Written by Sig Silber
With the El Nino weakening, the blocking high in the Pacific is now further offshore and spring storms are able to enter CONUS further south. Contrary to what you may hear in the media, warmer generally means wetter, especially if it is warmer water over which prevailing winds must travel or warmer land areas that seasonally draw in moist ocean air masses. We will be discussing a recent paper on the IPO which is the low-frequency Pacific Ocean Cycle.
This is the Regular Edition of my weekly Weather and Climate Update Report. Additional information can be found here on Page II of the Global Economic Intersection Weather and Climate Report.
This recent (2014) paper by Bo Dong and Aiguo Dai on The Influence of the Interdecadal Pacific Oscillation (IPO) on Temperature and Precipitation over the Globe (click here to read the full paper) confirms some of what we have known but adds new insight. For all practical purposes the PDO and the IPO are the same thing. They are highly correlated and the PDO was the earlier defined index and only covered the Northern Hemisphere Pacific. A less NH-Centric approach is to look at the Pacific in both Hemispheres and that is what the IPO does and it is highly correlated with the PDO. So either can be used.
It is surprising in a way that this paper focuses mostly on the Pacific both north and south and does not much consider the impact of the Atlantic (although it comments on this topic) and ignores the work of some other researchers who have either focused on the Atlantic or both the Pacific and the Atlantic. So to me that is a deficiency in the analysis but we can learn from this paper nevertheless. In a way, the below is the key graphic. It shows the correlations of temperature and precipitation to the IPO Index after removing the impact of the secular Global Warming trend.
Here are the conclusions from the study:
Summary and conclusions
To further quantify IPO’s influences on surface temperature (T) and precipitation (P) over the globe, we have analyzed T, P, and SLP [Editor’s Note: SLP means sea level air pressure] data from observations for 1920–2012, and atmospheric circulation fields from ERA reanalyses. We define the IPO as the second EOF mode of global (60° S–60°N) SST [Editor’s Note: SST means Sea Surface Temperature] fields, using its smoothed principal component as the IPO index. Spatial SST patterns of the IPO are ‘‘ENSO-like’’, and ‘‘PDO-like’’ over the North Pacific. This low frequency climate mode approximately has a 40–60 year cycle, of which the phase reverses about every 20–30 years (Fig.1b). From 1920 to 2012, there are roughly two warm IPO phases (1924–1945 and 1977–1998,with warm SSTs in the central and eastern tropical Pacific)and two cold IPO phases (1946–1976 and 1999–2012, with old SSTs in the same region). The most recent cold IPO phase is still continuing.
We found that phase switches of the IPO are concurrent with major climate transitions over the globe, including abrupt shifts in SST, SLP, T and P. Besides the well documented 1976/1977 climate shift associated with the IPO phase change (e.g., Trenberth 1990; Hartmann and Wendler 2005; Sabeerali et al. 2012), other IPO phase changes around 1945/1946 and 1998/1999 are also found to be associated with significant changes in SST, SLP, T and P over many regions, including many land areas. While the IPO composite T and P anomalies show a consistent horse-shoe pattern over the Pacific basin, T and P anomalies over extra-tropical land can be noisy and vary among different IPO phases (Figs.2, 3). Nevertheless, T and P over many land areas are found to be significantly correlated with the IPO phase changes.
Annual surface air temperature is positively correlated with the IPO index (i.e., higher T during warming IPO phases such as 192
4–1945 and 1977–1998) over western North America except its Southwest, mid-latitude central and eastern Asia, and central and northern Australia, but the correlation is negative over northeastern North America, northeastern South America, southeastern Europe, and northern India. Annual precipitation tends to be higher(lower) during warm (cold) IPO phases such as 1924–1945 and 1977–1998 (1946–1976 and 1999–2012) over south-western North America, northern India, and central Argentina, while it is the opposite over the maritime continent including much of Australia, southern Africa, and north-eastern Asia (Fig. 4b).
Besides the direct impacts on decadal variations in T and P, we also found some decadal modulations of ENSO’s influence on T and P on multi-year timescales by the IPO over northeastern Australia, northern India, southern Africa and western Canada. Over northern India, T is positively correlated with Nino3.4 ENSO index during cold IPO phases but the correlation turns negative or insignificant during IPO warm phases. Over northeastern Australia, the T versus ENSO and P versus ENSO correlations are stronger during the IPO cold phases than during the warm phases. The P versus ENSO correlation over southern Africa tends to be negative during IPO warm phases but becomes weaker or insignificant during IPO cold phases. The T versus ENSO correlation over western Canada are generally positive, but tends to be weaker during IPO cold phases. During the most recent IPO cold phase, interannual climate variability over the tropical Pacific was found to be weak (Hu et al. 2013). This could potentially affect ENSO’s influences on regional T and P. However, through what processes the IPO modulates ENSO’s influence requires further investigation.
