Provided in the 1st attachment are the recent (preliminary) southern oscillation index (SOI) values from the Long Paddock site. As of September 13th, the daily SOI value was down to -17.47, the 30 day avg was down slightly to -9.80, and the 90 day avg was down to –7.76. This is indicative of atmospheric conditions reflective of ENSO-neutral, but with weak El Nino like tendencies. According to the latest runs by GFS models, the current SLP pattern at Darwin and Tahiti is expected to continue for the next several days, with a difference in SLP between the two regions that should result in weak-moderate daily SOI values. The 30 day avg has not changed much over that past few days, but it has been slowly dropping as the daily SOI values entering the 30 day avg have been slightly more negative than those that are leaving. If the forecast holds up, the 30 day avg is likely to either continue slowly dropping or bounce around near what it currently is. As for the the 90 day avg, its about to move through a cluster of weak negative daily SOI values leaving the 90 day avg time period. Therefore, it will likely continue to drop, but at a slightly slower rate than it has been as of late. Regardless, the 30 day avg has now been in negative territory for just under 11 weeks, with values at or below -8 for almost 4 weeks. Also, the 90 day avg has now basically reached -8. That's probably of the most significance here. If this trend continues for even a few more weeks, then it may start to become safe to say that the SOI is starting to indicate at least weak El Nino conditions. Think about it, even the strong back to back active phases of the MJO earlier this year(Jan-Apr) were not enough drop the 90 day avg to at or below -8, which is usually the only other source of prolonged negative daily SOI values(consecutive negative daily SOI values for longer than a few weeks). Normal daily weather patterns certainly could not drop the 90 day avg to at or below -8. Now consider that even with suppressed convection over the Western Pacific late August early September, high pressure passing south of Tahiti multiple times, and periods where the SPCZ was absent or weak, we are still seeing day after day of negative daily SOI values. In the Past 40 days we've only seen 2 positive daily SOI values that were basically near 0.0. You have to start to wonder, if its not the MJO, daily weather patterns, etc... then what is it? Whats lurking in the background helping cause tropical weather patterns favor negative daily SOI values? I believe that it might just possibly be the beginnings of weak El Nino conditions manifesting in the SOI(or not). The fact that the MJO signal is weak, COULD be another sign that ENSO is deepening and beginning to take over and drive tropical weather patterns in the equatorial Pacific. This is just my opinion.
Included in the 2nd attachment are the TAO plots for zonal wind/anomalies(TOP ), the TAO plots for SST/anomalies(CENTER), and the TAO plots for subsurface temps/anomalies(BOTTOM). Data for all plots is valid through Sep 12th. The data shown in the attached plots suggest to me that we are about to see a slight warm up across the Central and Eastern equatorial Pacific in the coming weeks. Currently, there is no cool water of any concern in the equatorial Pacific between 140E and 95W, both at depth or on the surface. This means that the last of the cool water from the upwelling Kelvin wave phase is all but gone and the warm subsurface water from our current downwelling Kelvin wave is free to begin its surfacing process(with no cooler denser water blocking or slowing it down). As mentioned by ASLR, upper ocean heat anomalies appear to have peaked or are near peaking and will likely begin decreasing, which is a sign that warm subsurface water is about to move to the surface. This may actually not be such a bad thing as we need warm water to surface and fill in the Nino 3.4 region. This would likely help push the atmosphere further in the right direction. Once this happens and a positive feedback loop begins to develop, things should start happening more quickly. In the 2 center plots, notice what appears to be warm SSTA already beginning to fill in the Nino 3.4 region, likely due to a mixture of warm water from our new Kelvin wave beginning to seep to the surface and weak westerly wind anomalies. Looking at the very bottom plot, notice that in the Eastern Equatorial Pacific, there is a very thin layer of near neutral ocean temp anomalies. If you look at the zonal wind anomalies in the 2nd plot from the top, you will see weak easterly anomalies in that region. This is likely causing some local upwelling, but with weak westerly anomalies forecast to pick up in that region and a Kelvin wave set to surface very soon, we should see that area warm up as well. The NOAA weekly ENSO update issued tomorrow may not reflect this warm up yet as this is a relatively recent development(last 3-4 days), but I suspect that maybe in the NOAA weekly ENSO update on September 22. I guess we'll see