ENSO Updates (2007 thru 2023)

[cycloneye]

The SOI is back at El Nino threshold of below -8. Ntxw,it will be a close call about declaring El Nino official or not on Thursday's CPC monthly update as it can go both ways.

[Nairobi]

Interesting observation about the initiation of the 1997-98 El Nino by a westerly wind burst, which resulted from a combination of an MJO and a strong northerly surge from eastern Asia into the near-equatorial Pacific.
http://weather.ou.edu/~spark/AMON/v2_n1/FORUM/Yu/

An eastward extension of high sea surface height (SSH) anomaly starting in late December 1996, marked the beginning of one of the greatest El Niño events of the century. The SSH anomaly ... propagated rapidly along the equator and reached the South American coast in February 1997. One month later, another SSH anomaly with a greater amplitude developed near the western boundary and also subsequently propagated eastward. These eastward propagating signals are known as Kelvin waves.

...

Kelvin waves are usually generated directly by wind-stress forcing or result from the reflection of Rossby waves at the western boundary. A westerly wind burst forces downwelling Kelvin waves with a depression of the thermocline and so an increase in the depth of 20°C isotherm.... These waves can induce SST changes primarily through horizontal advection and through their impact on equatorial upwelling. In the eastern Pacific basin where both horizontal and vertical temperature gradients are considerably greater than those in the western warm pool area, Kelvin waves are much more effective in inducing SST changes. This explains why the wave signals are less clear in the SST plot as compared with the SSH plot.... In fact, the SST field was affected by the first Kelvin-wave group only in a small area near the eastern boundary as to March 1997. With the subsequent arrival of the second group of Kelvin waves in April and May, the thermocline in the east was greatly depressed and the sea surface warming in the east basin became more extensive ... and the unstable atmosphere-ocean interaction began to be actively involved. It is quite apparent that the two groups of downwelling Kelvin waves played a key role for the onset of the ... El Niño episode. The question is whether these Kelvin waves were generated by the reflection of the Rossby waves at the western boundary or by westerly wind bursts. ... Westerly wind bursts (eastward) preceded over western and central Pacific at the time when Kelvin waves were generated, with the first wind burst occurring in the period around late December 1996 and the second in late February 1997. These sudden changes in the wind fields were also recorded by the NSCAT satellite sensor and TOGA TAO moored measurements.... It is obvious that the Kelvin waves which led to the onset of the ... El Niño were generated by the westerly wind bursts....

Yu and Rienecker (1998) in a recent study discussed the genesis of the westerly wind bursts. By analyzing newly available satellite-derived wind fields, they found that those wind bursts resulted from interactions between the tropical intraseasonal oscillation, namely the Madden-Julian Oscillation (MJO) (Madden and Julian, 1972), and northerly surges from East Asia/Western North Pacific into the tropics. The ... two westerly wind bursts which triggered the ... El Niño were associated with the MJO. The possible link between ENSO and the MJO has been previously proposed.... However, it seems that the MJO alone is not sufficient to be a trigger for the ... El Niño since the ocean was already preconditioned with positive height anomalies in the western Pacific during 1995-96 and the MJO was active during that period. It is possible (and even likely) that the phase of the interannual oscillation is important in the MJO-ENSO interaction. It can be seen that during 1995 and 1996 the westerly wind anomalies over the equatorial Indian Ocean propagated no further than 130°E, while during December 1996 and May 1997 they extended to the dateline and even further east and their amplitudes were also locally enhanced in the Pacific sector. Yu and Rienecker (1998) found that the intensification of the westerly anomalies over the western Pacific was influenced by the intrusion of the extratropical atmospheric disturbances, i.e., the cold surges of northerly wind anomalies from East Asia/Western North Pacific into the tropical Pacific with a period of 1-5 days.... After the penetration of midlatitude cold air, a cyclone was subsequently induced just north of the equator and the westerly wind bursts were simultaneously generated. Meanwhile, a cyclone was also developed in the south of the equator under the influence of cross-equatorial winds. A cyclone pair ... was then formed. The combination of equatorward surges in both hemispheres prolonged and strengthened the westerly wind event so that strong enough downwelling Kelvin wave packets were excited to induce sufficient warming in the eastern basin to initiate El Niño development.

[cycloneye]

Warm pool at the sub-surface is hanging on good in latest update as of November 29.

[cycloneye]

CPC has not made official the declaration of El Nino but they raised from 58% in November to 65% in this December update.



EL NIÑO/SOUTHERN OSCILLATION (ENSO)
DIAGNOSTIC DISCUSSION
issued by
CLIMATE PREDICTION CENTER/NCEP/NWS
and the International Research Institute for Climate and Society
4 December 2014


ENSO Alert System Status: El Niño Watch


Synopsis: There is an approximately 65% chance that El Niño conditions will be present during the Northern Hemisphere winter and last into the Northern Hemisphere spring 2015.

