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posted on 20 October 2015

19 October 2015 Weather and Climate Report - New Seasonal Outlook - La Nina Next Winter

Written by Sig Silber

Not many changes in the Seasonal Outlook for the winter months this year but NOAA is now factoring in a transition to La Nina conditions this coming summer and next winter. No real sign of El Nino yet in the 6 - 10 Day Outlook. Above normal temperatures are still in the 6 - 14 Day Outlook for CONUS and Alaska.

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.

NOAA has Issued the new Seasonal Update. My analysis of the changes from the prior seasonal outlook are as follows:

With respect to temperature, the only two significant changes are:

  • Starting in Jun-Jul-Aug 2016, the warm anomaly in the west has been extended a bit to the east to encompass more of the Rocky Mountain States.
  • Sep-Oct-Nov now shows a warm anomaly for the Southeast

With respect to precipitation the significant changes are:

  • A wet anomaly in the Southeast in Apr-May-Jun 2016
  • La Nina impacts beginning in Sep-Oct-Nov 2016 with a dry anomaly in Arizona and New Mexico extending in subsequent time periods further east in the Southern Tier of CONUS and also a wet anomaly in the Northwest starting in Oct-Nov-Dec 2016.

Now let us take a look at the NOAA maps.

Prior Nov-Dec-Jan Temperature Outlook:

NDJ Temperature Outlook Issued Sept 17, 2015

New Nov-Dec-Jan Temperature Outlook:

NDJ Temperature Outlook Issued on Oct 15, 2015

As you can see there is no change.

Prior Nov-Dec-Jan Precipitation Outlook:

NDJ Precipitation Outlook Issued on Sept 17, 2015

New Nov-Dec-Jan Precipitation Outlook:

NDj Precipitation Outlook Issued Oct 15, 2015

As you can see there is essentially no change.

Looking at the Early Outlook for November compared to the three months: Nov-Dec-Jan

N and NDJ Issues on Oct 15, 2015

We could compare the "Early" November Outlook to the prior October Outlook or the OND Outlook but NOAA does not issue a forecast map for the single month two months out so there is not an earlier forecast map for the single month of November. I have chosen to work with the NOAA supplied graphic above.

One can mentally subtract the November Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely December 2015 and January 2016. When I do that I deduce that December and January will be:

  • perhaps colder than climatology in the Southeast and colder than climatology with higher probabilities in Texas, Louisiana and New Mexico and
  • even wetter than shown for Southern California and the lower Mississippi Valley..

Prior 14 month Temperature Outlook

15 Month Temperature Outlook Issued on Sept 17, 2015

New 14 Month Temperature Outlook (one month is dropped and one month is added so between the prior 14 month array and the new 14 month array we actually are looking at 15 months)

15 month Temperature Outlooks Issued on October 15, 2015

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 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. 

Prior 14 Month Precipitation Outlook:

15 month Precipitation Outlook Issued Sept 17, 2015

New 14 Month Precipitation Outlook:

15 Month Precipitation Outlook Issued on October 15

Larger versions of each map are available here .

Excerpts from the NOAA Discussion.

PROGNOSTIC DISCUSSION
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830AM EDT THURSDAY OCT 15, 2015

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

STRONG EL NINO CONDITIONS REMAIN IN PLACE ACROSS THE EQUATORIAL PACIFIC OCEAN AS REPRESENTED BY BOTH OCEAN AND ATMOSPHERIC DATA. THE ONGOING EL NINO EVENT IS EXPECTED TO PEAK IN STRENGTH IN LATE AUTUMN OR EARLY WINTER WITH SEASONAL AVERAGE SEA SURFACE TEMPERATURE (SST) ANOMALIES IN THE NINO 3.4 REGION NEAR OR EXCEEDING +2.0 DEGREES CELSIUS, DIMINISHING IN MAGNITUDE THROUGH THE LATE WINTER AND SPRING.

EQUATORIAL PACIFIC SST ANOMALIES EXCEED +2.0 DEGREES C FROM ABOUT 170 W LONGITUDE TO NEAR THE SOUTH AMERICAN COAST. SUBSURFACE OCEAN TEMPERATURES FROM NEAR THE DATE LINE EASTWARD TO THE SOUTH AMERICAN COAST ARE AT LEAST 2.0 DEGREES C ABOVE AVERAGE TO DEPTHS OF ABOUT 100 TO 150 METERS, EXCEEDING 6.0 DEGREES C ABOVE AVERAGE IN SOME LOCATIONS. THIS SUBSURFACE VOLUME OF ANOMALOUSLY WARM WATER PROVIDES A RESERVOIR OF HEAT TO HELP SUSTAIN CURRENT POSITIVE SEA SURFACE TEMPERATURES. WEST OF THE DATE LINE, NEAR-EQUATORIAL  PACIFIC, SUBSURFACE OCEAN TEMPERATURES ARE BELOW AVERAGE.

THE STRONG EL NINO EVENT IS ALSO WELL REPRESENTED BY THE LATEST ATMOSPHERIC CONDITIONS ACROSS THE TROPICAL PACIFIC. NEGATIVE OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES INDICATING ENHANCED CONVECTION EXTEND FROM THE DATE LINE ACROSS THE EASTERN TROPICAL PACIFIC TOWARDS [Editor's Note: But not reaching.] CENTRAL AMERICA. POSITIVE OLR ANOMALIES  INDICATING SUPPRESSED CONVECTION WERE OBSERVED OVER INDONESIA.  LOW-LEVEL (850-HPA) WESTERLY WIND ANOMALIES WERE OBSERVED FROM THE WESTERN TO THE EAST-CENTRAL TROPICAL PACIFIC WHILE UPPER-LEVEL (200-HPA) EASTERLY WIND ANOMALIES ARE PRESENT OVER THE CENTRAL EQUATORIAL PACIFIC WITH WELL DEFINED ANTI-CYCLONIC CIRCULATIONS BOTH NORTH AND SOUTH OF THE EQUATOR IN THE CENTRAL PACIFIC.

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 WHICH IS CONSIDERED IN THE OUTLOOK.

PROGNOSTIC DISCUSSION OF SST FORECASTS

NEARLY ALL MODELS (BOTH STATISTICAL AND DYNAMICAL) USED FOR THE CURRENT OUTLOOK PREDICT NINO3.4 SST ANOMALY VALUES OF AT LEAST +1.5 DEGREES C THROUGH THE WINTER MONTHS AND INTO SPRING 2016. THE CPC SST CONSOLIDATION FORECASTS A MAXIMUM  IN NINO 3.4 SST ANOMALIES OF ABOUT +2.5 DEGREES C DURING NDJ 2015-16 WITH A GRADUAL DECREASE THEREAFTER FALLING BELOW +1.5 DEGREES C IN FMA 2016 AND

ENTERING ENSO NEUTRAL TERRITORY DURING THE SUMMER 2016 (THROUGH JAS 2016). THE NMME ENSEMBLE MEAN NINO3.4 FORECAST PEAKS AT NEAR +2.5 DEGREES C IN THE NOVEMBER-DECEMBER TIME PERIOD AND DECREASES TO NEAR +0.5 DEGREES C BY MAY 2016. THE CPC/IRI CONSENSUS FORECAST INDICATES APPROXIMATELY A 95 PERCENT CHANCE FOR EL NINO TO CONTINUE THROUGH BOREAL WINTER WITH PEAK 3-MONTH MEAN SST DEPARTURES IN THE NINO3.4 REGION NEAR OR EXCEEDING +2.0 DEGREES C.

