Written by Sig Silber
We have a Warm Event which as of September 1 meets the NOAA criteria for being an official El Nino and which may end up being very close to or even be the highest rated El Nino since 1950 (when better records are considered to have begun to be kept). So far the impacts are hardly noticeable in CONUS (a confusing term which usually means the U.S. excluding Alaska and Hawaii) or worldwide really to any large extent. When will they start to show up in the U.S.?
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.
Last week I indicated that this week we would discuss the following four articles. The reason for doing so is both that the 1997/1998 Analogs are again showing up in the NOAA list of analogs issued each day (although only barely today) but also because the 1997/1998 is the most recent Super-El Nino. It may or may not be representative of what we will experience this winter. But it illustrates how complicated an El Nino is with respect to impacts.
El Niño– Generated Weather in the United States, Stanley A. Changnon Climatologist, Mahomet, Illinois. You can find the full paper here.
Technical Report 98-02 National Climate Data Center The El Nino Winter of “97-’98”. You can find that here.
Both of those focus on impacts.
The two meteorological papers I have been pouring through are:
Genesis and Evolution of the 1997-98 El Nino which can be found here. The author McPhaden is prolific and I have selected this particular document partly because it is easy to access.
Very strong 1997-98 Pacific warm episode (El Niño) and which can be found here. It is part of a longer NWS Climate Prediction Center analysis which can be found here. I have not read the longer analysis in its entirety and I need to because it deals with the entire world. What I presented perhaps three weeks ago was the evolution chapter of that analysis and that is what I will be using this evening mostly this graphic which I have presented a number of times before.
As you can see, the 1997 El Nino was not a wet event for CONUS in the Fall of 1997. It mainly was a wet event for Dec 1997 – Feb 1998. That is why it becomes important to know what we should be using for guidance. Both NOAA and JAMSTEC are projecting a wet Fall but the 1997/1998 El Nino did not result in a wet Fall. I do believe however that this El Nino is maturing earlier than the 1997/1998 El Nino and is likely to have an earlier schedule of impacts.
Following are some more graphics you might find interesting.
This first one shows that the three months Dec 1997 – Feb 1998 which was the heart of the 1997/1998 El Nino in terms of impacts was most noticeable in the Northern Tier for it being warmer than usual and with respect to precipitation in mainly:
- South Carolina
- North Carolina
So the impacts were specific and not necessarily where one might have guessed. Also there are some significant contrasts for example Utah and Colorado as compared to Arizona and New Mexico with respect to precipitation. Only the states with experiences that rank in the top 10 in their history are shaded but notice that Idaho was fairly dry as was Kansas and Tennessee. So there were significant differences between neighboring states.
And Stream Flow/ Flooding was an issue especially for parts of Alabama, Georgia and the Florida Panhandle. Does one normally think of Southeast flooding when they think of an El Nino and is it not interesting that a weather pattern along the Equator in the Pacific had the maximum negative impact in the Southeast U.S.?
And an overall assessment of extreme events. Notice most of these were from the Center of CONUS East even though an El Nino forms in the Pacific Ocean. A risk late in the life of an El Nino is a negative NAO or AO leading to frosts in Florida. This can also impact Europe. We do not know what we are going to get but we know that this El Nino as measured by the ONI is a top five Warm Event or better.
I have to admit that I do not even recall the El Nino of 1997-1998. I was living in Connecticut at the time and working on things that were not directly related to weather or climate and nothing about the weather seemed very strange to me. I probably did not even notice that it was a bit warmer. Of course I was living in a high rise condo and my car was in the underground garage. The point is that where you are determines what impacts you will incur from unusual weather. For Connecticut there was hardly any impact since being a bit warmer would hardly be noticed. On the other hand, if you had been living in Georgia or the Panhandle of Florida or Alabama, you probably noticed.
