The 2014/15 El Niño – Part 13 – More Mixed Signals

A few interesting things have happened since the July Update last week. On the ocean side, weekly sea surface temperatures in the NINO3.4 region have dropped (just) below the threshold of El Niño conditions (using the standard NOAA base years of 1971-2000 for their Reynolds OI.v2 data). On the atmospheric side, the 30-day running average of the BOM Southern Oscillation Index (SOI) has finally neared the threshold of El Niño conditions. But the SOI does not reflect what’s going on along the equator. And there is evidence that the trade winds are slightly stronger than normal across most of the equatorial Pacific.

SEA SURFACE TEMPERATURE-BASED ENSO INDICES

Sea surface temperature anomalies for the NINO3.4 region of the equatorial Pacific (5S-5N, 170W-120W) are a commonly used index for the strength, timing and duration of El Niño and La Niña events. (See the map here from the BOM for the location of the NINO3.4 region.) They indicate the surface temperature response of the equatorial Pacific (a part of the ocean processes) to variations in El Niño-Southern Oscillation. NOAA considers there to be El Niño conditions (not a full-blown official El Niño, though) in the equatorial Pacific when the sea surface temperature anomalies for the NINO3.4 region reach and exceed a threshold of +0.5 deg C. El Niño conditions had (past tense) existed in the equatorial Pacific for the past 9 weeks. Those elevated sea surface temperatures were a response to the strong downwelling Kelvin wave that had carried warm subsurface waters from the western to the eastern equatorial Pacific. (For more information about the Kelvin wave see Part 1 of this series.) But that warm water has been rising to the surface over the past few months, releasing heat to the atmosphere primarily through evaporation, and the supply of warm water has dwindled drastically. So drastically, the sea surface temperature anomalies of the NINO3.4 region have recently dropped (slightly) below the threshold of an El Niño. See Figure 1. For the week centered on July 9th, the Reynolds OI.v2 sea surface temperature anomalies for the NINO3.4 region are at 0.43 deg C.

01 NINO3.4 thru July 9

Figure 1 (NINO3.4 SSTa)

The NINO1+2 region (10S-0, 90W-80W) is in the eastern equatorial Pacific, south of the equator, just south and east of the Galapagos Islands. It had been showing the warmest sea surface temperature anomalies in response to that Kelvin wave. While not as low as the NINO3.4 values, the sea surface temperature anomalies of the NINO1+2 region are also falling, and falling quite rapidly. See Figure 2.

02 NINO1+2 thru July 9

Figure 2 (NINO1+2 SSTa)

Sea surface temperature anomaly data illustrated in the above graphs are available from the NOAA NOMADS website.

SEA LEVEL PRESSURE-BASED ENSO INDEX

The Southern Oscillation Index (SOI) is a product of Australia’s Bureau of Meteorology. The SOI is another commonly used metric for the strength, duration and timing of El Niño and La Niña events. It captures a portion of the atmospheric components of the El Niño-Southern Oscillation processes. We discussed the Southern Oscillation Index in more detail in Part 8 of this series. The Southern Oscillation Index is calculated from the sea level pressures of Tahiti and Darwin, Australia. El Niño events are strong negative values and La Niñas are strong positive values, which is the reverse of what we see with sea surface temperatures. El Niño conditions, according to the BOM, are a SOI value equal to or lower than -8.0 and a SOI value equal to or greater negative number than +8.0 indicates La Niña conditions.

Because surface winds are associated with sea level pressures, a drop in the Southern Oscillation Index reflects a weakening of the trade winds in the tropical South Pacific and an increase in the SOI reflects a strengthening of the trade winds there. To reinforce (provide positive feedback to) the evolution of an El Niño, the trade winds have to weaken. After April, this has not happened so far in 2014. According to the BOM’s Recent (preliminary) Southern Oscillation Index (SOI) values, however, the 30-day running average of the SOI is at the -8.0 threshold of El Niño conditions.

Because El Niño events take place along the equatorial Pacific, and because the Southern Oscillation Index is based on the sea level pressures off the equator (which can be effected by weather noise unrelated to El Niño processes), it’s difficult to tell whether this an indication that the equatorial trade winds are finally going to provide the necessary positive feedback and allow the El Niño to develop. So we have to look somewhere else.

