La Nina is coming. There is disagreement on the strength and duration of the La Nina or even if it will be strong enough to qualify as a La Nina rather than ENSO Neutral for this coming winter. What is clear to me is that McCabe Condition A appears to be in place for the next couple of decades so one can take a look at the graphic further down in this article to see what that means for CONUS winters. The paper I discussed last week provides somewhat similar information for the rest of the World.
This is the RegularEdition 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.
Updated Seasonal Outlook
NOAA issued their updated Seasonal Outlook on the third Thursday of the month i.e. April 21, 2016 as is their normal schedule. Let's take a look.
Prior Temperature Outlook for MJJ 2016
New Temperature Outlook for MJJ 2016
Not much change in the pattern. If you look closely, you can see a reduction in probabilities of warmer than climatology in the Upper Mississippi Area. Further south there is a narrowing of the EC area with warm anomaly encroaching from both the west and the east. The 50% probability of the West Coast warm anomaly now extends down through Southern California.
Prior Precipitation Outlook for MJJ 2016
New Precipitation Outlook for MJJ 2016
This is a big change. The small dry anomaly in the Northwest is now gone. The wet anomaly now extends from the Southwest all the way to the Atlantic Ocean. But the higher probability part of the warm anomaly has shifted to the west and north and is now shown as being mainly in Utah and Colorado.
Now let us focus on the long-term situation.
Prior 14 Month Temperature Outlook: May 2016 - Jun 2017
New 14 Month Temperature Outlook: Jun 2016 - Jul 2017
To compare maps from one release to another one needs to remember that the new release drops one three-month period and adds a later one. So to make the comparisons one has to shift the new maps to the right one position and that makes the map on the right drop down to become the left-most map in the next level. I do not have a computer software tool for doing that for you so you have to do it mentally. When I do the comparison I print them out and put them side by side and number the same three-month maps 1, 2, 3,.....,11 in both sets of maps to make it easier for me to easily compare the same three-month period in the new with the previous forecast. One uses the same procedure to compare the precipitation maps. Based on this procedure, I conclude that:
The changes are subtle re the area involved but with a larger area of a higher probability of warmer than climatology in the West in Jun - Jul - Aug and Jul - Aug - Sep. The changes further out are minor. The Transition to La Nina is evident in Oct - Nov - Dec which is not a change from the prior Seasonal Outlook.
Prior 14 Month Precipitation Outlook: May 2016 - Jun 2017
New 14 Month Precipitation Outlook: May 2016 - Jun 2017
The precipitation changes were far more extensive than those associated with temperature. There is now a horizontally elongated Mid-Rocky Mountain wet anomaly in Jun - Jul - Aug, a wet Southeast anomaly in Jul - Aug -Sep and also Aug - Sep - Oct, a horizontally elongated dry Rocky Mountain anomaly in Aug - Sep - Oct, a small wet Northwest anomaly in Sep - Oct - Nov and the extension of the previously forecast Great Lakes wet anomaly an additional month into Mar - Apr - May 2017. The switch to a La Nina Pattern can be seen in Jul - Aug - Sep which is two overlapping three-month periods earlier than in the prior NOAA Seasonal Outlook as described in their discussion and is attributed to an earlier development of La Nina. It now appears that the impact on precipitation will occur three months earlier than the impact on Temperature. This might be attributed to the PDO, AMO the secular Warming Trend on soil conditions which in some places are wetter than usual and in other places drier. The transition from El Nino to La Nina or even ENSO neutral creates a different pattern of temperature and precipitation mostly north to south with previously warm areas becoming cool areas warm while wet areas become dry and dry areas wet.
If you want larger versions of each map (temperature and precipitation) you can find them here. And each of those maps can be clicked on to further enlarge them.
Excerpts (somewhat reorganized) from the Discussion Released by NOAA on April 21, 2016
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
EQUATORIAL PACIFIC SSTS REMAIN ABOVE CLIMATOLOGICAL MEANS WITH THE LAST FOUR WEEK AVERAGE DEPICTING DEPARTURES FROM NORMAL OF +1.0C OVER THE ENTIRE EQUATORIAL PACIFIC BASIN WITH A FEW AREAS NEAR +1.5C. THE NINO3.4 REGION THREE-MONTH MEAN SST ANOMALY PEAKED AT +2.3C DURING NDJ 2015-2016, BUT HAS DECREASED TO +2.0C FOR THE MOST RECENT THREE MONTH SEASON OF JFM 2016. THE LATEST WEEKLY NINO3.4 REGION ANOMALY IS NOW +1.3C. [Editor's Note: The new weekly estimate by NOAA is 1.1 and my estimate calculated today is 1.2].
IMPORTANT AND RAPID CHANGES CONTINUE TO BE INDICATED IN SUBSURFACE OCEAN TEMPERATURES. ALTHOUGH OCEAN SURFACE TEMPERATURES REMAIN ABOVE AVERAGE ACROSS THE EQUATORIAL PACIFIC AS NOTED ABOVE, THIS LAYER IS SHALLOW AND ONLY EXTENDS DOWNWARD A FEW TENS OF METERS IN DEPTH, ESPECIALLY ACROSS THE EASTERN PORTION OF THE BASIN. BELOW AVERAGE OCEAN TEMPERATURES (MAGNITUDE OF GREATER THAN 2 DEGREES C) ENCOMPASS A LARGE VOLUME OF WATER FROM 130E TO 90W WITH A THICKNESS RANGING FROM 150 METERS IN THE WESTERN PACIFIC TO 50 METERS IN THE EAST-CENTRAL PACIFIC. ANOMALOUS INTEGRATED (0-300 METERS DEPTH) EQUATORIAL PACIFIC OCEAN HEAT CONTENT BECAME NEGATIVE IN MARCH AND CONTINUES TO DECREASE THROUGH APRIL.
THIS EXPANSE OF NEGATIVE HEAT CONTENT ANOMALIES AT DEPTH MAY BE AN INDICATOR OF A POTENTIAL RAPID TRANSITION TO LA NINA CONDITIONS DURING 2016.
WITH RESPECT TO THE TROPICAL PACIFIC ATMOSPHERE, ENHANCED CONVECTION CONTINUED ACROSS THE CENTRAL PACIFIC BUT WEAKENED EAST OF THE DATE LINE, AND LOW-LEVEL WIND ANOMALIES WERE CLOSE TO AVERAGE OVER THE PAST MONTH. ALTHOUGH THE UPPER-LEVEL ANOMALOUS CIRCULATION REMAINS CONSISTENT WITH EL NINO IT ALSO HAS WEAKENED AS COMPARED TO FEBRUARY AND MARCH 2016.
THE EXTRA-TROPICAL PACIFIC OCEAN REMAINS CONSISTENT WITH THE POSITIVE PHASE OF THE PACIFIC DECADAL OSCILLATION WITH ABOVE AVERAGE SSTS SOUTH OF ALASKA AND ALONG THE WEST COAST. POSITIVE SST ANOMALIES IN THE WESTERN ATLANTIC NEAR THE EAST COAST CONTINUE TO PERSIST AS WELL ESPECIALLY OFF THE NEW ENGLAND COAST.
