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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About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
This entry was posted in 2014-15 El Nino Series, El Nino-La Nina Processes, ENSO Update. Bookmark the permalink.

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

  1. Steve Keohane says:

    Thanks for the update Bob.

  2. Thanks, Bob. Yes, it would seem like this El Niño might not happen or be very weak.
    Global temperatures are going nowhere, hurricanes are not forming in the early season.

  3. craigm350 says:

    Reblogged this on the WeatherAction Blog and commented:
    Thanks Bob, especially the hovmoller explanation. This is proving to be a fascinating puzzle.

  4. Pamela Gray says:

    Do you think the wind blew that warm water West? Or do you think that area of ocean is simply running out of gas?

  5. Bob Tisdale says:

    Hi Pamela Gray: Some of it I’m sure was simply carried west and some poleward by ocean-atmosphere processes after it reached the surface. Much of it evaporated when it reached the surface. And in the following animation of subsurface temperature anomalies to depths of 300 meters, we can see some of it shifting off the equator (early June) and being carried west toward Indonesia.

    I suspect that occurred when the minor upwelling (cool) Kelvin wave came through (so small it doesn’t show up as a negative anomaly) and caused a portion of the warm water just east of the dateline to split off of the equator and then get caught in the south equatorial current.

  6. G. Y. Evan says:

    Another collapsed El Niño would be a big Q on present global weather pattern.

    If it does, it will be the second consecutive failed El Niño in weather history, doesn’t ti?

  7. Bob Tisdale says:

    G. Y. Evan, 1993 also had El Nino conditions early in the year and then failed to remain there for the normal ENSO season. The sea surface temperature record for the equatorial Pacific is poor before the satellite era so our knowledge of early start/failed El Ninos is somewhat limited.

    Regards

  8. Alec, aka daffy duck says:
  9. Eric Webb says:

    Nice post Bob, am noticing however, especially in the CPC diagrams, a new sub-surface equatorial downwelling Kelvin Wave is now in progress over the western Pacific, we have after all, been in a state for the last few months that favors upwelling over the Pacific, that is starting to change however, think it should effect NINO surface temp anomalies in time for Boreal Winter

  10. Bob Tisdale says:

    Eric Webb, I can see what you’re noticing, but right now it doesn’t look very strong.

  11. Eric Webb says:

    Yes, but that’s to be expected given the natural oscillatory behavior of the Eq. KW in the Pacific, the current intraseasonal upwelling phase of the Equatorial Kelvin Wave should diminish & give way to a new downwelling phase that should at the very least mitigate the ongoing & persistent upwelling in the Pacific, especially as we get later into Fall & into the Winter, when the Equatorial Pacific SST gradient weakens due to retreat of the ITCZ limiting the southeasterly fetch of winds coming off South America & the seasonal warming of the Antarctic fills the Peruvian Current w/ warmer water, (considering that the convective signals of the MJO in the Spring are relatively symmetric about the equator (likely induces focusing of WWBs there too), probably also why the Mar-May period represents the most unstable time for the Pacific in terms of rapidly changing ENSO states as it is also naturally the time the equatorial Pacific is generally most vulnerable to atmospheric & oceanic forcing on ENSO. I’m also a bit concerned as this oncoming El Nino is weaker than initially anticipated has left the door open to a plethora of ENSO possibilities next year & years to follow. I personally think this may be the beginning of a multi yr warm ENSO event, based on the conditions that if you look @ all years following 3 successive winters of -ONI, w/ at least one winter of -1 or greater, which is what we are going into this year, (2002-03, 1986-87, 1976-77, 1957-58, 1918-19, 1911-12), all but one of these years featured back to back warm ENSO neutral or El Nino events. In addition, the state of the Tropical Pacific Quasi Decadal Oscillation (TPQDO) involving a natural oscillation of the tropical pacific with reminiscence to El nino modes, gives evidence for warmer tropical pacific with increased solar forcing. Sverdrup transport pushes oceanic heat towards the subtropics, which lifts the thermocline, leading to the -TPQDO state. However, on the other hand during a solar minimum stronger easterlies move the Equatorial Pacific into a state that is conducive for heat accumulation that is subsequently discharged through El Ninos that tend to occur just after the culmination of the deepest portion of solar minimum. (Examples of this include the El Ninos of 2009-10, 1997-98, 1986-88, 1976-78, & 1965-66) http://catchmypicture.com/MFXyRt.jpg
    I’ll also add that I have observed what appears to be approximately a 17 yr oscillation or so of increasing La Nina intensity via MEI throughout each cycle of this oscillation that tends into end in multi yr warm ENSO events although the 1920s & 1930s don’t seem to exhibit this signature, it is quite evident, especially in the post 1950 period…. Certainly if one looked @ the MEI record going back to 1871-2006 using this 17 yr oscillation of successively increasing la nina intensity, one would predict the la nines in the late 2000s would become @ the very least the strongest we’ve observed since the 1988-89 La Nina, which is exactly what happened with the 2007-09 & 2010-12 La Ninas, with the latter being the stronger of the two. I guess only time will tell what happens.

