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El Nino Southern Oscillation (ENSO) Forecast

Issued: 12/4/2013
Updated as Warranted

See ENSO page for Links and Current Data
ENSO Archives

Neutral Pattern Takes Hold
Weak Cool Pattern Fades - Slight Warming Possible

Overview: After the El Nino of 2009-2010, La Nina took hold in early 2010 and remained a dominant factor into the early Spring of 2012. Much to everyones surprise a dropping Southern Oscillation Index (SOI) and prolonged Active Phase of the Madden-Julian Oscillation (MJO) developed and by July 2012 it looked as if a fully blown El Nino event was underway. But as quickly as it started, the trend began to erode, with a neutral MJO taking root and a slow bleed-off of warm tropical water occurring in the East Pacific through the Fall and Winter of 2012-2013. Even then, a neutral pattern was still in play, until the Spring of 2013, when cool water unexpectedly started developing along the coast of Peru and held through the summer of 2013, fueling a resurgence of a La Nina-like pattern that held into the end of Sept.  Only once October 2013 started did a slight turnaround begin. 

The 2012-2013 Winter season was unremarkable, with all the momentum that built during the semi-El Nino like summer months fully dissipated by the time the core of Fall arrived. Only a few significant class storms developed with the net effect being a year assessed after-the-fact at a value of 4.0 while previously predicted at a  5.5.  Rain and snowfall was depressed in California with the storm track displaced decidedly northward. If not for one solid precipitation cycle in Dec 2012, snow would have been almost non-existent. And moving into the Summer of 2013 there were no expectations for much, with a La Nina like pattern well entrenched.  Three significant class storms developed in the southern hemi, one of which provided really solid swell in late June and a second providing decent swell mainly for Southern CA in late July. But other than that, the season was unremarkable. The summer, like the winter before, was marked by a few solid swell events, bookmarked by long stretches on nothing in between. 'Sporadic' was the theme for the year, dominated by high pressure, providing much north windswell and cold water for California and stronger than normal trades for Hawaii. All this time a steady but weak flow of cooler than normal water was tracking north along the coast of Peru and then outflowing west off Ecuador along the equator. Nothing outrageous in terms of volume, but a slow steady bleed none-the-less. And a mirror image cool flow was also occurring off Western Africa indicative of a global teleconnection entrenched deep in the atmosphere. Even at that, a decent amount of tropical storm formation did manage to occur in the tropical East Pacific, but never with enough energy to really generate much swell.   

It is with that backdrop that we look to the coming Winter of 2013/2014.  Only recently has a neutral ENSO signal become evident, meaning that the upper global atmosphere is still being influenced by the cool surface regime that has dominated since the Spring of 2013, and it will not be till perhaps very late 2013 if not early 2014 till that trend is mitigated and a more normal storm and surf pattern becomes established for Hawaii, Canada and the US West Coast.  The paragraphs below describe the state of various indicators used to assess long-term global weather conditions (be it either El Nino or La Nina), followed by criteria for assessing it's impact on surf generation potential for the future.  

Each section first provides a basic tutorial on the feature being analyzed (in italics), and it's state during El Nino and La Nina years. It is followed by an analysis of how that feature is currently behaving. After all features are reviewed, an overall analysis is provided along with additional notes and conclusions summarizing the expected outcome for the future.   

 

MJO: The Madden Julian Oscillation (MJO) is a pattern of wind and weather anomalies that run along and over the equator circumnavigating the globe  from west to east in roughly 40-60 day cycles, roughly 20-30 days of the Active Phase followed by 20-30 days of the Inactive Phase at any one point on it's path.  The cycles alternate continuously year after year and are stronger during the northern hemisphere Fall, Winter and Spring season and lessen during the summer.  The classic pulse of the Active Phase of the MJO results in a slackening of trade winds and an increase in rainfall over the area it is present. The Active Phase is directly followed by the Inactive Phase which manifests itself though increased trades winds and reduced rainfall. The Active Phase of the MJO (when in the Pacific) has been implicated in fueling the development of Northern Hemisphere storms during winter months and tropical storms in the Fall over the Pacific , while the Inactive Phase (when in the Atlantic) has been implicated in fueling the formation of tropical storm in the Atlantic during summer months.  When the strength of Active Phases of MJO dominates, El Nino indicators strengthen. When the Inactive Phase dominates, La Nina moves to the forefront. That is not to say that the MJO causes either El Nino or La Nina, only that it appear to support the development of either extreme of the ENSO cycle. In other words, when the balance of energy favors the Active Phase, the odds of El Nino developing increases.  When the balance shifts towards the Inactive Phase, La Nina becomes more likely.  

Other than a good run of a couple of consecutive pulses of the Active Phase of the MJO during Jan and Feb 2013 which helped push the storm track in the right direction, a weak MJO signal has been evidenced all year. And by Spring into early Summer occasional stronger bursts of the Inactive Phase kept the 30 day running average up in the +8-10 range. This pattern held all through the summer.  This is critical because the late Spring into early Summer MJO trend is what sets the tone atmospherically for the Winter season. It wasn't until late September that the MJO actually turned modestly Active, with trades reversing themselves in the West Pacific for a 3+ week period providing evidence of the first real Active Pulse in what seems like years. A eastward moving Kelvin Wave even resulted (more below). But after that, the MJO returned to effectively a neutral state. That is, no real coherent MJO signal with just subtle hints of tradewind and precipitation variation to suggest perhaps a change in the MJO status, versus years prior to 2010 where the MJO was markedly defined from one phase to the next. As of right now we remain in effectively a neutral state. But as compared to the previous three years, the strength and duration of the Active Phases that do occur appear to be slightly dominant, and mitigating if not getting the slightest bit of headway on whatever negative impacts the Inactive Phases have. Looking at the models for the near term future, there no data to suggest a significant change one way or the other. More details of the MJO as it relates to the current forecast is presented below.     