PROGNOSTIC DISCUSSION OF SST FORECASTS
AS THE CURRENT EL NINO EVENT WEAKENS, SOME CHALLENGES MOVING FORWARD INCLUDE HOW QUICKLY ANY RELATED EL NINO IMPACTS DISSIPATE AS WE MOVE TOWARD ENSO-NEUTRAL CONDITIONS AND WHEN A POTENTIAL TRANSITION TO A LA NINA EVENT MAY OCCUR.
THE CPC SST CONSOLIDATION CONTINUES TO FORECAST A RETURN TO ENSO-NEUTRAL CONDITIONS BY MJJ AND WEAK LA NINA CONDITIONS BY OND, ALTHOUGH THIS IS INFLUENCED STRONGLY BY ONE STATISTICAL FORECAST WHICH MAINTAINS ENSO-NEUTRAL CONDITIONS THROUGHOUT THIS PERIOD INTO THE WINTER MONTHS. IT SHOULD BE NOTED THAT THE CFS AND CA PREDICTIONS INDICATE A TRANSITION TO LA NINA BY ASO 2016. PREDICTIONS FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) MEMBERS ARE IN BETTER AGREEMENT THIS MONTH AS COMPARED TO LAST MONTH AND EXHIBIT GENERALLY TIGHT CLUSTERING WITH THE ENSEMBLE MEAN ENTERING LA NINA TERRITORY (NINO3.4 ANOMALY AT OR LESS THAN -0.5) BY JULY 2016 AND ALL INDIVIDUAL MODELS BY AUGUST.
THE CPC/IRI CONSENSUS FORECAST INDICATES THAT THE TRANSITION TO ENSO-NEUTRAL IS MOST LIKELY BY EARLY SUMMER, AND THE PROBABILITY OF LA NINA DEVELOPING FIRST EXCEEDS 50% IN JAS 2016, TWO OVERLAPPING SEASONS EARLIER THAN FORECAST IN THE OFFICIAL OUTLOOK LAST MONTH.
30-DAY OUTLOOK DISCUSSION FOR MAY 2016
THERE IS LITTLE IN THE WAY OF COHERENT MJO ACTIVITY TO INFLUENCE THE OUTLOOK; THE MJO'S INFLUENCE IS DIMINISHED IN THE WARM SEASON, AND PLAYS NO ROLE HERE IN INFORMING THE MONTHLY FORECAST. SOIL MOISTURE, HOWEVER, IS TAKEN INTO ACCOUNT, AS INCREASING INCIDENT SOLAR RADIATION ALLOWS IT TO EXERT MORE INFLUENCE ON LOCAL TEMPERATURES.
THE CALIBRATED NMME TEMPERATURE PROBABILITIES INDICATE A FAIRLY WEAK TILT TOWARD WARMER-THAN-NORMAL TEMPERATURES ACROSS THE NORTHERN TIER OF THE CONUS, ALASKA, AND PARTS OF THE EASTERN CONUS. A NOTABLE WEAKNESS IS FORECAST OVER THE SOUTH-CENTRAL AND SOUTHWESTERN U.S. THIS IS GENERALLY CONSISTENT WITH LAGGED ENSO REGRESSIONS (USING LATE WINTER NINO 3.4 VALUES), OBJECTIVE COMPOSITE ANALOGS BASED ON THE RECENTLY OBSERVED SSTS IN THE TROPICAL AND NORTHERN PACIFIC AND ATLANTIC BASINS, AS WELL AS STATISTICALLY DERIVED LOCAL SOIL MOISTURE IMPACTS. THE SECULAR TREND EXPLAINS LESS VARIANCE ON MONTHLY TIMESCALES THAN ON SEASONAL TIMESCALES, BUT GENERALLY SUPPORTS THE SPATIAL STRUCTURE OF FORECAST TEMPERATURE PROBABILITIES.
ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ARE INDICATED FOR MUCH OF THE WESTERN, NORTHERN, AND EASTERN CONUS, BASED ON THE ABOVE FACTORS. THE LOWEST PROBABILITIES ARE FORECAST OVER NORTHERN NEW ENGLAND AND THE NORTHERN PLAINS. THE FORMER IS DUE TO HIGHER-FREQUENCY PATTERNS THAT FAVOR ANOMALOUS NORTHERLY FLOW INTO EARLY MAY FOR THAT REGION, WHILE THE LATTER IS DUE TO TRENDS AND SOIL MOISTURE TOOLS. THE LATEST CFS FORECASTS, WEEK 3/4 GUIDANCE FROM BOTH THE CFS AND ECMWF, SOIL MOISTURE CONSIDERATIONS, AND LAGGED ENSO REGRESSIONS FAVOR ENHANCED PROBABILITIES OF BELOW-NORMAL TEMPERATURES ACROSS A PORTION OF THE SOUTHWESTERN AND SOUTH-CENTRAL CONUS.
ALL OF THE AFOREMENTIONED OBJECTIVE GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE FORECAST PRECIPITATION OUTLOOK AS WELL. MODEST PROBABILITIES FAVORING ABOVE-MEDIAN PRECIPITATION ARE DEPICTED FOR MUCH OF THE CENTRAL AND SOUTHERN CONUS, EXTENDING WESTWARD TO PARTS OF CALIFORNIA AND THE GREAT BASIN.
MAY - JUNE - JULY
THE MAY-JUNE-JULY (MJJ) 2016 TEMPERATURE OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS MUCH OF THE CONTINENTAL U.S. AND ALL OF ALASKA, WITH THE ONLY EXCEPTION BEING AN AREA ACROSS THE CENTRAL AND SOUTHERN PLAINS. THE CHANCES OF ABOVE-NORMAL TEMPERATURES ARE HIGHEST FOR SOUTHERN ALASKA, THE FAR WEST AND THE NORTHEAST WHERE ODDS EXCEED 50 PERCENT.
THE MJJ 2016 PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR PARTS OF WESTERN AND NORTHERN ALASKA AND A REGION IN THE CONTIGUOUS U.S. THAT STRETCHES FROM NORTHERN CALIFORNIA ACROSS THE INTERIOR WEST SOUTHWARD AND THEN EASTWARD TO INCLUDE THE SOUTHERN PLAINS, GULF COAST AND PARTS OF THE SOUTHEAST. THE GREATEST ODDS FOR ABOVE-MEDIAN SEASONAL PRECIPITATION AMOUNTS ARE FOR NORTHERN ALASKA AND PARTS OF THE CENTRAL ROCKIES, ALTHOUGH ELEVATED CHANCES ARE VERY MODEST. BELOW-MEDIAN PRECIPITATION IS FAVORED FOR PARTS OF THE UPPER GREAT LAKES REGION.
