by Sig Silber
The Seasonal Outlooks were released on December 18. They are not very different from the November 20 release. However the complexity has not been reduced as one might have anticipated. NOAA is still struggling with how to integrate a “near El Nino” and an at least short-term change to PDO Positive into their Seasonal Outlook and at least this time they have acknowledged that the El Nino activity is more of a Central Pacific nature and shifts weather patterns to the west. Also the anomalous reappearance of the high pressure ridge off the West Coast makes short-term forecasting difficult both for the meteorologists and their computer models.
Today I will start with excerpts from the discussion released Dec 18 by NOAA. NOAA issues two different discussions: a 30 Day and a Long Lead which also covers the first month. I combine the two and eliminate the redundancy which is mainly related to ocean conditions which are discussed in both reports but sometimes not in the same detail. So in that case I am also combining the information as the two reports have different authors. I do the same for the discussion of the next month in the Long Lead report. I remove some of the detail on which models were used and why. Then I organize the combined discussion in a way that I think is easier to follow. You can find the original discussions here and here. NOAA will update the 30 Day Discussion at the end of the month.
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
ATMOSPHERIC AND OCEANIC CONDITIONS IN THE TROPICAL PACIFIC REMAIN MOST CONSISTENT WITH AN ENSO-NEUTRAL STATE. SST ANOMALIES REMAIN ABOVE +0.5 IN ALL THE ENSO CRITICAL REGIONS OF THE PACIFIC. SSTS ALONG THE EQUATOR ARE ABOVE +0.5 C EVERYWHERE FROM ABOUT 150 E TO JUST SHY OF THE SOUTH AMERICAN COAST, WITH SOME REGIONAL ANOMALIES IN EXCESS OF +1.0 C. OCEAN SUBSURFACE TEMPERATURE ANOMALIES REMAINED FAIRLY STEADY IN THE PAST MONTH, AND RANGE FROM +1.0 TO +4.0 C AT BETWEEN 50 AND 150 METERS DEPTH, EXCEPT NEAR SOUTH AMERICA WHERE ABOVE NORMAL OCEAN TEMPERATURES ARE CONFINED TO THE UPPER 50 METERS OR SO.
THE USUAL ATMOSPHERIC RESPONSE TO EL NINO ARE NOTABLY ABSENT FROM RECENT OBSERVATIONS. RECENT OLR ANOMALIES SUGGEST THAT CONVECTION IS NEAR TO BELOW NORMAL OVER THE CENTRAL EQUATORIAL PACIFIC IN AREAS THAT USUALLY SEE ABOVE-NORMAL CONVECTION DURING EL NINOS. BOTH LOWER AND UPPER LEVEL WIND ANOMALIES DURING THIS PERIOD ARE ONLY WEAKLY CONSISTENT WITH EL NINO. WITHOUT LARGE SCALE ATMOSPHERIC ANOMALIES NORMALLY ASSOCIATED WITH EL NINO PRESENT, ENSO-NEUTRAL STILL BEST DESCRIBES THE CURRENT CONDITIONS IN THE PACIFIC.
SIGNIFICANT EXTRA-TROPICAL ANOMALIES THAT MAY HAVE AN IMPACT ON THE CLIMATE OVER NORTH AMERICA INCLUDE A DISTINCT POSITIVE PDO SIGNAL, WITH ABOVE-NORMAL SSTS FORMING A HORSESHOE FROM THE SUBTROPICS TO THE WEST COAST OF NORTH AMERICA, AND EXTENDING WESTWARD ACROSS THE FAR NORTHERN PACIFIC.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THERE IS FAIRLY GOOD CONSENSUS AMONG BOTH STATISTICAL AND DYNAMICAL MODELS FOR ABOVE-NORMAL SSTS TO PERSIST IN THE NINO 3.4 REGION THROUGH THE BOREAL WINTER. MOST OF THE TROPICAL ATMOSPHERIC RESPONSE TO EL NINO IS USUALLY WELL ESTABLISHED BY THIS LATE IN THE YEAR, SO IN SPITE OF THE CONSENSUS OF PREDICTIONS, THE EL NINO IS EXPECTED TO BE WEAK, IF IT DEVELOPS AT ALL. THE CURRENT CONSENSUS OF OPINION AMONG FORECASTERS AT CPC AND IRI IS FOR A 60% CHANCE OF EL NINO DEVELOPMENT. THE MULTI-MODEL AVERAGE OF NINO 3.4 SSTS IS FOR ANOMALIES OF CLOSE TO +1.0 C LASTING INTO SUMMER 2015. IN FACT, THE LATEST DYNAMICAL MODELS SUGGEST A BETTER THAN NORMAL CHANCE AT A PROLONGED PERIOD OF ABOVE-NORMAL SSTS IN THE EQUATORIAL PACIFIC, PERHAPS LASTING THROUGH MOST OF 2015. HOWEVER, A CALIBRATED CONSENSUS OF BOTH STATISTICAL MODELS AND THE CFSV2 PREDICTIONS SUGGESTS AN EARLIER PEAK TO NINO 3.4 SSTS OF JUST OVER +0.7 C, IN NDJ 2014-15, DECREASING SLOWLY AFTERWARD AND REACHING +0.5 C BY JFM 2015 AND CONTINUING A SLOW DECREASE THROUGHOUT THE YEAR.
