Econintersect Climate and Weather Update, 21 July 21 2014
Written by Sig Silber
On Friday 18 July I provided the updated U.S. seasonal outlooks issued by NOAA on July 17.
I also provided the latest statement on the development of what might be an El Nino this winter and some of the issues related to the continued development of this very important weather pattern which can impact a very large percentage of the World.
I thought I would begin with some quotes from the recently released NOAA Seasonal Outlook. The maps are available by clicking at the end of this article and going to the addendum of my weather column where I maintain these maps which are updated on a schedule by the various issuing agencies and I attempt to maintain up-to-date commentary on these maps. But the discussions released with the updates add context to the maps, so I have extracted and posted below the key comments in the discussion that was released by NOAA with last Thursday’s map updates.
“30-DAY OUTLOOK DISCUSSION FOR AUGUST 2014
RECENT OCEANIC CONDITIONS ACROSS THE TROPICAL PACIFIC CONTINUE TO SUPPORT THE FAVORED TRANSITION FROM ENSO-NEUTRAL TO EL NINO LATER THIS SUMMER. HOWEVER, THE ATMOSPHERE REMAINS SOMEWHAT DECOUPLED WITH THE RELATIVELY WARM SEA SURFACE TEMPERATURES (SST) AND THE SUBSURFACE WARMTH OF THE TROPICAL PACIFIC. THESE OBSERVATIONS SUGGESTS THAT THE ENSO PHASE IS STILL NEUTRAL. IT NOW APPEARS THAT THE PREDICTED EL NINO MAY PEAK AT WEAK TO MODERATE STRENGTH BY LATE AUTUMN/EARLY WINTER, COMPARED TO PREVIOUS EXPECTATIONS OF FAVORED MODERATE INTENSITY PEAKING DURING THE SAME PERIOD.
DURING THE PAST FEW WEEKS, POSITIVE SST ANOMALIES PERSISTED (THOUGH WEAKENED SLIGHTLY) IN THE EASTERN EQUATORIAL PACIFIC, AND ANOMALIES ARE CLOSE TO ZERO IN THE CENTRAL PACIFIC (180W-150W). THE LATEST WEEKLY SST DEPARTURE IN THE EAST-CENTRAL PACIFIC (NINO 3.4 REGION) IS +0.3C. THE OCEANIC HEAT CONTENT (SUBSURFACE TEMPERATURE ANOMALIES IN THE UPPERMOST 300-METERS OF THE EASTERN AND CENTRAL EQUATORIAL PACIFIC) DECLINED FAIRLY RAPIDLY IN THE LAST FEW MONTHS, AND ANOMALIES ARE NOW CLOSE TO ZERO. DURING THIS SAME PERIOD, THE LARGE RESERVOIR OF SUBSURFACE WARMTH OVER THE CENTRAL AND EASTERN EQUATORIAL PACIFIC HAS DIMINISHED SIGNIFICANTLY IN COVERAGE AND MAGNITUDE, AND IS NOW CONFINED FROM ABOUT 145W-85W, AND EXTENDS DOWN TO A DEPTH OF ABOUT 75 METERS. DURING THE PAST 30-DAYS, TROPICAL RAINFALL WAS SLIGHTLY ABOVE-AVERAGE IN INDONESIA AND THE WESTERN EQUATORIAL PACIFIC, AND LOW-LEVEL (850-HPA) WINDS WERE NEAR LONG-TERM AVERAGES ACROSS MOST OF THE EQUATORIAL PACIFIC.
MONTHLY MEAN TEMPERATURES FOR AUGUST 2014 ARE FAVORED TO BE ABOVE-NORMAL ACROSS THE SOUTHERN HALVES OF BOTH THE LOWER GREAT PLAINS AND MISSISSIPPI VALLEY, THE SOUTHEAST, TENNESSEE VALLEY, AND MUCH OF THE MID-ATLANTIC REGION, AS WELL AS IN THE PACIFIC NORTHWEST, MOST OF NEVADA AND CALIFORNIA, AND ALASKA. BELOW-NORMAL MONTHLY MEAN TEMPERATURES ARE MOST LIKELY OVER PORTIONS OF THE NORTHERN GREAT PLAINS, UPPER MISSISSIPPI VALLEY, AND UPPER GREAT LAKES REGION.
