posted on 07 December 2015
Written by Sig Silber
El Nino is arriving to CONUS but its impacts are shifted to the north possibly because this El Nino has developed further west along the Equator as compared to the Super El Nino of 1997/1998. I am not comparing the NOAA Seasonal Outlook and December Update to the JAMSTEC Outlook this week as I had planned because I think it makes sense now to wait for the December release from JAMSTEC as that will be more meaningful now that we really understand what we have with this El Nino.
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.
Let's 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. This link 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.
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. Notice the deep trough covering most of CONUS but with a ridge of High Pressure on the East Coast. Those trying to sell winter coats on the East Coast may be taking some significant markdowns right now so buyers should have their way. The speed at which this deep trough travels across the nation will determine the timing of weather impacts.
Because "Thickness Lines" are shown by those green lines on this graphic it is a good place to define "Thickness" and its uses. You can find a full uk.sci.weather style explanation (thorough) at that link or just remember that Thickness measures the virtual temperature plus moisture content) of the lower atmosphere and is very useful especially in the winter at identifying areas prone to snow and in the summer areas which are going to be hot and humid. Here is a U.S. style explanation of "Thickness" by Jeff Haby who is a valuable source at Haby Hints for anyone who wants an explanation of a meteorological term. The thickness lines are now below 540 for some areas generally signifying equal chances for snow at sea level locations. This suggests that for the next two weeks, snow is likely to be prevalent in CONUS in areas of high elevation and at lower elevations in the area impacted by the trough where the thickness levels are projected to be 540 or less. The above uk.sci.weather link is is an explanation for the U.K. The levels for CONUS might be slightly different. Obviously these thickness lines do not tell you about mountain peaks. The particular definition of "thickness" on this graphic may not be the best way to define the snow line and this is discussed in the link provided but it is I believe the older method and gives a first approximation which can be further refined as per the discussion in the link.
The following table is useful but designed for Europe. I was not able to find the corresponding information for the U.S. but it would not be drastically different. In the U.S., the last zero is dropped off the Thickness Level so where it says 5640 that would show as 564 in the U.S. Also remember the temperatures shown are in Centigrade. So 580 would correspond to about 80F in full sunshine during the summer. That is why I say the 582 and 576 thickness levels still showing up in the Eastern half of CONUS are a bit unusual for the third week of December. Although this is an imprecise tool, it is useful for a first look at the situation. One can refine the tool by looking at the temperature distribution of the air column to take into account warm and cool bias the relative humidity of the air (evaporative cooling potential) and of course the altitude as higher thickness levels will produce snow at higher elevation locations.
More information on this table is available here.
The level of storm activity in the Western Pacific has declined recently but is picking up as the MJO transitions to its active phase. 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.
Looks like NOAA has ceased updating the Tropical Weather Outlook Graphic or at least it has not been updated since November 30 so I am not presenting it this evening so we have one less graphic to look at. The graphic below is harder to look at than the one I have deleted but it provides more detail on the water vapor in place which is a good proxy for where precipitation can occur. It covers a much larger area within CONUS so you can see where the moisture currently is and is going. This graphic is very good at pointing out the divisions between cloudy and not cloudy areas. As I am looking at this graphic Monday evening, I see a pattern which is much more active in the Northern part of CONUS than the Southern Tier. This graphic updates automatically so it most likely will look different by the time you look at it.
Below is an analysis of projected tropical hazards and benefits over an approximately two-week period. There are two views.
The first graphic (A) is focused on the Eastern Tropical Pacific including North and South America. It updates on Friday so on Monday when I write my report, I pay most attention to this graphic for information on the tropical area of North and South America but it is mostly the week-two part of the forecast that is still relevant by the Monday following the Friday update.
The second graphic (B) covers the same area as the first graphic but it also covers the Western Pacific and the Indian Ocean. Since it updates on Tuesday, the first graphic (A) is more current on Monday evening for the Eastern Pacific including the tropical part of North and Central America which includes the U.S. Southeast. But by Tuesday, Graphic (B) is the preferred choice for the entire area of interest.
When looking at a lot of graphics, the dates for which the graphic applies and the dates when issued and updated become very important in making sense out of the information. It is easy to draw incorrect conclusions by not considering or getting confused by the different timeframes. The below discussion is based on the two graphics as shown on Monday but they continue to auto-update during the week and may look different than what I am seeing by the time you view them. More information on these two graphics can be found here.
