......okay, you have the right. To get you started, you might look into the two refereces that are listed last in Emily's recent blog, at https://www.climate.gov/news-features/blogs/enso/exactly-same-completel…; These show comparisons between at least two of NOAA's most heavily used SST data sets, and help explain their differences. I don't think bandpass filtering is used, but averaging over a time period, such as 1 week, is done, and that might have a similar effect of eliminating the highest frequencies. The main problem comes from using both remote SST measurements (from satellites) and directly measured SST (called "in situ") and accounting for temporally and spatially varying biases in the former ones as best possible. The satellite measurements have much better spatial coverage than the in situ measurements, but the latter are usually more trustworthy where they are available. I can understand that you may not trust the quality of the final products. I would say that they can be trusted to within about 0.3C most of the time. Your last comment, about this El Nino being less warm than it is being measured to be, doesn't make any sense to me, even if we accept your distrust. Why would you be any more suspicious that it is being overestimated than being underestimated? It doesn't fit in with your other statements. I would expect that you judge the ERSST to be closer to the truth than the OISST during this event. Is that correct? Remember, there are PLENTY of in situ measurments contributing to these SST estimates, and the Nino3.4 region is enormous.

Yes, it's going to be a very interesting "horse race" among the 3 events. I agree that the 1997-98 will probably retain its number one rank. As for beating 1982-83 or not, it's going to be close! In terms of the ERSSTv4 SST data, we are currently running just a bit ahead of 1982-83, but in 1982-83 the SST slightly increased more for December, and stayed nearly as warm in January (using just 1-month average ERSSTv4) than it might do this December and January. So I wouldn't want to bet the farm either way, as fun as it might seem.

During some portion of the 1982-83 event and the 1997-98 event, the SST anomaly in the Nino1+2 region, which is in the far eastern tropical Pacific right along the coast of northern Peru and Ecuador, exceeded 4C. So far in this event the Nino1+2 SST anomaly has not made it to 3C, but was more than 2.5C for some of the months in middle 2015, including October. (I'm using the OISSTv2 for these statements, and remember that the OISSTv2 tends to have slightly stronger anomalies than the ERSSTv2 that's used for official historical diagnostics. We know that these two SST datasets are roughly proportional, even if one tends to be stronger than the other.) So this event doesn't have the extremes, at least so far, that the other two strongest El Ninos since 1950 had. The Nino1+2 SST index could still soar to hit 3C anomaly during the remainder of this event, if new westerly wind events in the western or central Pacific spur new strong Kelvin waves. A Kelvin wave that might have caused such warming right now, from a big wind event in October, does not seem to have amounted to much, other than maintaining a Nino1+2 anomaly of more than 2C. But "it's not over until it's over". I would mildly bet against it, but do not have high confidence at all. Remember also, perhaps most importantly,  that anomalies during the February - May time frame result in much more dramatic local rainfall consequences than anomalies at the current time of year, because the average (climatological) SST is normally higher during February - May than now. It is the ACTUAL SST that matters more than the anomaly of the SST. So a 2.5C anomaly in spring 2016 could have significant climate impacts along their coastline even though it does not have them now.

It's hard to make a medium-term (i.e., 2-week) prediction of the upper air flow for the very beginning of January. But, judging from past strong El Ninos, I would tend to expect your split flow pattern to emerge, and for you guys to dry up a bit while California (especially the southern half) starts getting more major storms that give them well above average rainfall. While most of the US has its strongest climate effects from ENSO during winter (December through mid-March), the West Coast's impact tends to happen just a bit later in the season, even if the El Nino itself starts winding down. So I'm not at all surprised that so far, the pattern of dryer in the Pacific Northwest and wetter in southern California has not yet appeared in earnest. It's possible that before that pattern does form, BOTH the southwest and northwest could receive alternating periods of pretty strong storm system passages.

I am not familiar with such a large equatorial storm. It can be looked up if needed. Do you know which hemisphere it was in? Tropical cyclones north of the equator do have westerly winds to their south, which would mesh with the ENSO-related westerly equatorial low-level wind anomalies. Do you have any idea which month, and which week within the month? Whatever is found, it's doubtful that a single storm could noticeably influence the progress of an ENSO episode. More likely, the existence of the ENSO state would influence cyclones outside of the approximately 12 degree hurricane-free band straddling the equator.

As we're entering the time of year when the response over the Pacific is typically strongest, we would certainly expect to see this pattern dominate the next couple of months.  However, the climate system is not just El Nino, so it's also possible (if not likely) that we'll see some breaks in the pattern, as sub-seasonal modes of climate variability such as the Madden-Julian Osillation (MJO) exert some influence on the circulation over the Pacific.

Nice thought!  There is some speculation that maybe the large amount of warmth just north of the equator might have resulted in reduced equatorial winds on the equator (relative to 1997-98).  I think there might be some physical support this, but it will take some research for it to be more than speculation.  

However, I think sea ice or snow is unlikely to be a culprit of the warm SSTs just north of the equator.