ENSO Updates (2007 thru 2023)

[RL3AO]

Is it possible this could be as strong as the 1997-1998 El Nino?

Unlikely. That was a historic event.

[Bailey1777]

It's dropping like a rock. I'm a little confused at why models and experts alike didn't see this coming. From all I have read with earlier post and links in this thread nobody sounded like this event was forseen at this speed/intensity.

[HURRICANELONNY]

When you read NCEP's summaries. They say March-June is the predictablity months. Until more data comes in. They don't know.

[jinftl]

Looking at 2008 SOI values for the period 5/16/08 (20080516) through 5/30/08 (20080530)....there is definitely a lot of day to day variation and interestingly enough, the SOI tanked to even lower SOI levels on an intra-day basis this time last year than current readings. What happens over the course of weeks and months is really more indicative of trends.

20080516 5.8
20080517 4.4
20080518 3.0
20080519 0.8
20080520 0.2
20080521 -2.1
20080522 -2.6
20080523 -3.3
20080524 -3
20080525 -2.9
20080526 -2.6
20080527 -3.3
20080528 -3.1
20080529 -3.6
20080530 -4.3


SOI values from 5/6/09 (20090506) thru 5/13/09 (20090513)
20090506 5.6
20090507 4.2
20090508 2.7
20090509 0.5
20090510 -0.2
20090511 -0.8
20090512 -2.2
20090513 -2.8

It almost looks like this time of year has a tendency for lower SOI values...what happens the next few months will be key...and note that we are no where near the level of negative SOI values seen in 2007...as of now



http://www.bom.gov.au/climate/enso/soi.dt3

[cycloneye]

At least the tanking stopped for one day.Lets see if it is a one day blip or a upward trend starts.

2009032820090426 10.3
2009032920090427 9.3
2009033020090428 9
2009033120090429 8.8
2009040120090430 8.6
2009040220090501 7.1
2009040320090502 7.3
2009040420090503 7.5
2009040520090504 7.6
2009040620090505 7
2009040720090506 5.6
2009040820090507 4.2
2009040920090508 2.7
2009041020090509 .5
2009041120090510 -.2
2009041220090511 -.8
2009041320090512 -2.2
2009041420090513 -2.8
2009041520090514 -2.6

http://www.bom.gov.au/climate/enso/soi.dt3

[jinftl]

Some reading on SOI values...

There are a few different methods of how to calculate the SOI. The method used by the Australian Bureau of Meteorology is the Troup SOI which is the standardised anomaly of the Mean Sea Level Pressure difference between Tahiti and Darwin.

The multiplication by 10 is a convention. Using this convention, the SOI ranges from about –35 to about +35, and the value of the SOI can be quoted as a whole number. The SOI is usually computed on a monthly basis, with values over longer periods such a year being sometimes used. Daily or weekly values of the SOI do not convey much in the way of useful information about the current state of the climate, and accordingly the Bureau of Meteorology does not issue them. Daily values in particular can fluctuate markedly because of daily weather patterns, and should not be used for climate purposes. A table of monthly SOI values is available here. Approximate 30-day values are often included in the weekly El Niño Wrap-Up.
http://www.bom.gov.au/climate/glossary/soi.shtml

[xironman]

Looks like an early Christmas present for 57

[cycloneye]

SOI continues to tank

2009032820090426 10.3
2009032920090427 9.3
2009033020090428 9
2009033120090429 8.8
2009040120090430 8.6
2009040220090501 7.1
2009040320090502 7.3
2009040420090503 7.5
2009040520090504 7.6
2009040620090505 7
2009040720090506 5.6
2009040820090507 4.2
2009040920090508 2.7
2009041020090509 .5
2009041120090510 -.2
2009041220090511 -.8
2009041320090512 -2.2
2009041420090513 -2.8
2009041520090514 -2.6
2009041620090515 -2.4
2009041720090516 -4.7
2009041820090517 -6.8

[cycloneye]

SOI continues to tank

Since the highest value of +10.3 on April 26,it has been falling like a rock,and on May 20 it was at -7.9.