     

SOI: First we look at the Southern Oscillation Index (SOI). This index/number compares surface pressure over Darwin Australia with pressure over Tahiti. If this value is negative for an extended period of time, that indicates average surface pressure is lower over Tahiti and higher over Darwin, symptomatic of El Nino (or over short durations, ~ 20 days, the Active Phase of the MJO). Positive values over longer times indicates La Nina (or the Inactive Phase of the MJO for shorter durations). The greater the negative or positive value over time, the stronger the ENSO (El Nino Southern Oscillation) configuration (be it El Nino or La Nina). During El Nino episodes wind flows from generally high pressure over Darwin towards generally lower pressure over Tahiti, which is a reverse of what a normal state is. When it's positive, the reverse it true, with higher pressure over Tahiti and lower pressure over Darwin, typical of La Nina, with wind flowing east to west, typical of the trade wind pattern for this region, only more so. The March-June time frame is called the 'Spring Unpredictability Barrier'.  During this time wild swings in the SOI can occur, driven by pulses of the MJO. These swings do not always reflect the start of a long term trend, and often can be 'red-herrings' or 'false starts'.

An attempt at ushering in El Nino started in Jan of 2012 with the 30 day average SOI dropping from +24 to -14 by July 1. There were hopes the big drop of the SOI would hold or even drop more, fueled by successive Active Pulses of the MJO. But that did not occur.  And over the Fall of 2012 the SOI slowly gave up ground, hovering near neutral (+3.0) until late December, when successive Active Phase of the MJO dropped the average back down the -4 range. But by March the Inactive Phase took control with the SOI climbing up to +12, and then near +15 by June, suggesting a return to almost a La Nina pattern. Over the course of the northern hemisphere summer starting in July, that pattern slowly subsided, with the Active Phase of the MJO starting to regain footing, but only weakly, with the SOI down to -1.0 in late August and -5 in late Oct/early Nov. So the trend is definitely down from it's peak in July, but only slowly fading with no clear signs of solidly negative trend yet emerging. As of today the 30 day SOI average is trending upwards from +2.0, due entirely to a building Inactive Phase of the MJO in effect at the moment.  But the overall trend the past 2 months is for the SOI remaining near 0, not positive nor negative.  


Anomalous Equatorial Sea Surface Temperature: El Nino is characterized by a thin stream of warmer than normal surface water temperatures extending from Ecuador west over the Galapagos Islands and onward to a point south of Hawaii or more. As El Nino matures, the water temps increase and cover more area, typically peaking in late December. Conversely La Nina is characterized by the opposite, cooler than normal water temps in the same region and time frames. It is the change in water temperature that theoretically sets up the weather changes associated with either El Nino or La Nina (though we believe that is more a symptom of greater atmospheric and oceanic changes already in play, that enabled the water temp changes to occur in the first place). During La Nina a 'Horseshoe Pattern' pattern can develop characterized by La Nina's cold water pushing west on the equator displacing warm water to the west and positioned both north and south of the cool pool). The Horseshoe is driven by stronger than usual northeast trades winds pushing off the US West Coast and southeast trades tracking off South America deflecting warm water to the west and poleward.

Looking at current seasonally adjusted equatorial Pacific Sea Surface Temperatures (SST), the pattern is as neutral as can be, signaling neither El Nino or La Nina. Warmer than normal water (+0.5-1.0 degs C) are pooled up along the immediate coast of Ecuador just north of the equator streaming west, loosing heat as it tracks towards the Central Pacific with remnants reaching to the dateline. But south of there a slightly cooler flow at about -0.5 to -1.0 deg C is running north along the coast of Peru, reaching the equator, then turning west and running just south of the warmer water to the Galapagos and a bit beyond before dissipating. This is actually a much more favorable pattern that what occurred earlier this year. Starting in April, even in the absence of any strong Inactive Phase of the MJO, sold water started building alongside of Peru and starting outflowing west over the Galapagos, with a mild La Nina pattern apparently building by mid-May. This flow was reinforced over several pulses of the MJO into August.  The net effect was that these cooler waters likely helped fuel (or at least reinforce) the Northeast Pacific High Pressure system, setting up brisk trades over the Islands and persistent north winds down the California coast.  Then, as quickly as it appeared, the pattern dissipated the first week of October. Since then modestly warm warm has persisted in the waters immediately north of the equator in the East Pacific with neutral or maybe -0.5 degree water south of there and not holding together nearly as far west as the warm water.  In total, a pure neutral water temp pattern was in place in early October and has not changed since, or only trended more toward the 0.0 degree mark. Also in July a solid cooler flow tracking from California under Hawaii to the equator started closing off, apparently the result of the Northeast Pacific High Pressure system collapsing and upwelling from winds generated by high pressure aloft fading. A large pool of warm water tracking from Japan eastward impacted the California coast momentarily, then retreated as the high rebuilt, then returned as the high collapsed again in mid-August. By mid-October the high returned weakly, and has held since. Still, the overall image is now indicative of a pure neutral water temperature pattern, reflecting neither El Nino or La Nina.  This is a very large step forward from Spring of the past 3 years dominated by cooler than normal waters in the equatorial East Pacific, and will likely have some positive impact on the Winter storm pattern when it gets traction in the upper atmosphere 3 months out (late Dec 2013). And there is some hope for reinforcements arriving in the form of Kelvin Wave (see below). 