Flavors of El Nino
What kind of El Nino do we have? Let’s review some of the concepts that we have discussed before which deal with more specifics with respect to the type of Warm Event that is taking place and how different types of Warm Events impact weather patterns differently not just for the U.S. but worldwide.
Let us talk a bit more about the work of Chunzai Wang and Xin Wang. From the abstract of their article.
Based on the opposite influence on rainfall in southern China during boreal fall, this paper classifies El Niño Modoki into two groups: El Niño Modoki I and II which show different origins and patterns of SST anomalies. The warm SST anomalies originate in the equatorial central Pacific and subtropical northeastern Pacific for El Niño Modoki I and II, respectively. Thus, El Niño Modoki I shows a symmetric SST anomaly distribution about the equator with the maximum warming in the equatorial central Pacific, whereas El Niño Modoki II displays an asymmetric distribution with the warm SST anomalies extending from the northeastern Pacific to equatorial central Pacific. Additionally, the warm SST anomalies in the equatorial central Pacific extend further westward for El Niño Modoki II than El Niño Modoki I. Similar to canonical El Niño, El Niño Modoki I is associated with an anomalous anticyclone in the Philippine Sea which induces southwesterly wind anomalies along the south coast of China and carries the moisture for increasing rainfall in southern China. For El Niño Modoki II, an anomalous cyclone resides east of the Philippines, associated with northerly wind anomalies and a decrease in rainfall in southern China. Canonical El Niño and El Niño Modoki I are associated with a westward extension of the western North Pacific subtropical high (WNPSH), whereas El Niño Modoki II shifts the WNPSH eastward. Differing from canonical El Niño and El Niño Modoki I, El Niño Modoki II corresponds to northwesterly anomalies of the typhoon steering flow which are unfavorable for typhoons to make landfall in China.”
When I look at the three SON graphics above, none really seem to match the current situation.
Here are the cyclone tracks for the three flavors of El Nino
As you can see:
- Traditional El Ninos generate cyclones that develop further east than Modoki cyclones
- Traditional El Nino cyclones tend to complete their journey further north than Modoki cyclones
- Modoki Type II cyclones have the best chance of providing precipitation to the far west of the Tropical Pacific. Modoki Type I cyclones have a better chance of providing precipitation to Southern China.
- Not shown in this graphic (I could have provided another set of graphics to show this) is the situation in the Philippine Sea. Modoki Type I tends to create an anomalous High Pressure System and Modoki Type II a Low Pressure System there. This changes the wind directions for the entire area.
In many respects what we now have is a Traditional El Nino but it retains some of the characteristics of the Modoki Type II from last year. To me it is a unique Warm Event not that any two are the same but this seems to not fit the mold and may have unpredictable impacts.
Now Let us Take 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 12 hour to 60 hour forecast of weather fronts shown as an animation. Beyond 60 hours, the 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.
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 is not shown as I am finalizing my report. That suggests to me that forecasting moisture entering CONUS from Mexico will be quite difficult. 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.
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.
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 appears to be a bit too far offshore to have a major impact. 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.
The below graphic 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 over the eastern half of CONUS. But one also sees moisture streaming up through Arizona and New Mexico from Mexico but it is not a wide or heavy stream and most likely will clear as Linda moves on. So I am thinking that there will be at least a short-term break in the action.
Looking at an even larger area, 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). The Eastern Pacific Subtropical High is back again serving as a total block to all storms attempting to move from the Pacific into CONUS. That is not consistent with an El Nino other than an El Nino Modoki Type II which we do not really have or do we? So it is hard to explain. The projected highs where temperatures are projected to be low is also confusing.
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 north rather than south. So the El Nino has not yet really impacted the weather situation for CONUS.
And when we look at Sea Surface anomalies we see a lot of them not just along the Equator related to El Nino.
I call your attention to the Atlantic and the warm area called the MDR or Main Development Area.
It has not worked out as forecast as the MDR is above average SSTs not below average SST’s.