IPO composite maps of DJF [Editor’s Note: DJF means December, January, February i.e. Boreal or Northern Hemisphere Winter] SLP, 850 hPa height and winds show a large low-level high pressure center and anti-cyclonic flows over the North Pacific, and negative SLP anomalies and increased wind convergence over the Indonesia and western Pacific region during IPO cold phases such as 1946–1976 and 1999–2012. These anomaly circulation patterns are roughly reversed during the IPO warm phases such as 1924–1945 and 1977–1998. The anomaly wind and SLP patterns can qualitatively explain the observed precipitation anomalies over North America, Australia, southern Africa, and other regions. Distinct wave patterns are evident in the 200 hPa height composite map, which shows the extra-tropical response to the tropical height anomalies over the maritime continent and eastern Pacific, and their northeast- and south-east-ward propagation into the higher latitudes.
Many aspects of the observed relationships between the IPO and surface T and P, and the atmospheric circulation patterns are reproduced by the CanAM4 model forced with observed SSTs from 1950 to 2009. This suggests that the SST anomalies associated with the IPO are capable of producing the observed anomalies associated with the IPO in the T, P, and atmospheric circulation fields.
The regions with T and P being affected by IPO on decadal time scales generally resemble those influenced by ENSO on multi-year time scales (e.g., McBride and Nicholls 1983 ; Ropelewski and Halpert 1986; Dai and Wig-Ley 2000; Giannini et al. 2008). Further, the IPO-composite circulation anomalies are also similar to those associated with ENSO events (Sarachik and Cane 2010). Thus, the IPO is an ENSO-like low-frequency mode not just in its SST and SLP patterns (Zhang et l. 1997), but also in its impacts on T and P and atmospheric fields. These results imply that many of the surface and atmospheric processes associated with ENSO also apply to the IPO phase changes, with the warm (cold) IPO phase resembling El Nino (La Nina). Our results also suggest that it is important to predict IPO’s phase change for decadal climate prediction
I have created the following Table to show the major findings:
| Interdecadal Pacific Oscillation (IPO) | |||
| Positive (1924 – 1945), (1977-1998) | Negative (1946 – 1976), (1999-2012) [Editor’s Note: study ends at 2012 – PDO currently is recording as positive] | ||
| Temperature | Warmer | western North American except its Southwest, mid latitude and central Asia, mid latitude central and northern Australia | northeastern North America, northeastern South America, southeastern Europe and northern India |
| Cooler | northeastern North America, northeastern South America, southeastern Europe and northern India | western North American except its Southwest, mid latitude and central Asia, mid latitude central and northern Australia | |
| Precipitation | Wetter | southwestern North America, northern India,and central Argentina | Maritime Continent including much of Australia, southern Africa, and northeastern Asia |
| Drier | Maritime Continent including much of Australia, southern Africa, and northeastern Asia | southwestern North America, northern India,and central Argentina | |
The paper also discussed the impact of the IPO on ENSO. The article likens the two phases of the IPO to the two phases of ENSO re impacts. But the phases of the IPO last longer than the phases of ENSO and we do not usually think about IPO Neutral although that exists but with ENSO, the Neutral State lasts for probably about half the cycle. To some extent it is about how Neutral is defined. At any rate the researchers in this article found cases where the IPO reinforced or muted or even reversed the normal direction of the ENSO event and I prepared this table to summarize what the authors had to say about that.
| Phase of the IPO | ||
| Positive | Negative | |
| Temperature | western Canada | northern India, northeastern Australia |
| Precipitation | southern Africa (reverse impact as this is the southern Hemisphere) | northeastern Australia |
This year the PDO has been positive so it is not surprising that El Nino impacts in northeastern Australia and and northern India have not been very significant. I think one could just as correctly since correlation is not an indication of causality (the in word these days is “attribution”) say that the PDO Positive has not been enhanced where shown in the above table by the El Nino. But it has been enhanced in western Canada (something NOAA has not noticed) and there has been significant drought in SE Africa. So it perhaps is not surprising that with a high reading of the PDO Index and the ONI that this El Nino has been northerly displaced.
I have a set of tables on Page II of my Report where I have tabulated the impacts identified by other authors. I have not had a chance to cross reference the above with what I have compiled previously. I will do that.
Let’s Now Focus on the Current (Right Now to 5 Days Out) Weather Situation.
A more complete version of this report with daily forecasts is available in Part II. This is a summary of that more extensive report. Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks will take you directly to
that set of information but it may take a few seconds for your browser to go through the two-step process of getting to Page II and then moving to the Section within Page II that is specified by this link.