Graphic "A" (which updates on Friday and from which I use the Week 2 of the forecast to look at North and South America). What is it telling us this Monday evening?
Graphic B (which updates on Tuesday and on a Monday I use the Week 2 of this Forecast to look at the Western Pacific and Indian Ocean). What is it telling us this Monday evening?
Mostly I see a dry conditions in the Western Pacific combined with the perhaps wet conditions in the Arabian Sea but dry conditions off of Mozambique including Madagascar. I also seen no (Tropical related) anomalies in North America but a combination of drought in Brazil and Uruguay. This graphic is scheduled to update on Tuesday and I am reading the Dec 1, 2015 Version.
Below is a view which highlights the surface Highs and the Lows re air pressure on Day 3. I usually only show the 6 day graphic on Page I of my report (they both are always on Page II of my report) but because of the volatility of the situation in the Pacific this time of the year, I am again showing both this week.
Here is the Day 6 forecast In recent weeks the projected location and strength of the Aleutian Low has varied a bit. On some days, the forecast is showing a split low with each of the two lows weaker than a combined single Low and this is not characteristic of El Nino. Right now the Aleutian Low is projected on Day 6 to be less ideally located than on Day 3 to provide precipitation to the Northwest. It's hPa of 972 is quite intense (the average in the winter is 1001hPa and 994 hPa for a non-split Low). The rapidly shifting position of the Low makes a big difference. As shown, the Day 6 forecast no longer calls for the RRR to valiantly "protect" the entire West Coast from Pacific storms but instead is steering storms into the U.S. Northwest but not as dramatically as one would expect with a strong El Nino. A longer discussion of the climate of Beringia and the role of the Aleutian Low is in Part II of this Report: 2. Medium Frequency Cycles such as ENSO and IOD.
Looking at the current activity of the Jet Stream one can certainly see the northern entry point for the Jet Stream which is not characteristic of El Nino.
And the forecast out five days. Of course this is a forecast and changes daily or perhaps even more frequently. The pattern has become increasingly meridional with the Jet Stream forming troughs and ridges as it moves across CONUS often with a split stream. But the point of entry to CONUS is further to the north than one might expect during a strong El Nino. But there certainly is an impressive trough.
To see how the pattern is projected to evolve, please click here. The activity is projected to become quite meridional which allows troughs to bring precipitation down to lower latitudes. 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.
And when we look at Sea Surface anomalies we see a lot of them not just along the Equator related to El Nino. Today one no longer sees a fading of the warm anomaly off of Ecuador except for north of the Equator and perhaps a continued reduction in the size of the warm anomaly around Baja California which sometimes is referred to as the "BLOB". It is an unusual occurrence which the Japanese have referred to as the California Nino. If they are correct about that, it could mean that this short cycle might reinforce the La Nina next winter.
The two graphics below show first the changes over the four weeks (ending November 4) as compared to the above graphic which shows the current SST anomalies and then the changes over the four weeks ending on December 2, 2015. Looking at both of these change in anomaly graphics is helpful in putting the current situation shown above into perspective.
First the four weeks ending on November 4, 2015
I am also showing the new version issued today which basically shows the changes over the last month in the Sea Surface Temperature anomalies.
These graphics are hard to interpret because they are four-week changes. But you have the daily values three graphics up. Here you see very little strengthening in the El Nino in the Nino 3.4 Measurement Area but some increase in the warm anomaly just off of Ecuador. More importantly you see the extreme cooling of the warm anomaly off of the West Coast of the U.S. (reducing the degree of PDO+) and also the pattern in the Indian Ocean eliminating the Positive IOD. The anomalies off the west coast of South America are much cooler also signaling the setting of the stage for the decline phase of this El Nino So there are some changes taking place. The cooling of the waters in Beringia is also quite important re the impact on CONUS.
6 - 14 Day Outlooks
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 available in Part II of this report.
To put the forecasts which NOAA tends to call Outlooks into perspective, I am going to show the three-month DJF and the "early" single month of December forecasts and then discuss the 8 - 14 day Maps and the 6 - 14 Day NOAA Discussion within that framework. Some of these graphics are repeats of graphics that I presented earlier as part of the discussion of the NOAA Update.
