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posted on 14 September 2015

14 September 2015 Weather and Climate Report - Waiting for El Nino

Written by Sig Silber

It may be a long wait as so far there are no indications of major El Nino impacts on CONUS in September. But Fall may be just around the corner and that may trigger a change in the pattern. 

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.

I thought this comparison of the three strongest El Nino's since 1950 with the current El Nino would be interesting. The red numbers are El Nino values; the blue are La Nina Values. I am just show the ONI values for the three strongest El Ninos and the current one. 

comparison of 72/82/97 and current El Nino

Obviously we do not know how this one will play out but I wanted to see if there were any clues as to which of the other three Super-El Ninos this one might most resemble.

What I see is that this one had an ONI of 0.5 or higher two months earlier than the 1997/1998 El Nino. But it has strengthened a lot faster than the 1982/1983 El Nino. Notice the 1972/1973 El Nino peaked in OND as this one most likely will also. But the PDO stayed negative during the entire duration of the 1972/1973 El Nino and the AMO also was negative. The 1982/1983 El Nino occurred during PDO+/AMO- conditions which are very favorable for the development of a traditional El Nino. The 1997/1998 El Nino occurred during PDO+ and AMO+ conditions but it was true PDO+ and not induced by the El Nino which most likely is the case with this El Nino. Also the AMO was far more positive at that time and now is close to neutral but may be reading positive during recent weeks.

So I conclude that we do not have a good model. The NOAA analogs are totally inconsistent with regards to suggesting that current conditions are reminiscent of past conditions. So we have little to go on. And yet NOAA and JAMSTEC are certain they know what the impacts will be. It is good to have confidence even if your basis for that confidence may make no sense.

Perhaps I should have shown 2014 also as it was close be recording as an El Nino which was not the case for the other three which were not immediately preceded by what was almost an El Nino. That is another reason why I have basically zero faith in the NOAA and JAMSTEC forecasts. To me this is uncharted territory. 

NOAA will issue an updated Seasonal Outlook on Thursday. At the end of this report I show the latest model runs from Australia. I was going to compare the NOAA and JAMSTEC seasonal outlooks but since both will have new maps soon that seems like a silly exercise to compare soon-to-be out of date information. And I am not inspired to discuss any particular weather or climate theme.  

I am overwhelmed by the beauty and effectiveness of the new NOAA short-term forecast animation so I think that I want to start by Taking a Look at 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 fuller report. This link Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks will take you directly to that set of information but in some Internet Browsers it may just take you to the top of Page II where there is a TABLE OF CONTENTS and you may have to wait for a few seconds for your Browser to redirect to the selected section with that Page or if that process is very slow you can simply click a second time within the TABLE OF CONTENTS to get to that specific part of the webpage.

First, here is a national animation of weather front and precipitation forecasts with four six hour updates and a second day of two 12 hour updates the second of which is intended to provide coverage out to 60 hours. Beyond 48 hours, additional maps are available at the link provided above.

current highs and lows

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 implement 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. You can see the location of the Four Corners area where Utah, Colorado, Arizona, and New Mexico meet. At this time of the year there is typically a high pressure system near that area and it is called the Four Corners High. When the Four Corners High is centered directly over the Four Corners area, it creates pretty much a block for the Sonoran Monsoon which only visits its northern neighbor when the highs and lows are located in a way that draws the moist air north.

Small changes in the location of that feature make a big difference in the weather of probably about ten or more states.

This High moves around a lot so by the time you view this report, it most likely it will be located somewhere else which results in a different circulation pattern. The current position as I am finalizing my report is shown way to the southeast . That suggests to me that forecasting moisture entering CONUS from Mexico will be quite difficult. Remember this is the mid-atmosphere High: the short-term location of the Surface High is shown in the above animation and it is in a more normal location but may not be very effective at influencing circulation that extends into Mexico. If you know where the High is, you can always imagine the clockwise circulation and how that might impact the movement of moisture in from the Gulf of Mexico and up from Mexico and in from the Gulf of California. So this graphic can be very very useful. And it auto-updates, I think every six hours. Even without a weather map, you generally can figure it out. Wind to your back, High to your right, Low to your left.

7 Day 500 MB Geopotential Forecast

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 (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 of Haby Hints for anyone who wants an explanation of a meteorological term.