MJJ 2016 TO MJJ 2017
THE SUITE OF TEMPERATURE OUTLOOKS THIS MONTH ARE SIMILAR TO THOSE RELEASED LAST MONTH AS THE GENERAL THINKING OVER THE OUTLOOK PERIOD REMAINS GENERALLY UNCHANGED, ALTHOUGH POTENTIAL LA NINA IMPACTS WERE CONSIDERED EARLIER THAN IN PREVIOUS SETS OF OUTLOOKS.
OVERALL FOR TEMPERATURE, CHANGES WERE PRIMARILY MINOR ADJUSTMENTS FOR THE FIRST SEVERAL LEADS WHERE PROBABILITIES ARE MODIFIED SOMEWHAT IN SOME AREAS BASED ON THE LATEST CALIBRATED DYNAMICAL MODEL GUIDANCE AND CURRENT SOIL MOISTURE CONDITIONS. FOR MJJ 2016, CALIBRATED MODEL GUIDANCE AND IN SOME AREAS POSITIVE DEPARTURES IN SOIL MOISTURE SUPPORT A SLIGHTLY ADJUSTED REGION OF EQUAL CHANCES (EC) AND A SLIGHT DECREASE IN PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR SOME LOCATIONS IN THE NORTHERN PLAINS, UPPER MISSISSIPPI VALLEY AND GREAT LAKES. PROBABILITIES FOR ABOVE NORMAL TEMPERATURES WERE INCREASED FOR PARTS OF THE FAR WEST AND SOUTHWEST CONUS BASED ON DYNAMICAL MODEL GUIDANCE, LONG TERM TRENDS AND BELOW AVERAGE WINTER AND EARLY SPRING PRECIPITATION.
FOR JJA AND JAS 2016, SIMILAR ADJUSTMENTS WERE MADE, AND PROBABILITIES WERE SLIGHTLY INCREASED ACROSS THE INTERIOR OF THE CONUS DURING ASO 2016 DUE TO POTENTIAL LA NINA CONSIDERATIONS. IN ADDITION TO CALIBRATED DYNAMICAL MODEL GUIDANCE, STATISTICAL GUIDANCE FROM THE SST BASED CONSTRUCTED ANALOGUE TOOL FURTHER SUPPORTS FAVORED ABOVE NORMAL TEMPERATURES FOR MOST OF THE FORECAST DOMAIN FROM JJA 2016 THROUGH SON 2016.
INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES FORECAST ACROSS PARTS OF THE SOUTHERN CONTIGUOUS U.S. AND A SLIGHT INCREASE IN THE PROBABILITY FOR BELOW-NORMAL TEMPERATURES ACROSS THE NORTHERN U.S. FROM NDJ 2016-17 THROUGH AMJ 2017 ARE BASED LARGELY ON THE IMPACTS FROM POTENTIAL LA NINA CONDITIONS.
AN INCREASED PROBABILITY OF ABOVE-NORMAL TEMPERATURES FOR THE NORTH SLOPE OF ALASKA DURING THE AUTUMN AND AGAIN IN THE SPRING IS DUE TO THE LIKELIHOOD OF ANOMALOUSLY OPEN SEA ICE AND THE FEEDBACK BETWEEN SEA ICE COVERAGE AND CHANGES IN THE CLIMATE STATE.
THE MJJ 2016 PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR A REGION STRETCHING FROM NORTHERN CALIFORNIA EASTWARD TO INCLUDE MUCH OF THE INTERIOR WEST, PARTS OF THE SOUTHWEST, SOUTHERN PLAINS AND SOUTHEAST. RESIDUAL EL NINO IMPACTS SUPPORT THE HIGHLIGHTED AREA ACROSS MUCH OF THE WEST AND SOUTHERN PLAINS WHILE DYNAMICAL AND STATISTICAL MODEL GUIDANCE FAVOR AREAS IN THE SOUTHEAST. IT IS IMPORTANT TO NOTE THAT THESE PROBABILITIES ARE QUITE MODEST AND REPRESENT ONLY A SLIGHT TILT TO THE ABOVE-MEDIAN CATEGORY, ESPECIALLY ACROSS THE SOUTHEAST CONUS. BELOW-MEDIAN PRECIPITATION IS MOST LIKELY FOR NORTHERN REGIONS OF THE PACIFIC NORTHWEST AND THE WESTERN GREAT LAKES CONSISTENT WITH ANY REMAINING EL NINO INFLUENCE AND DYNAMICAL MODEL GUIDANCE. AN INCREASED CHANCE OF ABOVE-MEDIAN PRECIPITATION IS ALSO FORECAST FOR WESTERN AND NORTHERN ALASKA THROUGH JJA 2016 BY DYNAMICAL MODELS, RESULTING FROM ANOMALOUSLY OPEN SEA ICE AND WARM OPEN OCEAN TEMPERATURES.
POTENTIAL LA NINA INFLUENCE AND STATISTICAL FORECAST GUIDANCE SUPPORT A SLIGHT TILT IN THE ODDS TO ABOVE-MEDIAN SEASONAL TOTAL PRECIPITATION AMOUNTS FOR COASTAL AREAS OF THE SOUTHEAST DURING JAS AND ASO 2016. POTENTIAL LA NINA CONDITIONS ALSO SUPPORT FAVORED BELOW MEDIAN PRECIPITATION ACROSS PORTIONS OF CENTRAL PLAINS WESTWARD TO THE CENTRAL ROCKIES DURING ASO 2016.
DURING AUTUMN OF 2016 AND WINTER OF 2016-17, THE POTENTIAL FOR ONGOING LA NINA CONDITIONS IS THE PRIMARY FACTOR FOR INCREASED PROBABILITIES OF BELOW-MEDIAN PRECIPITATION ACROSS THE SOUTHERN TIER OF THE CONTIGUOUS U.S. AND THE SOUTHERN COAST OF ALASKA, AND INCREASED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FOR THE PACIFIC NORTHWEST AND OHIO VALLEY AND CENTRAL GREAT LAKES.
Sometimes it is useful to compare the present month outlook to the three-month outlook
One can mentally subtract the May Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely June and July 2016. When I do that, I deduce that:
With respect to temperature, the area that is a cool anomaly in May will need warm anomalies June and July for the three-month period to work out as EC. The Precipitation Outlook for the three-months is similar to May except for the Great Lakes dry anomaly in the three-month period. This means the probabilities for that area to be dry in June and July probably are higher than what is shown for the three-month average. The three-month average shows the wet anomaly extending north into Tennessee but not so in the May Outlook. Given that the three-month average precipitation probability is the lowest level i.e. 33 percent, it probably does not make sense to do the math analysis and conclude that area is likely to be wetter in June and July than shown in the three-month average.
Let's Now Focus on the Current (Right Now to 5 Days Out) Weather Situation.
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.
Characteristics of a Weekly Weather Column.