Many graphics in this report are auto-updated by the source of the graphic. It is always my choice as the writer to allow these graphics to auto-update or “freeze them” to what they looked like when I write the article. Generally speaking graphics in research themes which appear above this point do not auto-update as they come from published scientific papers. When I make the decision to allow certain graphics to auto-update, it creates two issues: A. As the graphic updates, my commentary becomes out of sync with the new version of the graphic. This can be very extreme if for example you take a look at my report from months ago. B. On rare occasions, source sites for graphics go down and the graphic does not appear in the article and you probably see white space. If you experience such an event and that graphic is important to your understanding of the report, please return later to view my weather and climate column. Sometimes the “outage” is only for several minutes, but often the duration can be a number of hours or even one or more days. We feel that this inconvenience is preferable to looking at “frozen” weather map images that do not update since I write the article on Monday evenings and you probably do not read it until Tuesday and perhaps later in the week. So I want you to have the advantage of seeing the most up-to-date graphics. If the source is down, the white space is the price paid for most of the time being able to see the latest available graphics. |
First, here is a national animation of weather front and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at the link provided above.
The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.
The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients.This graphic auto-updates so when you look at it you will see NOAA’s latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot.
The MJO is not likely to have much of an impact for the month of April as a whole as this MJO cycle appears to be weak and the forecasts of phase changes are contradictory. The MJO is thought by some to be relatively unimportant during the winter but perhaps a strong El Nino increases the relevance of the MJO. It has had significant impacts this winter but the impact on April is not likely to be very noticeable. It probably will be more of a factor in the Summer. There is some thought that the MJO may have some impact in late April and early May.
Notice the Northern Pacific is like a giant anticyclone with clockwise motion so that which gets sent west due to El Nino is to some extent returned to North America but at higher latitudes. I am trying to see if I can discern a change in pattern towards lower latitudes for storms arriving from the Western Pacific but so far I do not see that in this animation.
As I am looking at the below graphic Monday evening April 18, I still see a northerly displaced pattern with the storm that hit the Southwest this weekend showing in the Plains States moving to the Midwest and on to the East Coast. This graphic updates automatically so it most likely will look different by the time you look at it as the weather patterns are moving from west to east.
Below is an analysis of projected tropical hazards and benefits over an approximately two-week period. This graphic is scheduled to update on Tuesday and I am reading the April 12. 2016 Version and looking at Week 2 of that forecast.
Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 6 (the Day 3 forecast is available on Page II of this Report). This graphic also auto-updates.
Looking at the current activity of the Jet Stream
And here is the forecast out five days.
To see how the pattern is projected to evolve, please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.
This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.
Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on “earth” adjusting the parameters and then clicking again on “earth” to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns.
And when we look at Sea Surface anomalies below, we see a lot of them not just along the Equator related to El Nino.
Below I show the changes over the last month in the Sea Surface Temperature (SST) anomalies.
6 – 10 Day Outlook
Now let us focus on the 6 – 14 Day Forecast for which I generally only show the 8 – 14 Day Maps. The 6 – 10 Day maps are always available in Part II of this report but in the Winter and Spring I often show both maps as the forecasted weather patterns change during that nine day period.
To put the forecasts which NOAA tends to call Outlooks into perspective, I am going to show the three-month AMJ Outlook and the recently updated Outlook for the single month of April and then discuss the 8 – 14 day Maps and the 6 – 14 Day NOAA Discussion within that framework.
First – Temperature
Here is the Three-Month AMJ Temperature Outlook issued on March 17, 2016:
Here is the Updated Outlook for April Temperatures issued on March 31, 2016.
Below are the current 6 – 10 Day and 8 – 14 Day Temperature Outlook Maps which will auto-update daily and thus be current when you view them. It covers the nine days following the tail end of the current week. I have included both today and probably will continue to do that as long as the patterns are moving from west to east fairly rapidly. I have also included the experimental Week 3 and 4 Outlook. I am not totally sure how often the Week 3-4 Experimental Outlook updates but it looks like it is weekly on Friday. Notice the Week 3-4 Experimental Outlook has fewer levels of probability starting with 50%.
6 – 10 Day Temperature Outlook
8 – 14 Day Temperature Outlook
Looking further out.
Now – Precipitation
Here is the three-month AMJ Precipitation Outlook issued on March 17, 2016:
April Updated Precipitation Outlook Issued on March 31, 2016
Below are the current 6 – 10 Day and 8 – 14 Day Precipitation Outlook Maps which will auto-update and thus be current when you view them. It covers the nine days following the tail end of the current week. I have included both today and probably will continue to do that as long as the patterns are moving from west to east fairly rapidly. I have also included the experimental Week 3 and 4 Outlook. I do not know for sure how often the Week 3-4 Experimental Outlook updates but it looks like it is weekly on Fridays. Notice the Week 3-4 Experimental Outlook has fewer levels of probability starting with 50%.
6 – 10 Day Precipitation Outlook
8 – 14 Day Precipitation Outlook
Here are excerpts from the NOAA discussion released today April 18, 2016. It covers the full nine-day period and this week I have shown both the 6 -10 Day and the 8 – 14 Day Maps.