The level of storm activity in the Western Pacific has tapered off quite a bit. There has been a lot of press about record numbers of strong storms in the Pacific but I do not see them as clearly as the media does. It seemed more active a few months ago. 

Western Pacific Tropical Activity

At this time of the year, warm water off of the coast of Mexico, such as from an El Nino or a positive PDO reduces the ocean/land temperature differential and can weaken the Monsoon overall but the cyclones generated by that warm ocean water can enhance the Monsoon for short periods if those cyclones stay close enough to the Mexican coastline. So that is what is being watched now and Linda has just about ceased to be a factor.

There is a trailing storm to Linda but this one seems to be further offshore. This graphic is showing the current water vapor with the location of storms forecast out two days so you see what I see. And what I see is a pattern that is keeping Mexico fairly dry.

But each of these El Nino related tropical storms off the coast of Mexico has the potential, if they are close enough to shore, to introduce moisture into the circulation that enters CONUS and that has been the case this summer but it is sporadic. It also mostly benefits the western side of Mexico and the western reach in CONUS of the Southwest Monsoon but there has been a tendency for some of that moisture to also benefit New Mexico. But overall it has diminished the impact of the Southwest Monsoon as it has cut off any Gulf of Mexico involvement and generally has impacted a smaller number of states than is usually the case. For Mexico, an El Nino is a drought event. 

.Eastern Pacific Tropical Storms

The graphic below is harder to look at but provides more detail on the water vapor being generated by these storms and the normal summer action of the Southwest Monsoon. 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 lot of clear sky especially east of the Mississippi. It seems to me the the Monsoon  is essentially over even though my local forecasters have not given up on it just yet but as of today have declared that probably this weekend is the last hurrah for this years Monsoon which in my opinion was not a true Monsoon but really a compromised Monsoon due to a reduced differential between land the ocean temperatures. The Spring was wet but during the summer the main action was the impact of cyclones off the coast of Mexico rather than a season shift in the direction of the prevailing wind which is the definition of a Monsoon.   

 Water Vapor Imagery

Here is a broader view of projected tropical hazards and benefits over an approximately two week period. There are two views. One is more focused on the Pacific and one that includes the Indian Ocean and covers Asia more completely. Both graphics auto-update on Fridays. More information can be found here. The discussion at that link there may update on Tuesdays. I am not sure. Looking at the first graphic, there is no indication of sustained Monsoonal activity in the U.S. The wet area is the Gulf of Mexico. As I have indicated, we seem to be cycling through wet and dry periods caused by tropical storms off the coast of Mexico which are in some cases providing a flow of moist air into CONUS which impacts the Southeast and sometimes a much wider area. 

Tropical Hazards

This graphic covers a larger part of the world. You see more activity over by Asia. 

Tropical Hazards

Below is a view which highlights the surface Highs and the Lows re air pressure on Day 6 (Day 3 can be seen in Part II of this Report). We now see something very different than what we have been seeing for a long time and that is a low-pressure system centered on the Alaskan Panhandle but moving east. I can not tell you if that Low originated as the Aleutian Low which is normally strong in the winter but it has the ability to move moisture into the northern tier of CONUS possibly all the way down to California but so far the NOAA forecast is not showing impacts quite that far south. One interesting question is the action of the weakened Subtropical High.  Will it able able to force the new storm moving north along the coast of Mexico out to sea as is normal or will that storm get "trapped" and provide moisture into CONUS. That will make a big difference in our weather over the next week or so.  

Day 6 Weather Forecast

We now need to monitor the Jet Stream to see if it is shifting to the South. This is the forecast out five days. The activity still appears to be mostly north rather than south but we are starting perhaps to see that changing a bit. 

Jet Stream Five Days Out

To see how the pattern is projected to evolve, please click here. Is this the beginning of the shifting to the south of the Jet Stream which one would expect with and El Nino? I think it is too soon to draw that conclusion but time will tell. Perhaps October.

And when we look at Sea Surface anomalies we see a lot of them not just along the Equator related to El Nino. But the extent of the warm water off the West Coast appears to be a bit less than recently. Also you can see along the Equator that the El Nino is less intense along part of the South American Coast. But the Atlantic has really heated up. But look at the colder water off of the U.K. You can tell a lot from this graphic.  

Daily SST Anomaly

This graphic actually shows the changes over the last four weeks. 

