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Saturday, December 30, 2006
The SOI is a 30-day moving average and with one day to go before the end of the month the index comes in near -4.9. After flirting with zero during the last few days of November and into the middle of December...by month/s end the SOI had been in steady decline.
+ENSO Lives...but for how long?
More evidence that +ENSO is holding its own is found in outgoing long wave radiation (OLR) anomalies. Decreased OLR caused by increased cloudiness produced by deep...moist convection is typical during +ENSO events. EEBE, increasing OLR (decreasing cloudiness) would suggest the current +ENSO is fading...but the data for December do not suggest that is happening.
Red areas depict cloudy areas where OLR is below climo.
December - Week 1
December - Week #2
December - Week #3
December - Week #4
Working against the current state are 1) the trade winds that have returned to near normal 2) cooling sub-sfc water...and 3) the continued steady decline in region 3.4 SSTAs. Weekly US and AU SSTA data cover different 7-day periods. The US lags AU by ~4 days.
Weekly anomalies through 12/24
US 1.4 1.3 1.2
Au 1.3 1.2 1.1
A steady decline...indeed.
Waters are still warm and producing plenty-o-convection...for now. The trade winds appear to be working against an eastward propagation of the warmer SST near 180°. It/s only a matter of time before the fuel in region 3.4 is exhausted and it/s over.
Update: End-of-month SOI was -2.4.
Wednesday, December 27, 2006
There/s plenty not to like in the LR progs...not the least of which is the rabid PAC jet flooding the lower 48 with unseasonably mild temperatures and a dearth of EC snowfall. Run after run its little mo' than mo' of the same.
Hints of change to the current pattern are hard to come by. Progs alone aren/t enough. Time to strap on the synopticoscope.
In recent days...several events have occurred that suggest changes to the status quo. Whether it/s a change for the better remains to be seen.
The most significant event is the relatively large anticyclone (1040+ mb) coming off the Asian continent. This has shifted a persistent PAC storm track along 40 / 50 into NW PAC to one where coastal storms rise rapidly in latitude into the Bering Sea and wrn AK. Previous HIGHs coming off the continent were relatively small and weak (1024 mb) with new 'fish' storms forming every three days off the coast of Japan. The storms crossed the PAC...crashing ashore INVOF SEA and with time...BC. Whistler Mt...BC has measured 20' of record snowfall YTD with four months left to go.
Over the past few days...the PAC storm track has farther shifted N into ANC and toward the Aleutian Is.
The second notable change is the erosion of the mid-lvl omega block with its closed center over England...France...and Germany. The area is in transition to a fast...zonal flow as the closed anticyclone sets up to the S over the NW coast of Africa.
Third...the Icelandic LOW...one of AO/s three poles... is W of Greenland today. This feature has generally been E of Greenland since November...a characteristic of +AO phase. A position W of Greenland is favorable for the negative AO phase.
Last...LR models retrograde the sub-tropical heat ridge into the Caribbean Sea and GOM by end of the forecast period.
The change in the PAC storm track is the best sign of improvement for downstream conditions b/c it strongly influences one pole of the AO teleconnection. Add in the fx of a strengthening pole in the N Atl. The third pole over the Azores is weak b/c of its proximity to the strong ridge.
Sunday, December 24, 2006
Friday, December 22, 2006
Wednesday, December 20, 2006
This week/s Nino 3.4 region SSTA comes in @ 1.3°C....down 7% from last week.
Is this the beginning of the end? Did it ever get started?
About a year ago...NOAM countries reached consensus on an operational definition for what conditions constitute 'el Nino' and his evil little sister.
"The index is defined as a three-month average of sea surface temperature departures from normal for a critical region of the equatorial Pacific (Niño 3.4 region; 120W-170W, 5N-5S)."
El Niño: A phenomenon in the equatorial Pacific Ocean characterized by a positive sea surface temperature departure from normal (for the 1971-2000 base period) in the Niño 3.4 region greater than or equal in magnitude to 0.5 degrees C (0.9 degrees Fahrenheit), averaged over three consecutive months."
Nino 3.4 region SSTAs "averaged over three consecutive months" which means there/s a lag built into the calculation. El Nino conditions don/t suddenly appear one day when the SSTA reaches 0.5°C and nor does it fade when an observation falls below the threshold.
The '06 el Nino began toward the end of September when the 12-week SSTA moving average breached 0.5°C. The first observation of an SSTA above the definition/s threshold occurred about six weeks earlier.