Here is the Three-Month Temperature Outlook issued on November 19, 2015:
Here is the Updated December Temperature Outlook issued on November 30, 2015.
Below is the current 8 - 14 Day Temperature Outlook Map which will auto-update and thus be current when you view it. It covers the week following the current week. Today's 6 - 14 Day Outlook is just nine days 0 the month and the map shown below of the 8 to 14 day Outlook only shows seven days. The 6 - 10 Day Map is available on Page II of this report. As I view this map on December 7 (it updates each day), it appears that the third week of December may be more of an east - west temperature divide than the north - south temperature divide forecast in the full month Outlook.
Here is the three-month Precipitation Outlook issued on November 19, 2015:
And here is the month of December Precipitation Outlook which was updated on November 30, 2015.
Below is the current 8 - 14 Day Precipitation Outlook Map which will auto-update and thus be current when you view it. It covers the week following the current week. Today's 6 - 14 Day Outlook is just nine days of the month and the map shown covers seven days of the nine. The 6 - 10 Day Map (the two maps overlap) is available on Page II of this report. As I view this map on December 7 (it updates each day) and also taking the 6 - 10 Day Outlook which you can find on Page II of this Report into account, it appears that the third week of December may be a transition period as a new storm enters CONUS from the Pacific while an East Coast Storm plays out. It is not inconsistent with the full-month Outlook.
Here are excerpts from the NOAA discussion released today December 7, 2015. It covers the full nine-day period not just the seven days shown in the 8-14 Day Map.
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. This first set applies to the 5 and 7 day observed pattern prior to today. The second set which I am not using relates to the forecast outlook 6 - 10 days out to similar patterns that have occurred in the past during the dates covered by the 6 - 10 Day Outlook. That may also be useful information but they put this set of analogs in the discussion with the other set available by a link so I am assuming that this set of analogs is the most meaningful.
One thing that jumped out at me right away was the wide spread among the analogs from November 16 to December 21 which is almost five weeks and there are seven analogs that are future dates really suggesting that we have a mix of Fall and Meteorological Winter analogs which is bit different than the 6 - 14 Day Outlook suggests. There are this time six El Nino Analogs and just one La Nina Analog and three ENSO Neutral Analogs so this does suggest that El Nino is a major factor in our weather over the next 6 - 14 Days but this is not fully reflected in the 6 - 14 Day Outlook released today. Actually it is but in a strange way. The phases of the ocean cycles are consistent with McCabe Condition B and D which are pretty much the exact opposite of each other. The Pacific is clearly in control in that the analogs are associated with previous conditions when the PDO was Negative not Positive. Earlier I indicated that the reported anomalies are clearly showing an easing of the PDO Positive Condition and the Analogs are consistent with that. 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.
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.
The Inactive Phase of the MJO is playing out and shifting to the Active Phase so we are again seeing more negative values of the SOI. The Active Phase may be with us for most of December and then switch back to the Inactive Phase in January.
The 30-day average, which is the most widely used measure, on December 7 is reported at -7.19 which unlike last week is again a reading that is associated with an El Nino (usually required to be more negative than -8.0 but some consider -6.0 value good enough). The 90-day average also is more negative this week and thus more in El Nino territory at -15.25. The SOI again is indicative of an El Nino Event in progress. This past week there have been early in the week some fairly extreme values but still much lower values than were recorded during the 1997/1998 Super-El Nino. It is not surprising that we are seeing another round of higher (negative) SOI values in December due to the change in phase of the MJO and that might be the end of it in terms of impact on winter weather but we probably will see January having a less active MJO and February a more active MJO. I do not mean to imply that the phases will line up exactly with the first of each month and will update the above discussion as the phases evolve.
Low-Level Wind Anomalies
Here are the low-level wind anomalies. In October, the area from 180W to 160W was of interest and quite intense. There then was an area of interest at 160W which also was quite intense. Now, calm appears to prevail but that likely will change as the MJO changes phase and becomes more active.
In the below graphic, you can see how the convection pattern (really cloud tops) no longer shows the pronounced pattern that has existed for a number of months. This is especially evident to the west of the Date Line. But east of the Date Line the wet anomaly is now more robust and drifting to the East which could be a precursor to more impacts on CONUS.