Many graphics in this report are auto-updated by the source of the graphic. It is always my choice as the writer to allow these graphics to auto-update or "freeze them" to what they looked like when I write the article. Generally speaking graphics in research themes which appear above this point do not auto-update as they come from published scientific papers. When I make the decision to allow certain graphics to auto-update, it creates two issues:
A. As the graphic updates, my commentary becomes out of sync with the new version of the graphic. This can be very extreme if for example you take a look at my report from months ago.
B. On rare occasions, source sites for graphics go down and the graphic does not appear in the article and you probably see white space. If you experience such an event and that graphic is important to your understanding of the report, please return later to view my weather and climate column. Sometimes the "outage" is only for several minutes, but often the duration can be a number of hours or even one or more days. We feel that this inconvenience is preferable to looking at "frozen" weather map images that do not update since I write the article on Monday evenings and you probably do not read it until Tuesday and perhaps later in the week. So I want you to have the advantage of seeing the most up-to-date graphics. If the source is down, the white space is the price paid for most of the time being able to see the latest available graphics.
First, here is a national animation of weather front and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at the link provided above.
The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.
The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients.This graphic auto-updates so when you look at it you will see NOAA's latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot.
Because "Thickness Lines" are shown by those green lines on this graphic, it is a good place to define "Thickness" and its uses. The 540 Level general signifies equal chances for snow at sea level locations. I am leaving this explanation in the report but it may not be very significant until next October or so. The 7 Day Outlook indicates a Ridge in the West and a strong Trough moving past the Great Lakes.
The MJO is not likely to have much of an impact for the month of May as a whole as this MJO cycle appears to be weak and the forecasts of phase changes are contradictory. The MJO has had significant impacts this winter but the impact on May is not likely to be very noticeable. However in the past week some of the models are suggesting a greater but still modest impact than was believed to be the case when NOAA prepared their analysis.
Notice the Northern Pacific is like a giant anticyclone with clockwise motion so that which gets sent west due to El Nino is to some extent returned to North America but at higher latitudes. I am trying to see if I can discern a change in pattern towards lower latitudes for storms arriving from the Western Pacific but so far I do not see that in this animation.
As I am looking at the below graphic Monday evening April 25, I still see a northerly displaced pattern. This graphic updates automatically so it most likely will look different by the time you look at it as the weather patterns are moving from west to east.
Below is an analysis of projected tropical hazards and benefits over an approximately two-week period. This graphic is scheduled to update on Tuesday and I am reading the April 19. 2016 Version and looking at Week 2 of that forecast.
Mostly I see for the period April 27 - May 3, 2016 I see a moderate risk of a dry anomaly over Indochina and a moderate risk of tropical cyclone activity for Northeast Australia plus a moderate risk of a dry anomaly off the coast of Brazil which I mention only because a slight change in position would impact Brazil. I also see a small area of moderate risk of above average rainfall forecast for Venezuela.
Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 6 (the Day 3 forecast is available on Page II of this Report). This graphic also auto-updates.
In recent weeks, the projected location and strength of the Aleutian Low has varied a lot. On some days, the forecast is showing a split low with each of the two lows weaker than a combined single Low. Right now the forecasted Low in the Gulf of Alaska has an hPa of 992 and the stronger part over by Kamchatka has an hPa of 888 (lower hPa is stronger). The average in the winter is 1001hPa and 994 hPa for a non-split Low. This is a split low so the two pieces each to me seem stronger than one would expect for the end of April. The location of the piece in the Gulf of Alaska is favorable for producing El Nino type weather for CONUS. But the High Pressure off of California is the familiar RRR so it still tends to protect or at least partially protect the West Coast from Pacific Storms. Thus most storms now are more likely to enter CONUS further north than usual but perhaps not as far north as during January, February and March. The rapidly shifting position of the Low makes a big difference in how storms are steered. 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
The path of the current weather pattern is fairly clear from this graphic. But the Jet Stream now is fairly weak.
And here is the forecast out five days.
Not all weather is controlled by the Jet Stream (which is a high altitude phenomenon) but it does play a major role in steering storm systems. In some cases however a Low Pressure System becomes separated or "cut off" from the Jet Stream. In that case it's movements may be more difficult to predict until they are again recaptured by the Jet Stream.
To see how the pattern is projected to evolve, please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.
This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.
Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on "earth" adjusting the parameters and then clicking again on "earth" to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns.
And when we look at Sea Surface anomalies below, we see a lot of them not just along the Equator related to El Nino.
Peru and Ecuador are no longer connected to the ENSO Warm Pool at the surface. So we essentially have a Modoki pattern at this point in terms of weather impacts. The Tropical Warm Anomaly west of about 140W is dramatically present south of but not north of the Equator. This is very important. There is now a growing cool anomaly off the coast of Ecuador and Peru which is the beginning perhaps of ENSO Neutral if not La Nina. The overall Northern Pacific is indeed PDO Positive (the horseshoe pattern with the cool anomaly inside the horseshoe shape). I have seen a report that the PDO Index rose to 2.4 in March which with El Nino fading may be significant. The set up is for a typical PDO-/AMO+ weather pattern. I provided additional commentary below as I looked at the four-week average. The water off the West Coast of North America is very warm. Further north in the Atlantic south of Greenland and Iceland rather than directly off the Coast of North America, the North Atlantic is cooler than normal which is consistent with AMO+ and has implications for the NAO and perhaps will reduce the summer tropical storm potential in the Atlantic. Again I have additional commentary on this below where I examine the four week change in these anomalies. The waters off of Japan remain warm. The Indian Ocean is very warm.
Below I show the changes over the last month in the Sea Surface Temperature (SST) anomalies.
Since these are "departures" or "anomalies", it is not a seasonal pattern that is being shown. Comparing a four-week graphic to a prior four-week graphic is always tricky since only 25% of the data has changed and I am not showing the former graphic (it is in last week's report). I add the new one, compare and comment on the change and then delete the old one to keep this report to a manageable size. What I see as I look at both (before deleting the prior version) is that the anomalies are less intense. It does seem to be getting warmer off the West Coast of North America. Also there may be some decline in intensity of the cold water northeast of Australia which may a first sign of the switch to La Nina.
6 - 10 Day Outlook
Now let us focus on the 6 - 14 Day Forecast for which I generally only show the 8 - 14 Day Maps. The 6 - 10 Day maps are always available in Part II of this report but in the Winter and Spring I often show both maps as the forecasted weather patterns change during that nine day period.
To put the forecasts which NOAA tends to call Outlooks into perspective, I am going to show the three-month AMJ Outlook and the recently updated Outlook for the single month of April and then discuss the 8 - 14 day Maps and the 6 - 14 Day NOAA Discussion within that framework.
First - Temperature
Here is the Three-Month MJJ Temperature Outlook issued on April 21, 2016:
Here is the "Early" Outlook for May Temperatures issued on April 21, 2016.