Sept 14, 2015 four week changes in SSTs

You can see the cooling off the west coast of the U.S. and the very small but important change in the El Nino situation. You can also see the change in the Atlantic which to me at this point is unexplained. The cool water off of the U.K. has actually warmed over the past four weeks. This is an important graphic but not much attention is paid to it. That is a shame.  

In theory the meteorological models take all this information into account but I have become skeptical about the ability of these models to make useful predictions. 

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 and single month of September forecasts 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 Temperature Outlook

SON Temperature Outlook Issued on August 20, 2015

And here is the September only Temperature Outlook Issued on August 31, 2015. It is slightly different but not much different from the three-month Sep-Oct-Nov Outlook  And we have to remember that the latest NOAA thinking is that the second half of September will be different from the first half so that the second half may well be very much like the prior Sep - Oct - Nov Outlook. However the Outlook released today does not support that earlier thinking with respect to temperature. 

Sept 2015 Temperature Outlook Updated on August 31, 2015

Below is the current 8 - 14 Day Temperature Outlook 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 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 September 14 (it updates each day) it appears that the map is consistent with the September Temperature Outlook issued on August 31 for the eastern part of CONUS but not for the western part of CONUS. Also it does not reflect the perspective that El Nino will be a factor in the next two weeks. 

8-14 Day Temperature Outlook

Now Precipitation 

Here is the three-month precipitation outlook which was issued on August 20.

SON 2015 Precipitation Outlook Issued on August 20, 2015

And here is the September Precipitation Outlook Update Issued on August 31, 2015. It is a bit different than the three-month outlook but it is not clear if that difference is simply the belief that the first part of September will be different than the second half which presumably then is related to the October and November Outlooks. 

September 2015 Precipitation Outlook Issued on August 31, 2015

Because the Precipitation Outlook is cycling week to week, I have decided to show both the 6 -10 day and the 8 to 14 day maps on Page 1 of my Report.

First the 6 - 10 Day Outlook:

Current 6 -= 10 day Precipitation Outlook

And then the current 8 - 14 Day Precipitation Outlook. Both the 6 - 10 Day and 8 - 14 Day Outlooks will auto-update daily and thus be current when you view them. As I view both maps on September 14 (it updates each day), one can imagine how these maps are related to the Monthly Outlook issued on August 31, 2015. 

Current 8 - 14 Day Precipitation Outlook

Here are excerpts from the NOAA discussion released today September 14, 2015.

6-10 DAY OUTLOOK FOR SEP 20 - 24 2015

TODAY'S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN GOOD AGREEMENT ON THE  500-HPA MEAN CIRCULATION PATTERN FORECAST OVER MOST OF THE NORTH AMERICA DOMAIN FOR THE 6-10 DAY PERIOD. A TROUGH IS PREDICTED OVER THE GULF OF ALASKA AND ALONG THE WEST COAST OF THE CONTINENT, WHILE A WEAK RIDGE IS EXPECTED OVER THE SOUTHERN PLAINS AND THE WEST GULF COAST. TODAY'S MANUAL BLEND CHART INDICATES BELOW-NORMAL HEIGHTS FOR THE NORTHWEST, WITH ABOVE-NORMAL HEIGHTS OVER THE NORTHEAST, WHICH IS BASED LARGELY ON TODAY'S ENSEMBLE MODELS, AS WELL AS THE HIGH RESOLUTION GFS, ACCORDING TO RECENTLY SKILL. TODAY'S 00Z ENSEMBLE SPAGHETTI DIAGRAMS INDICATE LOW TO MODERATE SPREAD ACROSS THE MAJORITY OF THE  FORECAST DOMAIN.

THE 500-HPA HEIGHT MANUAL BLEND FAVORS ABOVE AVERAGE TEMPERATURES ACROSS THE CONUS EXCEPT THE PACIFIC NORTHWEST, DUE TO A SOUTHERLY COMPONENT TO THE FLOW AND ABOVE AVERAGE HEIGHTS OVER MUCH OF THE CONUS EAST OF THE MISSISSIPPI. BELOW-NORMAL 500-HPA HEIGHTS AND TROUGHING INCREASE THE CHANCES FOR BELOW-NORMAL TEMPERATURES FOR THE PACIFIC NORTHWEST, ALASKA AND THE ALASKA PANHANDLE.