The el Nino reached moderate strength (> 1°) with the December 6 observation and continues at the same strength this week...even though the current SSTA declined 7% from last week. In fact...the 12-week moving average rose from 1.01°C to 1.05°C.
Even if the Nino 3.4 region SSTA came in @ 0°C each week for the next two months...el Nino conditions would continue until the first week of February.
How likely is it to see such a sharp drop off of SSTAs? Not very.
Heavy bars bracket Region 3.4
Granted...growth in SSTAs may be slowing or it may simply be evidence of a wave passing through the region. The index has been growing 6 - 9% / week but only 4% with the latest datum. Upstream...in Region 4...SSTAs have held steady @ 1.3°C the past four weeks.
Is it the beginning of the end?
Despite some buzz to the contrary...it/s doubtful. It/ll take some time for the region 3.4/s SSTA to decay.
Did it ever get started?
That seems doubtful...too. At least as far as the planetary flow regime over the CONUS is concerned...although the progs the past few days seem to be coming around to a pattern more representative of +ENSO.
Tuesday, December 19, 2006
In some circles...the stratosphere was long known as the 'ignorosphere' in large part b/c all sensible wx was observed in the troposphere so why should anyone care what was going up there.
The stratosphere has been getting a little extra attention recently. Some say there are big changes are afoot that will lead to big changes underfoot.
The phenomenon of 'stratospheric warming' (SW) has been bandied about around MET town of late...along with the strong suggestion that it will induce significant changes in the current planetary flow regime. The change would bring an end the abnormal warmth and snow drought in the E as winter finally gets started.
The PV is currently quite strong...as evidence by the long run of +QBO. Arctic air over the NHEMI is constrained to high latitudes as a result. These synoptic conditions produce positive values for AO and NAO.
When SW over the Pole is observed...the PV is disrupted and its zonal flow weakens. The weakening PV allows arctic air to drain in to lower latitudes.
The time section of 30 mb air temperature shown below has been offered as evidence of an impending stratospheric warming event. Note the warming INVOF the International Date Line (180°W). SW progresses as the warm pool propagates into lower altitudes.
The stratosphere warms...not from warm advection...but from a lowering of the tropopause. Vertical propagation of low numbered Rossby waves are involved but we/re not getting into all that.
- Lower tropopause ==> falling / colder geo-heights
- Lower heights ==> colder air
- Colder air ==> builds hi-lat anticyclone
- Hi-lat anticyclone ==> hi-lat blocking
- Hi-lat blocking ==> -AO
- -AO ==> Trof E
- Trof-E ==> strong outbreaks of arctic air in the E
- Strong outbreaks of arctic air in the E ==> increased chances for storminess
- Increased chances for storminess ==> snowfall forecasting contests
The longitude analysis shown above seems to support that idea; however, the latitudinal time-section of the same data shown below indicates the warming in not occurring over the Pole where it would have to be in order for the AO / NAO sign to flip from positive to negative.
Since the warming is observed INVOF 65°N and not INVOF 90°N...it/s doubtful this warming event will send the AO / NAO below 0.
Sunday, December 17, 2006
You know it/s bad. Maybe so bad you/re afraid to look.
NEWxSFC has 27 stations in play when snowstorms threaten the forecast area. Snowfall year-to-date (YTD) for 24 of these stations (no climo for HYA. NYC is proxy for ISP and JFK) are compared to YTD climo and YTD snowfall from last year.
WARNING: the deficits are large and for Snow Crows...they are depressing.
Granted...December isn/t yet over...but...GooFuS and the rest of that mangy LR NWP crowd still don/t have any good stocking stuffers up their sleeves.
Catalog: Regular Season
Friday, December 15, 2006
The restlessness is palatable and it has the unmistakabe taste of anchovies.
Will this year end up being another Steinbeck winter of discontent?
If you need a sports metaphor to know where we are at this point...it/s 3rd and 10...10 minutes into the first quarter.
The home team is scoreless and coming to bat in the bottom of the second inning. So what if we boggied the first three holes. Still believe we/ll own the back nine.
Models can tease all they want but the cold air just ain/t there over here. It/s all over there in Uzbekistan...Kyrgystan...Hotdogstan... and Trashcanistan.
Catalog: Regular Season
Thursday, December 14, 2006
Apparently it/s on the other side of the globe where snow has been causing major traffic trubbles of late in Krasnoyarsk...Russia.