2009032820090426 10.3
2009032920090427 9.3
2009033020090428 9
2009033120090429 8.8
2009040120090430 8.6
2009040220090501 7.1
2009040320090502 7.3
2009040420090503 7.5
2009040520090504 7.6
2009040620090505 7
2009040720090506 5.6
2009040820090507 4.2
2009040920090508 2.7
2009041020090509 .5
2009041120090510 -.2
2009041220090511 -.8
2009041320090512 -2.2
2009041420090513 -2.8
2009041520090514 -2.6
2009041620090515 -2.4
2009041720090516 -4.7
2009041820090517 -6.8
2009041920090518 -7.5
2009042020090519 -7.2
2009042120090520 -7.9

http://www.bom.gov.au/climate/enso/soi.dt3

[deltadog03]

This is also gonna go with a nice cool shot coming into the plains and east in about a week. But, SOI going down big time!

[cycloneye]

IRI May update of ENSO



Technical ENSO Update
21 May 2009

> Current conditions
> Expected conditions

Current Conditions
As of mid-May 2009 SSTs are near-average across much of the equatorial Pacific, indicative of neutral ENSO conditions. During April and the first 3 weeks of May, SSTs in the east-central tropical Pacific have warmed from the cool half of the near-average range to the warm half of that range. Enhanced easterly low-level winds that had been responsible for the cold SST anomalies earlier this year, led to a deepening of the thermocline in the western Pacific and concentration of the warmest waters in the far western Pacific. Recent relaxation of the easterly wind anomalies along the equator allowed warmer water in the west to move eastward. The equatorial Southern Oscillation Index (SOI) is still slightly positive, but the traditional SOI has now become slightly negative. Equatorial heat content has been increasing during the last several months, and with the ocean adjustment it has now become above average across much of the equatorial Pacific.

For April 2009, the SSTs in the NINO3.4 region were in the neutral range with anomaly of -0.18 C, having risen from being in the La Niña range during the four previous months; and for the Feb-Mar-Apr season they were -0.47 degrees C from average. Currently the IRI's definition of El Niño conditions rests on an index of SST anomalies, averaged over the NINO3.4 region (5S-5N; 170W-120W), exceeding the warmest 25%-ile of the historical distribution, and similarly for La Niña relative to the 25%-ile coldest conditions in the historical distribution. The NINO3.4 anomaly necessary to qualify as La Niña or El Niño conditions for the May-Jun-Jul and the Aug-Sep-Oct seasons are approximately (-0.50C, 0.45) and (-0.55, 0.50), respectively.


Expected Conditions
The most recent weekly SST anomaly in the NINO3.4 region is 0.3 C, indicating ENSO-neutral conditions in the tropical Pacific. What are the probabilities for maintaining neutral conditions, returning to La Niña conditions, or developing El Niño conditions? Persistent and large-scale easterly wind anomalies along the equator in the western-to-central Pacific two months ago have weakened over the last 1-2 months, and are currently largely weak and random. The thermocline, which contitutes the main element of the tropical Pacific system imparting ENSO predictability, has become slightly deeper than its long-time mean depth in the central and eastern part of the Pacific. Deep anomalies in the west 1-2 months ago have edged eastward, making it unlikely for Niña conditions to return in the coming few months.

May is near the middle of the so-called "predictability barrier" of boreal spring. It is typically easier to predict from this point forward than it was a few months ago and going through the boreal spring. The perturbations to the upper ocean structure, which impact predictability to ENSO, are currently quite weak. However, dynamical models are often more sensitive to these small perturbations than are statistical models that consider the sub-surface ocean, which may be why the dynamical models are all producing notably warmer ENSO forecasts than their statistical counterparts.

Currently, the models indicate probabilities of about 80% for ENSO-neutral conditions, about 5% for the return of La Niña conditions, and about 15% for developing El Niño conditions for the May-Jun-Jul season in progress. Going forward the models indicate that maintenance of ENSO-neutral conditions is the most likely scenario, but with the possibility of developing El Niño conditions only slightly less likely, and the possibility of returning to La Niña conditions much smaller than either of the above.


The above assessment was made in part on the basis of an examination of the current forecasts of ENSO prediction models as well as the observed conditions. For purposes of this discussion, El Niño SST conditions are defined as SSTs in the NINO3.4 region being in the warmest 25% of their climatological distribution for the 3-month period in question over the 1950-present timeframe. The corresponding cutoff in terms of degrees C of SST anomaly varies seasonally, being close to 0.40 degrees C in northern late-spring/early-summer season and as high as 0.75 degrees C in late northern autumn. La Niña conditions are defined as NINO3.4 region SSTs being in the coolest 25% of the climatological distribution. Neutral conditions occupy the remaining 50% of the distribution. These definitions were developed such that the most commonly accepted El Niño and La Niña episodes are reproduced.