AT EXTENDED LEADS, THE CPC SST CONSOLIDATION FORECASTS NINO3.4 SST ANOMALIES TO BECOME LESS THAN -0.5 DEGREES C IN ASO 2016 AND APPROACH -1.2 DEGREES C BY NDJ 2016-2017. [Editor’s Note NOAA is now forecasting a La Nina for next winter].

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

THE SEASONAL OUTLOOKS FROM NDJ 2015 THROUGH MAM 2016 RELY PRIMARILY ON THE TYPICAL CIRCULATION RESPONSE TO EL NINO CONDITIONS AND THE ASSOCIATED TEMPERATURE AND PRECIPITATION IMPACTS AS DETERMINED BY REGRESSION-BASED STATISTICAL MODELS AS WELL AS EL NINO COMPOSITES. THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) AND THE INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME), WHICH INCLUDE THE NCEP CLIMATE FORECAST SYSTEM (CFS), PLAYED A LARGE ROLE AS WELL. OUTLOOKS FOR MJJ 2016 THROUGH ASO 2016 RELY PRIMARILY ON THE CPC CONSOLIDATION FORECAST THAT COMBINES THE SMLR, CCA AND OCN STATISTICAL MODELS WITH THE CFS DYNAMICAL MODEL IN SEASONS FOR WHICH IT IS AVAILABLE. THE EXPECTATION IS FOR ENSO NEUTRAL CONDITIONS DURING THIS PERIOD. BASED ON THE BEHAVIOR OF SST ANOMALIES AFTER SEVERAL PAST STRONG EL NINO EVENTS AND THE CPC  CONSOLIDATION NINO3.4 SST FORECAST, POTENTIAL LA NINA CONDITIONS WERE CONSIDERED BEGINNING IN SON 2016 THROUGH NDJ 2016-2017.

30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2015

THE NOVEMBER TEMPERATURE AND PRECIPITATION OUTLOOK IS BASED ON PATTERNS TYPICALLY ASSOCIATED WITH EL NINO ALONG WITH GUIDANCE FROM THE DYNAMICAL MODELS. THE MJO REMAINS WEAK AT THIS TIME ALTHOUGH RECENT DYNAMICAL MODELS INDICATE AN INCREASE IN THE AMPLITUDE OF THE MJO SIGNAL DURING LATE OCTOBER.  THE MJO IS NOT A FACTOR IN THIS NOVEMBER OUTLOOK BUT MAY NEED TO BE CONSIDERED FOR THE UPDATE ON OCTOBER 31.

INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS MUCH OF THE CONTINENTAL U.S. AND ALASKA WHICH IS CONSISTENT WITH THE ONGOING STRONG EL NINO. RELATIVELY HIGH PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ACROSS THE EASTERN U.S. ARE A COMMON FEATURE AMONG CFS TEMPERATURES FORECASTS DATING BACK A WEEK AGO. HOWEVER, PROBABILITIES ARE REDUCED ACROSS THE EASTERN U.S. DUE TO UNCERTAINTY UPSTREAM ACROSS THE NORTH PACIFIC. THE SLIGHTLY HIGHER PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS THE NORTH SLOPE OF ALASKA ARE BASED ON A VERY ROBUST TREND DURING THE PAST 15 YEARS. A SLIGHT TILT IN THE ODDS TOWARDS BELOW-NORMAL TEMPERATURES FORECAST ACROSS THE UPPER RIO GRANDE VALLEY HAS MINOR SUPPORT FROM THE CFS MODEL AND IS CONSISTENT WITH THE BACKGROUND CLIMATE STATE.

CONSISTENT SIGNALS FROM DYNAMICAL MODEL GUIDANCE AND ENSO-BASED COMPOSITES OF PRECIPITATION SUPPORT ENHANCED ODDS OF ABOVE-MEDIAN PRECIPITATION ACROSS THE SOUTHWEST, SOUTHERN GREAT PLAINS, GULF COAST, AND SOUTHEAST. ABOVE-MEDIAN PRECIPITATION IS FAVORED ACROSS THE ALEUTIANS, SOUTHERN COAST OF ALASKA, AND ALASKA PANHANDLE, WHICH IS CONSISTENT WITH EL NINO. RECURVING TROPICAL CYCLONES ACROSS THE NORTH PACIFIC COULD ALSO ENHANCE PRECIPITATION AMOUNTS ACROSS THESE AREAS DURING EARLY NOVEMBER. A WEAK SIGNAL FOR BELOW-NORMAL PRECIPITATION EXISTS AMONG DYNAMICAL MODEL GUIDANCE ACROSS THE NORTHERN ROCKIES EXTENDING EAST TO THE GREAT LAKES.

Three-Month Outlook

THE NOVEMBER-DECEMBER-JANUARY (NDJ) 2015 TEMPERATURE OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR THE FAR WEST, ACROSS THE NORTHERN CONTIGUOUS U.S. TO THE NORTHEAST, AND SOUTHWARD TO THE MID-ATLANTIC.  WITHIN THE CONTIGUOUS U.S., THE CHANCES OF ABOVE-NORMAL TEMPERATURES ARE GREATEST ALONG THE PACIFIC COAST AND ALONG THE NORTHERN TIER FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES WITH PROBABILITIES EXCEEDING 50 PERCENT. BELOW-NORMAL TEMPERATURES ARE FAVORED FROM NEW MEXICO TO LOUISIANA WHILE ABOVE-NORMAL TEMPERATURES ARE ALSO MOST LIKELY FOR ALASKA.

THE NDJ 2015 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR CENTRAL AND SOUTHERN CALIFORNIA, THE SOUTHWEST, PARTS OF THE CENTRAL AND SOUTHERN PLAINS, THE LOWER MISSISSIPPI VALLEY, THE SOUTHEAST NORTHWARD TO THE MID-ATLANTIC. ABOVE-MEDIAN PRECIPITATION AMOUNTS ARE ALSO MOST LIKELY FOR THE SOUTHERN AND NORTHERN COASTS OF ALASKA.  BELOW-MEDIAN PRECIPITATION AMOUNTS ARE MOST LIKELY FOR PARTS OF THE PACIFIC NORTHWEST, NORTHERN ROCKIES AND GREAT LAKES.

PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2015 TO NDJ 2016

TEMPERATURE

THE TEMPERATURE OUTLOOKS FROM NDJ 2015-16 THROUGH MAM 2016 WERE ONLY SLIGHTLY CHANGED FROM THE PREVIOUS SET OF OUTLOOKS RELEASED IN MID-SEPTEMBER. FOR NDJ 2015-16, THERE ARE ENHANCED ODDS FOR ABOVE NORMAL TEMPERATURES FOR ALASKA, THE FAR WEST AND ALONG THE NORTHERN TIER OF THE CONUS. THE GREATEST PROBABILITIES ARE FOR THE ALASKA PANHANDLE AND IN THE CONTIGUOUS U.S. ALONG THE WEST COAST  AND NORTHERN TIER OF THE CONUS FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES.  BELOW NORMAL TEMPERATURES ARE FAVORED FOR A REGION THAT INCLUDES PARTS OF THE SOUTHWEST AND SOUTHERN PLAINS.