The other good news is the total absence of the 'Horseshoe Pattern' typical of La Nina. Yes, there is still a weak pool of cooler than normal water extending from Central CA south of Hawaii generated by high pressure off the California Coast, but it is very weak and not considered a factor at this time. In all, water temperatures reflect what is occurring in the air above them, and the data suggests a neutral configuration, or homeostasis. In short, there are no massive imbalances in temperature occurring to push the atmosphere one way or the other nor to drive ocean currents in any particular direction.  It's a well controlled campfire, with no strong wind to add oxygen or no fuel to cause explosive growth of storms.


Wind Anomalies: Trade winds over the equatorial Pacific typically blow east to west, towards the Philippines and New Guinea, stronger during the spring and summer and less so in the Fall and Winter as low pressure starts building in the upper latitudes with cold front sweeping south towards the equator.  During El Nino years and during the Active Phase of the MJO, rather than blowing east to west, they blow west to east, or at least blow less strong than normal, which has the same effect as a reversal of trades in that it supports the generation of a Kelvin Wave (more below). When trades are suppressed, this reduces the amount of upwelling along equatorial Central America, allowing the collection of warmer water there (El Nino).  Conversely stronger than average trades there increase upwelling producing cooler than average waters (La Nina).

A Westerly Wind Burst (WWB) is an stronger than normal extended duration of wind that blows from west to east along the equator over the West or even Central Pacific, contrary to normal trade winds and forcing warm surface waters to start moving in the same direction as the wind (details below), a hallmark of a strong Active Phase of the MJO and a precursor to El Nino. Historically if either El Nino or a strong burst of the Madden-Julian Oscillation is in-effect, trade winds that normally blow from east to west reverse themselves and blow west to east. That is, when the MJO is in an Active Phase, the trades reverse themselves in the West Pacific, and when the MJO is not active, trades return. During El Nino years the the MJO still has Inactive Phases, just not as prolonged or strong. Conversely during La Nina there are Active Phases, but they are not as strong or long in duration.  

A weak MJO signal has been in-play for the past year (since Fall of 2012). The only real exception has been a steady but generally small (in coverage) westerly wind burst that occurred over the West Pacific in late September. It helped fuel a prolonged run of tropical systems.  But more importantly it helped generate an eastward moving Kelvin Wave that is currently crossing the Pacific (more details below). Overall a weak tendency towards the Inactive Phase of the MJO has been in play all year up until October, which suggests trades has been slightly enhanced. But since then trades have been slightly depressed.  

Pacific Isotherm: Another key indicator in the evolution of either an El Nino or La Nina event is the depth and profile of the 20 degree isotherm (thermocline). During La Nina events, warm subsurface water remains pooled up in the far equatorial West Pacific while cold surface and subsurface waters dominate the East Pacific, resulting in a steep angle from east to west, or from a shallow pool of warm waters in the east to a deeper pool of warm water in the west. In El Nino events, warm subsurface water (i.e. Kelvin waves - more below) migrate from the West Pacific to the East and the angle flattens with the depth of warm water becoming more uniform across the width of the equatorial Pacific. 

During El Nino events though the MJO signal is weak, it appears that the Active Phases of the MJO are more productive than the Inactive ones.  That is warm water that successfully makes the multi-thousand mile subsurface journey east to Ecuador erupts to the surface just off the coast there, and weaker than usual trades then blow the warm surface water off to the east, also radiating north up the Mexican coast reaching into California during significant El Nino events. This results in a pool of warm water forming off Central America rather than it's usual place in the West Pacific, flattening the angle of the 20 degree C isotherm across the equatorial Pacific. At this time a La Nina pattern is clearly in control with cool water dominating in the east and no sign of warmer than usual waters pushing east towards Central America to flatten the isotherm angle. 

Subsurface water profiles for months now have indicated a pocket of blocking cool water that sat down 150 meters below the surface near 130W during the La Nina years broke up during the Spring of 2012 and was been held at bay until the Spring of 2013.  It returned slightly helping to block the flow of warmer than normal subsurface water to migrate east and erupt along the Central America coast.  With the warm water flow cut off, cooler water was enabled to flow off Ecuador. But in Oct 2013, that pocket of cooler water broke up and since then a neutral water pattern has been in play, if not slightly warmer waters getting a toe hold. This is neither good nor bad, just neutral. 

Kelvin Waves: A Kelvin Wave is a pocket of warm water that travels both under and at the oceans surface from west to east reaching to a depth of about 150-200 meters. It is generated by a burst of strong westerly winds blowing over the equator (a.k.a. Westerly Wind Burst (WWB) in the West Pacific and is typically associated with the Active Phase of the MJO. As the warm surface water gains eastward momentum by forcing of the WWB, it sinks near the dateline and travels well under the oceans surface, only to reappear at the surface when it impacts and erupts along the South America Coast. This results in the sudden appearance of warm waters along the coast of Peru and Ecuador. Occasional eruptions are normal. Large and consistent eruptions are the hallmark of solid El Nino events. The source of Kelvin Waves, a negative SOI and reversed trades, is directly related to the strength and frequency of the Active Phase of the Madden Julian Oscillation (MJO). This weather pattern is responsible for the periodic strengthening of the anomalous westerly winds in the West Pacific which drive production of subsurface Kelvin waves, and also drive the SOI negative. 