Let us now take a look at the progress of Kelvin Waves which are the key to the situation. Since February there have been three successive "genuine" downwelling Kelvin Waves without really an upwelling Kelvin Wave of any consequence to counter their impact. The first wave which started in February was the most effective at getting this El Nino started. The second wave reinforced to some extent but not much and this third (and I had believed would be the last) downwelling Kelvin Wave has created an El Nino that will have a major peak coming soon and an extended life but at a diminished strength. We now see a fourth Kelvin wave which will extend the life of this El Nino. The most extreme temperature anomaly colored gray in the graphic, is beginning to slowly cover a smaller part of the Equator but has shifted to the east and is now located at 128W to 90W which means a smaller portion is in the ONI/Nino 3.4 Measurement Area namely the part that is between 128W and 120W. We also see a slow steady retreat to the east of the western extreme of this pattern. There is also an expansion to the east of the cold anomaly which is undercutting the warm anomaly. NOAA has now recognized this as the upwelling phase of Kelvin Wave #4.
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. When I examine the current situation as compared to the 1997/1998 El Nino which I described graphically recently, the current El Nino has developed more rapidly. This El Nino is a couple of months further along in its evolution than the 1997/1998 El Nino and I previously thought that would result in this El Nino ending earlier in the winter than the 1997/1998 El Nino. Also the 1997/1998 had a slightly larger amount of warm subsurface water in the Eastern Pacific and that water takes time to surface, create convection, and thus cool. Something happens to allow the Easterlies to resume their strength and that in turn moves this water back towards the Western Pacific Warm Pool. This El Nino appears to be fading slowly from west to east. The real decline will be from east to west so that may be starting but has not progressed to any large extent as yet but there are signs that it is beginning.
Current Sub-Surface Conditions
Top Graphic (Anomalies)
The above graphic 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 top graphic is still the most useful of the two and shows where 2C (anomaly) water is impacting the area in which the ONI is measured i.e. 170W to 120W. The 2C anomaly now extends to 180W which is very impressive.The 3C anomaly now extends to beyond 160W so I am viewing the 3C anomaly as still encompassing 80% of the Nino 3.4 Measurement Area for the ONI. It explains why NOAA is coming up with such high ONI estimates. The 4C anomaly is now intersecting the surface at 125W to 110W and in some small areas to the west and east of this more obvious venting of Kelvin Wave #3.
It is important to differentiate between anomalies and actual temperature. The warm anomaly shown in the upper graphic is not covered by colder water as it might appear to be in the upper graphic but is shown as a warm anomaly because normally water at those depths is colder than it currently is. That is why this warm anomaly does not simply rise to the surface as warm water would normally do but it is preventing cooler water from entering the area as one would expect as summer transitions to Fall. That is why it takes time for this warm anomaly to dissipate.
Bottom Graphic (Absolute Values which highlights the Thermocline)
The bottom half of the graphic may soon become more 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 Warm Event. 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 no longer reaches 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. Right now that Isotherm intersects the surface close to 120W which which is consistent with the El Nino still intensifying.
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.
And then the current version of the TAO/TRITON Graphic..
With the current graphic, there is a lot of resemblance to the situation on October 4 in terms of the location of the warm anomaly but it is now much more intense. .
The new Kelvin Wave (#4) over at 170W appears to have merged with the overall warm pool. The 2C anomaly on Oct 4 was showing all the way over to 170W. Now it extends even further to the west.This graphic changes quite a bit from day to day so my commentary can be out of date as quickly as tomorrow. The 3C anomaly now extends to 160W. We do not see today a 3.5C Isotherm. The Easterlies are diminished but now show as Easterlies almost everywhere (top graphic) which is different than on October 4, 2015 when the anomalies were so strong that west of 150W they showed as having been converted into Westerlies. That could be an indication that the conditions for maintaining this El Nino are slowly changing.
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 December 7 in the afternoon working from the December 6 TAO/TRITON report, this is what I calculated.
My estimate of the Nino 3.4 ONI after rounding has decreased slightly to 2.8. NOAA has today reported the weekly ONI as being 2.9 insignificantly lower than last week but still lower and this is the second week in a row that the level has declined. Nino 4.0 is now reported as being 1.7, also slightly lower than last week, which probably reflects the passage of the new and fourth Kelvin Wave. Nino 3.0 is now being reported as 2.9 also slightly lower than last week. I believe it peaked at 3.7 during the El Nino of 1997/1998. This is one of many reasons for thinking that this El Nino is shifted to the west to some extent. Also, it may not be significant but I calculated an ever so slightly lower value in what I define as Area E as compared to Area D, but that is probably a short-term situation. But it is there where we would expect to see the first signs of a significant decline in the ONI.