Editor’s Note: If this occurs, the warm event will not be recorded as an El Nino due to being too short in duration.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS FROM JFM THROUGH MAM 2015 ARE INFLUENCED PARTLY BY THE POTENTIAL IMPACTS OF A WEAK EL NINO. THE LIKELY MARGINAL STRENGTH OF EL NINO RESULTS IN ONLY SLIGHTLY ENHANCED CHANCES OF CLIMATIC ANOMALIES IN THE REGIONS USUALLY INFLUENCED BY ENSO, AND IS WELL SHORT OF THE CONFIDENCE ASSOCIATED WITH EVEN A MODERATE EVENT. LARGE-SCALE INDICATORS, SUCH AS THE POSITIVE PDO, CURRENTLY ARE CONSISTENT WITH EL NINO CONDITIONS AND MAY INDICATE THE EVENTUAL ESTABLISHMENT OF THE USUAL TELECONNECTION PATTERNS ASSOCIATED WITH EL NINO IN SPITE OF THE CURRENTLY DISORGANIZED EQUATORIAL ATMOSPHERIC STATE. THAT SAID, THE OVERWHELMING SIGNAL FROM THE DYNAMICAL AND STATISTICAL MODELS IS THAT THE CONVECTIVE MAXIMUM IN THE EQUATORIAL PACIFIC IS LIKELY WEST OF THE DATE LINE, CASTING DOUBT ON THE DEVELOPMENT OF ANY ROBUST ENSO TELECONNECTIONS.
Special Note: I have constantly raised the possibility of this being a Modoki with the impact shifted a certain number of degrees to the west of the impacts of a traditional El Nino.
30-DAY OUTLOOK DISCUSSION FOR JANUARY 2015
THE JANUARY 2015 OUTLOOK REFLECTS A GENERALLY HIGH AMOUNT OF UNCERTAINTY AS COMPARED TO OTHER MONTHLY OUTLOOKS. SEVERAL FACTORS ARE LIKELY TO IMPACT THE TEMPERATURES AND PRECIPITATION DURING THE MONTH. SOME OF THE INPUTS SUGGEST A LIKELY TO FLIP IN SIGN OF TEMPERATURES AND PRECIPITATION ANOMALIES DURING THE MIDDLE OF THE MONTH, SPECIFICALLY INDICATED IN THE DYNAMICAL MODEL GUIDANCE PRODUCTS.
DYNAMICAL MODEL GUIDANCE FOR THE WEEKS 3 AND 4 PERIOD FROM THE CFS AND EUROPEAN CENTER DEPICT SIMILAR PATTERNS THROUGH THE MIDDLE JANUARY. BOTH MODELS SHOW A COLD START TO JANUARY FOR THE CONUS, EAST OF THE ROCKIES, WITH ABOVE NORMAL TEMPERATURES FAVORED ACROSS THE WEST AND FOR ALASKA. MODEL OUTLOOKS FROM THE CFS, NMME, AND IMME FOR THE ENTIRE MONTH DEPICT A MILD PATTERN ACROSS MOST OF THE CONUS AND ALASKA, IMPLYING THE POTENTIAL FOR A PATTERN SHIFT DURING THE MIDDLE OF THE MONTH.
A ROBUST ATMOSPHERIC RESPONSE TO THE ABOVE AVERAGE EQUATORIAL PACIFIC SSTS REMAINS LACKING. THE PDO REMAINS POSITIVE, AND REGRESSIONS OF JANUARY TEMPERATURE ON NOVEMBER PDO VALUES SUPPORT A COOLER PATTERN, ESPECIALLY EAST OF THE ROCKIES. IN CONTRAST, THE MJO IS FORECAST TO INCREASE INTENSITY OVER THE INDIAN OCEAN LATER IN DECEMBER, AND LAGGED COMPOSITES BASED ON THAT MJO FORECAST FAVOR WARMING OVER THE NORTHERN AND EASTERN CONUS.
THE JANUARY 2015 OUTLOOK INCORPORATES A WEAK ENSO WARM PHASE SIGNAL, SOME INFLUENCE OF THE POSITIVE PDO, AND SOME OF THE SIGNAL FOR COLDER CONDITIONS EAST OF THE ROCKIES IN THE DYNAMICAL GUIDANCE. THE MJO PLAYED LITTLE ROLE IN THE MONTHLY OUTLOOK AT THIS TIME SINCE THERE IS HIGH UNCERTAINTY WHETHER THE MJO WILL ACT TO ENHANCE CONVECTION OVER THE INDIAN OCEAN/MARITIME CONTINENT LATER THIS MONTH. GIVEN THOSE INPUTS, ABOVE NORMAL TEMPERATURES ARE FAVORED FOR ALASKA AND OVER THE CONUS FROM THE WEST COAST TO THE ROCKIES. BELOW NORMAL TEMPERATURES ARE FAVORED OVER THE CENTRAL AND SOUTHERN GREAT PLAINS, AS WELL AS PORTIONS OF THE OHIO VALLEY. SOME DYNAMICAL MODEL GUIDANCE SUPPORTS COOLER THAN NORMAL CONDITIONS FOR THE CENTRAL GREAT PLAINS, WHILE ENSO AND PDO COMPOSITES, AS WELL AS SOME DYNAMICAL GUIDANCE SUPPORT BELOW NORMAL TEMPERATURES ACROSS THE SOUTHERN GREAT PLAINS.