We have been monitoring a weak Kelvin Wave that is pushing through the Central Pacific.  It developed in association with a Westerly Wind burst over the dateline and West Pacific in late September and has been steadily progressing eastward tracking 150 meters under the surface.  Latest data has it's leading edge at about 142W (the leading edge of +2 deg C waters).  It has not made much eastward progress in the past 2 weeks. And there is some doubt as to whether it will make the entire journey eastward given mainly the lack of relative force associated with the WWB that generated it. But that could just as easily be due to an outage of buoys in the Eastern Pacific TOA array, used to monitor sub-surface water temps in that area. The hope is it continues it's migration to the east, erupting along the Central American coast. This, if it materializes, it could help to weakly reinforce the East Pacific warm pool, or at least prop it up some. Anything to help pump more heat into the atmosphere to fuel North Pacific storm development is welcome.  

Pacific Equatorial Counter-Current: There are three currents that run along the Pacific equator. Two run just abreast (a few degrees north or south) of the equator flowing east to west driven by the semi-permanent high pressure centers located in the center of the North and South Pacific.  These high pressure system are what drive equatorial trade winds too. But sandwiched between them is the Pacific Equatorial Counter Current, which flows against the two, running west to east.  Satellite based sensors are used to measure the strength/speed of the counter current. That data can be analyzed to determine if the current is flowing stronger or weaker than in years previous.  In essence,  anomalies in the current can be detected.  A curious fact becomes apparent when looking at long-term trends:  During El Nino years the counter current runs harder than usual to the east, and during La Nina years it runs harder to the west. This is what one would expect, especially since the exact same pattern appears when analyzing tradewinds. 

For the past several months anomalies to the current have been weak.  And those anomalies have been small in coverage. In short there is no evidence to suggest the anything unusual is occurring associated with the counter-current and it is not contributing to any weather foreseen changes. 

In all, the current was just reflecting what was ongoing in the air above it. If anything, the relative lack of velocity and coverage in the current is an anomaly.  Regardless, this situation in the ocean only contributes to the lack of energy in the atmosphere above it.  

OLR: When El Nino events unfold at the oceans surface, increased cloudiness/precipitation will develop in the atmosphere above the warmer surface waters, since warmer water supports higher condensation rates above it. The presence of consistent cloudiness or precipitation where it historically shouldn't be is a hallmark of El Nino. Satellite based Outgoing Longwave Radiation (OLR) measurements track reflectivity from clouds over time.  The greater the reflectivity, the less sunlight is being absorbed by clouds. Low reflectivity values represent greater cloud absorption. 

Current satellite data indicates a completely neutral OLR pattern.  That is, cloud cover for the equatorial Pacific, specifically in the West Pacific is normal. Even over the past few months when either the Inactive or the Active Phase of the MJO tries to take control, the precipitation anomalies  associated with either is marginal.  All this suggests is that the MJO signal is weak, and that the overall atmospheric imbalance is weak. This trend has been in play for over a year now. 

Analysis: Reviewing all the data over the past year, the evidence suggests that neither La Nina nor El Nino are in play over waters of the Pacific. We believe the last fading remnants of La Nina died with the demise of weak cool water outflowing off Peru in late September.  And even that event, which started in April and held for the entire summer, was by all standards, very weak. Still, it has had some effect on the atmosphere above it. As is typical when cooler waters prevail over the Eastern Tropical Pacific, high pressure was enhanced over the Northeast Pacific during the Spring and Summer (as was evidenced by north winds during the Spring of 2013 and prolonged runs of locally generated north windswell during the Summer relative to California).  The Summer swell pattern was also weak, typical of a neutral or La Nina ENSO pattern.  The East Pacific tropical season was a bit more active than years past, suggestive of the demise of La Nina (which suppresses tropical storm formation in the East), but there was no real support for storm formation either. If anything, a late season run of tropical activity in the West Pacific, culminating with Super Typhoon Hiayan east of the Philippines, suggests the atmosphere was biased towards La Nina.  But to counter that, if a strong La Nina were in play, those systems would not have recurved north or northeast. Yet there were several weaker tropical systems that made the journey to the dateline, helping to fuel some early season swell producing weather systems relative to both Hawaii and California. Nothing remarkable, but the tropical influence was evident none the less. 

The SOI is holding very much in neutral territory and the MJO signal has been very weak for at least the past year, if not more. And there is no real suggestion of anything of interest occurring with many of the other key indicators as well, including the Pacific Counter Current, Westerly Wind Bursts, and Kelvin Wave Activity. In essence we are in a stagnant and dead neutral atmospheric quagmire. 

It is typical for some some form of weak El Nino-like pattern to develop after a normal 2 year run of La Nina. In fact, this is how La Nina dies and the system moves towards a normal/neutral pattern. The normal timeframe for the change to try and occur is during the Spring. Whether it sticks is dependent upon a great many factors, not all clearly understood. Regardless, it is not unusual to have a few years of 'false starts' before a legitimate El Nino develops. The summer of 2012 was one such false start, and a year early at that. The normal expectation, statistically speaking, would be for that to have occurred in 2013. Regardless, we are effectively in a normal/neutral ENSO pattern now with no evidence of either El Nino or La Nina. And the expectation is that as we move forward from here with slow warming developing over the next 2+ years.  