In some fields when certain assumptions or forecasts fail to materialize, one begins to question the whole forecast. Apparently NOAA does not work that way. I think it should.
6 – 14 Day Outlooks
Now let us focus on the 6 – 14 Day Forecast for which I will 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.
Here is the Three-Month 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.
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 7(it updates each day) it appears that the map is consistent with the September Temperature Outlook issued on August 31 but does not much reflect the perspective that El Nino will be a factor in the next two weeks.
Here is the three-month precipitation outlook which was 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.
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:
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 this map on September 7 (it updates each day), one can imagine how this is related to the Monthly Outlook issued on August 31, 2015 but it takes a lot of imagining. I think more likely the precipitation outlooks are responding to the timing of storms moving up the western coast of Mexico.
Here are excerpts from the NOAA discussion released today September 7, 2015.
6-10 DAY OUTLOOK FOR SEP 13 – 17 2015
TODAY’S MODEL SOLUTIONS ARE IN ONLY FAIR AGREEMENT ON THE PREDICTED 500-HPA FLOW PATTERN OVER NORTH AMERICA AND VICINITY. THE 00Z ECMWF ENSEMBLE MEAN, THE 00Z AND 06Z GFS ENSEMBLE MEANS, AND TO A LESSER DEGREE THE GFS SUPER-ENSEMBLE MEAN, FORECAST A TROUGH ACROSS THE BERING SEA AND ADJACENT NORTHERN PACIFIC, A WEAK RIDGE OVER THE GULF OF ALASKA, AND ANOTHER TROUGH IN THE APPROXIMATE LOCATION OF THE UPPER MIDWEST. THE 00Z CANADIAN ENSEMBLE MEAN AND THE 00Z DETERMINISTIC GFS PREDICT A RELATIVELY LOW AMPLITUDE, FAST FLOW PATTERN. THE 06Z DETERMINISTIC GFS ANTICIPATES A BROAD TROUGH EXTENDING FROM THE NORTHERN ROCKIES TO THE GREAT LAKES REGION, WHILE THE 00Z DETERMINISTIC ECMWF FORECASTS ITS DOWNSTREAM TROUGH OVER THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. IT SEEMS THAT THERE IS SIGNIFICANT UNCERTAINTY REGARDING THE PREDICTED LOCATION OF THE DOWNSTREAM TROUGH OVER THE NORTHERN CONUS, WITHIN A CORRIDOR STRETCHING FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES REGION. ONE POSSIBILITY IS THE UPSTREAM CIRCULATION FEATURES ARE STILL IN A STATE OF FLUX, NOT ALLOWING THE DOWNSTREAM FEATURES TO SETTLE INTO A STABLE CONFIGURATION. ANOTHER POSSIBILITY IS EASTWARD-MOVING SHORT-WAVE TROUGHS ARE PROGRESSING AS FAR EAST AS THE GREAT LAKES, WHILE THE LONG-WAVE TROUGH KEEPS TRYING TO DIG ACROSS THE PACIFIC NORTHWEST REGION. AT ANY RATE, MUCH OF TODAY’S FORECAST UNCERTAINTY STEMS FROM THIS PREDICTED SHORT-WAVE CORRIDOR ACROSS THE NORTHERN TIER OF STATES. SPAGHETTI MAPS DEPICT MODERATE TO LARGE SPREAD AMONG INDIVIDUAL ENSEMBLE MEMBERS, ESPECIALLY OVER THE WESTERN CONUS AND ADJACENT EASTERN PACIFIC.