THE TROUGHING OVER THE GULF OF ALASKA AND ACTIVE STORM TRACK OVER THE PACIFIC FAVOR ABOVE MEDIAN PRECIPITATION OVER NORTHERN ALASKA AND THE ALASKA PANHANDLE, AND THE PACIFIC NORTHWEST. THE ACTIVE SHORT WAVES AHEAD OF THE TROUGH FAVOR ABOVE MEDIAN PRECIPITATION FROM THE SOUTHERN ROCKIES TO THE SOUTHERN PLAINS AND ACROSS THE OHIO VALLEY. A TROPICAL SYSTEM MAY PROVIDE ADDITIONAL MOISTURE TO SOUTHERN CALIFORNIA, BUT UNCERTAINTY IS HIGH AT THIS POINT. THERE ARE ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION FOR THE SOUTHEAST COAST EXCEPT FOR FLORIDA, CONSISTENT WITH PRECIPITATION ESTIMATES FROM THE GFS AND ECMWF ENSEMBLE MEANS. THE POSITIVE 500-HPA HEIGHT ANOMALIES OVER THE NORTHEAST FAVOR BELOW MEDIAN PRECIPITATION OVER THE NORTHERN PLAINS AND NORTHEAST CONUS.  

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  GOOD AGREEMENT AMONG THE MODEL SOLUTIONS AND SURFACE TOOLS.

8-14 DAY OUTLOOK FOR SEP 22 - 28 2015 

TODAY'S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN FAIR AGREEMENT ON THE 500-HPA MEAN CIRCULATION PATTERN FORECAST OVER MOST OF NORTH AMERICA FOR THE WEEK-2 PERIOD. THE PREDICTED CIRCULATION PATTERN IS SIMILAR TO THE 6-10 DAY PERIOD. A TROUGH IS PREDICTED OVER THE GULF OF ALASKA AND OVER THE WEST COAST OF THE CONTINENT, WITH RIDGING OVER THE SOUTHERN PLAINS. 

THAT UPPER-LEVEL PATTERN FAVORS NEAR TO ABOVE NORMAL TEMPERATURES FOR THE CONUS, WHILE BELOW NORMAL TEMPERATURES ARE FAVORED FOR ALASKA, THE ALASKA PANHANDLE, AND THE PACIFIC NORTHWEST. THE PATTERN IS SIMILAR TO THE 6-10 DAY PERIOD.

THE TROUGHING OVER THE GULF OF ALASKA FAVORS ABOVE MEDIAN PRECIPITATION OVER NORTHERN ALASKA AND THE ALASKA PANHANDLE, BUT FAVORS BELOW MEDIAN PRECIPITATION OVER SOUTHERN ALASKA. THE ACTIVE STORM TRACK OVER THE PACIFIC FAVORS ABOVE MEDIAN PRECIPITATION ACROSS THE CENTRAL AND WESTERN CONUS. THERE ARE ENHANCED CHANCES OF NEAR TO BELOW MEDIAN PRECIPITATION FOR THE EASTERN CONUS EXCEPT FOR THE GULF COAST, CONSISTENT WITH THE ABOVE NORMAL 500-HPA HEIGHT ANOMALIES OVER THERE. 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 OUT OF 5, DUE TO FAIR AGREEMENT AMONG THE MODEL SOLUTIONS AND SURFACE TOOLS. 

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.

Analog

Centered

Day

ENSO

Phase

PDO AMO

Other Comments

1952 Sept 2 Neutral - +  
1953 Sept 18 El Nino - +  
1953 Sept 20 El Nino - +  
1974 Sept 27 La Nina Neutral -  
1983 Sept 22 Neutral + - After a powerful El Nino
1992 Sept 10 Neutral + - After a strong El Nino
2000 Sept 18 La Nina - Neutral  

 

One of the first things I noticed was these analogs are mostly a week or two later than three or four days ago suggesting that we will have weather that is earlier than usual for this time of the year. Whether or not this is an El Nino impact I do not know but I am just reporting what the analogs are suggesting. But the temperature forecast is not consistent with this analysis so perhaps the analogs are more suggestive of the precipitation situation. Or perhaps those dates in the analogs were also periods of above average temperatures. The analogs are clearly suggesting neutral conditions. In fact two of the analogs are dates that followed the completion of an El Nino and one was in turn followed a year later by a fairly strong La Nina. Is anyone noticing this? The current situation looks like both oceans have about equal control  There is a slight bias towards McCabe Condition D which has been the dominant mode since probably 1998 and is highly correlated with Southwest drought The seminal work on the impact of the PDO and AMO on U.S. climate can be found here.