What occurs in the ocean influences the atmosphere above it. And as the atmosphere responds to changes in the water below it, it reinforces what is occurring in the ocean. A feedback loops results. As of today we have effectively passed over the La Nina hump. There is no evidence of it left in the atmosphere, the ocean, or anywhere else. The only slightly bothersome bit of evidence would be high pressure off California, but even that fluctuates during both both phases of the ENSO cycle. 

Always of interest is the effects of El Nino and La Nina on the relative level of the Atlantic hurricane season activity. Hurricane activity in the Atlantic is inversely tied to the strength and duration of El Nino and La Nina in the Pacific (inverse teleconnection noted above). A classic El Nino produces strong shearing winds over the Atlantic (during the summer it forms) that tear the tops off developing tropical storms, rendering them weak and ineffective at evacuating warm moist surface air up high into the atmosphere through the storms eye. In effect, a hurricane is the atmosphere's attempt to create equilibrium, or to restore balance to a system that is too warm, by creating a chimney to vent off the hot air to the upper atmosphere. So if an an inordinate number of hurricanes occur in the Atlantic, or if they are unusually strong, one could conclude that there is a build up of latent heat energy in the ocean and the shearing effects of El Nino are not in-play, which suggests at least a moderate La Nina might be in effect. 

Looking at Atlantic hurricane activity during the Summer of 2013, it was statistically forecast to be a very active season.  Clearly that did not occur.  It was the slowest season since 1982, with only 2 hurricanes forming. And even the number of tropical storms reported could be debated, with the total number likely amplified by improvements in satellite based monitoring of weather. In absence of other data, one could speculate that El Nino was shearing the tops off developing Atlantic systems.  But clearly that was not the case.  In reality, there just wasn't enough latent heat energy present in the oceans to fuel storm development, or the atmosphere was making it very difficult for developing system to mature. Whatever the theory, the season was non-productive, and it couldn't be attributed to El Nino. 

There are multiyear El Nino events, typically associated with the Midoki variety. A Midoki El Nino (Midoki is Japanese for 'the same but different') forms more in the center of the equatorial Pacific (south of Hawaii), in the Nino 4 region, and evolves there, rarely making much eastward headway through it's life and not typically reaching the Ecuador coast. These El Nino events tend to be more weak-to-moderate in strength too, with lesser impact on the northern hemisphere Fall, Winter and Spring storm pattern. They still have an enhancing impact, just not as strong. In contrast the Classic flavor of El Nino starts forming it's warm pool directly adjacent to Ecuador and expands westward as it matures. The environmental impact tend to be more severe.  The most recent El Nino's event (of 2009/2010) was of the classic variety, only one of 5 that have occurred since 1980 (82/83, 87/88, 91/92 [debatable], 97/98 and now 09).  

Regardless, the strength of a La Nina event often is in direct proportion to the strength of the preceding El Nino.  That is, El Nino and La Nina work in a pair.  It's almost as if the atmosphere, in trying to establish some form of equilibrium, compensating in a strong a fashion as the event which caused it to go out of equilibrium in the first place.  If one considers El Nino a warm anomaly, then La Nina is the cold anomaly that follows to set things 'right'. Most notable is the massive La Nina which followed the huge El Nino of '97/98.  In fact, that La Nina response was so strong it took till 2009 to mount a respectable El Nino event again (though the 2005/2006 El Nino was not too bad). and there were multiple false starts or weak El Nino's prior to that (02/03, 03/04, 04/05).

Given the historical perspective above, we are due for some flavor of false start El Nino.  Unfortunately, there is no evidence that such an event will occur during the 2013/2014 winter season.  

Models: Looking at the MJO models, and the history of the MJO so far this year, and for that matter the bulk of last year, there is little to indicate any extraordinary energy is to be expected from the MJO, with a weak Inactive Phase currently occurring and a weak Active Phase expected right behind starting in early December. In short, the Pacific is about where it was at the start of the Winter of 2012-2013, just waiting for something to push it one way or the other. Nothing of real interest occurred then, and nothing is expected this winter per the models. Yes, we are past the La Nina lockdown phase, which is very good news.  But we are now looking to move forward. Unfortunately we are seeing nothing to suggest anything more (or better) than what has been occurring of late.  Predicting the MJO more than 1-2 cycles ahead is notoriously unreliable. It's better to look at the ENSO models.

We've been following the CFS model. The current operational version (CFSv2) has been consistently suggesting some flavor of near El Nino like water temps (+0.5-+1.0 deg C above normal) in the Nino3.4 region (extending on the equatorial Pacific from south of California to nearly the dateline) by the Spring of 2014. Given all the other data, this seems like a reasonable outcome, but certainly nothing worth betting on. Neutral would be the safer bet. 

Looking at the entire population of models produced worldwide, the CFS sits in the middle of the pack. The mid-point trend through all models suggests a slow warming trend setting up with water temps moving into the 0.25-0.5 degree positive area by May-June 2014.  That is just below minimal El Nino thresholds. So there's some hope if one is inclined to believe the models. 