PRECIPITATION FOR AUGUST 2014 IS ANTICIPATED TO BE ABOVE-MEDIAN OVER MUCH OF THE INTERIOR WEST. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE SLIGHTLY FAVORED FOR MOST OF THE GULF COAST REGION, AND PORTIONS OF GEORGIA AND SOUTH CAROLINA. THE OUTLOOK IS BASED PRIMARILY ON THE SAME TOOLS NOTED ABOVE FOR TEMPERATURE. FOR THE SOUTHWEST, IT IS CONSISTENT WITH THE EXPECTATION OF BOTH AN ENHANCED MONSOON AND AN ENHANCED EASTERN PACIFIC HURRICANE SEASON. IN THE NORTHERN HIGH PLAINS AND NORTHERN ROCKIES, IT IS MOST LIKELY DUE TO FRONTAL ACTIVITY. PERHAPS THE MOST UNCERTAIN PART OF THIS FORECAST IS THE ANTICIPATED REGION OF FAVORED BELOW-MEDIAN RAINFALL OVER THE GULF COAST STATES AND ADJACENT PORTIONS OF GEORGIA AND SOUTH CAROLINA. THE CFS AND IMME SUPPORT SOME EXTENSION OF THIS AREA OF RELATIVE DRYNESS THROUGH NORTH CAROLINA AND PARTS OF THE MID-ATLANTIC REGION, WHILE THE NMME INCLUDES ONLY TEXAS AND LOUISIANA. THIS IS COMPLICATED BY WHAT APPEARS TO BE THE EARLY STAGES OF A FLASH DROUGHT TRYING TO DEVELOP FROM ALABAMA AND THE FLORIDA PANHANDLE NORTHEASTWARD INTO SOUTHWESTERN VIRGINIA.”
Editors note: I see no sign in the 6 day to 14 day forecast of such a drought but the above is about August and the 6 to 14 day forecast only extends through August 4 so we will have to watch to see what NOAA has in mind here.
Commenting on the three month outlook and beyond:
“CURRENT ATMOSPHERIC AND OCEANIC OBSERVATIONS SUGGEST A TRANSITION FROM ENSO-NEUTRAL TO EL NINO CONDITIONS IS UNDERWAY. EL NINO CONDITIONS ARE STILL FAVORED TO BE IN PLACE BY EARLY FALL, HOWEVER, THE UNCERTAINTY ABOUT PACE OF ONSET AND EVENTUAL INTENSITY HAVE INCREASED SLIGHTLY. DISAGREEMENT BETWEEN THE STATISTICAL AND DYNAMICAL MODEL ENSEMBLE MEAN FORECASTS HAVE SLIGHTLY DECREASED FROM LAST MONTH, BUT THE STRENGTH AND DURATION OF THE EVENT IS STILL UNCERTAIN. AT THIS POINT, AN EL NINO OF WEAK TO MODERATE STRENGTH IS MOST LIKELY.
THE TEMPERATURE OUTLOOK FOR AUGUST-SEPTEMBER-OCTOBER (ASO) 2014 INDICATES ELEVATED ODDS OF ABOVE-NORMAL TEMPERATURES ACROSS THE WESTERN CONUS AND FOR SOUTHERN TEXAS, THE SOUTHEAST U.S., AND PARTS OF THE MID-ATLANTIC STATES. BELOW-NORMAL TEMPERATURES ARE FAVORED FROM THE NORTHERN ROCKIES TO THE MIDWEST. THE CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE ENHANCED FOR ALASKA.
THE ASO 2014 PRECIPITATION OUTLOOK CALLS FOR SLIGHTLY ENHANCED PROBABILITIES OF BELOW-MEDIAN PRECIPITATION ALONG THE WESTERN GULF COAST. ELEVATED CHANCES FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS ARE FORECAST FOR MUCH OF THE INTERIOR WEST AND GREAT PLAINS, SPECIFICALLY FROM SOUTHERN CALIFORNIA, NORTHWARD TO WYOMING AND EASTWARD TO MISSOURI.