The models are somewhat split in their ENSO forecasts through the 10-month forecast period, with the statistical models mostly predicting maintenance of ENSO-neutral conditions and the dynamical models predicting warm ENSO-neutral to El Niño conditions. For the current May-Jun-Jul season, no models are predicting La Niña conditions, while more than three-quarters are predicting ENSO-neutral conditions. However, this distribution shifts during the second half of 2009, when the models continue to favor ENSO-neutral conditions, but with development of El Niño conditions not far behind. For the Apr-May-Jun 2009 season, 3 of 22 models (14%) predict El Niño developement, while 19 models (86%) predict neutral conditions. At lead times of 4 or more months into the future, statistical and dynamical models that incorporate information about the ocean's observed sub-surface thermal structure generally exhibit higher predictive skill than those that do not. Among models that do use sub-surface temperature information, none indicates the existence of La Niña, 8 of 16 (50%) indicate El Niño conditions for the Aug-Sep-Oct season, and 8 of 16 (50%) predict that SSTs will remain ENSO-neutral (Note 1). Caution is advised in interpreting the distribution of model forecasts as the actual probabilities. At longer leads, the skill of the models degrades, and skill uncertainty must be convolved with the uncertainties from initial conditions and differing model physics, leading to more climatological probabilities in the long-lead ENSO Outlook than might be suggested by the suite of models. Furthermore, the expected skill of one model versus another has not been established using uniform validation procedures, which may cause a difference in the true probability distribution from that taken verbatim from the raw model predictions.


An alternative way to assess the probabilities of the three possible ENSO conditions is to use the mean of the forecasts of all models, and to construct a standard error function centered on that mean. The standard error would be Gaussian in shape, and would have its width determined by an estimate of overall expected model skill for the season of the year and the lead time. Higher skill would result in a relatively narrower error distribution, while low skill would result in an error distribution with width approaching that of the historical observed distribution. This method shows probabilities favoring ENSO-neutral near 83% for May-Jun-Jul, decreasing to 49% for Aug-Sep-Oct. ENSO-neutral is favored as being consistently most likely throughout the forecast period, but with El Niño probabilities averaging only 10 to 15% less likely and La Niña probabilities less that 10%. The same cautions mentioned above for the distribution of model forecasts apply to this alternative method of inferring probabilities, due to differing model biases and skills. In particular, this approach considers only the mean of the predictions, and not the range across the models, nor the ensemble range within individual models.


The IRI's probabilistic ENSO forecast takes into account the indications of this set of models, the outcome of the standard error approach described above, and additional factors such as the very latest observations that may have developed after the initialization times of some of the models. It indicates a 70% probability for ENSO-neutral conditions in the May-Jun-Jul season in progress, declining to just below 50% by Jul-Aug-Sep and beyond as El Niño probabilities rise to a nearly matching 45%.

http://iri.columbia.edu/climate/ENSO/cu ... nical.html

wxman57,what do you think about when they say the statistical models are better than the dynamic ones to predict ENSO as those are sensitive to small pertubartions?

[wxman57]

...snip...
wxman57,what do you think about when they say the statistical models are better than the dynamic ones to predict ENSO as those are sensitive to small pertubartions?

[/b]

I believe that the dynamic models don't tend to do well this time of year. They look at short term trends and assume too much.

[jinftl]

One thing of interest is an excerpt from the latest NOAA forecast released last week...in essence, they state that during high-activity cycles like we are in, el nino does not automatically equate to below normal seasons..only 'occasionally'...otherwise, it may just offset favorable factors, resulting in an average season.

During a high-activity era such as the present, the occurrence of La Niña greatly increases the probability of an above-normal season, and the occurrence of El Niño often results in a near-normal or occasionally below-normal season. An important source of uncertainty in the 2009 outlook is the large spread in the computer model forecasts for ENSO. Most statistical models indicate a continuation of ENSO-neutral conditions through the summer, including ASO. However, some dynamical models are predicting El Niño to develop. Our outlook ranges reflect this uncertainty in whether or not El Niño develops.
http://www.cpc.ncep.noaa.gov/products/o ... cane.shtml

[cycloneye]

Does anyone has the data about when El Nino was declared in 2004? I ask because there has been much talk about 2004 being an analog year for 2009.