Typically La Nina throws all it has into it's first year of existence, and by the second year, it is fading, and is normally just a ghost of it's previous self.  Typically the worst time for storm production is during the second year of a 2 year La Nina, especially in February as it is moving into the Spring Predictability Barrier and likely getting ready to turn towards an ENSO neutral or El Nino favored long term outlook. This is because there is little energy left in the atmosphere, where it has almost reached a state of equilibrium.  It is at the extremes of the ENSO cycle (strong El Nino or strong La Nina) where North Pacific Storm formation is at it's best (and of course always favoring the strong El Nino). But as things settle down and things move into the no-mans land of a transition towards equilibrium, a rather stable pattern settles in.

LONG-RANGE NORTH PACIFIC STORM AND SWELL GENERATION POTENTIAL FORECAST

Fall/Winter/Spring 2013-2014 Swell Generation Potential (for California & Hawaii) = 4.0
Rating based on a 1-10 scale: 1 being the lowest (small and infrequent winter surf conditions), 5 being normal/average, and 10 being extraordinary (frequent events of large long period swells)

Methodology (2010+) : We are using the same methodology for making long term predictions since 2010. In the past we looked solely upon the presence El Nino using the approach that El Nino typically enhances the size, strength, frequency and duration of winter North Pacific storms in and around the Gulf of Alaska, thereby improving the likelihood for large winter surf in California and Hawaii. And that La Nina typically decrease the size strength, frequency and duration of such systems. After reviewing data from many such years, we still believe that to be true in an absolute sense over the course of an entire season, but also now recognize that the lingering effects of either a strong El Nino or La Nina event last far longer than previous suspected (up to 1 year). So in the Fall and early Winter season directly following a strong El Nino winter, even though La Nina may be in effect, the lingering effects of El Nino on the upper atmosphere could have an enhancing effect on net storm activity. We've are also turning towards the opinion that strong La Nina events can potentially have enhancing effects on net North Pacific storm formation during the Fall season. The net effect is the more extreme the divergence away from a neutral state, the greater the propensity for weather systems to try and return the system to a state of equilibrium in the form of storms (which create winds and therefore waves). In the El Nino state, the focus of the storm is centered more upon the dateline and the Western Gulf of Alaska and the storm track falls south and lasts longer into the winter season, where in a La Nina scenario the focus is more on the Eastern Gulf of Alaska with the track being displaced to the north and timed more on the Fall and early Winter. Therefore, as the swell source moves east, Hawaii becomes a less likely target. Conversely, a relative minimal ENSO or MJO signal suggests little energy in the atmosphere, and therefore little energy available to force storm development.   

Also the relative strength of MJO phases have an impact on the transport of tropical moisture from equatorial regions of the West Pacific northward to ultimately fall under the influence of the jetstream, increasing the probability for storm formation moving over the dateline and into the Gulf of Alaska. So MJO patterns are now considered in the forecast.

In addition we are become more convinced there is a teleconnection between storm activity in the southern hemisphere and that in the north 6 months later. That is, in years where the net storm activity is up in the southern hemisphere winter (summer in the N Hemi), a corresponding increase in activity could also be noticed in winter in the northern hemisphere (6 months later). The only exception is when there is a strong El Nino or La Nina up north in the winter, then that translates into a net increase in winter activity in the southern hemi 6 months later. Most of this focuses on the strength of the MJO, and seeing how the area it directly impacts is the equatorial Pacific which straddles both the north and south hemisphere's, it would seem reasonable to have an impacts at both poles.

And yet one more possible early indicator is the configuration of the jetstream over the North Pacific starting late July into August over the North Pacific. There is some evidence to suggests a healthy consolidated flow over the NP ac early in the Fall season might lead to a continuation of that pattern through the Winter season, and that if an early season split pattern develops, it will continue in that mode through Winter and Spring. A split Northern hemi jetstream does nothing to support surface level gale development.

Forecast Conclusion: All data suggests we are in a dead neutral state, with no evidence of El Nino or La Nina. Previous lingering momentum from 2+ years of La Nina has been totally erased. Unfortunately there is no momentum from any sort of a developing El Nino, or even a push from the Active Phase of the MJO.  If anything, the tiny but persistent cool water pool that developed over the East Pacific equator this summer and held till late September 2013 is still influencing the atmosphere. That cool pool died in early October, but it will take 3 months for whatever negative impact it has on the jetstream and associated atmospheric components to wash out. So if anything, storm production will be suppressed slightly through the end of December 2013.  After that, it is possible that storm development could return to normal, sometime in January 2014, in-sync with whenever the Active Phase of the MJO develops. But given the very weak MJO signal of the past year, it seems unlikely that anything extraordinary will occur. So based on the models and other data, it seems the trend will be for slightly suppressed development through December and then normally activity beyond. This season would have rated a 5 (normal) if not for the cool water pool experienced over the previous summer.   

Two other points of interest: The North Pacific jetstream was actually fairly well positioned in late July, and continues to be that way so far this season, even with the cold water influence in effect. We suspect its southward displacement actually had some impact in the suppression of tropical storm formation in the Atlantic this summer. And it also contributed to recurving tropical system in the West Pacific late in the season. So there's two contrary patterns at work, a favorable jetstream and an unfavorable cool water pattern that has some as-of-yet undefined impact on the atmosphere. Regardless, we are miles way from were we were during the La Nina years just prior.  Historically during decent El Nino years tropical systems in the West Pacific turn hard east, transitioning to extratropical status and build while moving over the dateline towards the Gulf.  

In the super El Nino of '97, the first Significant class storm of the year occurred in mid-Sept, an extratropical cyclone resulting in 65 kt winds over a large area aimed east producing swell of 10 ft @ 25 sec solid hitting the California coast on Sept 27. And lesser northwest swell producing systems had occurred as early as mid-August. And even in the El Nino of 2009, the first significant class swell of the season arrived on Sept 12th.