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
ATMOSPHERIC AND OCEANIC CONDITIONS IN THE PACIFIC BASIN INDICATE THAT A TRANSITION TO EL NINO CONDITIONS CONTINUES. THE LATEST WEEKLY OBSERVATIONS SHOW SST ANOMALIES OF +0.5 DEGREES C ALONG THE EQUATOR FOR MUCH OF THE EQUATORIAL PACIFIC BASIN EXCEPT FOR BETWEEN 150W AND THE DATE LINE, WHERE ANOMALIES ARE LESS THAN +0.5C. EAST OF ABOUT 130W, ANOMALIES EXCEED +1.0 C IN PLACES. HOWEVER, SUBSEASONAL VARIABILITY ACROSS THE TROPICS HAS SLOWED THE TRANSITION TO EL NINO IN RECENT WEEKS.. THE CURRENT SPATIAL DISTRIBUTION OF CONVECTION ACROSS THE CENTRAL PACIFIC IS STILL CONSISTENT WITH A DEVELOPING EL NINO. LOW-LEVEL WINDS ARE NEAR NORMAL ACROSS MOST OF THE PACIFIC, EXCEPT FROM 140W-120W, WHERE THERE WERE ANOMALOUS WESTERLY WINDS DURING THE PAST MONTH. THE SOI REMAINED POSITIVE DURING THE PAST MONTH, ALTHOUGH IT DECREASED FROM MAY TO JUNE.”
Updated El Nino Information
The above is another but different Hovmöller diagram than the one I included in theu 17 July report. I am presenting it because it clearly shows the warm Kelvin Wave that got everyone excited Feb through June but was followed inevitably by the “upwelling phase” where the cold water surfaces after the wave. Looks like there is another warming event taking place but so far it appears to be fairly moderate as compared to the one that got everyone excited. This type of diagram shows why it is possible to attempt to predict an El Nino.
Notice the week to week changes taking place in the wind patterns along the Equator with so far the failure to establish a pattern that is consistent with the rapid development of this El Nino. That is life in ENSO World. Many things are happening and the models integrate all this information but really……ONE DOES NOT NEED THE MODELS AS THE MODELS ARE DATA DRIVEN AND ONE CAN SIMPLY LOOK AT THE DATA WHICH IS ISSUED WEEKLY AND PERHAPS IS AVAILABLE MORE FREQUENTLY TO THOSE MAKING THE FORECASTS.
Skill at predicting ENSO events.
So let’s address the question of the skill level that exists with respect to forecasting an El Nino or a La Nina. I believe that Anthony G. Barnston, from what is known as IRI which is housed at Columbia University in NYC, is recognized as the authority on this and this is what he says in a recent paper which can be found here .
“ENSO prediction skill is slightly higher using today’s models than those of the 1990s (0.65 vs about 0.6 correlation).”
This means that forecasts of the start of an El Nino or La Nina six months in advance are correct 65% of the time an improvement of 5% in about ten years. There is another statement in that article which I am not sure I fully understand.
Decadal variability of ENSO predictability can strongly dominate the gradual skill improvements related to real advances in ENSO prediction science and models.
I am speculating here but I think they are saying that our knowledge of the PDO has given us an edge in predicting El Nino’s and La Nina’s and understanding those statistics improved our forecasting ability.
But then there is what is called the Northern Spring Predictability Barrier (SPB). I am providing this abstract of an article describing the issue because I was not able to find a full version for which I was authorized to post a URL. But this abstract conveys the issue.
“International Center for Climate and Environment Science (ICCES), Institute of Atmospheric Physics, Chinese Academy of Sciences, P. O. Box 9804, Beijing, 100029, China; State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
Global and Planetary Change (Impact Factor: 3.16). 01/2010; DOI: 10.1016/j.gloplacha.2010.01.021
ABSTRACT Based on an ENSO (El Niño-Southern Oscillation) ensemble prediction system (EPS), the seasonal variations in the predictability of ENSO are examined in both a deterministic and a probabilistic sense. For the deterministic prediction skills, the skills of the ensemble-mean are sensitive to the month in which the forecast was initiated. The anomaly correlations decrease rapidly during the Northern Hemisphere (NH) spring, and the root mean square (RMS) errors have the largest values and the fastest growth rates initialized before and during the NH spring. However, the probabilistic predictions based on the verification methods of the relative operating character (ROC) curve and area both show that there are no strong seasonal variations for the two extreme (warm and cold) ENSO events. For the near-normal events, the seasonal variations of the probabilistic skills are much more obvious, and the ROC areas of the ensemble forecasts made in the spring are clearly smaller than those of the ensemble forecasts that began during other seasons.At the same time, the probabilistic prediction skills of the EPS for all three events that only consider the initial perturbations are also clearly sensitive to the initial months. This was indicated by the fact that the most rapid decrease of the ROC area skill occurs as the hindcasts proceed through the spring season. A further signal-to-noise ratio analysis reveals that potential sources of the predictability barrier in the probabilistic skills for the EPS are namely that the spring is the period when stochastic initial error effects can be expected to strongly degrade forecast skill, and that small predicted signals can render the system noisier by further limiting the predictability. However, reasonable considerations of the model-error perturbations during the ensemble forecast process can alleviate the barrier caused by initial uncertainties through coordinately simulating the seasonal variations of the forecast uncertainty in order to significantly improve the probabilistic prediction skills and then to disorder the seasonal predictability related to the SPB.”