6-10 DAY OUTLOOK FOR APR 24 – 28 2016
TODAY’S ECMWF, GFS, AND CANADIAN ENSEMBLE MEANS ARE IN FAIRLY GOOD AGREEMENT ON THE PREDICTED 500-HPA FLOW PATTERN OVER THE FORECAST DOMAIN. THE ENSEMBLE MEANS AGREE ON FORECASTING AN ANOMALOUSLY DEEP TROUGH OVER ALEUTIANS, AN ANOMALOUSLY DEEP TROUGH OVER THE WESTERN CONUS, AND POSITIVE HEIGHT ANOMALIES OVER MUCH OF THE EASTERN CONUS, EXCEPT IN PARTS OF NEW ENGLAND WHERE TODAY’S ECMWF DETERMINISTIC MODEL AND ENSEMBLE MEAN AND RECENT GFS DETERMINISTIC MODELS ARE FORECASTING A DEEPER THAN NORMAL TROUGH. SINCE THE ECMWF ENSEMBLE MEAN HAS SHOWN VERY GOOD RUN-TO-RUN CONTINUITY LATELY, IT’S FAVORED IN TODAY’S 500-HPA HEIGHT MANUAL BLEND.
ABOVE NORMAL TEMPERATURES ARE HIGHLY FAVORED FOR MUCH OF ALASKA DUE TO ANOMALOUS SOUTHERLY FLOW. THERE’S AN INCREASED CHANCE FOR ABOVE NORMAL TEMPERATURES ALONG THE WEST COAST DUE TO LOW-LEVEL OFFSHORE AND DOWNSLOPING FLOW. NEGATIVE 500-HPA HEIGHT ANOMALIES FAVOR NEAR TO BELOW NORMAL TEMPERATURES FOR THE FOUR CORNERS REGION AND PARTS OF THE GREAT BASIN. SOUTHERLY LOW-LEVEL WINDS AND ABOVE NORMAL 500-HPA HEIGHTS INCREASE THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND EASTERN CONUS, EXCEPT FOR THE GREAT LAKES REGION AND NORTHEAST WHERE RELATIVELY COLD SURFACE HIGH PRESSURE ORIGINATING FROM CANADA IS FORECAST TO DOMINATE THE PATTERN.
SEVERAL STORM SYSTEMS FORECAST TO IMPACT PARTS OF ALASKA FAVOR ABOVE MEDIAN PRECIPITATION FOR THE ALEUTIANS AND THE SOUTHERN HALF OF ALASKA. OFFSHORE FLOW LEADS TO INCREASED CHANCES FOR NEAR MEDIAN PRECIPITATION ALONG THE WEST COAST. AN ANOMALOUSLY DEEP TROUGH FORECAST OVER THE WESTERN HALF OF THE CONUS FAVORS ABOVE MEDIAN PRECIPITATION THROUGH MOST OF THE WESTERN TWO THIRDS OF THE CONUS. A PERIOD WITH RELATIVELY FEW STORM SYSTEMS IN THE EASTERN U.S. FAVORS NEAR TO BELOW MEDIAN PRECIPITATION THERE.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE TEMPERATURE TOOLS AND RELATIVELY GOOD AGREEMENT AMONG THE TOOLS.
8-14 DAY OUTLOOK FOR APR 26 – MAY 02, 2016
THE 500-HPA PATTERN DURING THE WEEK-2 PERIOD IS FORECAST TO BE SIMILAR TO THAT IN THE 6-10 DAY PERIOD, EXCEPT LESS AMPLIFIED. THE TEMPERATURE PROBABILITY FORECAST IS VERY SIMILAR, EXCEPT THAT PROBABILITIES OF ABOVE NORMAL TEMPERATURES BECOME LESS FAVORED OVER PARTS OF THE CENTRAL CONUS DUE TO SOME SHORTWAVE TROUGH ENERGY FORECAST TO INFLUENCE THAT AREA IN THE WEEK-2 PERIOD.
THE PRECIPITATION PROBABILITY FORECAST IS ALSO VERY SIMILAR, EXCEPT THAT A COUPLE OF STORM SYSTEMS FORECAST TO AFFECT THE SOUTHEAST AND MID-ATLANTIC AFTER DAY 10 FAVOR NEAR TO ABOVE MEDIAN PRECIPITATION FOR THOSE AREAS.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE TEMPERATURE TOOLS AND RELATIVELY GOOD AGREEMENT AMONG THE TOOLS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON APRIL 21
Some might find this analysis interesting as the organization which prepares it looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of this El Nino.
Analogs to Current Conditions
Now let us take a detailed look at the “Analogs” which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. “Analog” means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 – 14 day Outlook.