THROUGH THE WINTER AND INTO SPRING 2016, ABOVE NORMAL TEMPERATURES REMAIN FAVORED FOR MUCH OF THE NORTHERN HALF OF THE CONUS WHILE THE COVERAGE FOR ELEVATED ODDS OF BELOW NORMAL TEMPERATURES EXPANDS EASTWARD TO INCLUDE THE SOUTHEAST. FORECAST COVERAGE MAXIMIZES IN JFM AND FMA 2016 WHEN EL NINO IMPACTS TYPICALLY ARE THE GREATEST. THE FORECAST EVOLUTION IS BASED ON TOOLS ASSOCIATED  WITH THE EL NINO TELECONNECTION, DYNAMICAL MODEL GUIDANCE AND ABOVE NORMAL PACIFIC OCEAN SSTS, FOR AREAS ALONG THE WEST COAST. CONSIDERATIONS OF A STRONG EL NINO EVENT RESULT IN A SLIGHT SHIFT SOUTHWARD OF FAVORED ABOVE NORMAL TEMPERATURES FOR SOME AREAS OF THE OHIO VALLEY AND MID-ATLANTIC AND A REDUCTION IN COVERAGE AND PROBABILITIES FOR BELOW NORMAL TEMPERATURES IN PARTS OF THE SOUTHEAST IN DJF 2015-16 AND JFM AND FMA 2016.

THE GREATEST CHALLENGE OF THE FORECAST IS THE EXTENT OF COLD AIR INTRUSIONS INTO THE MID-ATLANTIC AND SOUTHEAST AMIDST A STRONG EL NINO. FORECAST TOOLS DIVERGE IN THESE AREAS DURING THE WINTER MONTHS. THE CFS INDICATES EL NINO IS BY FAR THE DOMINANT PLAYER WITH A WARM FORECAST ACROSS THE MAJORITY OF THE CONUS. ON THE OTHER HAND, SOME STATISTICAL FORECAST TOOLS SUCH AS THE CA, CCA AND SMLR HINT AT A COLDER FORECAST FOR THE SOUTHEAST WHERE PREDICTORS ARE TAPPING INTO CONTINUED WARM NORTH PACIFIC SSTS. STRONG EL NINO CONDITIONS, AND THE ASSOCIATED CIRCULATION, HOWEVER, COULD VERY WELL MODIFY THIS STRUCTURE. THE FORECAST IS A BALANCE BETWEEN ALL OF THESE FACTORS.

A TRANSITION TO ENSO NEUTRAL CONDITIONS IS FAVORED DURING LATE SPRING AND SUMMER 2016 SO THE DRIVER OF THE OUTLOOK FROM MJJ THROUGH ASO 2016 IS THE CPC CONSOLIDATION FORECAST AND FAVORS ENHANCED ODDS OF ABOVE NORMAL TEMPERATURES FOR THE WESTERN CONUS AND PARTS OF ALASKA, THE SOUTHERN CONUS AND NORTHEAST AT VARIOUS TIMES DURING THIS PERIOD.

A COMBINATION OF THE CPC CONSOLIDATION FORECAST AND THE POTENTIAL FOR THE DEVELOPMENT OF LA NINA CONDITIONS ARE THE DRIVER FOR THE OUTLOOKS FROM SON 2015 THROUGH NDJ 2015-16. PROBABILITIES INDICATED ON THE FORECAST MAPS ARE ONLY SLIGHTLY TILTED BASED ON LA NINA ACROSS SOME AREAS OF THE INTERIOR AND SOUTHERN CONUS AT THE CURRENT TIME GIVEN THE FORECAST LEAD. A VERY HIGH PROBABILITY OF ABOVE-NORMAL TEMPERATURES IS INDICATED FOR THE NORTH SLOPE OF ALASKA DURING THE OND SEASON DUE TO ANOMALOUSLY OPEN SEA ICE DURING THAT TIME OF YEAR.  

PRECIPITATION

THE NDJ 2015-16 PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FROM PARTS OF CALIFORNIA ACROSS THE SOUTHERN TIER OF THE CONUS AND UP THE EASTERN SEABOARD TO THE MID-ATLANTIC. BELOW MEDIAN PRECIPITATION IS MOST LIKELY FOR PARTS OF THE PACIFIC NORTHWEST, NORTHERN ROCKIES AND HIGH PLAINS, AND GREAT LAKES. BOTH THE NORTH AND SOUTH COASTS OF ALASKA ARE FAVORED TO SEE ABOVE-MEDIAN PRECIPITATION OVER THE SEASON. ENHANCED CHANCES OF ABOVE-MEDIAN PRECIPITATION FOR THE NORTHERN COAST OF ALASKA ARE RELATED TO THE ANOMALOUSLY OPEN SEA ICE CONDITIONS.

AS WE PROGRESS THROUGH THE WINTER AND INTO THE SPRING OF 2016, THE ABOVE HIGHLIGHTED PATTERNS ARE ADJUSTED SO THAT BOTH COVERAGE AND PROBABILITIES ARE MAXIMIZED IN JFM 2016. PROBABILITIES PEAK AT GREATER THAN 70% FOR FLORIDA AND GREATER THAN 60% FOR SOUTHERN CALIFORNIA AND ARIZONA. FOR BELOW MEDIAN PRECIPITATION, ODDS INCREASE TO GREATER THAN 50% DURING THIS SEASON IN TWO AREAS, THE NORTHERN ROCKIES AND GREAT LAKES. THE EL NINO TELECONNECTION BASED ON COMPOSITES AND OTHER ASSOCIATED FORECAST TOOLS ALONG WITH THE NMME AND ITS COMPONENTS ARE THE PRIMARY DRIVER OF THE OUTLOOK THROUGH MAM 2016.

CONSISTENT WITH A SOUTHWARD AND EASTWARD SHIFTED STORM TRACK DURING EL NINO AND NMME DYNAMICAL MODEL GUIDANCE, BELOW MEDIAN PRECIPITATION IS HIGHLIGHTED FOR CENTRAL MAINLAND ALASKA FROM DJF 2015-16 THROUGH MAM 2016. DECADAL TRENDS AS DEPICTED IN SOME OF THE STATISTICAL FORECAST TOOLS IS THE DRIVER FOR THE SMALL HIGHLIGHTED AREAS FROM MJJ THROUGH JAS 2016.

 AT THE EXTENDED LEADS, THE POTENTIAL FOR LA NINA CONDITIONS ARE THE PRIMARY BASIS FOR THE VERY SLIGHT TILT IN THE ODDS FOR BELOW MEDIAN PRECIPITATION FOR SOME AREAS ALONG THE SOUTHERN TIER OF THE CONUS AND LATER THE SOUTH COAST OF ALASKA AND FOR ABOVE MEDIAN PRECIPITATION FOR THE PACIFIC NORTHWEST FROM SON 2016 THROUGH NDJ 2016-17.