 McCabe Maps modified to include the subtitles

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 significant. 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 + +          
M ASO 2006   DJF 2007 1.0 - - JAS 2007  MJJ 2008 -1.4 - +
M JJA 2009 MAM 2010 1.3 - + 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/rolling average.

Date Current Reading 30-Day Average 90 Day Average
  8 Sept -11.60 -14.18 -16.04
  9 Sept  -19.00 -14.66 -16.22
10 Sept -30.30 -15.51 -16.51
11 Sept -33.70 -16.25 -17.01
12 Sept -26.00 -16.47 -17.39
13 Sept -24.50 -16.28 -17.79
14 Sept -31.30 -16.27 -18.14

 

The 30-day average, which is the most widely used measure, on September 14 was reported as being -16.27 which is clearly a reading associated with an El Nino and quite a bit elevated from the reading last week. The 90-day average also is solidly in El Nino territory at -18.14 which is significantly higher than last week. The SOI is clearly indicative of an El Nino Event in progress. In fact it is so strong that it may be having impacts that are unusual. 

Here are the low-level wind anomalies. It has been fairly calm although there is some activity around 140W which is having an impact on the ONI values but it appears to be playing out.  

Low Level Wlind Anomalies

In this graphic, you can see how the convection pattern (really cloud tops has since May shifted to the East from a Date Line (180) Modoki pattern to a 170W to 120W Traditional/Canonical El Nino Pattern. But recently the signs of an El Nino are getting quite faint and shifting back to the west. You can see the lack of convection over at 120E which is Indonesia but the convection has withdrawn to the West not moved to the East as would be the case with a normal El Nino. That may still happen. In the 1997/1998 El Nino, that did not happen until 1998 which is why the Fall of 1997 was not wet for CONUS.

When I hear that with this El Nino the atmosphere is strongly coupled with the ocean, I really wonder what those meteorological agencies are smoking. It might be true on a worldwide basis but it does not appear to be the case as it impacts CONUS. The convection has not moved east. It has moved away from Indonesia which is an El Nino impact but it is remaining where one would expect it to be if this was a Modoki. This graphic may start to change very soon and we may be seeing the start of that process in the September 5 version of this graphic which does auto-update probably once per week. 

OLR Anomalies Along the Equator

Let us now take a look at the progress of the Kevin wave which is the key to the situation. Since February there have been three successive 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 believe 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.

The main impact of this latest Kelvin Wave has already moved east to 155W. You also see the intense activity between just west of 130W and 105W. Perhaps half of that is in the area where the ONI is measured. Kelvin waves move east. You also see the cooling down of the water east of 90W which may signify the end stage of this El Nino but this area of cooler water has filled in just a bit. It is a slow process and every El Nino has a different length. But if you think of an El Nino as typically lasting about a year or less, then this one is about half through its life.

Kelvin Waves Auto-updates

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 last week, 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 will end earlier in the winter than the 1997/1998 El Nino. Also the 1997/1998 had a larger amount of slightly warmer 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.

Current Sub-Surface Conditions

Subsurface Heat Anomalies

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 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 160W which is very impressive. There is also a small blip over at 175W. The subsurface warm water appears to be making its way to the surface in the Eastern Pacific but also to some extent working its way deeper. The 3C anomaly is over towards 140W which again is very impressive and which encompasses 40% of the Nino 3.4 Measurement Area for the ONI. It is difficult to see any significant change from last week other than possibly the rise of the warm water closer to the surface. One can see how the ONI can continue to increase for some time due to this warm subsurface water that is coming to the surface. 

One big issue is where will the +6C and +5C anomaly water go as it reaches the beaches of Ecuador? To the extent it surfaces, it can create convection and impact the Walker Circulation which could then provide positive feedback to this El Nino. But that warm water might tend to go north or south or both and there is some indication that some of it is working its way deeper where it probably will mix with cooler water coming north from further south. That is part of the phase out process for an El Nino and that is where we are in the life of this El Nino. It is peaking and will soon begin its decline. But it is certainly taking its sweet time probably because of the large amount of the subsurface warm water. Water is a very good insulator: I believe it has the second highest specific heat capacity of all known substances. 