Back in the day, Krasnoyarsk was a small part of the vast Union of Soviet Socialist Republics. The Siberian city of ~1x10-6 people is located ~1000 km N of Mongolia and about the same distance NE of Kazakhstan. Other nearby republics once under the thumb of the ol' USSR are Kickstan...Hotdogstan...and Trashcanistan...but I digress.
City authorities report ~300 accidents occurred today...not because of the snowy weather...but because of 'careless drivers' who don/t drive at the 'appropriate speed' given the 'complicated' wx conditions and they/re driving on summer tires with 'worn out protectors.'
Krasnoyarsk/s 'special services' were apparently not up to the task of 'sprinkling the roads' because there was too little special equipment and the 'schedule of snow cleaning and road sprinkling was violated.'
Despite the on-going chaos on local highways...the mayor found time to meet with Father Frosts and Snow Maidens to make final preparations for the upcoming New Year celebration.
"There will be 38 fir-trees in the yards in Soviet district, the biggest district in Krasnoyarsk. A Local Father Frost noted "there will be plenty of surprises at the main district fir-tree." "
"Sverdlovsky district Father Frost told a lot of residents had been removed from dilapidated accommodation to new apartments in his district in 2006. Apart from that, the water pipe on the Bazaikha River was changed into a new one..."
The city has been named the 'most dynamically developing town' of Russia this year.
As if that wasn/t enough excitement for one day...the city announced a dating agency for animals will sponsor a booth at the upcoming 'New Year Fairy Tale' trade show.
All of which begs the question: can it be harmful to live with too much snow?
Catalog: Snow International
Today...Tornado writes about his perceived fallacy concerning snowfall measurements...maintaining the musical question..."How much snow did you get?"...doesn/t matter one lick b/c all that/s really important is the water equivalent of those billions of frozen hydro-meteors piled up around his house.
To support this crumudgery...he cites as reasons the inherent uncertainty in getting accurate measurements b/c of blowing and drifting...variability of snow:H2O ratios...and a nebulous requirement to take an unspecified number of samples...which are later averaged.
Tornado demands scientific meaning from his atmospheric phenomenon declaring "(s)now depth measurements are arbitrary, inconsistent, misleading and hugely unscientific way to represent fallen winter precipitation."
But that attitude surely misses the point about why snow must be measured with a stick and not a cup.
Can you imagine the headlines on NWS winter storm advisories...watches...and warnings?
"Winter Storm Warning for Pressure Falls...NY
Heavy Snowfall with up to 3/4" Water Equivalent"
Or a second period zone forecast where 'additional snow accumulations between 1/4" to 1/2" water equivalent.
If measuring water equivalent became the standard...what would it do to Schwartz' Admonition? Schwartz found in an observational study conducted during the mid-80s...the amount of observed snowfall was inversely proportional to the excitement at the map wall.
How about a scenario where a principal has to make a decision about whether to close schools b/c of a winter storm based on the expected 'water equivalent?' Mike4Snow can take this one from here.
Arguing the phallacy of snowfall measurements is just being a dick in the mud. If this idea ever comes to pass...just shoot me.
Catalog: Snow Crow
Wednesday, December 13, 2006
The last five months have also been negative but the inter-decadal oscillation of the PDO is revealed by a five-year running average of values for October - March. The cool-season average going into this winter was weakly negative @ -0.15 driven mainly by two month/s of strongly cold values during the fall of '05.
Charting the PDO since 1915 produces a 'smooth' sinusoidal wave where the inter-decadal variability is readily apparent. Apparent that is...until the late '80s / early '90s when the pattern becomes fragmented.
The five-year moving average going into this winter was warm (0.30) as was the preceding year (0.33). The five years prior ('00 - '04) it was negative or just below zero. Going back a few more years further reveals the same weak back-n-forth signature; however, the forays into negative territory were less than one sigma of the mean during the current period...which began in 1980... when values are generally positive.
Despite the recent inter-annual variability...the five-year running average shows we/re in the positive phase of the oscillation.
The historical record of teleconnection indices varies from 1876 for the SOI to 1950 for many others such as QBO...MEI...AO...and NAO. The snowfall period of record varies too...so when evaluating analog years...1950 is usually the earliest.
Whether evaluating the current year/s PDO against the full period beginning in 1900 or only considering years since 1950...the best analog year is 1960...as it was last month.
The problem with '60 is there was a neutral ENSO that winter. All of the Top Five PDO analog years occurred during neutral or cold ENSOs.
So where/s all this analysis take us? Does it reveal anything about the coming winter?
Maybe. Probably not.