Not Let us Focus on the Current (Right Now to 5 Days Out) Weather Situation.

A more complete version of this report with daily forecasts is available in Part II. This is a summary of that more extensive report. This link Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks will take you directly to that set of information but in some Internet Browsers it may just take you to the top of Page II where there is a TABLE OF CONTENTS and you may have to wait for a few seconds for your Browser to redirect to the selected section with that Page or if that process is very slow you can simply click a second time within the TABLE OF CONTENTS to get to that specific part of the webpage.

First, here is a national animation of weather front and precipitation forecasts with four 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.

current highs and lows

The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic; because they are 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 indicates normal (progressive) for this time of the year west to east movement of air masses for the most part. There is a ridge across the west especially further north and a slight trough over the Great Lakes and again mostly north.

7 Day 500 MB Geopotential Forecast

Because "Thickness Lines" are shown by those green lines on this graphic it is a good place to define "Thickness" and its uses. You can find a full uk.sci.weather style explanation (thorough) at that link or just remember that Thickness measures the virtual temperature 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 thickness lines do not yet indicate winter conditions which might be thickness levels below 540 for most areas. The above uk.sci.weather link is is an explanation for the U.K. The levels for CONUS might be slightly different. Obviously these thickness lines do not tell you about mountain peaks. The particular definition of "thickness" on this graphic may not be the best way to define the snow line and this is discussed in the link provided but it is I believe the older method and gives a first approximation which can be further refined as per the discussion in the link.

The following table is useful but designed for Europe. I was not able to find the corresponding information for the U.S. but it would not be drastically different. In the U.S., the last zero is dropped off the Thickness Level so where it says 5640 that would show as 564 in the U.S. Also remember the temperatures shown are in Centigrade. So 580 would correspond to about 80F in full sunshine during the summer. That is why I say the 582 and 576 thickness levels are a bit unusual for late October and early November.

Thickness Table

More information on this table is available here.

The level of storm activity in the Western Pacific is quite active right now. 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. The immediate concern is Typhoon Champi which has grazed Japan and now may affect the prevailing westerlies as they reach CONUS.  

Western Pacific Tropical Activity

Looking at the graphic below, the cyclones generated by the warm ocean water west of Central America can provide Monsoon-like impacts for short periods if those cyclones stay close enough to the Mexican coastline. So that is what is being watched now and there seems to be an endless sequence of the storms forming. 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 was the case this summer and continues in early Fall but it is sporadic. For Mexico, an El Nino is a drought event. There is now yet another storm moving up the West Coast of Mexico. It looks like this storm will play out in Mexico and have very little impact on CONUS. It is a dynamic situation with a strong El Nino. 

.Eastern Pacific Tropical Storms

The graphic below is harder to look at but provides more detail on the water vapor being generated by these storms and the normal summer action of the Southwest Monsoon. It covers a much larger area within CONUS so you can see where the moisture currently is and is going. This graphic is very good at pointing out the divisions between cloudy and not cloudy areas.

As I am looking at this graphic Monday evening, I see mostly a a dry area from Texas east and north to the East Coast up to Delaware. But I also see storms originating in or off of California moving to the East. There is also a lot of water vapor in the Northern Rockies but I can not tell from just looking at this graphic what that is all about. The graphic updates automatically so it most likely will look different by the time you look at it.

 Water Vapor Imagery

Below is an analysis of projected tropical hazards and benefits over an approximately two-week period. There are two views. One is more focused on the Pacific and one that includes the Indian Ocean and covers Asia more completely. Both graphics auto-update weekly but each updates on a different day of the week so when you look at them both carefully you might see some differences due to the exact day when they were updated. More information can be found here. The discussion at that link updates on Fridays.

Looking at the first graphic (and as I am looking at it, it is the most recently updated) what stands out to me, at the time of publication, is the continued presence of precipitable water in place in the Southeast of CONUS and conditions favorable for the development of cyclones off the west coast of Central America. Notice in the second week of that forecast (which is the forecast for the current week as I write) the wet area in the Gulf of Mexico is less certain but closer to the coastline of Texas and Louisiana. The 6 - 14 Day Outlook does not indicate that this system will impact CONUS. But that may be because it happens prior to what is now Day 6. When I look at the current vapor imagery however it appears that this moist air is remaining offshore of CONUS. When looking at a lot of graphics, the dates for which the graphic applies and the dates when issued become very important in making sense out of the information. It is easy to draw incorrect conclusions by not considering or getting confused by the different timeframes.

Tropical Hazards

This graphic below covers a larger part of the world. With this graphic, at the time of publication, you see more activity over by Asia including dry conditions in Indonesia and the Philippines. There is also the potential for tropical storm activity east and north of Indonesia. That part of the Word appears to be bearing the brunt of this El Nino so far. At the time of publication, the above graphic was more current for North and South America but the below graphic might be updated by the time you read this report. It gets confusing and I realize that, but the two graphics update on different days. I think the bottom graphic updates on Tuesdays and the top graphic on Fridays.

Tropical Hazards

Below is a view which highlights the surface Highs and the Lows re air pressure on Day 6 (Day 3 can be seen in Part II of this Report). In recent weeks the projected location and strength of the Aleutian Low has varied a bit. On some days, the forecast is showing a split low with each of the two lows weaker than a combined single Low and this is not characteristic of El Nino. But right now, even though the low is split, the eastern branch of the Aleutian Low is projected to be fairly robust and shifted to the southeast and that is favorable for CONUS precipitation. A longer discussion of the climate of Beringia is in Part II of this Report 2. Medium Frequency Cycles such as ENSO and IOD. The RRR is currently not very prominent which is consistent with a true El Nino and is good news for California.

Day 6 Weather Forecast

We now need to monitor the Jet Stream to see if it is shifting to the South. This is the forecast out five days.

Jet Stream Five Days Out

We now see some slight evidence of a southern branch component. To see how the pattern is projected to evolve, please click here. The activity still appears to be mostly north rather than south but quite meridional which allows troughs to bring precipitation down to lower latitudes. We have not yet seen the pattern changing to a consistent presence of a southern branch of the Jet Stream which we would expect with El Nino. 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. You can see the progressive west to east nature of the pattern at the altitude of the Jet Stream. There is minimal meridional movement of air at that altitude which limits both cold intrusions and warm intrusions into CONUS. It is mostly what we get from the Pacific with not much opportunity for those air masses to be modified by the detours they take.

And when we look at Sea Surface anomalies we see a lot of them not just along the Equator related to El Nino. But the extent of the warm water off the West Coast appears to be a bit less than recently. The Atlantic has really heated up. You can tell a lot from this graphic. The warm anomalies are not evenly distributed around the world. There is more in the Northern Hemisphere possibly related to there being more land in the Northern Hemisphere. So there may be a connection to the ratio of land to water and the heating of the water surface. The warm water off of California is a wild card in the impacts of this El Nino.