Down south, over the southern hemisphere winter (Northern Hemi Summer), net storm activity was well below normal. But when it occurred it was focused on the preferred Southwest Pacific. Only 3 significant class summer time swells resulted for CA, just like 2012, well below normal. But 2 of them were obvious calls with the late June swell filling the Pacific with long period swell. 

The good news is that monster high pressure between Hawaii and California has faded and is not expected to return. And whatever energy the Kelvin Wave currently crossing the equatorial Pacific has when (and if) it emerges off Ecuador, might help impart some energy to the atmosphere and could breath some energy into the late winter storm season. But overall we are not overly optimistic about the coming late Fall/Winter season. But conversely, we are not pessimistic at all. At least La Nina is gone and warm water is trying to make a showing in the equatorial Pacific. Again, this is way better than where we've been for 2+ years. 

We have assigned a swell potential rating of 4.0 for the coming Fall/Winter season, suggesting a historically slightly less than 'normal' Winter swell production season. Diving down to the details, we expect the best odds for swell production to occur in the January and beyond timeframe, historically the peak window for North Pacific storm and swell production.  With luck the season could hold into March or so, but not much beyond unless a new warm pulse starts building during the Spring Unpredictability Barrier in March 2013.

During El Nino events the standard swell profile is for not only more storm frequency, but stronger and longer lasting ones producing larger and longer lasting swells. And with the jetstream shifting south, the swell angle tends to turn more westerly.  Such a pattern was in abundance during the glory days of the 90's and early 2000's.  Conversely the abysmal surf pattern of 3 year period between 2006/2007-2008/2009 (the 3 years after the 2005-2006 El Nino) where we would get one day, or even 12 hour swell events, was marked by the presence of La Nina.

For this year we expect initially a below normal pattern, with weak swell durations with longer than normal breaks in-between, but then picking up in the Jan-Feb timeframe. Most activity is to be confined to when the Active Phase of the MJO is occurring, but that will not preclude storm from forming during Inactive Phases, especially since the phases are expected to be rather muted in either direction.

During El Nino years the surf strategy is to plan for the long run, with endurance and stamina month after month outweighing short feasts and 'go-for-broke' assaults. Conversely during a La Nina winter one should get all you can while you can, cause the odds of it occurring anytime soon are low.

This year one should follow the La Nina strategy, and make the most of what you can get. 

Regarding local weather in CA: During El Nino years one expects more moisture than normal with increased snow pack levels in higher elevations of the Sierra on into Nevada and Colorado.  El Nino tends to shift the jetstream southward and flat over the continental US with the California high pressure  system retreating south and west more than normal if not evaporating completely, favoring precipitation for the more southerly positioned ski resorts in the Southwest. But it too causes surface temperatures to rise with a larger amounts of warmer tropical moisture in the mix, meaning the freeze line rises (in elevation) with increased odds for rain at lower lying resorts.   But for La Nina years, the California High pressure tends to take over the waters off the coast there with the jetstream focused on the Pacific Northwest (Central Oregon northward). It is not unusual to have much larger volumes of moisture up there if not outright flooding while a virtual lack of rainfall occurs down into California, especially from Monterey Bay southward. The exact north-south position of the dividing line varies significantly from event to event. Of note, during La Nina years, when moisture does move into the California region, and assuming there is sufficient snow base, there is a higher than normal tendency for it to be driven by backdoor fronts, those tracking directly down the Pacific Northwest coast.  They tend to be colder and drier, and when they do arrive, the snow quality is exceptional with bone dry power the result. They are not common, and like the surf profile, come only occasionally. So the strategy during such events is to get it when it comes and not expect more to follow directly. 

For the 2013-2014 season, expect somewhat less precipitation than normal, with a late start to the snow and rain season. High pressure has ruled supreme off the CA coast for 2 years now, getting particularly entrenched in 2012, and the cool water pattern in the tropical east Pacific this summer has done nothing to help eliminate it. But, as always with high pressure, it provides storm blockage and can result in pristine offshore days along the coast, with storms organizing on the dateline but getting deflected north as they approach the coast. This might set the potential for somewhat smaller surf, but it will be well groomed upon arrival. And so far this season, that seems to be case. If anything Hawaii might be better set up to catch whatever swell is produced, And it too will have the benefit of trades and offshores versus rain and Kona winds.

As always, this is a preliminary assessment, based on what is known at this time and does not guarantee any particular outcome. 

And there remains the nagging question of whether we have moved into the Inactive Phase of the Pacific Decadal Oscillation (PDO). The PDO is in-effect a 20-30 year cycle of weather than slightly mirrors El Nino in the active phase and La Nina symptoms in it's inactive phase. Our thinking is that if we are in-fact in the inactive phase of the PDO (probably since 2000, and will be for the next 20 years), then the odds for favorable winter storm generation conditions are stacked more in favor of La Nina than El Nino, since the inactive phase of the PDO mimics a weak La Nina. But this is mostly just pure speculation.  And there is other data that suggests that we we're only been in a 'corrective pattern' since the big 97/98 El Nino. Since that ENSO event was so large and strong, the atmosphere had been trying to re-establish some form of equilibrium for nearly a decade since, and the 2009/2010 season was the first chance since then for a normal pattern to manifest itself. Our thoughts are the historical record is too short and it too soon to know with any certainty whether we are in a down phase of the PDO. But the trend has certainly not been favorable of storm production for years now. 