GUIDANCE FROM SOME OF THE NMME CONSTITUENTS ALIGN WITH WARM ENSO COMPOSITES AND POSITIVE PDO REGRESSIONS TO SUPPORT ABOVE AVERAGE RAINFALL OVER PORTIONS OF CALIFORNIA. MODEL GUIDANCE AND ENSO WARM PHASE COMPOSITES SUPPORT WETTER THAN AVERAGE CONDITIONS ACROSS THE SOUTHWEST AND PORTIONS OF THE SOUTHERN GREAT PLAINS, WHILE FAVORING BELOW AVERAGE PRECIPITATION ACROSS PORTIONS OF THE NORTHWEST. NO RELIABLE SIGNALS ARE EVIDENT FOR PRECIPITATION ACROSS ALASKA.
Three Month Outlook
THE TEMPERATURE OUTLOOK FOR JANUARY-FEBRUARY-MARCH (JFM) 2015 INDICATES ELEVATED CHANCES OF ABOVE-NORMAL MEAN TEMPERATURES FOR ALASKA, THE WESTERN CONUS, AND IN PARTS OF NEW ENGLAND. THE CHANCES OF BELOW-NORMAL MEAN TEMPERATURES ARE ELEVATED ACROSS THE SOUTHEASTERN THIRD OF THE U.S..
THE JFM 2015 PRECIPITATION OUTLOOK INDICATES ENHANCED CHANCES OF BELOW-MEDIAN PRECIPITATION FOR PARTS OF THE PACIFIC NORTHWEST, NORTHERN ROCKIES, GREAT LAKES AND OHIO VALLEY. INCREASED PROBABILITIES FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS ARE FORECAST FROM CALIFORNIA EASTWARD TO THE SOUTHERN PLAINS, AND AGAIN ACROSS THE SOUTHEAST COAST. THE PROBABILITIES FOR ABOVE-MEDIAN PRECIPITATION ARE ALSO ENHANCED OVER PARTS OF COASTAL SOUTHERN ALASKA.
PROGNOSTIC DISCUSSION OF OUTLOOKS – JFM 2015 TO JFM 2016
THE OUTLOOK FOR JFM 2015 INDICATES ELEVATED CHANCES FOR ABOVE-NORMAL TEMPERATURES IN ALASKA, MOST OF THE WESTERN CONUS, AND FOR PARTS OF NEW ENGLAND. THERE IS NOTABLY HIGH SPREAD AMONG TOOLS FOR TEMPERATURES IN THE CENTRAL AND EASTERN CONUS, WITH SOME TOOLS AND DYNAMICAL MODELS FAVORING BELOW NORMAL TEMPERATURES, WHILE OTHERS FAVOR ABOVE. THIS MAY, IN PART BE RELATED TO THE DIFFERING STRENGTHS OF THE EL NINO PREDICTIONS FROM THE MODELS. STRONGER EL NINO EVENTS TEND TO BE ASSOCIATED WITH ABOVE-NORMAL TEMPERATURES IN THE UPPER MID-WEST AND GREAT LAKES, WHILE WEAK EVENTS SHOW COOLER AND MORE VARIABLE TEMPERATURE CONDITIONS. GIVEN THE EXPECTED WEAK NATURE OF THIS EL NINO, THE WARMER SOLUTIONS AMONG THE TOOLS WERE LARGELY DISCOUNTED. STATISTICAL SIGNALS FROM BOTH THE CA-SST AND THE OCTOBER EURASIAN SNOWCOVER STILL FAVOR A -AO/NAO PATTERN FOR THE UPCOMING THREE MONTH SEASON. THIS INTRODUCES UNCERTAINTY ACROSS THE NORTH-CENTRAL CONUS, WHERE NMME PROBABILITIES INDICATE ELEVATED ODDS OF ABOVE-NORMAL TEMPERATURES. SOME OTHER NUMERICAL GUIDANCE, INCLUDING THE ECMWF AND UKMET, FAVOR BELOW-NORMAL TEMPERATURES ACROSS THE REGION. COMBINING THIS VARIOUS GUIDANCE WITH THE STATISTICAL TOOLS SUGGESTS THAT EC IS THE MOST APPROPRIATE FORECAST FOR PARTS OF THE NORTH-CENTRAL CONUS. ALSO ADDING TO THE UNCERTAINTY IS THE FACT THAT NEARLY ALL OF THE NUMERICAL GUIDANCE PLACES THE ANOMALOUS CONVECTION WEST OF THE DATE LINE IN THE EQUATORIAL PACIFIC.
IT IS IMPORTANT TO NOTE THAT THE USE OF THE +PDO IN THIS CASE IS NOT SO MUCH BECAUSE WE EXPECT THE PATTERN OF SST ANOMALIES TO FORCE AN ATMOSPHERIC RESPONSE, BECAUSE THIS IS QUITE DEBATABLE. RATHER, DUE TO EXCEPTIONAL DYNAMICAL MODEL AGREEMENT, IT IS ASSUMED THAT THE ATMOSPHERIC CIRCULATION (+PNA) OVER THE NORTH PACIFIC IS CONSISTENT FROM MODEL TO MODEL, AND THUS CAN BE HARVESTED FOR PREDICTION. EVEN THIS ASSUMPTION IS NOT PARTICULARLY STRONG, THOUGH, SINCE IT HAS BEEN SHOWN RECENTLY THAT THE CFS HAS LITTLE SHILL IS [SIC: SKILL IN] PREDICTING PDO CHANGES ON MONTHLY TIMESCALES.