So that means that other than by mixing, that warm water under the surface will stay warm until it rises to the surface where it can be cooled by evaporation (while making clouds) or moves to the north where it will impact Mexico and the Southern Coast of the U.S. That is part of the basis for models predicting that the ONI of this El Nino will continue to rise.

Bottom Graphic (Absolute Values which highlights the Thermocline)

The bottom half of the graphic is not that useful in terms of tracking the progress of this Warm Event as it simply shows the thermocline between warm and cool water which pretty much looks like this as shown here during a Warm Event and you can see that the cooler water is not yet fully making it to the surface to the east along the coast of Ecuador. However, one now can see the increase in the slope of the thermocline (look at the 25C dividing line for example which has now reached the surface). We can now begin to monitor the 20C Isotherm which is often thought of as being the middle of the thermocline where the slope is also steepening and looks like it may reach the surface fairly soon. I have been saying that for a while but there has been essentially no change. We may want to 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 just east of 140W but may have moved ever so slightly to the east. I believe that the centering of the convection west of 120W rather than moving all the way over to the South American Coast may be why this El Nino is so far having essentially no impact on CONUS other than from the cyclones that are moving up the coast of Mexico.

TAO/TRITON GRAPHIC

Taking a close look at the bottom half of the TAO/TRITON graphic, notice that things are really heating up. The 1.5C+ anomaly in the western part of the Nino 3.4 Measurement Area north of the Equator which had almost vanished a few weeks ago but has now strengthened significantly. However, you can still see the impact the diminished Easterlies has had on the area north of the Equator at the west end of the warm event. I do not know enough to say if that has impacted convection. The overall pattern seems to have shifted to the north which is more in line with what one might expect. You can see a growing area of 3C+ surface water at about 125W and thus just beginning to enter into the ONI calculation and a much larger area of 2C to 3C water extending from 150W all the way to the Coast of Ecuador. The part of this warm anomaly (not within the even warmer isotherm) that extends from 160W to 120W enters into the ONI calculation in Nino 3.4. That is an average of about 2.5C which would be a record high reading if it extended throughout the Nino 3.4 Area and lasted for three months. But in the western half of the Nino 3.4 measurement area, you had up until recently an ONI of perhaps 1.2 or slightly higher which is pretty much a run of the mill El Nino. But right now that is also showing to be close to 2C but with areas of 1C  to 1.5C water intruding into the measurement area. In the eastern end of Nino 3.4, the warm subsurface water is rising. These dynamics are all part of the process of maturation and decline of this El Nino but for now the ONI is clearly increasing. 

But so far there are few if any impacts on CONUS. So this raises real questions about how we measure an El Nino and how we do regression analysis on historical El Ninos. Are the likely impacts to be correlated with a 1.0 ONI which has minimal impact or a 2.5 ONI which is off the charts? I guess we will find out. The distribution of SST anomalies has changed dramatically over the last month but it has changed first one way and now another way.

For my own amusement, 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 (that I have designated A through E (from west to east) with a location bar shown under the TAO/TRITON Graphic) and have mentally integrated what I see below and recorded that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.

 Current SST and wind anomalies

Location Bar for Nino 3.4 Area Above
-----------------------------------------------  A      B      C      D      E      ----------------

 

So as of Monday September 14 in the afternoon working from the September 13 TAO/TRITON report, this is what I calculated which is basically the same as my calculation last week although the patterns of the anomalies have been changing around quite a bit but the changes have been cancelling each other out.

Calculation of ONI from TAO/TRITON Graphic
Anomaly Segment Estimated Anomaly
A. 170W to 160W 1.4
B. 160W to 150W 1.6
C. 150W to 140W 2.1
D. 140W to 130W 2.3
E. 130W to 120W 2.6
Total 10.0
Total divided by five subregions i.e. the ONI (10.0)/5 = 2.0

 

My estimate of the Nino 3.4 ONI remains at 2.0. NOAA with again the gradient from west to east being  accentuated. NOAA has today reported the weekly ONI as being 2.3 an increase from what was reported last week and certainly a very high level for an ONI even though it is a weekly value not a three-month average. The increase in the NOAA estimated ONI is I believe mostly due to the subsurface water in the Eastern Pacific backing up to the west as it comes to the surface or rising to the surface in the Nino 3.4 Measurement Area. This warm water certainly impacts the weather in Ecuador and Peru but may not have a direct impact on weather in CONUS other than by spawning tropical cyclones which move north and enter the circulation of the Southwest Monsoon.