During November 2014, sea surface temperature (SST) anomalies increased across the central and eastern equatorial Pacific (Fig. 1). At the end of the month, the weekly Niño indices ranged from +0.4oC in the Niño-1+2 region to +1.0oC in the Niño-3.4 region (Fig. 2). The subsurface heat content anomalies (averaged between 180o-100oW) also increased during November (Fig. 3) as a downwelling oceanic Kelvin wave increased subsurface temperatures in the central and eastern Pacific (Fig. 4). However, the overall atmospheric circulation has yet to show a clear coupling to the anomalously warm waters. The monthly equatorial low-level winds were largely near average, although weak anomalous westerlies appeared in a portion of the eastern tropical Pacific. Upper level easterly anomalies emerged in the central and eastern tropical Pacific during the month. The Southern Oscillation Index has been somewhat negative, but the equatorial Southern Oscillation Index has been near zero. Also, rainfall continued to be below average near the Date Line and over Indonesia, and near average east of the Date Line (Fig. 5). Although the SST anomalies alone might imply weak El Niño conditions, the patterns of wind and rainfall anomalies generally do not clearly indicate a coupling of the atmosphere to the ocean. Therefore, despite movement toward El Niño from one month ago, the combined atmospheric and oceanic state remains ENSO-neutral.

Similar to last month, most models predict SST anomalies to be at weak El Niño levels during November-January 2014-15 and to continue above the El Niño threshold into early 2015 (Fig. 6). Assuming that El Niño fully emerges, the forecaster consensus favors a weak event. In summary, there is an approximately 65% chance of El Niño conditions during the Northern Hemisphere winter, which are expected to last into the Northern Hemisphere spring 2015 (click CPC/IRI consensus forecast for the chance of each outcome).



http://www.cpc.noaa.gov/products/analys ... odisc.html

http://iri.columbia.edu/our-expertise/c ... cpc_update

[cycloneye]

Ntxw,I am eagered to see your take on this CPC monthly update and especially this part.Can we call this El Nino a hybrid one?

Although the SST anomalies alone might imply weak El Niño conditions, the patterns of wind and rainfall anomalies generally do not clearly indicate a coupling of the atmosphere to the ocean. Therefore, despite movement toward El Niño from one month ago, the combined atmospheric and oceanic state remains ENSO-neutral.

[cycloneye]

Great blog by CPC explaining why they were very close to declare El Nino officially but held based on some factors they see as not reaching El Nino threshold.



December's ENSO Update: Close, but no cigar.

Author: Emily Becker.

Thursday, December 4, 2014

The first Thursday of every month is when we do the CPC/IRI ENSO status update, when NOAA officially answers the question “Are we there yet?” This month, the answer is...close, but no cigar.

Sea surface temperatures (SSTs) in the Niño3.4 region of the Pacific were quite warm during November, with the most recent weekly Niño3.4 index value at +1.0°C above average. The threshold for El Niño is +0.5° above average for one season (any 3-month period), and most of the climate models are forecasting that SSTs will stay above average for at least a few more months. Then why haven’t we changed from an “El Niño Watch” (favorable for development of El Niño conditions) to an “El Niño Advisory” (El Niño conditions are present)?

The atmosphere just won’t get with the program

First, a quick review of what we mean by “El Niño conditions.” There are three components:

(1) A one-month SST anomaly of +0.5°C or greater in the Niño3.4 region (check!),

(2) An expectation that the warm SSTs will meet or exceed that threshold for the next few months (seems very likely!),

(3) An atmospheric response typically associated with El Niño (not quite there yet).


ENSO diagnostic flowchart



Figure 1: Summary of decision process in determining El Niño conditions.


In a nutshell, the typical El Niño atmospheric response includes reduced rainfall over Indonesia, more rainfall over the central Pacific, and some weakening of the low-level easterly winds and upper-level westerly winds (the Walker circulation) along the equator. As of the beginning of this month, we have seen reduced Indonesian rainfall, but we have not seen more rain over the central Pacific (the opposite, in fact), and changes in the Walker circulation are unclear.

The most common way of looking at the rainfall patterns in the tropics is to use outgoing longwave radiation, which is monitored by satellites. Solar energy reaches Earth as shortwave radiation, is absorbed by the surface, and heats it up. The warmed surface then radiates longer-wavelength energy back out to space. This outgoing longwave radiation (OLR) is intercepted by clouds, so when the satellites see less OLR than average in a location, it was probably cloudier—and in the tropics, that means rainier—than usual there. And vice versa: more OLR means fewer tropical clouds and less rainfall.

Can we get a little more rain over here?