Daily SST Anomaly

The two graphics below show first the changes over the four weeks (ending September 16) as compared to the above graphic which shows the current SST anomalies and then the changes over the four weeks ending on October 14. Looking at both of these change in anomaly graphics is helpful in putting the current situation shown above into perspective.

First the four weeks ending on September 16.

Sept 21, 2015 four week change in SST Anomalies

Now the four weeks ending on October 14.

 October 19, 2015 four week change in SST Departures

In both graphics you can see the increasing change of the warm anomaly in the Nino Area but lately all of a sudden we see some decrease in the anomaly along the Equator in the Eastern Pacific and to the south the waters off of South America cooling while further north the warm anomaly continues to become more extreme. I think you can see the IOD off of Australia. You can see the colder water surrounding Indonesia and you can see the waters off of the U.K. becoming warmer or at least less cold. Remember these are four-week averages and graphic above the two four-week average of the changes in the anomalies is the daily readings of the anomalies which auto-updates. You can get a better feel there for the current impacts. It is difficult to relate the actuals to the four-week changes but it paints a picture. Remember the observed values in the first graphic are expressed as anomalies which is the change from climatology (normal) so we are talking in these two bottom two graphics about the change in the change. It is kind of like the first derivative of the "anomalies" which to confuse things NOAA interchanges the word "anomaly" and "departures" which are the same thing.

6 - 14 Day Outlooks

Now let us focus on the 6 - 14 Day Forecast for which I generally only show the 8 - 14 Day Maps. The 6 - 10 Day maps are available in Part II of this report.

To put the forecasts which NOAA tends to call Outlooks into perspective, I am going to show the three-month OND and single month of October forecasts and then discuss the 8 - 14 day Maps and the 6 - 14 Day NOAA Discussion within that framework. 

First Temperature

Here is the Three-Month Temperature Outlook issued on October 15,  2015:

NDJ Temperature Outlook Issued on Oct 15, 2015

And here is the "Early" Temperature Outlook issued on October 15, 2015

November 2015

Below is the current 8 - 14 Day Temperature Outlook Map which will auto-update and thus be current when you view it. It covers the week following the current week. Today's 6 - 14 Day Outlook is just nine days 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 October 19 (it updates each day) it appears that the end of October and the start of November will be even more widely warmer than climatology and the recently issued "Early Outlook" for November. Of course we are only talking about a couple of days in November as I look at these maps. When they update tomorrow it might look very different. 

8-14 Day Temperature Outlook

Now Precipitation 

Here is the three-month Precipitation Outlook issued on October 15, 2015:

NDj Precipitation Outlook Issued Oct 15, 2015

And here is the "Early" November Precipitation Outlook Update Issued on October 15, 2015.

November Early Precipitation Outlook Issued Oct 15, 2015

Below is the current 8 - 14 Day Precipitation Outlook Map which will auto-update and thus be current when you view it. It covers the week following the current week. Today's 6 - 14 Day Outlook is just nine days of the month and the map shown covers seven days of the nine. The 6 - 10 Day Map (the two maps overlap) is available on Page II of this report. As I view this map on October 19 (it updates each day) it appears that end of October and the start of November will be quite different than the "Early Outlook" for November except for the Southeast. Again this map as I look at it on Monday only covers two days in November. It may look somewhat or very different when it is issued tomorrow.

Current 8 - 14 Day Precipitation Outlook

Here are excerpts from the NOAA discussion released today October 19, 2015. It covers the full nine day period not just the seven days shown in the 8-14 Day Map.

6-10 DAY OUTLOOK FOR OCT 25 - 29 2015

TODAY'S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT  ON THE 500-HPA MEAN CIRCULATION PATTERN FORECAST OVER MOST OF THE NORTH AMERICA DOMAIN FOR THE 6-10 DAY PERIOD. TROUGHS ARE PREDICTED OVER THE BERING SEA,  EASTERN CANADA, AND NEAR THE WEST COAST, WHILE ANOMALOUS RIDGING IS EXPECTED OVER ALASKA. GENERALLY LOW AMPLITUDE OR ZONAL FLOW IS FORECAST OVER THE CONUS. TODAY'S MANUAL BLEND CHART INDICATES WEAK ABOVE-NORMAL HEIGHTS OVER MOST OF THE CONTINENT. TODAY'S MANUAL 500-HPA HEIGHT BLEND IS COMPOSED PRIMARILY OF THE ENSEMBLE MEAN SOLUTIONS AND 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. THE ENSEMBLE SPAGHETTI DIAGRAMS INDICATE LOW TO MODERATE SPREAD ACROSS THE MAJORITY OF THE FORECAST DOMAIN.

GEFS REFORECAST GUIDANCE AND BIAS CORRECTED TEMPERATURES FROM THE ECMWF FAVOR  NEAR TO ABOVE NORMAL TEMPERATURES FOR THE UPPER MISSISSIPPI VALLEY, MOST OF THE WEST, AND THE SOUTHEASTERN CONUS. BELOW NORMAL TEMPERATURES ARE EXPECTED OVER MUCH OF THE NORTHEAST CONUS NEAR A TROUGH FORECAST OVER EASTERN CANADA. ABOVE NORMAL TEMPERATURES ARE LIKELY OVER ALASKA DUE TO PREDICTED RIDGING AND ABOVE NORMAL HEIGHTS. 

TROUGHING ALONG THE WEST COAST AND SOUTHWESTERLY ANOMALOUS FLOW ENHANCE CHANCES  OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST, THE NORTHERN GREAT BASIN AND NORTHERN CALIFORNIA. THERE ARE ENHANCED PROBABILITIES OF BELOW MEDIAN PRECIPITATION FOR MUCH OF THE CENTRAL CONUS AND ALSO IN MAINE, CONSISTENT WITH GEFS REFORECAST GUIDANCE. PRECIPITATION ESTIMATES FROM THE GFS AND ECMWF ENSEMBLES FAVOR ABOVE MEDIAN PRECIPITATION FOR MOST OF THE EASTERN CONUS, THE ALEUTIANS AND THE ALASKAN PANHANDLE. CONVERSELY, BELOW MEDIAN PRECIPITATION IS FAVORED FOR REMAINDER OF ALASKA UNDERNEATH PREDICTED POSITIVE HEIGHT ANOMALIES.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE TEMPERATURE TOOLS OFFSET BY ZONAL FLOW OVER THE CONUS. [Editor's Note: It is hard to see how zonal flow would reduce the level of confidence other than questions about the speed of the flow and this is not specifically mentioned other than it will be low amplitude which should make forecasting easier.]

8-14 DAY OUTLOOK FOR OCT 27 - NOV 02, 2015 

TODAY'S ENSEMBLE MEAN AND DETERMINISTIC SOLUTIONS ARE IN GOOD AGREEMENT ON THE 500-HPA MEAN CIRCULATION PATTERN FORECAST OVER MOST OF NORTH AMERICA FOR THE WEEK-2 PERIOD. THE PREDICTED CIRCULATION PATTERN IS SIMILAR TO THAT EXPECTED FOR THE 6-10 DAY PERIOD. TROUGHS ARE PREDICTED NEAR THE WEST COAST OF THE CONTINENT, WITH ZONAL FLOW OVER MOST OF THE CONUS. 