Here are today’s analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the Outlook but I have not been analyzing this second set of information. The first set which is what I am using today applies to the 5 and 7 day observed pattern prior to today. The second set, which I am not using, relates to the correlation of the forecasted outlook 6 – 10 days out with similar patterns that have occurred in the past during the dates covered by the 6 – 10 Day Outlook. The second set of analogs may also be useful information but they put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so.
Centered Day | ENSO Phase | PDO | AMO | Other Comments |
| Apr 28, 1957 | El Nino | + | – | |
| Apr 14, 1969 | El Nino | – | + | Modoki Type II |
| Apr 7, 1988 | La Nina | + | + | Following Modoki Type I |
| Mar 29, 1993 | Neutral | + | – | |
| Mar 29, 2004 | Neutral | + | + | |
| Mar 30, 2004 | Neutral | + | + | |
| Apr 15, 2005 | El Nino | + | + | Modoki Type II |
| May 1, 2006 | Neutral | + | + | |
| Mar 28, 2007 | Neutral | N | + |
One thing that jumped out at me right away was the spread among the analogs from Mar 28 to May 1 which is just under five weeks. It suggests that the prior week conditions are highly correlated with weather patterns which in the past occurred over a fairly wide range of dates as shown. There are this time three El Nino Analogs, five ENSO Neutral Analogs and one La Nina Analog suggesting that El Nino is slightly in control over our weather for the next 6 – 14 Days or perhaps more accurately the forecast best correlates with periods of time when ENSO was Neutral or in the El Nino state.
The phases of the ocean cycles in the analogs point clearly towards McCabe Condition C which suggests a dry northern tier and a wet southern tier. That is kind of where the 3-4 Week Experimental Outlook is headed. The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. Water Planners might usefully pay attention to the low-frequency cycles such as the AMO and the PDO as the media tends to focus on the current and short-term forecasts to the exclusion of what we can reasonably anticipate over multi-decadal periods of time.
You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.
Historical Anomaly Analysis
When I see the same dates showing up often I find it interesting to consult this list.
With respect to relating analog dates to ENSO Events, the following table might be useful. In most cases this table will allow the reader to draw appropriate conclusions from NOAA supplied analogs. If the analogs are not associated with an El Nino or La Nina they probably are not as easily interpreted. Remember, an analog is indicating a similarity to a weather pattern in the past. So if the analogs are not associated with a prior El Nino or prior La Nina the computer models are not likely to generate a forecast that is consistent with an El Nino or a La Nina.
| El Ninos | La Ninas | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Start | Finish | Max ONI | PDO | AMO | Start | Finish | Max ONI | PDO | AMO | |
| DJF 1950 | J FM 1951 | -1.4 | – | N | ||||||
| T | JJA 1951 | DJF 1952 | 0.9 | – | + | |||||
| DJF 1953 | DJF 1954 | 0.8 | – | + | AMJ 1954 | AMJ 1956 | -1.6 | – | + | |
| M | MAM 1957 | JJA 1958 | 1.7 | + | – | |||||
| M | SON 1958 | JFM 1959 | 0.6 | + | – | |||||
| M | JJA 1963 | JFM 1964 | 1.2 | – | – | AMJ 1964 | DJF 1965 | -0.8 | – | – |
| M | MJJ 1965 | MAM 1966 | 1.8 | – | – | NDJ 1967 | MAM 1968 | -0.8 | – | – |
| M | OND 1968 | MJJ 1969 | 1.0 | – | – | |||||
| T | JAS 1969 | DJF 1970 | 0.8 | N | – | JJA 1970 | DJF 1972 | -1.3 | – | – |
| T | AMJ 1972 | FMA 1973 | 2.0 | – | – | MJJ 1973 | JJA 1974 | -1.9 | – | – |
| SON 1974 | FMA 1976 | -1.6 | – | – | ||||||
| T | ASO 1976 | JFM 1977 | 0.8 | + | – | |||||
| M | ASO 1977 | DJF 1978 | 0.8 | N | – | |||||
| M | SON 1979 | JFM 1980 | 0.6 | + | – | |||||
| T | MAM 1982 | MJJ 1983 | 2.1 | + | – | SON 1984 | MJJ 1985 | -1.1 | + | – |
| M | ASO 1986 | JFM 1988 | 1.6 | + | – | AMJ 1988 | AMJ 1989 | -1.8 | – | – |
| M | MJJ 1991 | JJA 1992 | 1.6 | + | – | |||||
| M | SON 1994 | FMA 1995 | 1.0 | – | – | JAS 1995 | FMA 1996 | -1.0 | + | + |
| T | AMJ 1997 | AMJ 1998 | 2.3 | + | + | JJA 1998 | FMA 2001 | -1.6 | – | + |
| M | MJJ 2002 | JFM 2003 | 1.3 | + | N | |||||
| M | JJA 2004 | MAM 2005 | 0.7 | + | + | |||||
| T | ASO 2006 | DJF 2007 | 1.0 | – | + | JAS 2007 | MJJ 2008 | -1.4 | – | + |
| M | JJA 2009 | MAM 2010 | 1.3 | N | + | JJA 2010 | MAM 2011 | -1.4 | + | + |
| JAS 2011 | FMA 2012 | -0.9 | – | + | ||||||
| T | MAM 2015 | NA | 1.0 | + | N | |||||
Progress of the Warm Event
Let us start with the SOI.