THE LOW LEVEL ZONAL WIND ANOMALIES ALONG THE EQUATOR

In their weekly ENSO update, NOAA includes a Hovmoller diagram of low level wind anomalies along the equator (5S-5N) for the eastern Indian Ocean and the Pacific Ocean. (See their page 16.) I’ve added some notes to it in my Figure 3.

03 Equatorial Pacific Trade Wind Anomalies

Figure 3

Don’t be intimidated by the Hovmoller. The vertical axis is time, with January 2014 at the top and July 2014 at the bottom. The horizontal axis are longitudes, starting on the left at 60E, which is in the western Indian Ocean, and ending on the right at 80E  80W, which is at the coast of South America. For the sake of discussion, I’ve added a fine highlight at 120E to separate the eastern equatorial Indian Ocean from the western equatorial Pacific. The color-coding is such that westerly wind anomalies are in shades of red and easterly wind anomalies are in blues. The latitudes for the wind anomaly data are 5S-5N, so they capture the equatorial Pacific, which is where El Niño processes take place. And the units are trade wind anomalies (not absolutes) and the trade winds normally blow from east to west. NOAA has provided three arrows to point out the westerly wind (anomaly) bursts, which indicate severe weakening and possible reversals of the normal east to west trade winds along the western equatorial Pacific.

And I’ve also circled their note and the corresponding place on the Hovmoller:

In the last week, weak low-level easterly wind anomalies have been evident across most of the Pacific.

“Weak low-level easterly wind anomalies” indicate the trade winds are slightly stronger than normal…not weaker than normal. And that indicates that the equatorial trade winds are not providing the feedbacks necessary to help evolve the El Niño. Note also that there have not been any additional westerly wind bursts since early April 2014, contradicting all of the proclamations from around the blogosphere that there have been additional wind bursts.

Unless there are additional westerly wind bursts and/or unless the trade winds weaken, it looks like this El Niño is going to disappear before it really got started.

EARLIER POSTS IN THIS SERIES

And for additional introductory discussions of El Niño processes see:

ENSO Basics: Westerly Wind Bursts Initiate an El Niño

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33 thoughts on “The 2014/15 El Niño – Part 13 – More Mixed Signals

  1. Once upon a time latitude was determined with the north star, the horizon, a piece of wood and a knotted cord. Worked for centuries. I’m not certain things have improved. Maybe too much information and not enough knowledge.

  2. “60E, which is in the western Indian Ocean, and ending on the right at 80E”
    Ending on the right at 80W (not 80E)
    Thanks for this series.

  3. CPC is still maintaining the increased odds (80%) chance of an El Nino developing after the summer months while maintaining the 70% chance throughout this summer. Its a long slow process sort of like watching the weather, looking for it to change. I’d like to see an El Nino bring moisture to the western mountains breaking the current California drought but that is my bias.

  4. The bottom line question for us skeptics….or so it seems to me…is how much atmospheric warming will develop and whether that warming…drum roll please…will be enough to pause the pause. Likely not without the yearned for super el nino.

    How heartbreaking for the warmists.

  5. Let’s see the sudden inhibition of growth of ice in Antarctica. This means that the lock polar vortex. This will allow the inflow of cold air from the Arctic Circle to the north. It’s already cold in Australia.

    http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html

    You can see here the temperatury increase in temperature in the stratosphere due to ozone changes.

    I anticipate further disruption of the polar vortex, due to the growth of cosmic rays in the next few days (low solar activity).

  6. Two quick things. I follow the BoM data because I do operational forecasting in the SW Pacific and have never understood why BoM and NOAA use 850mb as the basis for trade anomalies.
    This is around 5000 feet and has no relation to surface trades . The inversion level in the tropics is closer to 700mb which is roughly the friction free level. This is why a sailor can be enjoying a nice SE wind but gets confused when he sees puffy cumulus going west to east.
    The other thing : how is the anchovy fishing doing ? After all that’s how all of this got started!

  7. Correction,sorry. 850 is near the friction free area, actually around 3000 feet in the tropic . 700 mb is the driving level for much of the cloud clusters . Mod, if you can change this I would be grateful.

  8. In the last week, weak low-level easterly wind anomalies have been evident across most of the Pacific.

    That is a very obscure statement, I am glad you clarified it, Bob.

    “Weak low-level easterly wind anomalies” indicate the trade winds are slightly stronger than normal…not weaker than normal

    I can grasp a temperature anomaly, but a wind strength/direction anomaly ? Does it have a baseline?