THE PATTERN OF FORECAST TEMPERATURE PROBABILITIES FAVORED IN JFM 2015 EXTEND INTO FMA 2015 AND THEN DIMINISHES THEREAFTER. PREDICTED ANOMALIES FOR AMJ 2015 AND BEYOND ARE LARGELY DETERMINED BY RECENT TRENDS, THE CA-SST, DYNAMICAL GUIDANCE WHERE AVAILABLE, AND CONTEMPORANEOUS +PDO REGRESSIONS. SIGNALS FROM TRENDS AND THE CA-SST DOMINATE DURING THE SUMMER AND FALL MONTHS, RESULTING IN ELEVATED CHANCES FOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF ALASKA, AND AS WELL AS MUCH OF THE CONUS EXCEPT FOR INTERIOR PORTIONS.
BY NEXT WINTER, THE CON IS USED HEAVILY, WHICH EMPHASIZES TRENDS, ALONG WITH THE CA-SST. SOME THOUGHT WAS PUT INTO WHAT ENSO STATE IS MOST FAVORED FOR NEXT WINTER, AS CAN BE APPROPRIATE WHEN THERE IS A ROBUST ENSO ONGOING. FOR EXAMPLE, IF WE ARE CURRENTLY IN A MODERATE TO STRONG EL NINO, AN EL NINO THE FOLLOWING WINTER IS LESS LIKELY. HOWEVER, THERE ARE NOTABLE DISAGREEMENTS BETWEEN THE DYNAMICAL AND STATISTICAL TOOLS THROUGHOUT 2015 WHICH, COMBINED WITH OUR CURRENT WEAK/NEUTRAL ENSO STATE, YIELDS LITTLE SIGNAL FOR NEXT WINTER.
SUBSTANTIALLY ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ARE FORECAST FOR NORTHERN ALASKA FROM ASO 2015 THROUGH OND 2015 DUE TO THE LIKELY ANOMALOUS DELAY IN ARCTIC OCEAN AND BERING SEA SEA-ICE COVER FOR OCTOBER AND NOVEMBER IN THE LAST DECADE RELATIVE TO 1981-2010.
THE ELEVATED CHANCES FOR A WEAK EL NINO EVENT INFLUENCES THE PRECIPITATION OUTLOOK MAPS THROUGH FMA 2015. DYNAMICAL MODEL FORECAST GUIDANCE FROM THE NMME AND IMME AND THEIR PARTICIPANT MODELS GENERALLY SUPPORT WARM EVENT COMPOSITES. PRECIPITATION FORECASTS FROM THE GLOBAL SST BASED CONSTRUCTED ANALOG TOOL WAS ALSO CONSIDERED.
THE CHANCES FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS ARE ELEVATED FOR CALIFORNIA, ACROSS THE SOUTHWEST, PARTS OF THE SOUTHERN GREAT BASIN, THE SOUTHERN PLAINS AND THE SOUTHEAST CONUS FROM JFM THROUGH FMA 2015. ENHANCED PROBABILITIES FOR BELOW-MEDIAN PRECIPITATION ARE INDICATED FOR THE PACIFIC NORTHWEST THROUGH FMA 2015, AND FROM THE CENTRAL MISSISSIPPI VALLEY INTO THE GREAT LAKES REGION FROM JFM THROUGH MAM 2015. PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION ARE ENHANCED FOR PARTS OF SOUTHERN ALASKA THROUGH FMA 2015.
ODDS OF ABOVE-MEDIAN PRECIPITATION ARE ENHANCED DURING AMJ AND MJJ 2015 FOR PARTS OF THE PACIFIC NORTHWEST AND CENTRAL ROCKIES BASED ON NMME, CA-SST, AND PDO REGRESSIONS. THE MODEL GUIDANCE FROM NMME HAS HIGH PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION ACROSS PARTS OF THE SOUTHWEST DURING THIS PERIOD, WHICH CONTRADICTS GUIDANCE FROM THE CON BASED LARGELY ON TRENDS AS WELL AS THE CA-SST. THEREFORE, EC REMAINS FOR THE SOUTHWEST DURING THESE LEADS FOR THE TIME BEING, THOUGH THIS WILL BE MONITORED CLOSELY OVER THE NEXT COUPLE OF MONTHS. TRENDS IN PARTS OF THE SOUTHEAST CONUS INDICATE ELEVATED CHANCES FOR BELOW-MEDIAN PRECIPITATION AMOUNTS IN DJF 2015-16.”
Here is the previous Jan/Feb/March Temperature Outlook
And here is the new Outlook released on December 18, 2014.
As you can see, there is not much of a change from last month’s Seasonal Outlook.
Here is the previous Jan/Feb/March Precipitation Outlook.
And here is the Outlook released on December 18.
As you can see, there is very little change from last month’s Seasonal Outlook.