Basically what they are saying is to ignore El Nino and La Nina forecasts made during the first quarter of the year as they tend to be unreliable. And yet that is when we saw articles being published on this being a Monster El Nino. But of course we are now in July well past the Spring Barrier. Apparently the best predictions are after the fact, something I learned early in my consulting career. Forecasting is very difficult especially if it is about the future. Being able to “calibrate” a model to replicate the past (i.e. you input parameters from a previous period of time and the model spits out what the weather was like) is usually fairly easy.
But that is what all models are about. They are to varying degrees good at predicting the past or at least predicting what will happen if conditions that occured in the past occur again. Do these models have value at predicting the future if the conditions that exist now are different than those that existed in the past? That of couse is an important question. You do not need a model to predict the recent past; you can look it up.
Are conditions in our oceans changing permanently or on a multidecadal basis?
And now back to the NOAA discussion issued on July 17. Let us focus on the most provocative statement in the NOAA discussion:
“THE EXTRATROPICAL PACIFIC (POLEWARD OF 20N) CURRENTLY PROJECTS STRONGLY ONTO A POSITIVE PDO PATTERN, THE STRONGEST SUCH PROJECTION IN LATE SPRING IN MANY YEARS. THE STATE OF THE NORTHERN ATLANTIC OCEAN IS ALSO A BIT DIFFERENT THAN IN RECENT YEARS, WITH THE MOST RECENT INDEX VALUE OF THE AMO BEING JUST SLIGHTLY POSITIVE, THE WEAKEST IN SEVERAL YEARS.”
To get the discussion going I am starting by presenting two graphics that show up on Bob Tisdale’s blog in a post that you can find here. I can’t vouch for the accuracy of the data but they are presented as showing the actual sea surface temperature versus the ICCP AR5 RCP 6.0 historical data (and regression line) of sea surface temperature in one case for the Overall Tropical Pacific. (See coordinates shown on the graphic.)
And in this graphic the Eastern Pacific (see coordinates shown on the graphic).
Bob Tisdale maintains that there has not been a warming trend in the Tropical Pacific. But you do notice that there has been a lot of variability in the sea surface temperature of the Tropical Pacific and Eastern Pacific. So the challenge is to explain this variability and that will be one of the topics that I address or begin to address next week.
Here is one more graphic from Tisdale.
I wish I could have found a similar graphic by Tisdale related to the Northern Eastern Pacific. The above graphic pretty much covers one part of the area associated with the PDO index. It would be very nice to have a similar graphic for the other area which is the eastern part of the Pacific north of 20 degrees north latitude and I think cutting off at 65 degrees north latitude. One of the interesting aspects of this graphic is that is shows that the Northern Pacific was warming before the PDO index went negative. This is important because many people treat the PDO and AMO like a binary index..one state or the other when it is truly an oscillation and the value of the index rises and falls.
It is important to understand what the PDO is and is not. It is not a measure of the temperature of the Pacific Ocean but rather a measure of the distribution of warm water so it really measures the variability between the temperature of the surface water in the Eastern Pacific versus the Northern and Central Pacific. That is very important to understand.
From the Joint Institute for the Study of Atmosphere and Ocean the official definition is provided as being:
Updated standardized values for the PDO index, derived as the leading PC of monthly SST anomalies in the North Pacific Ocean, poleward of 20N. The monthly mean global average SST anomalies are removed to separate this pattern of variability from any “global warming” signal that may be present in the data.
And this from the Japanese Meteorological Agency (JMA) which is a different organization than JAMSTEC which is more of a research organization. It may not be a perrfect analogy but to me it seems a bit like the difference between NOAA and NCAR.