  12. Eric Webb says:

    The TPQDO can also give evidence as to why the PDO tends to spike following solar maximum, which through modulation of the Pacific Jet & planetary wave breaking events, can also cause upticks & dramatic shifts in the Quasi-Biennial Oscillation, effectively presenting a rough linkage of the QBO to solar forcing…

  13. Bob Tisdale says:

    The TPQDO, Eric? That’s about as obscure as an acronym gets. I assume you’re referring to the Tropical Pacific Quasi-Decadal Oscillation and the work by Misios.
    http://lpc2e.cnrs-orleans.fr/~ddwit/TOSCAdoc/STSM_Misios.pdf

    I hope you understand that it’s a study of response of a climate model.

  14. Eric Webb says:

    “I hope you understand that it’s a study of response of a climate model.”
    That’s really a lame excuse in this case, seems like many AGW skeptics, including even myself at one time, think most if not all climate models were crap, but I’m a bit more lenient here because of the fact that this particular study built a climate model that actually tried to simulate natural processes instead of infusing it w/ copious amounts of nonexistent positive co2-water vapor feedback. Solar correlations with many anything, especially ENSO are elusive in of itself but that does not mean there is some correspondence or quasi-synchronicity between the two, after all it certainly isn’t a bad idea to look towards the Earth’s Primary source of energy to find correlative value & a possible inter-connected physics mechanism. There are some aspects I have personally picked up on that this study further verified, many of which I knew even before reading it… El Ninos have a tendency to occur immediately following the deepest portion of the solar minimum as has been the case in every Schwabe cycle since solar cycle 19, and that there is a tendency for PDO spikes immediately following solar maximum, with the ongoing PDO spike serving as yet another good example of this. The PDO is known to spike especially following El Ninos, with negative crashes evident in response to (not necessarily forcing them as many seem to inherently believe) La Ninas. I noticed that the TPQDO did accurately pick up on the multi-yr warm ENSO events in near & just before the positive the peak of the TPQDO (1957-59, 1968-70, 1976-78, 1990-94 & 2002-04) & of course they were all accompanied by +PDO spikes, with obvious variance in the longevity, intensity, & character between each individual event. Given this along w/ other things mentioned earlier, I think a multi-yr El Nino or warm ENSO event is certainly on the table, especially considering this El Nino is very likely not to be as strong as the 1997-98, 1982-83, & 1972-73 events w/ ONI > 2 @ their peaks, which were so strong that they forced a multi-yr La Nina to follow immediately in their footsteps, Thus w/ a weaker El Nino more like that of the 1957-58, 1991-92, & 1986-87, 2002-03 events, it opens the door to the possibility of this El Nino or @ least El Nino-like conditions lasting more than 1 yr…

  15. Bob Tisdale says:

    Eric Webb says: “That’s really a lame excuse in this case…”

    Actually, it’s not a lame excuse. Climate models differ greatly from reality.