Below is the Southern Oscillation Index (SOI) reported by Queensland, Australia. The first column is the tentative daily reading, the second is the 30 day moving/running average and the third is the 90 day moving/running average.
| Date | Current Reading | 30-Day Average | 90 Day Average |
| Apr 12 | -13.2 | -7.89 | -13.41 |
| Apr 13 | -14.8 | -8.62 | -13.34 |
| Apr 14 | -19.7 | -9.86 | -13.28 |
| Apr 15 | -30.8 | -11.62 | -13.36 |
| Apr 16 | -24.7 | -12.70 | -13.27 |
| Apr 17 | -19.8 | -13.55 | -13.27 |
| Apr 18 | -19.8 | -14.21 | -13.26 |
The 30-day average, which is the most widely used measure, as of April 18 is reported at -14.21 which is again clearly associated with an El Nino (usually required to be more negative than -8.0 but some consider -6.0 value good enough). It is quite a bit stronger this week due to strong SOI values all week. The 90-day average remains in El Nino territory at -13.26 not much changed from last week. Usually but not always the 90 day average changes more slowly than the 30 day average but it depends on what values drop out. The SOI continues to be indicative of an El Nino Event in progress but it is pretty much passed the time of year where it is very meaningful re El Nino development. I believe we will see a moderating trend in the SOI from here on with the possible exception of the current impact of the MJO and continued local stormy conditions in Tahiti which should end very soon.
The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.
Low-Level Wind Anomalies
Here are the low-level wind anomalies. We now see light Easterly anomalies, the blue area at the bottom of the Hovmoeller graphic. This is part of the process of cleaning up after this El Nino.
And now the Outgoing Longwave Anomalies which tells us where convection has been taking place.
Kelvin Waves
Let us now take a look at the progress of Kelvin Waves which are the key to the situation. From the earliest to the most recent they can be named #1 through #5. Kelvin Wave #1 is being pushed off the top of this graphic as more recent information is added at the bottom.
One should keep in mind that for a new Kelvin Wave, the period of time from initiation to the termination of impacts is about six months. So when you have four or five this winter six in a row, the pattern of impacts on different indices and geographic areas becomes quite complex. It is further complicated as you can see above because the Kelvin Waves do not necessarily originate at the same location i.e. longitude.
We are now going to change the way we look at a three dimensional view of the Equator and move from the surface view to the view from the surface down. This El Nino appears to be fading slowly from west to east. The real decline will be from east to west.
Current Sub-Surface Conditions. Notice the lag in getting this information posted so the current situation may be a bit different than shown.
And now the pair of graphics that I regularly provide and which as I publish are currently able to be accessed from the NOAA website:
The above pair of graphics showing the current situation has an upper and lower graphic. The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters.
The bottom half of the graphic (Absolute Values which highlights the Thermocline) perhaps is a now equally useful in terms of tracking the progress of this Warm Event as it converts to ENSO Neutral and then La Nina.
It shows the thermocline between warm and cool water which pretty much looks like this as shown here during a the transition from a Warm Event to ENSO Neutral. You can see that the cooler water is not yet fully making it to the surface to the east along the coast of Ecuador. In fact, the 25C Isotherm temporarily is not reaching the surface but almost. But there is a lot of compression of the Isotherms so from 120W on east, the 20C is close to the surface even though the 25C Isotherm does not quite reach the surface. We now will pay more attention to the 28C Isotherm as west of that temperature is where convection is more easy to occur. The 28C Isotherm had retraced east to 140W. So we are still in a weak El Nino condition not La Nina. If it passes the Dateline, the El Nino is over in terms of being able to impact CONUS weather. But we may remain in what is more like an El Nino Modoki situation for longer than most models predict although JAMSTEC is pretty much predicting that or at least something closer to a Neutral ENSO.
Here are the above graphics as a time sequence animation. You may have to click on them to get the animation going.
TAO/TRITON GRAPHIC
Let us compare the situation as reported on October 4 to the most recent graphic. Remember each graphic has two parts the top part is the average values, the bottom part is those values expressed as an anomaly compared to the expected values for that date. Generally I am mainly discussing the bottom of the pairs of graphics namely the anomalies
First the October 4 version which I am providing for purposes of comparison. I “flash froze” the daily value that day so that it would not auto-update.
And then the December 14 version which I also “flash froze” to stop it from updating.