Below are the current 6 - 10 Day and 8 - 14 Day Temperature Outlook Maps which will auto-update daily and thus be current when you view them. It covers the nine days following the tail end of the current week. I have included both today and probably will continue to do that as long as the patterns are moving from west to east fairly rapidly. I have also included the experimental Week 3 and 4 Outlook. The Week 3-4 Experimental Outlook updates weekly on Friday. Notice the Week 3-4 Experimental Outlook has fewer levels of probability starting with 50%.
As I view these maps on April 25, it appears that the main feature for Early May will be the continued zonal progression of the alternating cool and warm anomalies. Later in May an El Nino pattern is projected to establish itself.
6 - 10 Day Temperature Outlook
8 - 14 Day Temperature Outlook
Looking further out.
It will be interesting to see if that cool anomaly in Arizona, New Mexico and Texas does indeed develop and develop where it is now forecasted to be. The warm swath across the Northern Tier which is now (and remember this is a forecast for a week later than the prior forecast) projected to cover more area especially in the East is also a feature to watch.
Now - Precipitation
Here is the three-month MJJ Precipitation Outlook issued on April 21, 2016:
"Early" Precipitation Outlook for May Issued on April 21, 2016
Below are the current 6 - 10 Day and 8 - 14 Day Precipitation Outlook Maps which will auto-update and thus be current when you view them. It covers the nine days following the tail end of the current week. I have included both today and probably will continue to do that as long as the patterns are moving from west to east fairly rapidly. I have also included the experimental Week 3 and 4 Outlook. The Week 3-4 Experimental Outlook updates weekly on Fridays. Notice the Week 3-4 Experimental Outlook has fewer levels of probability starting with 50%.
As I view these maps on April 25 (they update each day), it looks like precipitation for early May will be generally widespread wet conditions which will be fairly stationary unlike the temperature which is forecast to be zonal/progressive from west to east. Then beyond two weeks it is projected to revert to an El Nino pattern with a less geographically expansive wet anomaly in the Southwest (but extending to the north almost to the Canadian border and a dry anomaly in the East but not Florida.
6 - 10 Day Precipitation Outlook
8 - 14 Day Precipitation Outlook
It will be interesting to see if this week three and four experimental Outlook works out. I note that the higher probabilities for the wet anomaly are over Utah suggesting that the storm track is still somewhat northerly displaced but not as much as earlier this year.
Here are excerpts from the NOAA discussion released today April 25, 2016.
6-10 DAY OUTLOOK FOR MAY 01 - 05 2016
TODAY'S MODEL SOLUTIONS ARE IN FAIR AGREEMENT ON THE PREDICTED 500-HPA CIRCULATION PATTERN ACROSS MOST OF THE FORECAST DOMAIN. A TROUGH IS FORECAST OVER THE ALEUTIANS EXTENDING TO THE NORTH PACIFIC OCEAN WHILE RIDGING IS PREDICTED DOWNSTREAM OVER THE NORTHWEST CONUS EXTENDING TO WESTERN CANADA. ANOTHER TROUGH IS ANTICIPATED DOWNSTREAM OVER THE NORTHEAST CONUS. THE ENSEMBLE SPAGHETTI DIAGRAMS INDICATE MODERATE TO HIGH SPREAD ACROSS THE MAJORITY OF THE FORECAST DOMAIN. TODAY'S 500-HPA BLEND CHART DEPICTS BELOW NORMAL HEIGHTS OVER MOST OF THE SOUTHEAST CONUS, WHILE ABOVE NORMAL HEIGHTS ARE INDICATED OVER MUCH OF THE NORTHWEST CONUS. TODAY'S MANUAL 500-HPA HEIGHT BLEND IS COMPOSED PRIMARILY OF THE ENSEMBLE MEAN SOLUTIONS, BASED LARGELY ON CONSIDERATIONS OF RECENT SKILL AND ON ANALOG CORRELATIONS, WHICH MEASURE HOW CLOSELY THE MODEL SOLUTIONS RESEMBLE CASES THAT HAVE OCCURRED IN THE PAST.
ABOVE NORMAL HEIGHTS AND FORECAST RIDGING OVER THE NORTHWEST CONUS ENHANCE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR MUCH OF THE WESTERN CONUS, AND PARTS OF THE NORTHERN PLAINS AND THE UPPER MISSISSIPPI VALLEY. NEAR TO BELOW NORMAL HEIGHTS AND TROUGHING PREDICTED OVER THE NORTHEAST CONUS FAVOR BELOW NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND THE NORTHEASTERN CONUS. ABOVE NORMAL TEMPERATURES ARE FAVORED FARTHER TO THE SOUTH FOR MUCH OF THE SOUTHEASTERN CONUS. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR ALASKA AHEAD OF A TROUGH PREDICTED NEAR THE ALEUTIANS.
ABOVE MEDIAN PRECIPITATION IS FAVORED FOR MUCH OF THE EASTERN CONUS IN ASSOCIATION WITH THE TROUGH PREDICTED OVER THE NORTHEAST CONUS. CONVERSELY, THERE ARE ENHANCED PROBABILITIES FOR BELOW MEDIAN PRECIPITATION FOR THE WEST COAST EASTWARD ALONG THE NORTHERN TIER TO THE UPPER GREAT LAKES IN ASSOCIATION WITH FORECAST RIDGING. PRECIPITATION ESTIMATES FROM THE GFS FAVOR ABOVE MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHERN PLAINS, THE CENTRAL PLAINS, AND THE CENTRAL ROCKIES. ABOVE MEDIAN PRECIPITATION IS FAVORED FOR MOST OF SOUTHEASTERN ALASKA AHEAD OF A TROUGH PREDICTED NEAR THE ALEUTIANS, WHILE NEAR TO BELOW MEDIAN PRECIPITATION IS FORECAST FOR NORTHWESTERN ALASKA.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 3 OUT OF 5, DUE TO FAIR AGREEMENT AMONG THE MODELS.
8-14 DAY OUTLOOK FOR MAY 03 - 09 2016
TODAY'S ENSEMBLE MEAN DYNAMICAL MODEL FORECASTS ARE IN FAIR AGREEMENT ON THE PREDICTED 500-HPA CIRCULATION PATTERN OVER NORTH AMERICA FOR THE WEEK-2 PERIOD. THE 500-HPA PATTERN DURING THE WEEK TWO PERIOD IS FORECAST TO BE SIMILAR TO THAT IN THE 6-10 DAY PERIOD. TROUGHS ARE FORECAST OVER THE ALEUTIANS AND NORTHEASTERN CONUS, WHILE A RIDGE IS INDICATED OVER THE NORTHWEST EXTENDING TO WESTERN AND CENTRAL CANADA. THE 500-HPA BLEND CHART DEPICTS ABOVE NORMAL HEIGHTS OVER THE NORTHWEST, WHILE BELOW NORMAL HEIGHTS ARE ANTICIPATED OVER MOST OF THE SOUTHERN AND EASTERN CONUS. THE ENSEMBLE SPAGHETTI DIAGRAMS INDICATE MODERATE TO HIGH SPREAD ACROSS THE MAJORITY OF THE FORECAST DOMAIN.