Negative phase is correlated with above normal heights over the SE...which is a characteristic of La Nina.
Positive phase finds warm water collecting along the west coast...low SLP over the Aleutian Is. and cold SSTA between 20°N and 60°N. These synoptic features would favor a LW pattern of ridge-W implying +PNA and would complement the fx of +ENSO. +PDO is positively correlated with +ENSO.
Warm water along west coast - not so much
PDO as a leading indicator seems to be a wash this year. No signature features and all the best analog years are conflicted with the current ENSO phase.
Most graphics and background information from Mantua.
Monday, December 11, 2006
Quibblers might claim since the threshold for a moderate event is 'near 1'...the current ENSO reached that point last week when the 12-week moving average was 0.95°C......but this week/s 3.4 anomaly of 1.4°C nudged the number just over the top.
So if we/re on the threshold of a moderate +ENSO...where/s this LW pattern that we expect to accompany these SSTs?
Instead...we have this over NOAM today...
Hold the despair. There are similarities in the planetary flow this year compared to the onset of the last +ENSO.
The previous +ENSO began during the late summer of '04. The region 3.4 anomaly stayed at or slightly above 0.75°C from the fall through mid-winter before fading by early spring.
In the run-up to that winter from 11/1 through 12/9...the mean LW regime over NOAM was...
And this is where we are today for the same period...
Not much difference, eh?
Compare that to the mean 5H Z during the '04 / '05 +ENSO/s MET winter.
That/s more like it! Ridge-W, Trof-E and split flow across the southern tier.
This strongly suggests we might just have to take our shoes off and sit a spell before the main event gets a'goin'. By the end of Dec '04...the LW pattern had transitioned to one more akin to the 5H composite for +ENSO winters (as shown above).
The snows of '04 were generally near or below period of record normal (PORN) in the Mid-Atlantic and better than PORN across New England.
Keep your snow pants on...it/ll get here when it gets here.
Sunday, December 10, 2006
Today/s ECMWF progs depict a buckling in the hi-index (zonal) LW flow regime over the PAC early in the forecast period. By D+7...a deep trof b/comes established in the W and a heat ridge bulges over the SE.
Also notable by D+7 is the lowering (rising) 5H heights over the Azores (Greenland) suggestive of a developing hi-lat block.
Given the hi-amp western ridge just upstream of the cold pool in the full-latitude western trof...the upr LOW could retrograde into a 'bowling ball' as the progressive ridge rolls over then aligns near 125W.
Moose: Eenie meanie, chili beanie--the spirits are about to speak!
Saturday, December 9, 2006
Having arrived on the doorstep of the '06 / '07 winter ragged and disheveled with hearts shattered from past season/s disappointments...we look longingly and lovingly to the Pro METs whose vision of future events own us all.
How much for Philly?
While feasting on tales of warring indices...3-D mass fluxes...and seasonal anomalies...the Pros throw us a few scraps and bone or two to keep our interest...only to find the -AO won/t be coming today but it will surely be here tomorrow.
But when tomorrow comes...the Pros suddenly go blind and proclaim just because the -AO hasn/t arrived...they can/t see where their forecast is wrong and yet...if we just wait until tomorrow...then -AO will come.
If we/re stuck waiting for -AO...shouldn/t we just move along...but we wait anyway...knowing full well -AO may never come.
There was...and still is...a widely held expectation that the dominant planetary flow regime this winter would comport itself in such a way to produce net negative index values of the Arctic Oscillation (AO) and the AO/s first-cousin...the North Atlantic Oscillation (NAO).
So...how/s that forecast working out? AO this month to date is 1.55 sigma. NAO at 0.648 sigma.
As we moved into meteorological fall...the AO was about one-half sigma above the normalized monthly mean for September (0.606) and November (0.521). October was a different animal coming is just over one sigma (-1.029) below the mean.
The AO is a measure of polar vortex/s circulation. When the index is negative...the vortex is weak. This weakness allows arctic air to escape...some would say drain...into lower latitudes. When the three-week moving average index of daily values is positive like it is now and has been since the second week of November...the vortex is strong and arctic air is contained.
So what/s going on? What other index gives a measure of the polar vortex? QBO...perhaps?
The QBO has been red hot from the west since April. It/s eight months into its warm cycle with about five months to go before it flips east.
When QBO is anomalously strong from the west...as it is now and has been since May...it indicates the polar vortex is cold and strong...which is complementary...and more importantly...coupled to a positive AO index.
As long as QBO is west...seems to me we/re stuck until spring waiting for -AO.