BELOW-NORMAL TEMPERATURES ARE FAVORED FOR MOST OF THE LOWER HALF OF THE MISSISSIPPI VALLEY, EASTERN PORTIONS OF THE SOUTHERN PLAINS, MUCH OF THE TENNESSEE AND LOWER OHIO VALLEYS, AND A SIGNIFICANT PORTION OF CENTRAL AND EASTERN ALASKA. THIS IS BASED ON TOOLS AND FACTORS SUCH AS REFORECAST AND NAEFS TEMPERATURES, NEAR- TO BELOW-NORMAL 500-HPA HEIGHTS, AND NORTHERLY ANOMALOUS FLOW. ABOVE-NORMAL TEMPERATURES ARE FAVORED FROM THE HIGH PLAINS WESTWARD TO THE PACIFIC COAST, THE EAST COAST STATES, PARTS OF THE GREAT LAKES REGION, AND EXTREME NORTHERN AND WESTERN ALASKA. THIS IS BASED ON TOOLS AND FACTORS SUCH AS REFORECAST AND NAEFS TEMPERATURES, NEAR- TO ABOVE-NORMAL 500-HPA HEIGHTS, RELATIVELY WARM SEA SURFACE TEMPERATURES, AND SOUTHWESTERLY FLOW ALOFT.
THERE ARE ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FOR MOST OF ALASKA, THE ATLANTIC AND GULF COAST STATES, AND FOR A SMALL PORTION OF THE DESERT SOUTHWEST. ODDS OF BELOW-MEDIAN PRECIPITATION ARE ELEVATED FOR MUCH OF THE WESTERN AND CENTRAL THIRDS OF THE CONUS. THE PRECIPITATION OUTLOOK IS BASED ON TOOLS SUCH AS NAEFS AND REFORECAST PRECIPITATION, HISTORICAL ANALOGS, THE EXPECTED LOCATION OF STORM TRACKS, AND THE ANTICIPATED 500-HPA HEIGHT PATTERN.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO FAIR AGREEMENT AMONG THE MODEL SOLUTIONS AND TOOLS, AND MODERATE TO LARGE SPREAD AMONG THE ENSEMBLE MEMBERS.
8-14 DAY OUTLOOK FOR SEP 15 – 21 2015
TODAY’S WEEK-2 MODEL SOLUTIONS CONTINUE TO EXHIBIT RELATIVELY LARGE SPREAD AND UNCERTAINTY FOR MUCH OF THE FORECAST DOMAIN. MUCH OF THE FLOW ACROSS THE EASTERN PACIFIC AND THE CONUS IS PREDICTED TO BE QUASI-ZONAL. TWO AREAS WHERE TROUGHS ARE FAVORED ARE NEAR THE WEST COAST OF ALASKA, AND THE NORTHWESTERN AND NORTH-CENTRAL CONUS (THE SHORT-WAVE CORRIDOR NOTED IN THE EARLIER 6-10 DAY SECTION). THE TIMING OF THIS LATTER FEATURE DIGGING BACK NEAR THE NORTHERN ROCKIES IS UNCLEAR, THOUGH THE SURFACE TOOLS ARE CONSISTENT WITH AT LEAST A WEAK TROUGH IN THAT AREA DURING WEEK-2.
THE EXPECTED TEMPERATURE AND PRECIPITATION ANOMALY PATTERNS FOR WEEK-2 DIFFER SOMEWHAT FROM THOSE FORECAST FOR THE 6-10 DAY PERIOD. WITH THE TROUGH FORECAST TO DIG BACK OVER THE NORTHERN ROCKIES, THERE ARE ELEVATED CHANCES FOR BELOW-NORMAL TEMPERATURES ACROSS THE NORTH-CENTRAL CONUS, WITH A CORRESPONDING WESTWARD RETREAT OF FAVORED ABOVE-NORMAL TEMPERATURES IN THE WEST. FOR PRECIPITATION, THERE IS A PREDICTED, CORRESPONDING WESTWARD SHIFT OF ABOVE-MEDIAN PRECIPITATION FROM THE EASTERN CONUS INTO THE EAST-CENTRAL AND CENTRAL CONUS.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: BELOW AVERAGE, 2 OUT OF 5, DUE TO LARGE MODEL SPREAD AND UNCERTAINTY.