THE FORECAST TEMPERATURE PROBABILITIES FOR THE WEEK-2 PERIOD ARE SIMILAR TO THOSE IN THE 6-10 DAY PERIOD. ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE ANTICIPATED FOR THE NORTHWESTERN CONUS AS WELL ALASKA, WHILE NEAR- TO BELOW-NORMAL TEMPERATURES ARE PREDICTED FOR MUCH OF THE EASTERN AND SOUTHERN CONUS EXCEPT FOR MAINE AND SOUTHERN FLORIDA WHERE ABOVE-NORMAL TEMPERATURES ARE FAVORED.
ENHANCED PROBABILITIES FOR ABOVE-MEDIAN PRECIPITATION ARE INDICATED FOR THE EAST COAST AND SOUTHEAST IN ASSOCIATION WITH THE TROUGH OVER THE SOUTHEASTERN CONUS. BELOW MEDIAN PRECIPITATION IS FAVORED FOR PARTS OF THE PACIFIC NORTHWEST, THE NORTHERN PLAINS, THE UPPER AND THE MIDDLE MISSISSIPPI VALLEY, THE GREAT LAKES, AND THE OHIO VALLEY IN ASSOCIATION WITH FORECAST RIDGING.
PRECIPITATION ESTIMATES FROM THE GFS FAVOR ABOVE MEDIAN PRECIPITATION FOR MOST OF THE SOUTHERN AND SOUTHWESTERN CONUS. EXCEPT FOR THE FAR NORTHWEST, ABOVE MEDIAN PRECIPITATION IS FAVORED FOR MOST OF ALASKA AHEAD OF A TROUGH PREDICTED NEAR THE ALEUTIANS.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: AVERAGE, 3 OUT OF 5, DUE TO FAIR AGREEMENT AMONG THE MODELS.
THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON MAY19
Some might find this analysis interesting as the organization which prepares it looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of this El Nino.
Analogs to Current Conditions
Now let us take a detailed look at the "Analogs" which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. "Analog" means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 - 14 day Outlook.
Here are today's analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the Outlook but I have not been analyzing this second set of information. The first set which is what I am using today applies to the 5 and 7 day observed pattern prior to today. The second set, which I am not using, relates to the correlation of the forecasted outlook 6 - 10 days out with similar patterns that have occurred in the past during the dates covered by the 6 - 10 Day Outlook. The second set of analogs may also be useful information but they put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so.
Apr 15, 1992
Modoki Type I or II
Apr 4, 1994
Between El Nino's
Apr 23, 1994
Between El Nino's
May 8, 1995
Between an El Nino and a La Nina
May 9, 1995
Between an El Nino and a La Nina
Apr 13, 1996
May 8, 2005
Modoki Type II
May 9, 2005
Modoki Type II
May 1, 2009
Before El Nino Modoki Type II
One thing that jumped out at me right away was the spread among the analogs from Apr 4 to May 9 which is five weeks. It suggests that the prior week conditions are highly correlated with weather patterns which in the past occurred over a fairly wide range of dates as shown. There are this time three El Nino Analogs, three ENSO Neutral Analogs and three La Nina Analogs suggesting that it is the PDO rather than El Nino which is in control over our weather for the next 6 - 14 Days or perhaps more accurately the forecast best correlates with periods of time when ENSO was Neutral or the El Nino Modoki state.This makes sense because of the pattern of the warm anomaly along the Equator is consistent with a Modoki even if it did not originate as a Modoki but that can be argued if one looks at the past two winters and not just this winter.
The phases of the ocean cycles in the analogs point clearly towards McCabe Condition A which suggests a low probability of drought for most of the southern tier. That is kind of where the 6 - 14 Day Outlook and the 3-4 Week Experimental Outlook is headed. So it all fits together nicely this week. 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.
J FM 1951
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.
90 Day Average
[Waiting for Queensland to update their site. When they do I will complete the below discussion. The Queensland Site was working on Apr 28 and the below discussion was updated at that time.]
The 30-day average, which is the most widely used measure, as of April 25 was reported at -18.04 which is again clearly associated with an El Nino (usually required to be more negative than -8.0 but some consider -6.0 value good enough). It is quite a bit stronger this week due to strong SOI values all week possibly related to a tropical storm in that area. The 90-day average remains in El Nino territory at -13.71 little changed from last week. Usually but not always the 90 day average changes more slowly than the 30 day average but it depends on what values drop out. The SOI continues to be indicative of an El Nino Event in progress but it is pretty much passed the time of year where it is very meaningful re El Nino development. I believe we will see a moderating trend in the SOI from here.
The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.
Low-Level Wind Anomalies
Here are the low-level wind anomalies. We now see light Easterly anomalies, the blue area at the bottom of the Hovmoeller graphic. This is part of the process of cleaning up after this El Nino.
And now the Outgoing Longwave Anomalies which tells us where convection has been taking place.
In the above graphic, the convection zone east of the Dateline has gone away. The non-convection zone to the west of the Dateline appears to be vanishing
Let us now take a look at the progress of Kelvin Waves which are the key to the situation. From the earliest to the most recent they can be named #1 through #5. Kelvin Wave #1 has now been pushed off the top of this graphic as more recent information is added at the bottom.
We now see the major Upwelling Phase which is the Coup de Grace for this El Nino.
One should keep in mind that for a new Kelvin Wave, the period of time from initiation to the termination of impacts is about six months. So when you have four or five this winter six in a row, the pattern of impacts on different indices and geographic areas becomes quite complex. It is further complicated as you can see above because the Kelvin Waves do not necessarily originate at the same location i.e. longitude.
We are now going to change the way we look at a three dimensional view of the Equator and move from the surface view to the view from the surface down. This El Nino appears to be fading slowly from west to east. The real decline will be from east to west.
Current Sub-Surface Conditions. Notice the lag in getting this information posted so the current situation may be a bit different than shown.
And now the pair of graphics that I regularly provide and which as I publish are currently able to be accessed from the NOAA website:
The above pair of graphics showing the current situation has an upper and lower graphic. The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters.
The top graphic shows surface temperature anomalies. The 2C, 3C, 4C, 5C and 6C anomalies are gone. the 0.5 C and 1C anomaly extends from 130W to 170E. From the West, cool water has now made it all the way to the Coast of Ecuador and in some places the anomaly exceeds negative 4C. Along the Coast of South America the cool water at depth is still down at 200 meters.
The bottom half of the graphic (Absolute Values which highlights the Thermocline) perhaps is a now equally useful in terms of tracking the progress of this Warm Event as it converts to ENSO Neutral and then La Nina.