The action which I think is most important to track right now is in Nino 1+2 which is now reported as being 2.4 which is the same as last week. One issue remains the extent to which warm water off of Ecuador and Peru impacts CONUS weather. I think it has very little impact except from the tropical storms that move up the west coast of Central America and sometimes contribute moisture to the circulation over CONUS. Most El Ninos decay from east to west so it will be observed most clearly first in Nino 1+2 and we are now probably seeing that process starting but very slowly.
This is summarized in the following NOAA Tables and I am showing both the table for six weeks ago and the updated table.
And here are the values this week.
One can in the bottom chart on the right see the significant decline in the Nino 1+2 measurement area but it has not increased this week. It is higher than two weeks ago but that is probably the impact of Kelvin Wave #3 but should be short lived. This is confirmed in a graphic that I present later. I think it is quite possible that this El Nino has now peaked and has begun its decline. But NOAA is still reporting increases in the ONI value but not this week.
One wonders about these calculations as they appear to not be related to the "adjusted" version of the NOAA forecast model which was discussed recently. So it is not clear to me how this El Nino will be officially recorded. September-October-November has now been recorded as having an ONI of 2.0.
In the NINO value graphic one graphic up, eyeballing it you might conclude that the three months were observed as being 2.3, 2.4, and 2.5. So the impact of adjusting these observed values to what is considered "adjusted" is not obvious to me. If 2.3, 2.4, and 2.5 when averaged and adjusted by NOAA come to 2.0 how should we interpret the unadjusted weekly value of 2.9? To me (and some other knowledgeable folks) it is meaningless but I dutifully report it. One expects that OND value will be higher than 2.0 and rival or exceed the 2.3 max value (not shown in this graphic but which can be found here) for the 1997/1998 El Nino but the Nino 3.0 value for this El Nino, which is the value that many Asian Weather services put a lot of emphasis on, is much lower for this El Nino than the 1997/1998 El Nino. That is because this El Nino is centered further to the west than the 1997/1998 Super El Nino.
Although I discussed the Kelvin Waves earlier, now seems to be the best place to show the evolution of the subsurface temperatures.
I do not see much change week to week as watching an El Nino evolve is like watching paint dry. A couple of things are interesting. The cool anomaly in the west under the warm anomaly is slowly creeping east undercutting the warm anomaly and now is now a bit further east of 150W. In the east at around 100W it still looks like the warm anomaly is gradually splitting into two pieces. This sequence of four Kelvin Waves has made for a complex pattern.
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. 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. One can easily see the historical evolution of this El Nino and also the current "hot spots" that are showing up and leading to the very high ONI readings. But one can also see the western edge of the warm anomaly starting to shift to the East.
The advantage of the above graphic is that it auto-updates. The advance of the NOAA version released on Mondays is that it is easier to read (it is prettied up) and today it is very informative so I include it.
You can more clearly see at the very bottom of this graphic, which shows the most recent readings, the slight easing of the extreme temperature anomalies in the Nino 3.4 Measurement area (see the scale on the right: red is less warm than dark red) namely 170W to 120W. That explains the slight reduction in NOAA ONI estimate. That is likely to continue to be the trend.
Recent Impacts of Weather Mostly El Nino but possibly Also PDO and AMO Impacts.
First the Temperature and Precipitation Departures from about six months ago (Ending Date June 13)
Then the same graphic one month later (Ending Date July 11)
And then the same graphic (Ending Date August 8).
And now the view from September 5 which is one month later.
And again four weeks later (Ending Date October 3, 2015)
And again four weeks later (Ending Date October 31, 2015)
This provides a six-month sequence of snapshots of the four-week departures from normal as this El Nino has progressed.
You can see these graphics as well as I can and it is difficult to describe the changes that have taken place over six periods of time because of the large number of changes. Currently we see:
And one more:
Strangely, it looks generally warmer and bit wetter but the warmer is fairly unusual for El Nino especially in the Southwest. But this is a 30 day average. I have not shown the graphic from last week but the warm areas are a bit less intense than last week and that should change a lot by next week. The wet areas are a typical El Nino pattern but that might change by next week if the Jet Stream remains mostly to the north.
