Quicky Early August 2015 ENSO Update: NINO3.4 Sea Surface Temperature Anomalies Still Just Above the Threshold of a Strong El Niño

The post provides a look at the most recent weekly sea surface temperature anomalies for the equatorial Pacific.  It also includes a Hovmoller diagram of the wind stress (not anomalies) along the equator…to confirm that there was another westerly wind burst at the beginning of last month. 

NOAA’s weekly sea surface temperature anomalies for the NINO regions (based on Reynolds OI.v2 data) are furnished on Mondays. Today’s update for the week centered on July 29, 2015 shows the sea surface temperature anomalies of the NINO3.4 region (5S-5N, 170W-120W), which NOAA uses to define an El Niño and its strength, is at 1.7 deg C, just above the 1.5 deg C threshold of a strong El Niño…where it’s been hovering for a few weeks. But it’s still early in the development of an “average” El Niño, which typically peaks in December.

The weekly NINO region sea surface temperature anomaly data for Figures 1 and 2 are from the NOAA/CPC Monthly Atmospheric & SST Indices webpage, specifically the data here. The base years for anomalies for the NOAA/CPC data are referenced to 1981-2010.

Figure 1 includes the weekly sea surface temperature anomalies of the 4 most-often-used NINO regions of the equatorial Pacific. They start in January 1990. From west to east they include:

  • NINO4 (5S-5N, 160E-150W)
  • NINO3.4 (5S-5N, 170W-120W)
  • NINO3 (5S-5N, 150W-90W)
  • NINO1+2 (10S-0, 90W-80W)

NINO Region SSTa Time Series

Figure 1

And for Figure 2, the evolutions of the sea surface temperature anomalies in 2015 are compared to 1997 as a reference for a very strong El Niño and compared to 2014 as a reference for a very weak El Niño. Keep in mind that 2015 started the year at or near El Niño conditions, where that was not the case in 1997 and 2014.

NINO Region SSTa Evolutions

Figure 2

ANOTHER WESTERLY WIND BURST

In the post ENSO Basics: Westerly Wind Bursts Initiate an El Niño, we discussed how westerly wind bursts prompt the downwelling Kelvin waves that appear early in the development of an El Niño. Later in the process of El Niño evolution, westerly winds bursts also help to push more warm surface water than normal eastward along the Pacific Equatorial Countercurrent.   So they too help to strengthen an El Niño.

The most recent update at the NOAA GODAS website includes the 12-month Hovmoller of wind stress (not anomalies) along the equator through July 27th. See Figure 3. It shows yet another westerly wind burst in late June/early July. That westerly wind burst should be the response to the two tropical depressions that recently straddled the equator in the west-central tropical Pacific.

pent_anom_xt_tauxave_0n_current

Figure 3

That’s all for now. I’ll try to provide the full update next week when the data for July are available. I’ll also try to provide an update on The Blob next week.

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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 2015-16 El Nino Series, ENSO Update. Bookmark the permalink.

12 Responses to Quicky Early August 2015 ENSO Update: NINO3.4 Sea Surface Temperature Anomalies Still Just Above the Threshold of a Strong El Niño

  1. Werner Kohl says:

    Hi Bob,
    many thanks for your excellent information service.

    A small typo:
    “NINO3.4 region (5S-5N, 170W-1250W)” –> “NINO3.4 region (5S-5N, 170W-120W)”

  2. Bob Tisdale says:

    Thanks, Werner. Fixed. I’ll blame it on my insufficient intake of coffee this morning.

    Cheers.

  3. Thanks, Bob for Your very good work.

    MEI-value +1,97 for June/July 2015 shows no rise from May/June with +2,06.
    MEI-value for June/July 1997 was +2,83 rising from +2,34 in May/June to max +3,0 for July/August and August/September 1997. http://www.esrl.noaa.gov/psd/enso/mei/table.html

    There’s something going on…, doesn’t it?

    Cheers

  4. Pingback: Wieder nix mit “Super El Niño”? MEI schwächelt im Juli 2015! | wobleibtdieglobaleerwaermung

  5. Neville says:

    Bob, I wonder what you think about Ken Stewart’s graphs of the UAH data? Ken was one of the drivers behind the latest inquiry into the BOM data.
    Here’s the link, showing the pause over all regions. https://kenskingdom.wordpress.com/2015/07/09/pause-update/#comments

    Also the HAD 4 data-set preferred by the IPCC only shows about 0.8c warming since 1850 or the last 165 years.
    And this slight warming comes after the end of a minor ice age and coldest period for thousands of years.

  6. Bob Tisdale says:

    Neville, thanks for the link. I’d never seen the breakdown like that for the new UAH TLT data.

  7. Jeff Bennett says:

    Bob, there was talk that the typhoon hitting eastern China might create more wind bursts and thus another Kelvin Wave. What say you?

    Do you see anything in your ‘radar’ yet? Did in fact create a wind burst.

    Jeff Bennett

  8. Bob Tisdale says:

    Hi Jeff. Looking at the Earth.nullschool.net website illustration of winds in the western tropical Pacific from July 30th…
    http://earth.nullschool.net/#2015/07/30/2100Z/wind/isobaric/1000hPa/orthographic=168.27,16.10,440
    …it appears there was a westerly wind burst early on in the typhoon’s development.

    It also shows up in the latest Hovmoller diagram of wind stress along the equator from the GODAS website (but not the one in the post ). I’ll include that in the ENSO update this week.

    Cheers

  9. Neville says:

    Bob I hope you may find the time to check Ken’s efforts one day. Also why is the “super” el nino of 1997-8 not noticeable in the Australian and USA graphs?

  10. Jeff Bennett says:

    Thanks Bob, that is a really great link. I’ve never seen that one before. Thanks for sharing it with me. What a great way to see the impact of the wind across the Pacific. Look forward to hearing your next report…..in fact, why don’t you link that to your reports?

    Jeff

  11. Bob Tisdale says:

    Neville says: “Also why is the “super” el nino of 1997-8 not noticeable in the Australian and USA graphs?”

    The responses of both subsets to the 1997/98 El Nino are masked by the monthly weather noise. Smooth both with 12-month filters and you’ll see the responses.

    Cheers.

  12. Pingback: Blog-Statistik der Woche: 2450 Aufrufe von 600 Besuchern aus 31 Ländern | wobleibtdieglobaleerwaermung

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