    Eric Webb says: “…and that there is a tendency for PDO spikes immediately following solar maximum, with the ongoing PDO spike serving as yet another good example of this…”

    The PDO is an aftereffect of ENSO. Using the PDO in a discussion of ENSO is a meaningless way to verify your claims about ENSO. Also, the PDO data do not appear to support your claim.

    PDO v Sunspots

    Eric Webb says: “El Ninos have a tendency to occur immediately following the deepest portion of the solar minimum…”

    Really? Data contradict you, Eric.

    NINO3.4 v Sunspots

    The 1982/83 El Niño, the 1991/92 El Niño, and the 2002/03 El Niño occurred immediately after the peaks of their respective solar maximums, not minimums. The 1994/95 El Niño, the 2004/05 El Niño and the 2006/07 El Niño occurred before the solar minimum. That’s 6 out of 9 El Niño events over the past 30+ years that contradict your claim, Eric.

    Sorry to say, Eric, I don’t have time to do your research for you. While I enjoy your enthusiasm, you need to study the subject matter before making claims that aren’t supported by data.

  16. Eric Webb says:

    It is a misnomer to claim climate models differ from reality because for one this claim is being geared towards positive feedback of water vapor via C02, and it should be a given that climate models differ some from reality however to use this as primary footing to attempt to discredit my claims that are focused around natural, not anthropogenic variance is rather puerile. The PDO doesn’t spike after solar peaks? Unless I’m missing something, that’s clearly evident in your graph above, as the solar cycle & PDO are clearly in opposing juxtaposition w/ one another, w/ PDO spikes and subsequent crashes evident near dramatic changes in solar output
    Solar Peak Mar 1958, PDO spike (using a 6 month running mean to smooth out some noise in the data) 1958-1960
    Solar Peak Nov 1968, PDO spike in 1970,
    Solar Peak Dec 1979, PDO briefly dipped negative after 1977-78 EN, up ticked again in 1980 after solar peak
    Solar Peak Jul 1989, PDO actually dipped, but spiked once the 1991-92 EN arrived
    Solar Peak Mar 2000, PDO in the Multi Yr La Nina was @ lowest levels since the 1970s, rose for the next 2 years after solar peak back to positive levels w/ the 2002-03 El Nino
    Solar Peak ~2014, PDO is currently in the process of rising & should continue to do so as this El Nino cranks up, in May rose to highest value since 2005…
    http://www.esrl.noaa.gov/psd/cgi-bin/data/climateindices/corr.pl?tstype1=12&custname1=&custtitle1=&tstype2=0&custname2=&custtitle2=&year1=&year2=&itypea=0&y1=&y2=&plotstyle=0&length=5&lag=&iall=0&iseas=0&mon1=0&mon2=11&anom=1&climo1_yr1=&climo1_yr2=&climo2_yr1=&climo2_yr2=&Submit=Calculate+Results
    .”That’s 6 out of 9 El Niño events over the past 30+ years that contradict your claim, Eric.”
    I guess it didn’t occur to you that the backside of the solar cycle after solar maximum is longer than the front side preceding solar maximum, and the fact that I am only focused on a relatively inconsiderable portion of this front side of the solar cycle just after solar minimum, so there should be more El Ninos on the decaying portion of the Schwabe Cycle simply due to time. As far as El Ninos just after solar minimum…
    2009-10, 1997-98, 1987-88/1986-87, 1976-77/1977-78, 1965-66, 1923-24, 1913-14/1914-15, 1902-03
    Since 1900 8 out of 11 of the Solar Minimums featured an El Nino in relatively short order upon initiation of the upward potion of the solar cycle, since 1950 this number increases to 5 out of 6, with the only exception being the extremely strong solar cycle # 19. Not bad for something that supposedly “isn’t supported by data”…

  17. Bob Tisdale says:

    Eric Webb says: “The PDO doesn’t spike after solar peaks?”