And one more. And here you see some major changes which is a bit of a surprise given that the difference between the below graphic and one above is just fourteen days out of thirty.
I realize this is a lot of graphics but one needs to look at the history of an event to assess it and this 30 average really shows the shift in the temperature pattern and precipitation pattern. The wet area is the Central part of CONUS not the Southwest but the Southeast is joining in. The Southwest and really all the West has actually been quite dry. The warm anomaly has shifted east. There has been less (but still some) impact (mostly Texas) from tropical storms moving up the west coast of Mexico. The Northeast has been dry. Sometimes data and the media and even local weather forecasters are not in sync.
This graphic illustrates the northern tendency of this El Nino which typically impacts the Southeast and to a lesser extent the Southwest. That might happen as the Winter unfolds.
View from Australia
I do not see much change from the graphic released two weeks ago. Here is the discussion just released:
IOD (Indian Ocean Dipole)
I see a change from the graphic released two weeks ago in that the IOD index no longer looks to be pushing up against the limit later this year. The graphic comes with only a very short discussion and here is that discussion most if not all of which was covered under the El Nino discussion.
The interrelationship between the IOD and El Nino is complicated and not fully understood. But it does appear that the impact of this El Nino on the Indian Ocean and Western Pacific has become less intense and the focus is now on CONUS (and South America) and possibly also Western Europe.
El Nino in the News
This article is interesting.
It is sort of accurate but the records are kept based on three-month averages and so far the highest has been 2.0 so that is not breaking any records yet. It is a little early to declare this one the strongest. It will probably record the highest in Nino 3.4 which is what NOAA uses but not the highest in Nino 3.0 which Asia considers very important. The reason for this is that this El Nino is shifted a bit further to the west. The three strongest El Ninos were in 97/98, 82/83 and 72/73. So I am not sure that you can say that 2015/2016 represents an increasing trend towards strong El Ninos. Plus the way they adjust the base climatology, it makes it hard to even compare them. The ratio of El Nino to La Nina is higher when the PDO is positive which should happen soon if not already but that is a cycle and it is thus not correct to attribute that to Climate Change. This information i.e. how the ratio of El Nino to La Nina events is tied to the phase of the PDO is well known and I have myself calculated it and reported on it in this Weather Column, but many writers including many of the older meteorologists seem not to understand this. There is much new information on the science of meteorology and it is important for practitioners to remain up to date.
Putting it all Together.
The subsurface reservoir of warm water in the Eastern Pacific has reached its maximum and is now beginning to discharge. This would have occurred earlier if not for Kelvin Wave #4.
El Nino I believe has peaked in intensity and plateaued but NOAA continues to report ever increasing values for the ONI but they are marginal increases and should start to decline soon.
The actual impacts on CONUS are not clear. The impacts in the Indian Ocean seem to have peaked and are moderating. Same goes for the Western Pacific. Now the focus shifts to North and South America. So far the impacts to CONUS appear to be shifted further north than usual for an El Nino. That may change as the winter unfolds but that is by no means certain.
There does not seem to be an obvious match to any prior El Nino in the modern era which to me means there is no model to use to predict impacts. That is a complicated subject which is probably best dealt with on a post mortem basis.
We may or may not have a Pacific Climate Shift as the PDO+ may be simply related to the Warm Event and quite frankly at this point appears to be and may be moving back to PDO Negative. But for now we do have PDO+ but less so than a couple of months ago. The AMO being an overturning may be more predictable so the Neutral status moving towards AMO- is probably fairly reliable but not necessarily proceeding in a straight line as indeed the storm track for hurricanes in the Atlantic is suddenly unusually warm.
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.
We are beginning to speculate on the winter of 2016/2017 which it now seems increasingly likely will be a La Nina. One thing that is fairly certain for the U.S.based on historical patterns is that compared to this winter the following winter is likely to be:
The below is the recently issued CPC/IRI forecast (which has not been updated since two weeks ago) and you can see the rapid shift away from El Nino that is now predicted starting in AMJ and really showing up in MJJ 2016 i.e. late Spring early Summer 2016.
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)
1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)
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
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