  9. Said it before, saying it again.
    ‘el nino’ and ‘la nina’ are not technically accurate, comprehensive terms.
    They are strictly speaking ‘colloquialisms’ identifying one element of a much more complex pattern.
    So, good luck with predicting that!

  10. “A few interesting things have happened since the July Update last week. On the ocean side, weekly sea surface temperatures in the NINO3.4 region have dropped (just) below the threshold of El Niño conditions”

    We just went through a perigee full moon when unusually strong lunar tidal are adding to solar tidal forces.

    Lunar declination ( latitude ) is at its maximum deviation from the ecliptic ( plane of the motion of sun as seem from earth ). It was about 18S at the time of the full moon, meaning its tidal force will be pulling waters towards both 18S and 18N. Similarly the smaller solar tidal force is pulling towards 22N and 22S

    Warms surface water will be being drawn away from the Nino regions in both directions in the last few days. This may account for the current drop.

  11. Please, please let it not happen. Oh the fun in telling our climate experts in the media that we cannot predict the worlds largest weather event even a few months out.

  12. Thanks Bob.

    Will the large tropical cyclone developing in the west Pacific have any bearing on ENSO – or is it too far away?

  13. Thanks for the info Bob.
    Quick question……..If an El Nino causes a spike in global temps, as some believe, and it doesn’t develope this year, what will the temps look like after summer in the northern hemisphere? I have seen reports of summer snow in the French Alps as well as some places in Russia and cold air is moving down this week in the U.S. I know these are isolated events and have little bearing on the temps globally….but it is fun to watch.

  14. Kenny says: “Quick question……..If an El Nino causes a spike in global temps, as some believe, and it doesn’t develope this year, what will the temps look like after summer in the northern hemisphere?”

    Kenny, sorry to say, I don’t make short-term predictions about weather.

  15. phlogiston says: “Will the large tropical cyclone developing in the west Pacific have any bearing on ENSO – or is it too far away?”

    Typhoon Rammasun is centered at about 13N as of today. That’s about 900 miles (1450km) from the equator. I suspect that’s too far.

  16. Keith Minto says: “I can grasp a temperature anomaly, but a wind strength/direction anomaly ? Does it have a baseline?”

    I’ve never seen the climatology. In fact, I just did a quick scan of the weekly report and I can’t find which reanalyses they’re presenting.

  17. We had a very cold July in 2009 with over 7,800 low temperature records broken. Followed by an El Niño with a very cold winter in the southern US.
    Canada had a mild one that winter.
    Now here we have the July cold shot again. But followed by an El Niño that couldn’t make it official. Where does the cold go this winter, does the winter get very bad in the south again or stay in the Great Lakes? This baby isn’t enough to change the polar vortex pattern is it?
    Summer Polar Vortex vs. 2009 Year Without a Summer? – Jesse Ferrell Weather Blog

    http://m.accuweather.com/en/weather-blogs/weathermatrix/summer-polar-vortex-vs-2009-year-without-a-summer/30431014

    why the 2009-2010 winter was so cold

    https://sites.google.com/site/whythe2009winterissocold/

    http://wattsupwiththat.com/2009/07/13/record-cold-in-portland-maine-in-july/

  18. Next they’ll invoke Murphy’s Continuum, whatever doesn’t happen now is just waiting to happen worse in the future.

  19. Cap’n, thuh capacitors have discharged ….

    I believe it spiked the Southwestern Monsoon but by winter all the energy may already be dissipated. Not a good prognosis for California.

  20. Maybe it’s just me but there seems something wrong with the tendency over many years for surface thermal surface lows to form cyclonic “rotten centers” beneath subtropical Rossby ridges. The idea has always been that these ridges are salients of tropical air moving northward aloft and they are supposed to be cooling and sinking. So how in this regime do you get monsoonal moisture and warm sea surface anomalies moving north as is happening right now off California?

    The obvious answer is that all that sunshine bakes the surface so much that convecting air overmatches the sinking pressure and forces the subsidence to the edges. That notion works pretty well over land which is where monsoons are supposed to be, but the current rascal is offshore and it is a tongue rather than a circular cyclone and its moisture is being entrained in the macro anticyclonic flow and flung eastward across the Klamaths and the Rockies.

    Just noticing.

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