    It doesn’t only peak after solar maximums. The PDO spiked BEFORE AND AFTER solar maximum. That’s why I presented the graph. Here’s, the data smoothed w/ 12-month filters.

    PDO v Sunspots 12-Month Smooth

    Eric Webb says: “Unless I’m missing something, that’s clearly evident in your graph above, as the solar cycle & PDO are clearly in opposing juxtaposition w/ one another, w/ PDO spikes and subsequent crashes evident near dramatic changes in solar output…”

    It’s not that you’re missing something, you HAD missed something. Additionally, now you’ve to conveniently changed your claim once the data have been presented. Also, if you hadn’t noticed, the relationship collapses in 2008.

    And if you had done your own research instead of having me present data that contradict your erroneous claims, you would have also discovered that the “opposing juxtaposition w/ one another, w/ PDO spikes and subsequent crashes evident near dramatic changes in solar output” also do not exist beforehand:

    PDO v Sunspots 12-Month Smooth 1950 Start

    Next, in my earlier reply, I noted that the PDO index was worthless in a discussion of ENSO because the PDO index is not an ENSO index. Yet, you insisted in your latest comment on making erroneous speculative claims about the solar cycle and the PDO…claims that were easy to verify if you had only bothered to plot the data yourself. And in my earlier reply, I also advised you that I did not have the time to do your research for you, yet you insisted on speculating. I continue not to have the time to create graphs that clearly contradict your speculations, so consider yourself banned from this blog temporarily. For years, others have been making the same old tired claims you’re making and we’ve already seen that those claims are not supported by data.

    Good bye, Eric.

  18. Eric Webb says:

    [SNIPPED WITHOUT BEING READ!]

  19. Pingback: El Niño 2014-2015: sarà un bambinello o un bimbetto? | Climatemonitor

  20. Gary says:

    Bob, have you seen this visualization of near real-time global wind patterns? http://earth.nullschool.net/#

  21. Bob Tisdale says:

    Thanks for asking, Gary. Yes. I’ve seen it. It’s a great tool for watching weather-related variation in a couple of variables.

  22. Sig Silber says:

    Bob, I think you may have misinterpreted the Low-level (850-hPa) Zonal (east-west) Wind Anomalies (m s-1) diagram. I think blue signifies a weakening of the Easterlies not a strengthening. I deduce this from the legend on the right hand side of the hovmoller diagram.

    This means that two weeks ago things looked a bit better not worse and this week they look a bit less better. But we have not seen the substantial weakening of the Easterlies needed to get a robust El Nino. It is getting late but there is still time.

    Thanks for organizing this wonderful thread.

  23. Bob Tisdale says:

    Sig Silber says: “Bob, I think you may have misinterpreted the Low-level (850-hPa) Zonal (east-west) Wind Anomalies (m s-1) diagram. I think blue signifies a weakening of the Easterlies not a strengthening.”

    Hi Sig Silber. I believe my representation is correct. In my Figure 3, please read the description NOAA provides for their color coding:
    “Westerly Wind Anomalies (orange/red shading)
    “Easterly Wind Anomalies (blue shading)”

    Cheers.

  24. Sig Silber says:

    I started writing this post from the position of defending my prior post but as I am writing it I am not sure.

    Yes for sure blue means an Easterly wind anomaly. But the color coding for the red is positive numbers and the color coding for the blue is negative numbers. So it looks to me like there is really just one parameter here which is west to east wind speed. So it looks to me that red means stronger west to east winds and blue means weaker west to east winds which is the same as saying stronger east to west winds as the variable is the anomaly not the absolute value. .

    Ok Have I just shown that you are correct? Is that your argument? These double negatives can drive you crazy.