The other consideration is though the is no longer in a true La Nina state, we might be approaching a year or two run in a slightly warm state, perhaps a Midoki state, as part of the run up to a true El Nino a few years out. This is the preferred option. A slow but steady run-up to an El Nino sets the entire atmosphere in motion slowly moving towards El Nino, and builds much momentum year to year, significantly enhancing the storm track and net storm activity both in summer and winter but without all the negative affects of a full blown El Nino. There is no evidence to suggest that this is in-fact occurring other than the models suggesting slightly warmer water temps in Spring of 2014. But a few False Starts to El Nino typically result in such a configuration.

So assuming La Nina is gone and a pure neutral state is in effect, but did not start till early October, with the effects not manifesting in the atmosphere till January 2014, we calculate net storm activity will be something less than normal over the Fall-Winter season with the best support for storm formation occurring during Active Phases of the MJO in the Jan-Mar 2014 timeframe. In that window swell producing Pacific storms, when they occur will be normal in duration and average in intensity with the potential to cover slightly less than normal surface area, resulting in smaller than normal sized fetches of average duration and intensity. This should result in statistically somewhat smaller surf, and of less consistency, period and size. And swell direction will be displaced slightly to the north (293 degs relative to NCal). 

Prior to the Jan-March 2014 timeframe, little is expected in terms of the number and intensity of storms, all attributable to the cool tropical flow that held control all Spring and Summer of 2013. If anything, the 4.0 rating above might be on the high side.  

Over the long term, we're looking for either a marked increase in activity in the Active Phase of the MJO, resulting in several Westerly Wind Bursts over the equatorial West Pacific, or a complete collapse of the MJO with tropical warm water slowly but steadily migrating towards the east. Unfortunately, neither of those options shows any signs of developing.       

(This forecast is highly speculative and based on historical analysis of past La Nina/El Nino events and the latest long-range forecast models)

Sea Surface Temperature Anomalies
Courtesy: NOAA OSDPD
Notice the weak and somewhat diffuse area of warmer than normal water temperatures (yellow shades) extending along the equator from the Ecuador all the way to the dateline and beyond. This is a recent development with previous cooler waters in place here into Aug 2013. This is the key area to monitor for El Nino, but currently represent only a neutral pattern. Temps were cooler over the summer, but are warming somewhat. Also notice some warm water has built up near Japan extending east almost to the US West Coast. But minimal concern is the cooler than normal water (blue shades) extending from the US West coast southwest below Hawaii. This is a weak sign of La Nina and generated by higher than normal pressure and increased trades over the North Pacific causing upwelling.  


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Sea Surface Temperature and Surface Wind Anomalies on the Equatorial Pacific
Courtesy: NOAA PMEL
In the top image notice trades wind blowing firmly east to west over the width of the equatorial Pacific. But also notice what appears to be normal trades (no arrows or small ones) associated with just a normal wind pattern. No apparent phase of the MJO nor a Westerly Wind Burst (WWB) in effect over the equator. This has been the pattern all year.  The arrows indicate the strength and direction of wind anomalies (if there were any), which are trending towards a neutral trade pattern in the East and the West.  


 

20 Degree Thermocline Depth and Position Time Series
Courtesy: CPC NCEP NOAA
(Top Image) The core of warm subsurface water is centered just west of the dateline and making some indication of moving east, but not remarkable.
(Lower Image) Notice the building pocket of warmer than normal water 
(2.0 degs C above normal) at 170W and 150 meters deep. This pocket is extending east now to 110W symptomatic of an eastward moving Kelvin Wave (warm subsurface water) traveling from west to east. This is some good news in that it will erupt off the coast of Ecuador and provide mild warming to equatorial waters off the Galapagos.  


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Equatorial Pacific Sea Surface Temperature Forecast
Courtesy: NOAA/NCEP
Notice that the average of many separate runs of many models generally suggesting slow warmer of waters well off Ecuador into Summer of 2014 perhaps suggesting development of a weak El Nino.


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Southern Oscillation Index (SOI)
Courtesy: BOM
The SOI depicts the difference in pressure between Tahiti and Darwin Australia. When it is consistently negative (that is surface pressure is lower in Tahiti than Darwin Aust), the trend is towards El Nino. And when it is positive the trend is towards La Nina. Notice the generalized trend of a rising index in early 2013 then falling in the later half of 2013 (indicative of a developing weak La Nina like pattern then falling back to neutral). Small pauses or fluctuations in the trend occurred as the Active and Inactive pulses of the MJO move over the West and Central Pacific at 30-45 days each. Dips are the Active Phase of the MJO and rises are the Inactive Phase. 




Pacific Countercurrent Anomalies
Courtesy: OSCAR/NOAA
This image depicts the zonal flow of the Pacific Counter current, which runs roughly on the equator between the West and East Pacific. The top panel depicts the absolute flow of the current.  When it runs east to west as it normally is (blue arrows), this means nothing, unless is is strong, then that suggest La Nina.  When the flow reverses and moves west to east (red) that suggest El Nino.  

The bottom panel depicts anomalies in the current as compared to historical and seasonal averages. Departures from normal are clearly obvious, with strong red arrows reflective of El Nino and strong blue of La Nina.  The images suggest a very weak state with neither a La Nina or an El Nino/Westerly Wind Burst signal occurring.  



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