It shows the thermocline between warm and cool water. The 25C Isotherm is now reaching the surface. There is a lot of compression of the Isotherms so from 120W on east, the 20C is close to the surface and will reach the surface soon. We now pay more attention to the 28C Isotherm as west of that temperature is where convection is more easy to occur. The 28C Isotherm has now moved all the way to the Dateline which means to me that the El Nino no longer is able to significantly impact CONUS weather but the decline of impacts takes time to show up re CONUS. But we may remain in what is more like an El Nino Modoki situation for longer than most models predict although JAMSTEC is pretty much predicting that or at least something closer to a Neutral ENSO.
Here are the above graphics as a time sequence animation. You may have to click on them to get the animation going.
This discussion is longer than necessary to describe current conditions but I am retaining the snap shots of the earlier TAO/TRITON graphics to allow the reader to understand how this El Nino evolved and how it is now decaying.
Let us compare the situation as reported on October 4 to the most recent graphic. Remember each graphic has two parts the top part is the average values, the bottom part is those values expressed as an anomaly compared to the expected values for that date. Generally I am mainly discussing the bottom of the pairs of graphics namely the anomalies
First the October 4 version which I am providing for purposes of comparison. I "flash froze" the daily value that day so that it would not auto-update.
And then the December 14 version which I also "flash froze" to stop it from updating.
And then the current version of the TAO/TRITON Graphic.
Location Bar for Nino 3.4 Area Above and Below
The overall pattern is quite a bit less intense than on December 14. We now see a cool anomaly jutting out from Ecuador and sub 0.5C anomalies now extend to 130W. The 3.5C anomaly is no longer visible. Neither is the 3.0C anomaly or the 2.5C anomaly. The 2C anomaly no longer exists in the Nino 3.4 Measurement Area except in a small area south of the Equator where it has recently appeared. So the maximum anomalies (which do not appear everywhere) have declined by a full two degrees Centigrade almost everywhere. This means that if one is attempting to mentally estimate the daily ONI, an approach would be to make an initial estimate of the midpoint of the 1.5C to 2.0C or 1.75C and subtract the reductions from there where the anomaly is less and add back in the small area south of the Equator. Soon we will be subtracting from 1.25C. What I have just described is not exactly the approach I use in my calculation below but it does provide a quick way to get a feel for the current strength of this El Nino. There is actually shading in the TAO/TRITON Graphic that might allow one to try to refine estimates a bit more than the contour lines but I rely on the contour lines. The 1.5C anomaly is also now shrinking although it expanded some this past week. And the western part of the 1.5C anomaly is almost all south of the Equator which means that it has less than half the impact of an anomaly that extends from 5 degrees north latitude to 5 degrees south latitude. This El Nino is crashing.
And an earlier but recent reference point close to the peak of this El Nino re the bottom half of the TAO/TRITON Graphic. You can certainly see the difference that three months makes.
The below table tracks the changes. It only addresses the situation right on the Equator so visually the TAO/TRITON graphic contains more information. But the below table turns visual information into quantitative information so it may be useful. The degrees of coverage shown in the rightmost two columns shows that the extent of the warm water directly on the Equator has been reduced in recent weeks. The way I constructed the table, the 1.0C anomaly as an example includes all water warmer than 1.0C so the 1.5C anomaly is included within it as well as the 2.0C anomaly which you can tell by the way I recorded the westward and eastward coordinates. I could have constructed this table in a different way. Note the 3C anomaly no longer exists. The 2.5C anomaly also no longer exists. As this El Nino decays I am including the less warm anomalies in the table below.
Comparing Now to January 19, 2016
Subareas of the Warm Anomaly
Degrees of Coverage
January 19, 2016
January 19, 2026
January 19, 2016
* The 2.0 C anomaly is almost all South of the Equator and the 1.5C anomaly which had been South of the Equator again shows up on the Equator. In the above graphic, only the extent to which anomalies exist on the Equator are shown.
The above table which only looks at the Equator shows that there is very little left of the warm anomaly. I have been adding less warm anomalies to the bottom of the table and soon will be removing the warm anomalies from the top of this table since they will no longer be a factor as we go to ENSO Neutral or ENSO La Nina.
I calculate the ONI each week using a method that I have devised. To refine my calculation, I have divided the 170W to 120W ONI measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions. So as of Monday April 25, in the afternoon working from the April 24 TAO/TRITON report, this is what I calculated.
Calculation of ONI from TAO/TRITON Graphic
A. 170W to 160W
B. 160W to 150W
C. 150W to 140W
D. 140W to 130W
E. 130W to 120W
Total divided by five subregions i.e. the ONI
(6.6)/5 = 1.3
(6.2)/5 = 1.2
My estimate of the daily Nino 3.4 ONI after rounding is slightly down this week to 1.2. NOAA has now reported the weekly ONI to be down to 1.1. Nino 4.0 is being reported again at 0.8. This is interesting as it suggests the warm pool is not moving back to Indonesia but just dissipating. However, my calculations for the western part of Nino 3.4 which is the eastern part of Nino 4.0 were in the 1.7 to 1.6 range which means the western part of Nino 4.0 would have to be very cool to average out to 0.8. Nino 3.0 is being reported as being much lower at 0.6. The action which I think is most important to track right now is in Nino 1+2 which three weeks ago had soared to 1.5. This probably was due to Kelvin Wave #5 surfacing with some help from the MJO and marked the last Hurrah for this El Nino. It then two weeks ago was reported as being down to 1.3. Then last week it was reported at 0.1 which is essentially Neutral. But now it is down to -0.6 which is a La Nina value. But La Nina is not measured in that area but it is significant. For the Coast of South America, the El Nino is over. This is summarized in the following NOAA Table. I am only showing the currently issued version as the prior values are shown in the small graphics on the right with this graphic. Only Nino 3.4 is still showing significant El Nino values.
ONI Recent History
The official reading for Jan/Feb/Mar is now reported as 2.0. I have discussed before the mystery of how the CFSv2 values above get translated into the ERSST.v4 values shown below and if NOAA feels that working with two sets of books is a good way to operate, who am I argue. Many businesses do the same thing. As you can see this El Nino peaked in NDJ and is now declining and depending on what system you use it is either the 2nd or 3rd strongest El Nino since modern records were kept which is considered to be 1950. You could argue for it being #1 based on a week of readings but few are buying that argument. Still #2 or #3 means it is one of the strongest ever based on the way these events are measured. I will be writing more about that soon in a separate article. I believe the measurement system is inadequate re being useful in forecasting Worldwide weather impacts.
The full history of the ONI readings can be found here. The MEI index readings can be found here.
Is this El Nino a Modoki?
It did not evolve as a Modoki unless you consider it to be a continuation of the Faux El Nino Modoki of 2014/2015 which is a possible interpretation. But the Walker Circulation appears to be much like that of a Modoki. These graphics help explain this.
Although I discussed the Kelvin Waves earlier, now seems to be the best place to show the evolution of the subsurface temperatures.