Let us take a look at the 8 – 14 day outlook that was issued today December 22, 2014. It will auto-update every day so it will be changing day by day (and thus be up to date whenever you elect to read this report) but my comments may become out of sync with the map since my comments do not auto-update.
I am only showing the “second week” namely the day 8 -14 outlook. The first week can be found in Part II of my report but 8 – 14 days covers most of the 6 – 14 day period.
Here is the 8 – 14 Day Temperature Outlook
And here is the Updated December Temperature Outlook released November 30.
And here is the early January Temperature Outlook issued on December 18.
As you can see, December through the end of the year and the beginning of January looks to be much colder than projected in the Outlook issued on November 30 and also the Early Outlook for January. The Outlook yesterday was even colder but it was scaled back today.
And here is the 8 – 14 Day Precipitation Outlook issued today December 22 (but it will also auto-update and change every day so my comments may become out of sync with the map).
And here is the updated December Precipitation Outlook released November 30.
And here is the Early January Precipitation Outlook.
The last week of December and the beginning of January is looking to be have a different patterns that the prior Monthly Outlook and the Early Outlook for January. But you can visualize how this can evolve into the Monthly Outlook if and when the ridge off the West Coast dissipates.
And excerpts from the NOAA discussion covering the December 22 6 – 14 Day Outlook.
“6-10 DAY OUTLOOK FOR DEC 28, 2014 – JAN 01, 2015
TODAYS MODEL SOLUTIONS ARE IN GOOD AGREEMENT ACROSS THE WESTERN CONUS AND ALASKA. THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEANS FEATURE A TROUGH OVER THE BERING SEA, A RIDGE ACROSS THE NORTHEAST PACIFIC, AND A TROUGH EXTENDING FROM HUDSON BAY SOUTHWEST TO THE SOUTHERN ROCKIES. THE 0Z CANADIAN ENSEMBLE MEAN IS DISMISSED AS AN OUTLIER SOLUTION DUE TO ITS MUCH DIFFERENT FORECAST ACROSS THE NORTH PACIFIC. POOR MODEL CONTINUITY EXISTS EAST OF THE ROCKIES WITH TODAY’S 0Z ECMWF ENSEMBLE MEAN INDICATING MUCH HIGHER 500-HPA HEIGHTS ALONG THE GULF COAST AND EASTERN CONUS COMPARED TO ITS MODEL RUN FROM YESTERDAY. SPREAD IS RELATIVELY SMALL AMONG TODAY’S 0Z ECMWF ENSEMBLE MEMBERS AND SUPPORTS THE 0Z ECMWF ENSEMBLE MEAN SOLUTION EAST OF THE ROCKIES. TELECONNECTIONS UPON A POSITIVE 500-HPA ANOMALY CENTER WEST OF BRITISH COLUMBIA (50N 135W), PREDICTED BY ALL MODEL SOLUTIONS, SUPPORTS THE ORIENTATION OF A POSITIVELY TILTED LONGWAVE TROUGH DEPICTED BY THE 0Z ECMWF ENSEMBLE MEAN AND THE FLOW DOWNSTREAM OVER THE EASTERN CONUS. THEREFORE, THE 500-HPA MANUAL BLEND IS WEIGHTED MOST HEAVILY WITH THE 0Z ECMWF ENSEMBLE MEAN BUT FORECAST CONFIDENCE IS REDUCED DUE TO POOR MODEL CONTINUITY. TODAY’S HIGH RESOLUTION 12Z GFS MODEL IS IN REASONABLY GOOD AGREEMENT WITH THE 0Z ECMWF ENSEMBLE MEAN.
THE COVERAGE OF BELOW-NORMAL TEMPERATURES ACROSS THE SOUTHEASTERN CONUS, ON YESTERDAY’S TEMPERATURE OUTLOOK, IS REDUCED DUE TO HIGHER 500-HPA HEIGHTS PREDICTED BY THE PREFERRED 0Z ECMWF ENSEMBLE MEAN. MEANWHILE, FORECAST CONFIDENCE ACROSS THE WESTERN AND CENTRAL CONUS IS ABOVE-AVERAGE AS A 1044-HPA SURFACE HIGH IS EXPECTED TO BUILD SOUTH FROM CANADA ON DAYS 6 AND 7. TEMPERATURES ARE FORECAST TO AVERAGE AS MUCH AS 20 DEGREES F BELOW-NORMAL ACROSS THE NORTHERN/CENTRAL PLAINS BY DAY 7. BELOW-NORMAL TEMPERATURES ARE FAVORED FOR MOST OF THE WESTERN/CENTRAL CONUS DUE TO THE ANOMALOUS COLD PREDICTED EARLY IN THIS PERIOD.
ABOVE-MEDIAN PRECIPITATION IS FAVORED ALONG THE TRACK OF A SHORTWAVE TROUGH ON DAY 6. THAT SHORTWAVE TROUGH IS EXPECTED TO MOVE NORTHEAST FROM THE LOWER MISSISSIPPI VALLEY TO NEW ENGLAND. SOUTHWEST FLOW ALOFT TILTS THE ODDS TOWARDS ABOVE-MEDIAN PRECIPITATION ACROSS CENTRAL AND EASTERN TEXAS. A BUILDING SUBTROPICAL RIDGE INCREASES CHANCES FOR BELOW-MEDIAN PRECIPITATION ACROSS SOUTH FLORIDA, WHILE THE AMPLIFIED RIDGE CENTERED OVER THE NORTHEAST PACIFIC IS LIKELY TO SUPPRESS PRECIPITATION ALONG THE WEST COAST.