And then the current version of the TAO/TRITON Graphic.
| ———————————————— | A | B | C | D | E | —————– |
The overall pattern is quite a bit less intense than on December 14. The 3.5C anomaly is no longer visible. Neither is the 3.0C anomaly. The 2.5C anomaly and the 2C anomaly no longer exists in the Nino 3.4 Measurement Area. So the maximum anomalies (which do not appear everywhere) have declined by a full two degrees Centigrade. This means that if one is attempting to mentally estimate the daily ONI, an approach would be to make an initial estimate of the midpoint of the 1.5C to 2.0C or 1.75C and subtract the reductions from there where the anomaly is less. Soon we will be subtracting from 1.25C. What I have just described is not exactly the approach I use in my calculation below but it does provide a quick way to get a feel for the current strength of this El Nino. There is actually shading in the TAO/TRITON Graphic that might allow one to try to refine estimates a bit more than the contour lines but I rely on the contour lines. The 1.5C anomaly is also now shrinking although it expanded some this past week. And the western part of the 1.5C anomaly is almost all south of the Equator which means that it has less than half the impact of an anomaly that extends from 5 degrees north latitude to 5 degrees south latitude. This El Nino is crashing.
And an earlier but recent reference point close to the peak of this El Nino re the bottom half of the TAO/TRITON Graphic. You can certainly see the difference that three months makes.
The below table tracks the changes. It only addresses the situation right on the Equator so visually the TAO/TRITON graphic contains more information. But the below table turns visual information into quantitative information so it may be useful. The degrees of coverage shown in the rightmost two columns shows that the extent of the warm water directly on the Equator has been reduced in recent weeks. The way I constructed the table, the 1.0C anomaly as an example includes all water warmer than 1.0C so the 1.5C anomaly is included within it as well as the 2.0C anomaly which you can tell by the way I recorded the westward and eastward coordinates. I could have constructed this table in a different way. Note the 3C anomaly no longer exists. The 2.5C anomaly also no longer exists. As this El Nino decays I am including the less warm anomalies in the table below.
| Subareas of the Warm Anomaly | Westward Extension | Eastward Extension | Degrees of Coverage | |||
| Today | January 19, 2016 | Today | January 19, 2026 | Today | January 19, 2016 | |
| 3C Anomaly | Gone | 158W | Gone | 134W | 0 | 24 |
| 2.5C Anomaly | Gone | 165W | Land | 110W | 0 | 55 |
| 2.0C Anomaly | Gone | 170W | Land | 100W | 0 | 70 |
| 1.5C Anomaly | Gone* | 175W | Land | Land | 0* | 80 |
| 1.0C Anomaly | 165W | 175E | Land | Land | 70 | 90 |
| 0.5C Anomaly | Dateline | Inf | Land | Land | 85 | Inf |
* The western portion of the anomaly is almost all South of the Equator and the above graphic only shows where the anomalies are only on the Equator. It does show on the Equator now with just over 10 degrees of coverage so I could have included it in the table.
I calculate the ONI each week using a method that I have devised. To refine my calculation, I have divided the 170W to 120W ONI measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions. So as of Monday April 18, in the afternoon working from the April 17 TAO/TRITON report, this is what I calculated.
| Anomaly Segment | Estimated Anomaly | |
| Last Week | This Week | |
| A. 170W to 160W | 1.0 | 1.1 |
| B. 160W to 150W | 1.2 | 1.3 |
| C. 150W to 140W | 1.4 | 1.5 |
| D. 140W to 130W | 1.2 | 1.4 |
| E. 130W to 120W | 1.2 | 1.3 |
| Total | 6.0 | 6.6 |
| Total divided by five subregions i.e. the ONI | (6.0)/5 = 1.2 | (6.6)/5 = 1.3 |
My estimate of the daily Nino 3.4 ONI after rounding is actually slightly up this week to 1.3. NOAA has again reported the weekly ONI to be 1.3. Nino 4.0 is being reported as being slightly lower at 0.8. Nino 3.0 is being reported as being lower at 1.2. The action which I think is most important to track right now is in Nino 1+2 which two week ago had soared to 1.5. This probably was due to Kelvin Wave #5 surfacing with some help from the MJO and marks the last Hurrah for this El Nino. It then last week was reported as being down to 1.3. Now it is reported at 0.1 which is essentially Neutral. For the Coast of South America, the El Nino is over. This is summarized in the following NOAA Table. I am only showing the currently issued version as the prior values are shown in the small graphics on the right with this graphic.