Watching an El Nino evolve is like watching paint dry. The undercutting cool anomaly is again expanding to the east quite rapidly actually now edging east of 90W which means it has now undercut all of the warm anomaly and is ready to reach the coast of South America. All that remains is for "The Grand Switch" to occur with the cool anomaly reversing positions with the warm anomaly. So either this will be a slow process or some event will just flush the warm water to the west. It may be the next Inactive Phase of the MJO that does just that. You can also see cooler water rising but still at depth (200m) in the Eastern Pacific. It will replace the warm water in a few months. You can also see that there is not much left of the warm pool. It is not really moving back to the Western Pacific as one would expect. It is just disappearing. That may turn out to be very significant.
SST Surface Anomaly Hovmoeller
Here is another way of looking at it: Unlike the Upper Ocean Heat Anomaly Hovmoeller (I call it the Kelvin Wave Hovmoeller) which takes an average down to 300 meters, this just measures the surface temperature anomaly. It is the surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snap shots of the conditions at different points in time. Nevertheless this Hovmoeller provides a good way to visually see the evolution of this El Nino and later track its demise.
One can easily see the historical evolution of this El Nino. You can easily see how the intensity peaked in November 2015, declined in December and then declined substantially in late February and continues to decline. At the very bottom of this graphic, which shows the most recent readings, you can see the 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 reduction in NOAA ONI estimates. That is likely to continue to be the trend. You can see the steady decay in the anomalies from the east between 80W and beyond the Dateline. We should be starting to see a cool (shades of blue) anomaly developing of the coast of Ecuador. We see it in the TAO/TRITON Graphic which has more up to date information. But if you look closely in lower right corner you can see the blue. There are other graphics which show it better but I prefer this one because it auto-updates.
Recent Impacts of Weather Mostly El Nino but possibly Also PDO and AMO Impacts.
Below are snapshots of 30 Day temperature and precipitation departures over the life of this El Nino. The end date of the 30 day period is shown in the graphic. It is a way of seeing how the impacts of this El Nino have unfolded.
Remember this is a 30 day average and last week I used a different graphic so this can not be compared to last week but is best compared with last month. The La Nina pattern persists for much of the West with respect to both precipitation and temperature but is a normal El Nino for the Mississippi Valley in March. Northern California was wet but it is hard to say if that looks like El Nino or La Nina. This is one strange El Nino and for the 2nd or 3rd strongest in modern history it is a mystery that has not been given adequate attention.
Lets take a look at the combined results for the first three months of 2016: January, February and March.
Well that does not look like an El Nino pattern to me but more like a La Nina pattern for precipitation and just plain warm pretty much everywhere which is neither an El Nino nor a La Nina Pattern.
And here is the April weekly (30 day) graphics.
We are seeing a gradual change in April to a more typical El Nino pattern. The Northwest is dry and the Southwest is a bit wetter than neutral. One area along the Southern California western Arizona border had typical El Nino precipitation. The lee side of the Rockies for some reason were wet. It certainly has remained dry in Mexico.
I realize this is a lot of graphics but one needs to look at the history of an event to assess it. As you can see, so far we are not having the expected El Nino Impacts in CONUS.
Below is the discussion just released. Notice the discussion re forecasting a La Nina for next winter.
El Niño enters its final weeks
The 2015–16 El Niño is in its last stages. Recent changes in the tropical Pacific Ocean and atmosphere, combined with current climate model outlooks, suggest the likelihood of La Niña forming later in 2016 is around 50%, meaning the Bureau's ENSO Outlook is at La Niña WATCH.
Eastern tropical Pacific sea surface temperatures have cooled significantly in the past fortnight, and are now approaching neutral levels. As temperatures under the surface are below average, more surface water cooling is expected. However the atmosphere is not responding immediately to these changes, and hence the Southern Oscillation Index (SOI) and cloudiness near the Date Line continue to fluctuate around El Niño thresholds.
Six of eight international climate models suggest the tropical Pacific Ocean will return to neutral levels within the next month. By September, seven of eight models suggest La Niña thresholds are likely. However, individual model outlooks show a large spread between neutral and La Niña scenarios.
La Niña is often, but not always, associated with above-average winter-spring rainfall over northern, central and eastern Australia.
Australia's climate is also being influenced by record warm temperatures in the Indian Ocean. The warmth in the Indian Ocean may provide extra moisture for rain systems as they cross Australia during the southern autumn.
IOD (Indian Ocean Dipole)
The graphic comes with only a very short discussion and here is that discussion:
Indian Ocean Dipole outlooks
The Indian Ocean Dipole (IOD) is neutral. The weekly Dipole Mode Index value to 24 April was −0.16 °C. The IOD does not typically influence Australian climate during the months December to May, when the monsoon trough is in the southern hemisphere (as positive and negative events are typically unable to form in monsoonal flow).
Currently all international models monitored by the Bureau indicate negative IOD conditions are possible by July. However, model skill is generally lower at this time of year, and outlooks should be used with caution. Negative IOD events are more likely to occur during La Nina.
Sea surface temperatures (SSTs) remain significantly warmer than average across the tropical Indian Ocean.
Information on the impact of a negative IOD on Australia can be found here.
Putting it all Together.
This El Nino has peaked in intensity and is now in rapid decline. We are beginning to speculate on the winter of 2016/2017 which now according to most of the models seems increasingly likely to be a La Nina.
The below is the CPC/IRI forecast issued on April 21, 2016. It is important to remember that the first report in each month is based on a survey of meteorologists and the second report later in the month is based on the analysis of the forecast models. It is a minor difference but a difference.
The new forecast shows increased confidence that next winter will be a La Nina winter. In fact the forecast is for El Nino to be over (switching to ENSO Neutral) by the May - Jun - Jul three month period which means Jun. So one does not have much confidence that May will be much impacted by El Nino although El Nino impacts lag the demise of the El Nino.
We have suggested that it is possible the models will be wrong about how fast the Eastern Pacific Warm Pool moves back towards its La Nina location and it may well be that next winter will be more of a Neutral year or even have some characteristics of an El Nino Modoki and thus be wetter than a typical year as the Warm Pool may still be more in the Central Pacific than shifted all the way west to its La Nina position.
We have reason to believe that the models may not be taking into account all factors such as the Equatorial ocean currents and that this El Nino may not transition to a La Nina quite as rapidly as some of the models are predicting.
But, notice the mean of the NOAA model is now forecasting a fairly strong La Nina for next winter but the most recent forecast members (shown in blue) are less La Nina-ish. It is too soon to begin discussing the Spring Prediction Barrier this week but I would take all these forecasts with a grain of salt at this point in time. It is only April 25 and too early to forecast next winter.
Forecasting Beyond Five Years.
So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast. The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS. It includes decade by decade predictions through 2050. Predicting a particular year is far harder.
The odds of a climate shift for CONUS taking place has significantly increased. It may be in progress. It may require one more La Nina. But it appears that "McCabe Condition A" is coming soon. Right now we seem to have a blend of McCabe Conditions A and C which are opposites which may explain some of the forecasting difficult. The AMO is pretty much neutral at this point so it may need to become a bit more negative for the McCabe A pattern to become established.
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.
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.
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