ANOMALOUS SOUTHERLY FLOW, EAST OF THE TROUGH OVER THE BERING SEA, INCREASES CHANCES FOR ABOVE-NORMAL TEMPERATURES AND ABOVE-MEDIAN PRECIPITATION FOR MUCH OF ALASKA.
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO POOR MODEL CONTINUITY AND LARGE DIFFERENCES AMONG THE ENSEMBLE MEANS ACROSS THE EASTERN CONUS.
8-14 DAY OUTLOOK FOR DEC 30, 2014 – JAN 05, 2015
THE ENSEMBLE MEANS DIFFER ON THE LONGWAVE PATTERN ACROSS THE EASTERN HALF OF THE CONUS DURING THE WEEK-2 WITH THE 0Z/6Z GFS ENSEMBLE MEANS MAINTAINING MUCH LOWER 500-HPA HEIGHTS OVER THIS REGION. THE PREFERRED 0Z ECMWF ENSEMBLE MEAN IS VERY SIMILAR TO THE HIGH RESOLUTION 6Z GFS MODEL. THESE MODEL SOLUTIONS DEPICT A TROUGH PERSISTING ACROSS THE SOUTHWESTERN CONUS AND A SUBTROPICAL RIDGE CENTERED OVER SOUTH FLORIDA, THE BAHAMAS, CUBA. THE 0Z/6Z GFS ENSEMBLE MEANS WERE NOT USED IN CREATING THE 500-HPA BLEND SINCE THOSE SOLUTIONS DIFFER GREATLY WITH THE 0Z ECMWF ENSEMBLE MEAN.
THE HIGHER 500-HPA HEIGHTS ACROSS THE EASTERN CONUS, PREDICTED BY TODAY’S PREFERRED MODEL SOLUTIONS, RESULTED IN A TWO CATEGORY SHIFT IN PROBABILITIES ACROSS PARTS OF THE SOUTHEASTERN CONUS. THE TEMPERATURE OUTLOOK IS BASED PRIMARILY ON THE 2-METER CALIBRATED TEMPERATURE FORECAST FROM THE 0Z ECMWF ENSEMBLE MEAN. AN UPPER-LEVEL TROUGH ENHANCES ODDS FOR BELOW-NORMAL TEMPERATURES ACROSS MUCH OF THE WEST-CENTRAL CONUS, WHILE NEAR OR ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS THE EASTERN CONUS.
THE 500-HPA HEIGHT ANOMALIES ACROSS THE HIGHER LATITUDES OF THE NORTHERN HEMISPHERE BECAME NEGATIVE AMONG TODAY’S MODEL SOLUTIONS WHICH IS A LARGE CHANGE FROM PREVIOUS DAYS. THE MAJORITY OF 0Z GFS ENSEMBLE MEMBERS INDICATE A POSITIVE ARCTIC OSCILLATION (AO) INDEX DURING WEEK-2 WHICH IS TYPICALLY A SIGNAL FOR MILD TEMPERATURES ACROSS THE EASTERN CONUS.
SOUTHWEST FLOW ALOFT, DOWNSTREAM OF A TROUGH AXIS OVER THE SOUTHWEST, INCREASES CHANCES FOR ABOVE-MEDIAN PRECIPITATION ACROSS PARTS OF NEW MEXICO AND TEXAS, THE GULF COAST, AND MID-ATLANTIC. THE AMPLIFIED UPPER-LEVEL RIDGE ANCHORED OVER THE NORTHEAST PACIFIC, AT LEAST EARLY IN WEEK-2, IS EXPECTED TO MAINTAIN BELOW-MEDIAN PRECIPITATION ALONG THE WEST COAST.
THE TROUGH OVER THE BERING SEA INCREASES CHANCES FOR ABOVE-NORMAL TEMPERATURES AND ABOVE-MEDIAN PRECIPITATION ACROSS ALASKA. LATER IN WEEK-2, ANOMALOUS SOUTHERLY FLOW IS EXPECTED TO EASE.
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: BELOW AVERAGE, 2 OUT OF 5, DUE TO POOR MODEL CONTINUITY AND LARGE SPREAD AMONG THE GFS AND ECMWF ENSEMBLE MEMBERS ACROSS THE NORTH PACIFIC.
Analogs to Current Conditions
Now let us take a more 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.
What are they telling us today?
|1975 December 27||La Nina||–||–|
|1986 December 25||El Nino||+||–||Modoki Type I|
|1986 December 26||El Nino||+||–||Modoki Type I|
|1987 December 9||El Nino||+||Neutral||Modoki Type I|
|2003 January 2||El Nino||+||–||Modoki Type I|
|2006 December 10||El Nino||–||+||Marginal in Duration|
|2006 December 11||El Nino||–||+||Marginal in Duration|
|2006 December 29||El Nino||–||+||Marginal in Duration|
|2006 December 30||El Nino||–||+||Marginal in Duration|
The analogs are indicative of El Nino conditions. The fact that four of the analogs are El Nino Modokis is consistent with the location of the warm water. The 2006 El Nino is not universally recognized as having been an El Nino probably because of its short duration and it occurred when the ocean conditions were not favorable for the development of an El Nino.