Figure 2 shows the average November OLR anomaly over the tropical Pacific. That big orange spot near the Date Line means higher OLR than average: fewer clouds and less rainfall. With El Niño conditions, we’d normally expect more rain than usual in this region, so the decreased rain tells forecasters that the atmosphere may not be adequately coupled to the warm SSTs yet. The presence of convection (storminess) in this region matters so much because this is how El Niño communicates between the equatorial Pacific and the higher latitudes, kicking off a cascade of global impacts.

Another measurement also suggests we’re not quite in El Niño conditions: The Southern Oscillation Index (SOI; the surface pressure anomaly difference between Tahiti and Darwin, Australia) is in negative territory (-0.9), but the Equatorial SOI, which compares the pressure anomalies between the western and eastern equatorial Pacific, is near zero. With El Niño, we’d expect to see negative SOI, because that indicates a weakening of the Walker Circulation.

On the other hand, there is some orange over Indonesia in Figure 2, meaning fewer clouds and reduced rainfall, which is compatible with El Niño conditions. As well, November upper-level westerly winds and lower-level easterly winds were both slightly weaker than average. The atmosphere may be beginning to respond, but not convincingly enough for forecasters to declare an El Niño Advisory.

For some El Niño impacts, “close” is close enough

El Niño impacts can emerge in different parts of the globe, even if the NOAA definition hasn’t yet been formally satisfied. Different countries have different thresholds for El Niño, which are tailored to their specific interests.

For example, the Peruvian National Committee on El Niño Studies (ENFEN) declared a “moderate coastal El Niño” in May of this year; SST anomaly in the easternmost Niño1+2 region is the primary metric for their declaration of coastal El Niño. Their event peaked in July, and is still ongoing. Atmospheric coupling is not required for them to see impacts: the strong downwelling Kelvin wave in the spring and associated warm SSTs near the Peruvian coast reduced the spatial distribution of anchovies, an important fishery for Peru.

What next?

Recently, the observed increase in SST anomalies has generally matched up well with forecasts from most climate models. The August, September, and October forecasts from the NMME predicted a November Niño3.4 SST anomaly between +0.7°C and +0.9°C. Due to the recent warming and our expectation that ocean temperatures will continue to be above-average, forecasters this month have again increased the odds of El Niño this winter to an approximately 2-in-3 chance.

http://www.climate.gov/news-features/bl ... e-no-cigar

[Ntxw]

So it seems the western Pacific rainfall trends have been the reason they are holding back? The recent MJO passage there probably didn't help. Still though, MEI rose back up so just about everywhere else Nino-like conditions exists. It's still just a formality, it's been dominating the weather pattern over North America.

[Ntxw]

ONI for SON came in at 0.5C the first trimonthly at El Nino threshold

[cycloneye]

Is still raining in WPAC and CPAC as CPC says and the ESPI is way down in negative.



http://trmm.gsfc.nasa.gov//trmm_rain/Ev ... y_day.html

[dexterlabio]

Maybe the El Nino pattern has set in North America but not yet felt in Asia? I notice as the equatorial Pacific warms up, the waters in SE Asia remain to be warmer than average. I read an article about El Nino and from some posts here that cooler sea surface temp in SE Asia is indication of a coming drought- which is a prime effect of El Nino in Asia. But so far there is no indication of that.

[cycloneye]

Another interesting blog by CPC about coral reefs and El Nino. Ntxw,what is your take on this?

An outbreak of coral bleaching—the loss of corals’ food-producing algae—in the Pacific and the Caribbean occurred this past summer, most likely tied to a brewing El Niño. The reefs of the Florida Keys observed their worst bleaching impacts since 1997-1999, when a major El Niño was quickly followed by a major La Niña. The surprising intensity of bleaching across multiple ocean basins in 2014 has scientists wondering what to expect in 2015, when El Niño is forecasted to finally develop.

Read rest of CPC Blog here

[asd123]

Another interesting blog by CPC about coral reefs and El Nino. Ntxw,what is your take on this?

An outbreak of coral bleaching—the loss of corals’ food-producing algae—in the Pacific and the Caribbean occurred this past summer, most likely tied to a brewing El Niño. The reefs of the Florida Keys observed their worst bleaching impacts since 1997-1999, when a major El Niño was quickly followed by a major La Niña. The surprising intensity of bleaching across multiple ocean basins in 2014 has scientists wondering what to expect in 2015, when El Niño is forecasted to finally develop.

Read rest of CPC Blog here

http://oi61.tinypic.com/jpa3oi.jpg

Just a quick thought, you know that this past summer (2014), SST anomalies in the darkest color region skyrocketed. I remember looking at the SST maps and seeing water temps were in the mid 90s. Maybe that might have something to do with the high coral mortality?

