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.cgiay, 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 di.cgiaced 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
i.cgiicated 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 i.cgiicated 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 co.cgie 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.cgiay, that enabled the water temp
changes to occur in the first.cgiace). During
La Nina a 'Horseshoe Pattern' pattern can develop characterized by La
Nina's cold water pushing west on the equator di.cgiacing 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.cgiace 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 e.cgiosive 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.cgiay 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.cgiay 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.cgiace
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 .cgiay, 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.cgiay 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.cgiay 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.cgiay,
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.cgiay, 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
a.cgiified 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.cgiace. 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 mult.cgie 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
di.cgiaced 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 .cgiit pattern develops, it will continue in that mode through Winter and Spring. A .cgiit
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 di.cgiacement 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.cgian 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 di.cgiaced 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.cgiace 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.
.
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.
.
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.
.
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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