 GEFS REFORECAST GUIDANCE AND BIAS CORRECTED TEMPERATURES FROM TODAY'S GFS, ECMWF FAVOR ABOVE NORMAL TEMPERATURES FOR ALMOST THE ENTIRE CONUS SUGGESTING  THAT AIR OF PACIFIC ORIGIN MAY DOMINATE MUCH OF THE COUNTRY DURING THIS TIME PERIOD. MOST TOOLS ALSO FAVOR ABOVE NORMAL TEMPERATURES FOR MOST OF ALASKA.

THERE ARE ENHANCED CHANCES OF ABOVE-MEDIAN PRECIPITATION FOR MOST OF THE EASTERN, WESTERN, NORTHERN CONUS, AND THE ALEUTIANS, CONSISTENT WITH PRECIPITATION ESTIMATES FROM THE GEFS AND ECMWF ENSEMBLE MEMBERS. MOST TOOLS ALSO SUPPORT BELOW-MEDIAN PRECIPITATION FOR CENTRAL AND NORTHERN ALASKA, MAINE, PARTS OF THE CENTRAL AND SOUTHERN PLAINS.  

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 OUT OF 5, DUE TO GOOD AGREEMENT AMONG THE TEMPERATURE TOOLS OFFSET BY ZONAL FLOW OVER THE CONUS. [Editor's note: Same comment about zonal flow and I note no mention of El Nino.]

Analogs to Current Conditions

Now let us take a detailed look at the "Analogs" which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. "Analog" means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 - 14 day Outlook.

Here are today's analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the outlook but I have not been analyzing this second set of information. This first set applies to the 5 and 7 day observed pattern prior to today. The second set which I am not using relates to the forecast outlook 6 - 10 days out to similar patterns that have occurred in the past during the dates covered by the 6 - 10 Day Outlook. That may also be useful information but they put this set of analogs in the discussion with the other set available by a link so I am assuming that this set of analogs is the most meaningful.

Analog

Centered

Day

ENSO

Phase

PDO AMO

Other Comments

1962 Oct 27 Neutral - +  
1965 Oct 26 El Nino - - Possibly a Modoki
1974 Oct 18 La Nina - -  
1974 Oct 19 La Nina - -  
1974 Oct 23 La Nina - -  
1978 Oct 14 Neutral - -  
1979 Oct 17 El Nino - - Modoki Type II
1980 Oct 29 Neutral + -  
1980 Oct 31 Neutral + -  

 

One thing that jumped out at me right away was the tight spread among the analogs from Oct 14 to Oct 31 just over two weeks which is unusually tight. Also they are late October anomalies with mid-October temperatures forecast in the 6 - 14 Day Outlook. Not sure how that works. There are two El Nino Analogs and three La Nina Analogs and three ENSO Neutral Analogs so that does not suggest that El Nino is much of a factor over the next 6 - 14 Days other than the tropical storms that come up along the Mexico West Coast. The phases of the ocean cycles are very consistent with McCabe Condition B which is a wet pattern and somewhat consistent with the 6 - 14 Day Outlook. Both the Atlantic and the Pacific are influencing our weather about equally. The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. My take away from this and other information presented in this report is that the PDO has not changed phase and the current PDO plus is related to the current El Nino and the prior near El Nino. It most likely will return to PDO - or PDO neutral next winter and seems to be doing that gradually now. 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.

 McCabe Maps modified to include the subtitles

You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.

Historical Anomaly Analysis

When I see the same dates showing up often I find it interesting to consult this list.

With respect to relating analog dates to ENSO Events, the following table might be useful. In most cases this table will allow the reader to draw appropriate conclusions from NOAA supplied analogs. If the analogs are not associated with an El Nino or La Nina they probably are not significant. Remember, an analog is indicating a similarity to a weather pattern in the past. So if the analogs are not associated with a prior El Nino or prior La Nina the computer models are not likely to generate a forecast that is consistent with an El Nino or a La Nina.

  El Ninos La Ninas
  Start Finish Max ONI PDO AMO Start Finish Max ONI PDO AMO
            DJF 1950 J FM 1951 -1.4 - N
T   JJA 1951  DJF 1952 0.9 - +          
   DJF 1953  DJF 1954 0.8 - + AMJ 1954  AMJ 1956 -1.6 - +
M MAM 1957   JJA 1958 1.7 + +          
M SON 1958  JFM 1959 0.6 + -          
M   JJA 1963  JFM 1964 1.2 - - AMJ 1964  DJF 1965 -0.8 - -
M  MJJ 1965 MAM 1966 1.8 - - NDJ 1967 MAM 1968 -0.8 - -
M OND 1968   MJJ 1969 1.0 - -          
T  JAS 1969   DJF 1970 0.8 N -  JJA 1970  DJF 1972 -1.3 - -
T AMJ 1972  FMA 1973 2.0 - - MJJ 1973 JJA 1974 -1.9 - -
            SON 1974 FMA 1976 -1.6 - -
T ASO 1976  JFM 1977 0.8 + -          
M ASO 1977  DJF 1978 0.8 N -          
M SON 1979  JFM 1980 0.6 + -          
T MAM 1982  MJJ 1983 2.1 + - SON 1984 MJJ 1985 -1.1 + -
M ASO 1986  JFM 1988 1.6 + - AMJ 1988 AMJ 1989 -1.8 - -
M MJJ 1991    JJA 1992 1.6 + -          
M SON 1994   FMA 1995 1.0 - - JAS 1995 FMA 1996 -1.0 + +
T AMJ 1997   AMJ 1998 2.3 + + JJA 1998 FMA 2001 -1.6 - +
M MJJ 2002   JFM 2003 1.3 + N          
M  JJA 2004 MAM 2005 0.7 + +          
M ASO 2006   DJF 2007 1.0 - - JAS 2007  MJJ 2008 -1.4 - +
M JJA 2009 MAM 2010 1.3 - + JJA 2010 MAM 2011 -1.4 + +
            JAS 2011 FMA 2012 -0.9 - +
T MAM 2015 NA 1.0 + N          

 

Progress of the Warm Event

Let us start with the SOI.

Below is the Southern Oscillation Index (SOI) reported by Queensland, Australia. The first column is the tentative daily reading, the second is the 30 day moving/running average and the third is the 90 day moving/running average.

Date Current Reading 30-Day Average 90 Day Average
 13 Oct -28.7 -22.05 -18.96
 14 Oct -42.2 -22.41 -19.08
 15 Oct -31.5 -22.65 -18.22
 16 Oct -12.6 -22.64 -19.22
 17 Oct  -3.8 -22.61 -19.22
 18 Oct  -1.2 -22.49 -19.11
 19 Oct  -9.8 -22.48 -19.25

 

The 30-day average, which is the most widely used measure, on October 19 was reported as being -22.48 which is a very high (negative) level and is clearly a reading associated with an El Nino and insignificantly stronger (lower) than last week due to very strong readings early in the week. The 90-day average also is solidly in El Nino territory at -19.25 which is also insignificantly lower (stronger) than last week. The SOI is clearly indicative of an El Nino Event in progress. In fact it is so strong that it may be having impacts that are unusual. The SOI appears to have plateued. This can be important as some studies show that the change in the level of SOI is at least as important as the actual level in terms of predicting precipitation.