ONI Recent History
The official reading for Jan/Feb/Mar is now reported as 2.0. I have discussed before the mystery of how the CFSv2 values above get translated into the ERSST.v4 values shown below and if NOAA feels that working with two sets of books is a good way to operate, who am I argue. Many businesses do the same thing. As you can see this El Nino peaked in NDJ and is now declining and depending on what system you use it is either the 2nd or 3rd strongest El Nino since modern records were kept which is considered to be 1950. You could argue for it being #1 based on a week of readings but few are buying that argument. Still #2 or #3 means it is one of the strongest ever based on the way these events are measured. I will be writing more about that soon in a separate article. I believe the measurement system is inadequate re being useful in forecasting Worldwide weather impacts.
The full history of the ONI readings can be found here. The MEI index readings can be found here.
Is this El Nino a Modoki?
It did not evolve as a Modoki unless you consider it to be a continuation of the Faux El Nino Modoki of 2014/2015 which is a possible interpretation. But the Walker Circulation appears to be much like that of a Modoki. These graphics help explain this.
Although I discussed the Kelvin Waves earlier, now seems to be the best place to show the evolution of the subsurface temperatures.
Watching an El Nino evolve is like watching paint dry. The undercutting cool anomaly is again expanding to the east quite rapidly actually now edging east of 90W which means it has now undercut all of the warm anomaly and is ready to reach the coast of South America. All that remains is for “The Grand Switch” to occur with the cool anomaly reversing positions with the warm anomaly. So either this will be a slow process or some event will just flush the warm water to the west. It may be the next Inactive Phase of the MJO that does just that. You can also see cooler water rising but still at depth (200m) in the Eastern Pacific. It will replace the warm water in a few months. You can also see that there is not much left of the warm pool. It is not really moving back to the Western Pacific as one would expect. It is just disappearing. That may turn out to be very significant.
It SST Surface Anomaly Hovmoeller
Here is another way of looking at it: Unlike the Upper Ocean Heat Anomaly Hovmoeller (I call it the Kelvin Wave Hovmoeller) which takes an average down to 300 meters, this just measures the surface temperature anomaly. It is the surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snap shots of the conditions at different points in time. Nevertheless this Hovmoeller provides a good way to visually see the evolution of this El Nino and later track its demise. You can easily see how the intensity peaked in November 2015, declined in December and then declined substantially in late February and continues to decline.
Recent Impacts of Weather Mostly El Nino but possibly Also PDO and AMO Impacts.
Below are snapshots of 30 Day temperature and precipitation departures over the life of this El Nino. The end date of the 30 day period is shown in the graphic. It is a way of seeing how the impacts of this El Nino have unfolded.
Remember this is a 30 day average and last week I used a different graphic so this can not be compared to last week but is best compared with last month. The La Nina pattern persists for much of the West with respect to both precipitation and temperature but is a normal El Nino for the Mississippi Valley in March. Northern California was wet but it is hard to say if that looks like El Nino or La Nina. This is one strange El Nino and for the 2nd or 3rd strongest in modern history it is a mystery that has not been given adequate attention.
Lets take a look at the combined results for the first three months of 2016: January, February and March.
And here is the latest
I realize this is a lot of graphics but one needs to look at the history of an event to assess it. As you can see, so far we are not having the expected El Nino Impacts in CONUS.
El Nino in the News
Central U.S. Dousing this past weekend.
Oklahoma City Rainfall Record Broken
Putting it all Together.
This El Nino has peaked in intensity and is now in rapid decline. We are beginning to speculate on the winter of 2016/2017 which now according to most of the models seems increasingly likely to be a La Nina.
The below is the CPC/IRI forecast issued on April 14, 2016. It is important to remember that the first report in each month is based on a survey of meteorologists and the second report later in the month is based on the analysis of the forecast models. It is a minor difference but a difference.
We have suggested that it is possible the models will be wrong about how fast the Eastern Pacific Warm Pool moves back towards its La Nina location and it may well be that next winter will be more of a Neutral year or even have some characteristics of an El Nino Modoki and thus be wetter than a typical year as the Warm Pool may still be more in the Central Pacific than shifted all the way west to its La Nina position.
On the other hand, JAMSTEC is predicting more of a NEUTRAL situation
Forecasting Beyond Five Years.
So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast. The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS. It includes decade by decade predictions through 2050. Predicting a particular year is far harder.
TABLE OF CONTENTS FOR PART II OF THIS REPORT The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.
A. Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks (Usefully bookmarked as it provides automatically updated current weather conditions and forecasts at all times. It does not replace local forecasts but does provide U.S. national and regional forecasts and, with less detail, international forecasts)
B. Factors Impacting the Outlook
1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)
2. Medium Frequency Cycles such as ENSO and IOD
3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.
C. Computer Models and Methodologies
D. Reserved for a Future Topic (Possibly Predictable Economic Impacts)
TABLE OF CONTENTS FOR PART III OF THIS REPORT – GLOBAL WARMING WHICH SOME CALL CLIMATE CHANGE. The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.
D2. Climate Impacts of Global Warming
D3. Economic Impacts of Global Warming
D4. Reports from Around the World on Impacts of Global Warming