    It would be a lot better if they defined anomaly better. By having two statements on the graphic defining westerly and easterly anomalies separately I think that adds confusion to the graphic. I think it is really a scale that relates to westerly winds. Not sure why they made that choice other than that is what you are looking for when looking for an El Nino. .

    I tried to correlate the graphic with the comments in the July 17 seasonal forecast where they discuss the state of tropical winds. I might attempt that again.

    I want to really get this straight. So perhaps someone needs to call the issuer of that graphic to get clarification as it is very important. Also if some others chimed in that would be helpful. .

    I write a column on climate and weather and discussed some of your work this week. http://econintersect.com/b2evolution/blog1.php/2014/07/22/july-21-weather-and-climate-forecast-1 I hope you do not mind that I used some of your graphics. My main interest is the economic impact of climate but this week I discussed (something I do not usually do) some of the issues related to the IPCC view of the world and began to describe your theory of the role of El Nino. If you think I have it wrong let met know. You can do that by private communication or just post your comments. I do not embarrass easily so if you point out flaws in my arguments I will appreciate that and not be annoyed.

    At the last minute I changed what I had planned to say about the easterlies because I was not sure your interpretation of the anomaly was correct. So I really would like to get that straight.

    Thanks again for operating this blog. I think it is a major contribution to peoples understanding of ENSO and other things as well.

  25. Bob Tisdale says:

    Hi Sig Silber: Sorry I did not expand on my previous reply.

    The “normal” direction for trade winds along the equatorial Pacific is east to west. Although this seems counterintuitive, “positive” trade wind anomalies (reds) represent a weakening of the trade winds (more toward westerlies) and possibly a reversal of the trade winds to westerlies. “Negative” trade wind anomalies (blues) represent a strengthening of the easterly trade winds.

    I think (don’t know for sure) NOAA selected that color coding and their way of presenting it so that red (warm color) anomalies would be associated with El Nino events and blue (cool color) anomalies with La Nina events.

    It can, however, get confusing, which is why in my monthly updates I present the trade wind Hovmollers from GODAS in absolute form first…

    …before I present them as anomalies:

    Cheers

  26. Sig Silber says:

    Thanks. I had it right initially then panicked that I had it confused but I am now believe I had it correct all the time.

    I do believe however that the explanation on the NOAA diagram adds to the confusion by having the two-line explanation when it is simply one thing…a change in the Westerlies the way they have it set up Red is an increasing from the normal condition and blue is a decrease from the normal condition.

    And for sure I know the Trades are normally Easterly in the Eastern Pacific and they should be relaxing if this is to be an Eastern Pacific El Nino and not another El Nino Modoki. .

    But the way that NOAA graphic is set up, the normal condition may be + or -. i.e. from the West or from the East. So the normal condition may be a westerly in the Western Pacific and Easterly in the Eastern Pacific but the color coding applies no matter what the normal wind direction and strength is as the color coding is the anomaly and as set up by the graphic artist is an “increase in the westerlyness of the wind”. So red always means more westerly and blue always means less westerly. .But it is simply arithmetic so less westerly means more easterly.

    I will look for your monthly reports. I was not consciously aware of them before but I may have come across them. I will look for them now.

    Thanks again for the clarification. I appreciate it.

  27. Bob Tisdale says:

    Sig, I assume we’re discussing the Hovmoller in Figure 3 of this post. Could part of the confusion between us be we’re looking at “easterlies” and “westerlies” as different directions? Easterly winds travel out of the east–from east to west, while westerlies are out of the west–from west to east.

    Sig Silber says: “So the normal condition may be a westerly in the Western Pacific and Easterly in the Eastern Pacific…”

    Nope. Normal is “trade wind” or easterly, which is east to west.

    Sig Silber says: “So red always means more westerly…”

    Nope. Red can also mean weaker easterly (east to west) trade winds.

  28. Sig Silber says:

    Sig Silber says” So red always means more westerly”.

    I think that is a correct statement. Since if the norm is Easterly, coloring it red would mean more westerly which equates to less Easterly.