Low-Level Wind Anomalies

Here are the low-level wind anomalies. The area from 180W to 160W is now of interest but appears to be playing out. Will it initiate yet another Kelvin Wave? NOAA says it has. But I do not see that in the data or if it is there, this new Kelvin Wave is quite weak.

Low Level Wlind Anomalies

In the below 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 120W 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. For sure the SOI is behaving like it would be expected to behave in a strong El Nino. The Easterlies in the Pacific along the Equator are suppressed. So if this is all that is meant, that part has fallen into place. But the Walker Circulation may not be consistent with a standard El Nino. That is my point. 

The interconnection with the Indian Ocean seems to be unusual to say the least. The convection in the Pacific along the Equator 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 soon. But it may not be in the direction of more convection further east. The October 15 Update, which is what I am looking at on Monday October 19, suggests that the area of anomalies in convection is strongest over by the Date Line and has not expanded to the east as one might have expected and may even have retreated to the west a bit. This is not your standard El Nino. But the dryness has expanded to the west. Both anomalies have increased in intensity.

OLR Anomalies Along the Equator

Let us now take a look at the progress of the Kevin wave which is the key to the situation. Since February there have been three successive downwelling Kelvin Waves without really an upwelling Kelvin Wave of any consequence to counter their impact. The first wave which started in February was the most effective at getting this El Nino started. The second wave reinforced to some extent but not much and this third (and I had believed would be the last) downwelling Kelvin Wave has created an El Nino that will have a major peak coming soon and an extended life but at a diminished strength. There is a hint of something new at 175W to 160W. This could be another Kelvin Wave but I think it is simply the warm water rising in that area. NOAA has indicated that they think this is yet another Kelvin Wave. I believe that NOAA is incorrect on this or, if correct, this will be a very weak Kelvin Wave of little consequence. I think we are seeing the surface temperature anomaly marginally declining from both west to east and east to west. More on that later.

Kelvin Waves Auto-updates

We are now going to change the way we look at a three dimensional view of the Equator and move from the surface view to the view from the surface down. When I examine the current situation as compared to the 1997/1998 El Nino which I described graphically recently, the current El Nino has developed more rapidly. This El Nino is a couple of months further along in its evolution than the 1997/1998 El Nino and will end earlier in the winter than the 1997/1998 El Nino. Also the 1997/1998 had a slightly larger amount of warm subsurface water in the Eastern Pacific and that water takes time to surface, create convection, and thus cool. Something happens to allow the Easterlies to resume their strength and that in turn moves this water back towards the Western Pacific Warm Pool. This El Nino appears to be fading from west to east. 

Current Sub-Surface Conditions

Subsurface Heat Anomalies

Top Graphic (Anomalies)

The above graphic showing the current situation has an upper and lower graphic.  The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters.

The top graphic is still the most useful of the two and shows where 2C (anomaly) water is impacting the area in which the ONI is measured i.e. 170W to 120W. The 2C anomaly now extends to 170W which is very impressive. The 3C anomaly is over beyond 150W which again is very impressive and which now encompasses 60% of the Nino 3.4 Measurement Area for the ONI. The 4C anomaly is no longer close to intersecting the surface. It is not clear exactly how the measurements here relate to the TAO/TRITON graphic which is not showing such warm anomalies.

It is important to differentiate between anomalies and actual temperature. The warm anomaly shown in the upper graphic is not covered by colder water as it might appear to be in the upper graphic but is shown as a warm anomaly because normally water at those depths is colder than it currently is. That is why this warm anomaly does not simply rise to the surface as warm water would normally do but it is preventing cooler water from entering the area as one would expect as summer transitions to Fall. That is why it takes time for this warm anomaly to dissipate.  

Bottom Graphic (Absolute Values which highlights the Thermocline)

The bottom half of the graphic may soon become more useful in terms of tracking the progress of this Warm Event as it converts to ENSO Neutral and then La Nina. It shows the thermocline between warm and cool water which pretty much looks like this as shown here during a Warm Event. You can see that the cooler water is not yet fully making it to the surface to the east along the coast of Ecuador. We now will pay more attention to the 28C Isotherm as west of that temperature is where convection is more easy to occur. Right now that Isotherm intersects the surface near 130W which has been the case for some time but it appears to have moved a bit to the west. It should soon start to move back to the east.

TAO/TRITON GRAPHIC

Taking a close look at the TAO/TRITON graphic but first let us compare the situation two weeks ago which is shown below to the most recent graphic shown below it. 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.

Oct 4, 2015 TAO/TRITON

With the current situation. There is quite a bit of difference. Last week my assessment of the TAO/TRITON graphic available on Monday (not shown) was that:

the warm water is further east and intensified. The Easterlies are further suppressed which may explain the shift in the anomalies. We now see a large area of 3C+ anomaly.

This Monday when I look at the TAO/TRITON Graphic shown below it looks somewhat similar to the copy I "froze" two weeks ago and which is shown above. However

the wind anomalies in the Eastern Pacific are now slightly stronger Easterlies.  We will monitor this very carefully.

The look of this graphic varies from day to day. I do not know if this is true change or simply the variability in measurements of sea surface and wind anomalies. Since I have no way of assessing that variability I am forced to just comment on what shows up on my computer screen.

So far there are few if any impacts on CONUS of this intense El Nino other than those related to the Pacific Cyclones. So this raises real questions about how we measure an El Nino and how we do regression analysis on historical El Ninos to predict weather.

I calculate the ONI each week using a method that I have devised. To refine my calculation, I have divided the 170W to 120W ONI measuring area into five subregions (that I have designated A through E (from west to east) with a location bar shown under the TAO/TRITON Graphic) and have mentally integrated what I see below and recorded that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.

 Current SST and wind anomalies

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

 

 

So as of Monday October 19 in the afternoon working from the October 18 TAO/TRITON report, this is what I calculated.

Calculation of ONI from TAO/TRITON Graphic
Anomaly Segment Estimated Anomaly
A. 170W to 160W 1.7
B. 160W to 150W 2.2
C. 150W to 140W 2.3
D. 140W to 130W 2.4
E. 130W to 120W 2.6
Total 11.2
Total divided by five subregions i.e. the ONI (11.2)/5 = 2.2

 

My estimate of the Nino 3.4 ONI after rounding has decreased to 2.2 with less of a gradient from west to east. NOAA has today again reported the weekly ONI as being 2.4 and that is certainly a very high level for an ONI even though it is a weekly value not a three-month average. The base used to calculate the anomalies changes with the calendar and I do not have those numbers so it is a little hard for me to tell if the surface is actually warming or if what is happening is that the surface temperature is remaining constant and the base declines as winter approaches so a constant surface temperature records as an increased anomaly. In theory I could compare the graphics from week to week and perhaps figure that out. This warm water or at least warmer than normal for this time of year 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 troughs off of Baja California which then enter CONUS. It gets complicated because it seems that north of the Equator the water is definitely warmer and that is where tropical storms form. 