“In the North Pacific, the atmosphere and the ocean display a trend of co-variance with a period of about 20 years. This variability is called the Pacific Decadal Oscillation (PDO). Supposing that SSTs are lower than their normals in the central part of the North Pacific, they are likely to be higher than their normals both in the eastern part of the North Pacific and in the equatorial Pacific. This seesaw pattern varies slowly, and appears repeatedly with a period of about 20 years. In this case, the Aleutian Low and the jet stream in the upper troposphere tend to be strong. The North Pacific Index (NPI) is utilized as an indicator for the strength of the Aleutian Low. As described above, ocean-atmosphere coupling causes decadal oscillation in the North Pacific. Although some hypotheses have been proposed to elucidate the mechanism behind the PDO, it is not yet fully understood.”
Thus the PDO is different than the Atlantic Multidecadal Oscillation (AMO) which is related to the North Atlantic Meridional Overturning Circulation (MOC) sometimes incorrectly referred to as the Thermohaline Circulation and represents to some extent a vertical change in the distribution of heat in the North Atlantic whereas the PDO is mainly about the spacial distribution of heat and changes in atmospheric pressure.
This is very important to understand. The PDO is an index of anomalies in the distribution of the surface temperatures not a measure of the overall surface temperature of the Pacific or the heat content of the waters of the Pacific Ocean. Of course the distribution of surface temperatures impacts the amount of evaporation that takes place which converts sensible heat into latent heat and and it impacts the amount of and location of areas of significant convection and thus clouds which impacts the amount of both short-wave radiation (SWR) that heats the ocean and the amount of long-wave radiation (LWR) that may be trapped by clouds and becomes an important focus of climate change models.
Thus the PDO and ENSO may very well have an impact on Global Warming but you can can not tell what that impact is simply by looking at the indices used to measure either the PDO or ENSO. So this is where the dispute between one category of Climate Change Skeptics and the mainstream IPCC comes into play. I am presenting the arguments of the Skeptics this week and next week not because I necessarily agree with them but I do believe that understanding their arguments helps in understanding what determines our climate in the short and intermediate term which is what this column is all about. It is not a science column, but sometimes one has to understand the science to be able to make sense out of that which shows up in the literature.
So we have kind of a dispute between the TOA (top of the atmosphere IPCC types) and one category of skeptics which says the main thing going on is the periodic change in the amount of surface in oceans that is warm rather the heat content of the oceans. With more warmer surface there is more evaporation (indisputable) and more heat is transferred from the ocean to the atmosphere. Thus Tisdale argues that El Ninos spread out the warm pool of the Pacific and this causes more evaporation. Tisdale does not argue that the PDO has any impact although it is not clear to me that the amount of surface that is warm versus cool does not change as the PDO goes through its different phases but perhaps it does not.
It is interesting to read the two very different explanations for the “Hiatus” in rising temperatures. I will talk more about that next week and I am sure again many times because it is not just a question of are the IPCC models correct (they clearly are not and the IPCC agrees that they are not) but more importantly to me, what is our climate likely to be like over the next forty years. The IPCC models mainly predict climate at the End of this Century. That is a little far out to be of much personal value to me. It is also perhaps not that useful for water planning although many organizations are clueless on that issue. But most likely no current employee of these organizations will be around at the end of this Century to be contrite about their lack of understanding of climate.
I am more short-term oriented so my focus is now through the next forty years.
Totally Different Topic….a Few Thoughts on the North American Monsoon
The following map is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer and less confusing picture as it shows the major pressure gradients – after all, the weather takes place above the ground not at ground level (fog excluded).
Notice the “Four Corner’s High” is as of today’s forecast i.e. July 21, NO LONGER projected to be next week in the optimal position to enhance the North American Monsoon especially in the absence of tropical activity in the Gulf of Mexico. Being on the edge of what really is the Sonoran Monsoon makes one in a vulnerable position as you need a lot of different factors to fall into place to really get a good Monsoon. It is predicted to happen in August but we will see. It impacts many states not just New Mexico and Arizona. The 6 – 14 Day Outlook issued today is not particularly encouraging but things can change very quickly. It seems to me that the infusion of cold air into the Midwest and Eastern part of the U.S. has influenced the location of the Four Corners High and other features that influence the North American Monsoon. Curiously, this cold air mass intrusion into the Eastern part of the CONUS is described as having originated over the Pacific and thus is not as cold as an air mass that originates over Canada. I think I have read that this is the result of a tropical storm near Japan so it is truly amazing how air masses move around and impact our weather.
Click here for the latest data from NOAA (National Oceanic and Atmospheric Administration) and other sources on the Econintersect Weather and Climate page.
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