    I am a methematician by training so I am just discussing coordinates and scalers etc. NOAA designed that graphic. And I think it is confusing for a number of reasons. I don’t think the label at the top is clear,

    “Low level (850 hPa) Zonal (east-west) Wind Anomalies (m s”

    What does “east-west” mean? Perhaps there is something wrong with me but I do not know what “east – west” means. If I had to guess I would have guessed it means Easterly Winds but then coding a westerly wind burst red does not agree with that interpretation. So I conclude that this Graphic reflects anomalies where red means more westerly (or equivalently less easterly) and blue means more easterly or equivalently (less westerly). That is why I say the anomalies is to be added to how westerly a wind is which means that if a wind is easterly you have to subtract the anomaly which is exactly what you have done correctly in your interpretation.

    The scale on the right is not clear as to what it is (there is no legend associated with that scale), and the two lines describing how to interpret that scale add confusion. The two lines imply that westerlies are treated differently than easterlies when in fact the color scale treats all winds the same way as it simply indicates the magnitude of the anomaly and that anomaly could apply to a westerly wind or an easterly wind.

    This then leaves it to the viewer to figure out what that means. I hope I am not confusing the issue or appearing to be argumentative as neither is my intent and at this point I clearly agree with your interpretation but am simply commenting on why that graphic issued by NOAA is difficult to understand.

    As an aside, my article today resulted in someone posting this on a web serve where my article was posted.

    http://thinkprogress.org/climate/2014/07/22/3462647/global-surface-temperatures/

    So that is kind of like homework for me and most of it is familiar to you and things you have previously commented on.

  29. Bob Tisdale says:

    Sig Silber, “zonal” winds are east to west and west to east, as opposed to “meridional” that are north to south and south to north.

    Cheers

  30. Sig Silber says:

    Sig Silber, “zonal” winds are east to west and west to east,

    I get that.. I know what “zonal” means. But you have the word “and” in there (and you could have said “or” and that is where the confusion springs. It is not clear the wind direction to which the anomaly shown color coded should be applied. The graphic does not say. I am a mathematician so I know what I am talking about. If “b” is the anomaly that is color coded, then a + b is different than -a + b. So you need to know the sign of “a”. And “a” is not provided on that diagram and we are left to speculate whether it is + “or” -. Indeed it is Westerly. That is why red which for different shades is shown as a positive number on the color code means “more westerly”. That is the clue that the not-shown wind speeds are Westerlies. I bet you that your raw data shows negative numbers for the Easterlies on the Eastern Pacific or at least they would be or could be coded that way in the computer. They have a different sign than the Westerlies and this can done with a scalar and a wind direction (two pieces of information) or by just one number similar to the way Kelvin is shown. When you translate Kelvin into Centigrade you need to add a sign. That is inconvenient for doing calculations so Kelvin works better. I think they have used a similar system here for wind speed. .

    I am not sure why you are disagreeing with me when we have no disagreement. It is clear from your discussion in Post 13, your current post, that you had to explain that a “weak easterly anomaly” noted on the Hovmoller diagram really meant that the Easterlies had strengthened. If the explanation on the graphic was better, you would not have needed to explain it. It would have been obvious to the viewer/reader.

    I don’t wish to beat a dead horse so I will not be posting again on this issue since I am clear and you are clear so the only disagreement is over how to describe why there was a need for you to explain that which was not properly (clearly/adequately) described on the NOAA Hovmoller diagram.

    I am far more interested in reading what you have to say about ENSO and other related matters and what others post than arguing over how NOAA could have made their diagram easier to interpret with respect to anomalies.

  31. Bob Tisdale says:

    Sig, sorry for the obvious confusion over wording.

  32. Sig Silber says:

    Me too. I initially was looking for clarification and received it and certainly did not wish to create additional confusion.

    I am looking forward to reading your Post #14. In the meantime I will just track the comments in #13.

    Have a great day.

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