Nino 4.0 is now reported as being 1.1 a slight increase. The action which I think is most important to track right now is in Nino 1+2 which is now reported as being down to 2.5 which is high but lower than last week. One issue remains the extent to which warm water off of Ecuador and Peru impacts CONUS weather. I think it has very little impact and that is what we are seeing right now. The other issue is that most El Ninos decay from east to west so it will be observed most clearly first in Nino 1+2 and we are now possibly seeing that process starting.

This is summarized in the following NOAA Tables and I am showing both the table for two weeks ago and the updated table. 

Oct 5, 2015 NINO Departures

And here are the values this week.

Oct 19, 2015 NINO SST Departures.

One can see the slight decline in the Nino 1+2 measurement area. I think it is quite possible that this El Nino has now peaked and has begun its decline!

One wonders about these calculations as they appear to not be related to the "adjusted" version of the NOAA forecast model which was discussed recently. So it is not clear to me how this El Nino will be officially recorded. July-August-September has been recorded as having an ONI of 1.5. In the above graphic eyeballing it you might conclude that the three months were observed as being 1.6, 2.0 and 2.3. So the impact of adjusting these observed values to what is considered "adjusted" is not obvious to me. 

Although I discussed the Kelvin Waves earlier, now seems to be the best place to show the evolution of the subsurface temperatures.

Oct 19, 2015 History of Kevin Waves.

The conditions down to 150 meters have not changed in a long time. But now we see the 6C anomaly getting significantly reduced in size (volume). Also to the west, the evidence of a new Kelvin Wave is scant at best. But the graphics available are always some number of days out of date so it is hard to be definitive about that but it does not seem to show up in the TAO/TRITON Graphic which is more current information so that is why I am quite skeptical about the significance of any Kelvin Wave at this point. Also I am not sure there is sufficient Warm Pool water in that area to move east.

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. As you can see the warm water rising off the South American Coast had (or at least the value of the anomaly when calculated) worked its way all the way over to beyond 170W so it fully contributes to the increasing ONI but the western edge of the warm anomaly is showing some signs of stalling and drifting to the east. So far the various graphics many of which are looking at the same information from a different perspective are not indicating to me that there is a new Kelvin Wave although NOAA has suggested that we may indeed have a new Kelvin Wave. But I think they may not be correct although they have shown it in their ENSO Report today. If there is another significant Kelvin Wave, it could get very interesting. We have certainly had the strong wind gusts necessary to initiate a Kelvin Wave in the area where NOAA is showing it but I think the Pacific Warm Pool will not support a major event of that type right now.

SST Anomalies Hovmoeller

I have added a second version of this graphic with some lines to show the trend of the complicated evolution of the El Nino. I did not do a perfect job with the scaling but I think you can follow it. One can clearly see how the warm water on the western edge has migrated to the east. That to some extent might be viewed as the transition of the former Modoki into a true El Nino. Similarly one sees the westward expansion of the warm anomaly. It is quite dramatic which is why this is a very strong El Nino. It seems to have stalled and I see only minimal evidence of the new Kelvin Wave that NOAA has declared. The eastern end of this pattern is very complex. We see when it formed and we see a period where it weakened but then was strengthened by a subsequent Kelvin Wave. There may be a tendency to again weaken but it is not yet clear.  There is a clear gap between the anomaly right along the coast and a bit further out to sea. I do not know enough to explain that but I suspect it has to do with the pattern of local currents.

Octtober 19, 2015 SST Hovmoeller with trend lines

The version where I have added the lines will not auto-update. The version above it will but the change on a day by day basis is hardly discernable.

El Nino in the News

Nothing 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 four months ago (Ending Date June 13)

June 15, 2015 30 Day Temperature and Precipitation Departures.

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

July 13, 2015 30 Day Temperature and Preciptiation Departures

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

August 10 2015 30 Day Temperature and Precipitation Departures

And again four weeks later (Ending Date October 3, 2015)

Oct 3, 2015 30 day Temperature and Precipitation Departures

And again two weeks later (Ending Date October 17, 2015)

Oct 19, 2015 30 day temperature and precipitation departures

This provides more than a four-month sequence of snapshots of the four-week departures from normal as this El Nino has progressed.

You can see these five graphics as well as I can and it is difficult to describe the changes that have taken place over five periods of time because of the large number of changes. Currently we see:

  • A general pattern of fairly extreme warm anomalies in most of CONUS especially the West.
  • More dry areas than wet areas in CONUS with much of the dry areas contiguous and in the Northwest and the Great Plains. The east coast is wetter than climatology and we know about the flooding in South Carolina, North Carolina and Virginia (which might be partially attributable to El Nino). We are starting to see some El Nino impacts in the Southwest. The pattern in Mexico has become less dry.

Putting it all Together.

We are in El Nino conditions now. The El Nino I believe has peaked in intensity and has begun its decline. The actual 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 although that is starting to change. The El Nino is probably influencing the IOD to tend towards being positive thus providing a double whammy for parts of Asia and Australia. Indonesia and the Philippines have been hit by drought. 

The length and intensity of this El Nino is still not clear mostly in terms of whether or not it will extend into the early part of 2016. There does not seem to be an obvious match to any prior El Nino in the modern era which to me means there is no model to use to predict impacts. That is a complicated subject which is probably best dealt with on a post mortem basis. 

We may or may not have a Pacific Climate Shift as the PDO+ may be simply related to the Warm Event and quite frankly at this point appears to be and may be moving back to PDO Negative. But for now we do have PDO+. The AMO being an overturning may be more predictable so the Neutral status moving towards AMO- is probably fairly reliable but not necessarily proceeding in a straight line as indeed the storm track for hurricanes in the Atlantic is suddenly unusually warm. 

So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast. The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.  It includes decade by decade predictions through 2050. Predicting a particular year is far harder.

We are beginning to speculate on the winter of 2016/2017 which it now seems increasingly likely will be a La Nina. One thing that is fairly certain for the U.S.is that compared to this winter the following winter is projected to be:

  • warmer in the south and less warm in the north and
  • more dry in the south and less dry in the north

The below is the CPC/IRI forecast and you can see the rapid shift away from El Nino that is now predicted starting in AMJ and really showing up in MJJ 2016 i.e. late Spring early Summer 2016. .

Oct 19, 2015 CPC-IRI ENSO Probabilities.

TABLE OF CONTENTS FOR PART II OF THIS REPORT  The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you. 

A. Worldwide Weather: Current and Three-Month Outlooks: 15 Month Outlooks  (Usefully bookmarked as it provides automatically updated current weather conditions and forecasts at all times. It does not replace local forecasts but does provide U.S. national and regional forecasts and, with less detail, international forecasts)

B. Factors Impacting the Outlook

1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)

2. Medium Frequency Cycles such as ENSO and IOD

3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.

C. Computer Models and Methodologies

D. Reserved for a Future Topic  (Possibly Predictable Economic Impacts)

TABLE OF CONTENTS FOR PART III OF THIS REPORT - GLOBAL WARMING WHICH SOME CALL CLIMATE CHANGE. The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

D1. Introduction

D2. Climate Impacts of Global Warming

D3. Economic Impacts of Global Warming

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

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

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