Sometimes it is useful to take a look at the location of the Jet Stream or Jet Streams. You can see how the ridge of high pressure off the West Coast is forcing the Jet Stream inland and then creating a large trough in the center of the Lower 48.
And sometimes the forecast is revealing. Below is the forecast out five days. And it looks quite similar to current conditions.
To see it in animation, click here. At the time this article was published, the animation shows a tendency for there not to be a consistent Southern Branch of the Polar Jet Stream in addition to the usual Northern Branch. A southern stream can bring storms further south than usual. But I think you can see the impact of the high pressure ridge off the West Coast which is forcing the meander of the Jet Stream to be further east that usual. This is not typical of an El Nino situation.
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. One can imagine that attempting to forecast this 6 – 14 days out is quite challenging.
El Nino Discussion
Now let us look at the latest NOAA Hovmollers.
First Sea Surface Temperatures
Not much change since last week but you can see how the warm water has been moving west rather than east. At 140W one sees what might be the beginning of a patch of cooler water. Overall it is still sufficiently warm in the Central Pacific where the ONI Index is measured to indicate El Nino “conditions”. I suspect that might change within two months or less. See discussion of the Kelvin Waves later in this report.
Of most interest to NOAA is 120 W to 170 W as that is where the ONI Index is measured. More information can be found here. If you look at the color coding in the above Hovmoller they are looking for shades where the redder the better re conditions being El Nino but so far it is just showing shades of tan and brown i.e. marginal especially when averaged over the entire area of interest. But that explains why we have a situation where some of the factors are in place for an El Nino but so far it is marginal at best.
And now the low-level wind anomalies.
Not a lot of change from last week. The bottom shows the most recent readings as this type of graphic is read from top to bottom with bottom being the most recent readings. In recent weeks, the “reddish” area has been much reduced and there is much more “blue” including over towards Ecuador.
The Southern Oscillation Index (SOI) was not cooperating at the beginning of this week but that changed dramatically in the middle of the week. You can find the daily and 30 and 90 day averages here. It seems that the SOI is fluctuating on a weekly basis from strongly negative to barely negative and the last four days has been strongly negative which favors the development of an El Nino. You can see the impact of this in the above Hovmoller. However I should point out that the Hovmollers included in the Monday ENSO report issued by NOAA are NOT UP TO DATE. For example the Low Level Wind Anomalies are only updated through December 18 so they do not reflect the last four days of favorable winds for the development of an El Nino. I do not know why it is done this way which seems like a disservice to the public but I can only work with the information provided. With the SOI there is always a cause and effect issue. Is the SOI a cause of or a result of warm water being to the east? The SOI is an imperfect index as the two reference points are not on the Equator. The 30 day average is now not even marginal for El Nino conditions (-8.0 is considered to be consistent with El Nino conditions) and is not suggestive of El Nino conditions being in place. Today’s reading is -20.1 which is an indication of a short-term tendency to reinforce this potential El Nino by reducing the normal Easterlies and allow the warm water to proceed east.
16 Dec 2014 +1.76
17 Dec 2014 +2.44
18 Dec 2014 +2.75
19 Dec 2014 -12.82
20 Dec 2014 -16.04
21 Dec 2014 -15.93
22 Dec 2014 -20.1
You can not deduce anything from one day but it reminds us that situations can change rapidly. October and November were actually more favorable for the development of an El Nino than December. But mid-week the situation has changed a bit. We will see if this reversal continues.
And then the third part of the equation (there are more than three but I focus on three): Kelvin Waves.
Not much change from last week but this Kevin Wave has moved further east due to some relenting in the Easterlies. I believe that this Kelvin Wave is the only reason for continued optimism that we will have an El Nino this year but it will be late arriving if it arrives at all. NOAA has highlighted the next upwelling phase of this Kelvin Wave which is the cooling phase and suggests the termination of this El Nino or its transformation into a Modoki i.e. a Central Pacific El Nino which behaves very differently in terms of weather impacts than a traditional/canonical El Nino. Notice that the upwelling phase is still warmer than normal so clearly we have a warm event but most likely not warm enough to qualify as an El Nino. You can also see to the left what probably is the next Kelvin wave which will not arrive in time to reinforce this El Nino event but may extend it longer than NOAA until recently has acknowledeged.
And one more:
This graphic is a modified version of the graphic that appears on Page II of this Report. It is modified by NOAA to be consistent with the maps on the right which can be found here. Those maps have been processed to adjust for the observed skill of the models. As you can see, December was the peak of this El Nino and January is already sub-El Nino on the ONI scale. Although these models are not reliable further out, there are signs that this warm event will last beyond the April/May timeframe suggested by the just released maps in Page II of this Report.
So this continues to look to me like a warm event that is not a full fledged El Nino this year and may last longer than NOAA thinks but have different impacts than they think also. We shall see. I am still thinking the Japanese (and the Australians) sized this up from the start and that this is really more like a Modoki than a traditional El Nino and that weather patterns will be shifted some number of degrees further west than would be the case for a traditional El Nino. This is now acknowledged in the NOAA discussion above. This may turn out to be a two-year event.