[Nairobi]

From http://www.esrl.noaa.gov/psd/enso/mei/index.html

The updated (October-November) MEI has increased by 0.35 standard deviations to +0.71, recovering about 70% of the losses incurred since July-August. Its current ranking has increased by 5, thus returning to weak El Niño conditions, here defined as the top 20 values since 1950. The long anticipated emergence of El Niño conditions in 2014 appears to enter its second round, after a four-month stint from April-May through July-August. Looking at the nearest 12 rankings (+/-6) in October-November, but requiring a one-month increase by at least 0.05 since September-October yields the following five 'analogue' cases: 1958, '68, '69, '79, and '04. All but 1968 were already in the list of analogues from last month. In the subsequent six months, only 1969-70 did not include at least four bimonthly seasons with El Niño rankings, so the odds of continued El Niño conditions into 2015 look better than just a month ago.

[Nairobi]

Maybe the El Nino pattern has set in North America but not yet felt in Asia? I notice as the equatorial Pacific warms up, the waters in SE Asia remain to be warmer than average. I read an article about El Nino and from some posts here that cooler sea surface temp in SE Asia is indication of a coming drought- which is a prime effect of El Nino in Asia. But so far there is no indication of that.

Parts of Malaysia, Papua New Guinea, and Indonesia are experiencing drought already:

[Nairobi]

Top End and far eastern Australia experienced serious rainfall deficiencies in November.

[Nairobi]

Much of Australia experienced the hottest November on record:

[cycloneye]

I am calling this a hybrid El Nino because some parameters are Nino-like but others are not so we continue to wait and see if after all the hype this year we get the declaration sometime in 2015 or maybe ENSO goes back to dead Neutral.Time will tell.

[Ntxw]

Another interesting blog by CPC about coral reefs and El Nino. Ntxw,what is your take on this?

An outbreak of coral bleaching—the loss of corals’ food-producing algae—in the Pacific and the Caribbean occurred this past summer, most likely tied to a brewing El Niño. The reefs of the Florida Keys observed their worst bleaching impacts since 1997-1999, when a major El Niño was quickly followed by a major La Niña. The surprising intensity of bleaching across multiple ocean basins in 2014 has scientists wondering what to expect in 2015, when El Niño is forecasted to finally develop.

Read rest of CPC Blog here

http://oi61.tinypic.com/jpa3oi.jpg

I've never dove into anything beyond just the weather for ENSO impacts but that is neat thanks for sharing! Areas of the Carib experienced a lot of drought earlier in the summer and with lack of tropical systems (strong shear over the Caribbean-ENSO related? I know you felt this in Puerto Rico ) probably didn't help and just allowed the waters to warm unabated likely having effects on the coral population it seems. I know they are quite sensitive to temperature changes.

[asd123]

Another interesting blog by CPC about coral reefs and El Nino. Ntxw,what is your take on this?

An outbreak of coral bleaching—the loss of corals’ food-producing algae—in the Pacific and the Caribbean occurred this past summer, most likely tied to a brewing El Niño. The reefs of the Florida Keys observed their worst bleaching impacts since 1997-1999, when a major El Niño was quickly followed by a major La Niña. The surprising intensity of bleaching across multiple ocean basins in 2014 has scientists wondering what to expect in 2015, when El Niño is forecasted to finally develop.

Read rest of CPC Blog here

http://oi61.tinypic.com/jpa3oi.jpg

I've never dove into anything beyond just the weather for ENSO impacts but that is neat thanks for sharing! Areas of the Carib experienced a lot of drought earlier in the summer and with lack of tropical systems (strong shear over the Caribbean-ENSO related? I know you felt this in Puerto Rico ) probably didn't help and just allowed the waters to warm unabated likely having effects on the coral population it seems. I know they are quite sensitive to temperature changes.

NTXW, I don't know if you saw my post, it was kind of buried. Yeah, warming might have had something to do with the coral die off.

Another interesting blog by CPC about coral reefs and El Nino. Ntxw,what is your take on this?

An outbreak of coral bleaching—the loss of corals’ food-producing algae—in the Pacific and the Caribbean occurred this past summer, most likely tied to a brewing El Niño. The reefs of the Florida Keys observed their worst bleaching impacts since 1997-1999, when a major El Niño was quickly followed by a major La Niña. The surprising intensity of bleaching across multiple ocean basins in 2014 has scientists wondering what to expect in 2015, when El Niño is forecasted to finally develop.

Read rest of CPC Blog here

http://oi61.tinypic.com/jpa3oi.jpg

Just a quick thought, you know that this past summer (2014), SST anomalies in the darkest color region skyrocketed. I remember looking at the SST maps and seeing water temps were in the mid 90s. Maybe that might have something to do with the high coral mortality?

[Ntxw]

NTXW, I don't know if you saw my post, it was kind of buried. Yeah, warming might have had something to do with the coral die off.

]

I saw it and you're probably onto something. Wasn't TCHP much higher than usual over the NW Carib this year?