Nino 4.0 is again reported as being 1.0. The action which I think is most important to track is in Nino 1+2 which is now reported as being down again to 2.0. One issue remains the extent to which warm water off of Ecuador and Peru impacts CONUS weather. I think it has very little impact and that is what we are seeing right now. The other issue is that most El Ninos decay from east to west so it will be observed most clearly first in Nino 1+2. The highest readings are in Nino 3.0 which some use as a better indicator of an El Nino than Nino 3.4. The reading there is 2.6. 

This is summarized in the following NOAA Table. You can also see the trends in this table. I believe that watching Nino 1+2 is the best way to track when this El Nino will begin to seriously decay. Curiously some of the warm water appears to be going deeper which I think accelerates the decline but I am not sure of that. The subsurface warm water has to be disposed of one way or another for ENSO to move back towards neutral or all the way to La Nina. 

Sept 14, 2015 NINO Departures

Here is another way of looking at it: Unlike the Upper Ocean Heat Anomaly 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. As you can see the warm water rising off the South American Coast has worked its way all the way over to beyond 170W so it fully contributes to the increasing ONI but it is beginning to reverse and nor move further west and may even be moving a bit to the east. And at the same time one can now clearly see that the water immediately off the coast of South American is generally cooling down although that process was reversed around 100W. It is a dynamic process and this El Nino is both continuing to grow while beginning to wane. But there remains a lot of subsurface warm water to be disposed of. That is a slow process and will continue for some time. But there are some signs that the process is close to peaking.

.SST Anomalies Hovmoeller

When you break it down by the areas used to track ENSO you get this which I have already shown above but it is perhaps easier to read when shown separately. 

SST Anomalies

El Nino in the News

One could argue that this article is not about El Nino. But it is about ocean cycles. 

From Thursday's Scientific Discussion from the Albuquerque NM Nationakl Weather Service:

GFS AND ECMWF CONTINUE WITH IDEA OF SUBSEQUENT TROUGHS MOVING THROUGH THE WRN CONUS MID WEEK NEXT WEEK AND BEYOND. THESE ARE LIKELY THE INITIAL SIGNS THAT THE EFFECTS OF A VERY ACTIVE AREA OF TROPICAL CONVECTION IN THE EAST PACIFIC (THANKS TO A STRONG/EXTREME EL NINO) ARE STARTING TO HAVE ON THE POLAR JET STREAM. 2.43" OF RAIN FELL AT THE ALBUQUERQUE SUNPORT IN SEPTEMBER DURING THE LAST VERY STRONG/EXTREME EL NINO BACK IN 1997. [Editor's Note: There certainly were some extreme events early on with the 1997/1998 El Nino. I think this El Nino is different but it is useful to remember that extreme events can occur with almost any weather pattern and when you have a near record or perhaps even a record El Nino, one needs to be prepared for strange things although I think the Albuquerque NWS is wrong on this call.]

Recent Impacts of Weather Mostly El Nino but possibly Also PDO and AMO Impacts.

First the Temperature and Precipitation Departures from three months ago (Ending Date June 13)

June 15, 2015 30 Day Temperature and Precipitation Departures.

Then the same graphic one month later (Ending Date July 11)

July 13, 2015 30 Day Temperature and Preciptiation Departures

And then the same graphic (Ending Date August 8). 

August 10 2015 30 Day Temperature and Precipitation Departures

So this gives us a three-month sequence of monthly departures and that series of graphics showed a drying trend which is not exactly what you would expect with an El Nino arriving. For many parts of CONUS, it was a cooling trend also which may be associated with an El Nino.

And now the view from September 5 which is one month later. 

Sept 5, 2015 30 Day Temperature and Precipitation Departures

One can see the continued drying out but some easing of the drying in Mexico. There has also been a shift in the temperature regime. The El Nino ate the Monsoon that is for sure.That does not mean there can not be Monsoonal Bursts but that they are now likely to be less frequent and weaker than on average for this time of the year. 

And now the same graphic one week later which means the addition of the most recent week's data and the dropping out of the data from the seven days which are no longer in the 30 day period. 