“Tropical Pacific Ocean close to El Niño thresholds
Issued on 16 December 2014
The tropical Pacific remains close to El Niño thresholds, with a number of countries around the Pacific Ocean basin and further afield showing some El Niño-like impacts in recent months.
The equatorial Pacific Ocean remains warm, with surface temperatures exceeding El Niño thresholds for several weeks. Typically, after the ocean has exceeded thresholds for an extended period, an El Niño is considered to be underway. However some atmospheric indicators, such as the trade winds, cloudiness and tropical rainfall, have not shown sustained and widespread patterns consistent with El Niño. The Southern Oscillation Index, which has remained negative for several months, has recently eased back from El Niño thresholds; this is likely to be a weather related short-term fluctuation in the index.
The Bureau’s ENSO Tracker status is currently at ALERT, indicating at least a 70% chance that the atmosphere will start to reinforce the ocean in the coming months. Regardless of whether El Niño is declared, El Niño-like impacts are likely to continue, as shown by recent seasonal outlooks. For Australia, this means a drier and warmer summer is likely for many.
All climate models surveyed by the Bureau indicate little change is likely in the tropical Pacific Ocean in the coming weeks and months, with ocean temperatures forecast to either remain close to, or just above, El Niño thresholds. If the atmosphere does start to reinforce the ocean, models suggest the resulting El Niño would most likely be weak or moderate at most.
A new video explaining El Niño, La Niña and the link between the tropical ocean and atmosphere is available on the Bureau’s YouTube channel.
Next update expected on 23 December 2014″
“December 19, 2014
NB: This month’s forecast is based on 9 ensemble members, because TMI and TMI-AMSRE SST datasets used to initialize other ensemble members are unavailable since November 2014.
ENSO forecast: The SINTEX-F model prediction shows that a warmer-than-normal condition over the tropical Pacific will continue until the early next year and then turn into El Niño Modoki with the SST anomalies peaking in the central tropical Pacific.
In consideration of the actual societal impacts, our tentative definition of ENSO (or Modoki) is based on the overall tropical structure and its influences, and is not based only on the single criterion of the Niño 3.4 index scalar variable.
We believe that this new approach must be elaborated more in a quantitative way.
Indian Ocean forecast: Basin-wide warming will continue to develop in the Indian Ocean in response to the Pacific El Niño/El Niño Modoki until the next boreal summer.
Regional forecast: In this boreal winter, as a seasonally averaged view, most parts of western Europe, Africa, Middle East, eastern/western Russia, India, China, Southeast Asia, South American Continent, Canada, western U.S. and the Far East including Japan will experience a warmer-than-normal condition. On the other hand, U.K., southern Russia, and eastern U.S. in particular will be in a colder-than-normal condition.
The forecasts of seasonally averaged rainfall in this boreal winter show that most parts of Southeast Asia, northern Australia, southern Africa, and Brazil will experience a drier-than-normal condition. This may be partly related to the present weak El Niño and subsequent development of an El Niño Modoki. A wetter-than-normal condition will be expected in U.S., in particular the western U.S., partly due to the warmer-than-normal SST associated with persistence of the newly identified regional phenomenon “California Niño”.
I still do not see a traditional El Nino of any significant strength likely to happen this winter, especially in the early part of winter, although a “near” El Nino appears to be making its presence known. It appears to be a very complicated situation. There are many possibilities on the table in my opinion:
- A short weak traditional El Nino which arrives late. (The NOAA projection)
- A short weak traditional El Nino which arrives late and then weakens
- A weak traditional El Nino arriving late but being reinforced and turning into a long lasting stronger traditional El Nino. (Not forecast by NOAA but not inconsistent either) This would be somewhat like the 1982/1983 Super El Nino but not likely to be strong this year.
- A weak traditional El Nino that turns into a Modoki next year (The Japanese Forecast)
- Other variations of the above all related to warmer water further east than usual in the ENSO cycle but not necessarily translating into the usual El Nino that would normally be here now if it fit the usual mold.
Click Here for the Econointersect Weather and Climate Page where you will find:
- NOAA and other agency graphics (including international agencies) that auto update. So this includes both short term- and seasonal “updates”. It will ALWAYS be up to date even if my commentary on the graphics is not. I update my commentary when it seems necessary and certainly every Monday but some of these graphics auto update every six hours.
- Economic and other Impacts of major weather events. Not sure there is any other place to obtain this information consistently other than very specialized subscription services.
- Information on Climate Cycles both those which are fairly short term i.e. less than a decade in duration and multi-decadal cycles.
- Economic and other Impacts of those Climate Cycles which are referred to by the IPCC as Internal Variability as opposed to secular Climate Change which is always in the same direction. Again I am not sure if there is another source for this information where it is pulled together in one place as I have.
- Information on Anthropogenic Global Warming science i.e. the secular change in our climate that overlays both short term weather and historical climate cycles as well as black swan events like volcanic eruptions. I prefer to call this Global Warming as it is the warming that triggers the other changes.
- Economic and other Impacts of Global Warming. The IPCC AR5 WG2 attempts to describe and quantify these and I have some excerpts from their report. Over time I will go beyond their report.
For now this is all in one article which may be a little difficult to navigate but that will soon change and the information will be accessed easily by topic. I have included a Table of Contents but so far have not implemented hyperlinks to move quickly to topics of most interest. For now you have to scroll down.