[jinftl]

As determined by the ONI (Oceanic Nino Index = 3 month running mean of SST anomalies in the Nino 3.4 region), the threshold for weak el nino (anything greater than or equal to 0.5C is considered el nino for ONI reading, enso neutral are readings from -0.5C to +0.5C) was first met in the summer of 2004

ONI Values from 2004:
Dec03-Jan04-Feb04 = 0.4 (enso neutral)
Jan-Feb-Mar = 0.3 (enso neutral)
Feb-Mar-Apr = 0.2 (enso neutral)
Mar-Apr-May = 0.2 (enso neutral)
Apr-May-Jun = 0.3 (enso neutral)
May-Jun-Jul = 0.5 (el nino threshold just met)
Jun-Jul-Aug = 0.7 (weak el nino)
Jul-Aug-Sep = 0.8 (weak el nino)
Aug-Sep-Oct = 0.9 (weak el nino)
Sep-Oct-Nov = 0.8 (weak el nino)
http://www.cpc.ncep.noaa.gov/products/a ... ts-web.pdf


I will always remember this update from Dr. Gray in early August 2004 in which he reduced his remainder of season forecast for the '04 season (mid-season update). Excerpt from that update:

Factors currently observed that lead us to believe that Atlantic hurricane activity in 2004 will be reduced are as follows:

*Enhancement of warm ENSO conditions - especially in the Nino 4 and Nino 3.4 regions

*Stronger-than-average trade winds across the equatorial Atlantic - resulting in generally increased wind shear across the main development region

*Strong 200 mb easterly anomalies in the eastern equatorial Pacific - typically associated with warm ENSO conditions and reduced Atlantic seasonal activity

Consequently, based on these mixed climate signals, we are reducing our forecast somewhat from our early April and late May updates; however, we are not reducing the forecasts as much as suggested by the sum of our monthly forecasts.
http://hurricane.atmos.colostate.edu/Fo ... 4/aug2004/

A week later, the parade of Florida storms began with Charley....

Does anyone has the data about when El Nino was declared in 2004? I ask because there has been much talk about 2004 being an analog year for 2009.

[cycloneye]

Interesting those stats that show the weak El Nino didnt have a detrimental effect on the activity of the 2004 season on the peak months.

[jinftl]

I wonder if there is an impact of not only whether el nino/la nina conditions exist, but also if they are just developing at the peak of the season or if they are full-blown and have been around for months prior. There may not be an immediate impact of when these conditions develop to the resulting atmospheric conditions that tend to favor less activity. There could be a lag of months.

In other words, it may take the atmospher some time to really feel the effects of an el nino....just as it takes months of SST anomalies to develop. An el nino first making an appearance in August or September may not really impact the upper air dynamics across the basin until november or decemeber, for example.

Interesting those stats that show the weak El Nino didnt have a detrimental effect on the activity of the 2004 season on the peak months.

[cycloneye]

From +10.3 on April 26 to -10.6 on May 22,wow that is a huge crash of the SOI in less than a month.

2009032820090426 10.3
2009032920090427 9.3
2009033020090428 9
2009033120090429 8.8
2009040120090430 8.6
2009040220090501 7.1
2009040320090502 7.3
2009040420090503 7.5
2009040520090504 7.6
2009040620090505 7
2009040720090506 5.6
2009040820090507 4.2
2009040920090508 2.7
2009041020090509 .5
2009041120090510 -.2
2009041220090511 -.8
2009041320090512 -2.2
2009041420090513 -2.8
2009041520090514 -2.6
2009041620090515 -2.4
2009041720090516 -4.7
2009041820090517 -6.8
2009041920090518 -7.5
2009042020090519 -7.2
2009042120090520 -7.9
2009042220090521 -8.5
2009042320090522 -10.6



http://www.bom.gov.au/climate/enso/soi.dt3

[jinftl]

The current flooding in eastern Australia (see thread in Global Weather forum)...the worst in 30 years in parts of Queensland...is the exact opposite of what one would expect during an el nino period....those are characterized by drought conditions in eastern and northern australia...anecdotal evidence to support the numbers (ONI) that we are not in an el nino pattern at this time.

[wxman57]

NCEP ensembles get warmer with each run. Now approaching +2 above normal late this year. Already approaching El Nino threshold of +0.5 deg.