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.
|1952 Sept 11||Neutral||–||+|
|1952 Sept 12||Neutral||–||+|
|1953 Aug 24||El Nino||–||+|
|1968 Sept 20||El Nino||Neutral||–||Just Before a Modoki Type II|
|1995 Aug 17||La Nina||+||–|
|1995 Aug 18||La Nina||+||–|
|1997 Sept 13||La Nina||+||Neutral|
|2002 Sept 1||El Nino||Neutral||+||Modoki Type I|
|2002 Sept 2||El Nino||Neutral||+||Modoki Type I|
Again the analogs do not suggest that this El Nino will impact our weather over the next two weeks. There are four El Nino analogs at least two of which are associated with a Modoki. I have not seen the 1953 El Nino classified. A Neutral Analog preceded an El Nino Modoki Type II. There are two La Nina Analogs. Overall it seems like we are in a pre-El Nino situation waiting for the El Nino to fully present itself. The current situation looks like both oceans have about equal control right now with perhaps a slight advantage to the Atlantic 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.
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||–||+|
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|
The 30-day average, which is the most widely used measure, on September 7 was reported as being -13.93 which is clearly a reading associated with an El Nino but reduced from the reading last week. The 90-day average also is solidly in El Nino territory at -15.83 which is slightly higher than last week illustrating the difference between 30 and 90 day moving averages The SOI is clearly indicative of an El Nino Event in progress.
Here are the low-level wind anomalies. It has been fairly calm although there is some activity between 160E and the Date Line which is further West than has been the case the last number of weeks. I do not think it is a factor.
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.
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 160W. You also see the intense activity between 140W and 110W Two-thirds of which is in the area where the ONI is measured. 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.
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 a few weeks ago, 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
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 from 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. 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.
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. 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 or lower edge of the thermocline where the slope is also steepening and looks like it may reach the surface fairly soon. I said that two weeks ago and two weeks have gone by with 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. I believe that is why this El Nino is having essential no impact on CONUS other than from the cyclones that are moving up the coast of Mexico.
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 two weeks ago has now strengthened significantly. You can see a small area of 3C+ surface water just east of 120W and thus not entering into the ONI calculation and a much larger area of 2C to 3C water from 145W to 120W which enters into the ONI calculation. 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 half of the Nino 3.4 measurement area, you had up until last week 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.The warm subsurface water is rising. It is part of the process of maturation and decline 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.
So as of Monday September 7 in the afternoon working from the September 6 TAO/TRITON report, this is what I calculated.
|Anomaly Segment||Estimated Anomaly|
|A. 170W to 160W||1.7|
|B. 160W to 150W||1.8|
|C. 150W to 140W||2.0|
|D. 140W to 130W||2.2|
|E. 130W to 120W||2.3|
|Total divided by five subregions i.e. the ONI||(10.0)/5 = 2.0|
My estimate of the Nino 3.4 ONI has increased to 2.0. NOAA has today reported the weekly ONI as being 2.1 a slight decrease 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. That activity seemed to have decreased recently but it looks like we are getting another spurt of it.
Nino 4.0 is now reported as being 1.0. The real action is in Nino 1+2 which is now reported as being back up to 2.2. The 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 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 2.4.
This is summarized in the following NOAA Table. You can also see the trends in this table.
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 at the same time one can now clearly see that the water immediately off the coast of South American is generally cooling down. 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.
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. .
El Nino in the News
I did not find anything particularly useful to report this week.
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)
Then the same graphic one month later (Ending Date July 11)
And then the same graphic (Ending Date August 8).
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.
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.
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. 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. 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). 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 none of this is very difficult to figure out actually if you are looking at say a five-year 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 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. JAMSTEC is predicting that the Spring of 2017 will begin a mild La Nina.
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
D,4. Reports from Around the World on Impacts of Global Warming.