September 12, 30 day temperature and precipitation departures.

As you can see Linda changed the situation a bit for Mexico. But overall there has not been much change. 

View from Australia

El Nino

Australia POAMA ENSO model run

Here is the discussion just released:

A strong El Niño and record warm Indian Ocean continue

Issued on 15 September 2015

El Niño continues to strengthen. Recent oceanic and atmospheric indicators are at levels not seen since the 1997–98 El Niño. Persistently weak or reversed trade winds and a strongly negative Southern Oscillation Index (SOI), in conjunction with the ongoing warming in the tropical Pacific Ocean, indicate the El Niño is unlikely to end before early 2016.

Climate models indicate sea surface temperatures in the central tropical Pacific are likely to rise further over the next few months, coming close to, or possibly exceeding, monthly values observed during the 1997–98 event. All models suggest the event will peak around the end of the year, followed by rapid weakening heading into autumn 2016. It is too early to accurately determine the likely pattern beyond autumn, but a continued El Niño is considered the least likely outcome at this stage.

Temperature patterns in the Indian Ocean are continuing to have a strong influence on Australian climate. The whole Indian Ocean remains warmer than average with sea surface temperatures in the southern Indian Ocean the highest on record for winter. Some localised cooling near Indonesia means the Indian Ocean Dipole (IOD) index has been above the +0.4 °C threshold for six weeks. If this continues for at least another fortnight, this will be considered a positive IOD event. Most models indicate this is likely.

El Niño is usually associated with below-average winter–spring rainfall over eastern Australia, and a positive IOD typically reinforces this pattern over central and southeast Australia. However, this pattern has been offset in central and some southern areas by the record warm Indian Ocean. Warmth in the Indian Ocean is likely to continue.

Next update expected on 29 September 2015

 IOD (Indian Ocean Dipole)

IOD POAMA Model Run

It comes with only a very short discussion and here it is:

Values of the Indian Ocean Dipole (IOD) index have been at or above the threshold level of +0.4 °C for six weeks. The weekly value of the IOD index to 13 September was +0.97 °C. This is the highest weekly value since the very strong positive IOD event of 2006.

Sea surface temperatures (SSTs) in the Indian Ocean are warmer than average over much of the basin, and the southern Indian Ocean as a whole has been at record temperatures in recent months. Typically, a positive IOD event is characterised by cooler-than-average water off the coast of the Indonesian island of Sumatra Positive IOD events are often associated with lower rainfall in parts of central and southeastern Australia. Positive IOD events are more likely to occur during El Niño, which also is typically associated with a reduction in winter–spring rainfall in eastern Australia.

However, sea surface temperatures in the Indian Ocean basin also affect Australia's climate—it's likely that the widespread warm anomalies have moderated the influence of these two climate drivers Most of the five surveyed international climate models indicate this event is likely to reach the threshold of eight weeks above +0.4 °C required for 2015 to be considered a positive IOD year. Positive values of the IOD are likely to decay by early summer.

 To me it is interesting that the IOD appears to have peaked and is on the way down. But the interrelationship between the IOD and El Nino is complicated and not fully understood. 

Putting it all Together.

We are in El Nino conditions now. The actually impacts on CONUS are not clear. We started in the Spring by having wetter conditions than usual in the Southwest but that has tapered off quite a bit. It is probably influencing the IOD to tend towards being positive thus providing a double whammy for parts of Asia and Australia but this is projected above to continue for only a month or two. That by itself should make us wonder what exactly is going on. 

The length and intensity of this El Nino is still not clear mostly in terms of whether or not it will extend into the early part of 2016. 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.  

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+. 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 2016/201 which I believe will tend to be ENSO Neutral but I am not so sure that it will not lean towards being a cool event or at least closer to a La Nina than neutral. One thing is fairly certain for the U.S. it will be less wet and warmer than the winter of 2015/2016 which will be quite wet and cool but perhaps for a shorter portion of the winter than NOAA has been predicting. JAMSTEC is predicting that the Spring of 2017 will begin a mild La Nina. That is a long way to make a prediction for a number of reasons including the Spring Prediction Barrier

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

. 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.

D1. Introduction

D2. Climate Impacts of Global Warming

D3. Economic Impacts of Global Warming

D,4. Reports from Around the World on Impacts of Global Warming.

Click here for a list of Sig Silber's Weather Posts

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