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Friday, December 8, 2006
For your consideration - 00z 12/15 @ 156 HRS
Baggy...negative mid-lvl trof and a Miller 'B'. More than one system this fall has plunked a large luggie of cold air deep into the lower latitudes and coughed up a strong coastal cyclone. Interesting change depicted in the PAC NW where progged amplitude of LW is increasing and the coast-to-coast wave length is shortening. Will need 2m temps to get on-board.
Catalog: MR Teaser
The Gloucester Daily Times in Gloucester, MA published an article with some quotes from Dr. Joe D'Aleo today called... "Despite mild weather, a bear of a winter is in the forecast."
What caught my eye in this general interest story was Dr. Joe/s hefty snowfall forecast for parts of eastern Mass. Riding this winter/s moderate el Nino...he/s going 200% climo with 70-76" for the area.
Dr. Joe likens this winter/s potential to the '02 / '03 el Nino where Cape Ann picked up almost 120" (50" is average) and Boston saw 71.3". That winter ranks as the 4th best MEI analog this year but PDO E flipped W by late summer (the opposite of this year) and QBO ended its positive run in December which won/t happen this year. This analog may be illustrative as to how el Nino years can produce good snows...but it isn/t one of the better matches.
He also noted the snows from the '04 / '05 el Nino when Boston got 86.6". That winter is the 6th ranked MEI analog for '06 / '07. PDO ranks 9th and QBO 11th. Not a terrible analog...but there are better ones.
For each of his analog years...BOS almost picked up its normal yearly snowfall (43.3") in one month/s time. In '02 / '03...a big dump of 41.6" came in February...more than half coming from from the PD2 storm (23.6"). During '04 / '05...43.3" of snow came in January...22.5" over two days on the 22nd and 23rd.
So...what about '57? Near normal with 44.7"...most of it (23.9") falling in February.
Thursday, December 7, 2006
Latest Multivariate ENSO Index (MEI) comes in @ 1.293...up 26% from 1.027 during Sept / Oct.
Klaus Wolter of NOAA's Earth System Research Laboratory - Physical Science Division notes this is the 5th highest of all Oct / Nov values and the highest ranked value since Apr / May '98.
Wolter expects +ENSO to remain moderate (near +1)...if not stronger (near +1.5 or higher) into early '07. His analog years are 1951-2, 1963-4, 1976-7, and 2002-3. Not sure why '86 / 87 wasn/t included since it lines up so well with the the '06 YTD observations on a regression line.
'57 is ranked 7th as an MEI analog. The '57 QBO is ranked 5th and is the only top-ranked QBO year during +ENSO. Even the '57 PDO is close...although the current index leads the historical by three months...there are intriguing similarities.
MEI - '06 (observed) and '57 (analog) YTD (Dec/Jan - Oct/Nov)
'57 snows were quite good in NE and especially so across the M-A.
Too bad analog forecasting produces such poor results.
Wednesday, December 6, 2006
The UKMET Office issued their Winter Forecast yesterday.
Temperature across Europe - slightly above climo with occasional cold outbreaks. In the UK, December is expected to be mild with colder temperatures during mid and late winter.
Sounds vaguely familiar.
Precipitation across Europe - equal chances for above or below normal. In the UK, they expect normal to slightly above normal.
Sounds like they/re expecting a +NAO to dominant this winter...which is au contraire to many US forecasters who 'see' the opposite as the most likely outcome.
The Brits have been torturing the NAO index in recent years in a dogged attempt to make it confess to what it knows about the coming winter. The MET Office claims their winter NAO forecasts...which are based on May/s SST anomalies in the NW Atlantic near Newfoundland... have a 66% accuracy regarding it/s sign.
May SST Pattern - Winter Z500 Pattern
May 2006 SST Anoms
Nothing negative about the correlated 5H pattern this season.
Tuesday, December 5, 2006
Near-normal NAO but still...0.440 is disappointing to those eager for a quick transition to winter weather. Not that November/s number comes as any surprise seeing how mean monthly temperatures in the NE and M-A were well above normal.
With the addition of November/s datum...top three NAO analog years for this winter ('52...'81...'02) hold fast. '94 moves up one click to 4th, '80 sinks to 6th, and '01 moves into 5th. '02...which had very good snows for most stations in NE and the M-A except ORF and RDU....also shows up in the top five SOI analog years.
CW has it this season would be cold and stormy in the E...strongly influenced by +ENSO and -NAO. So...what/s up with the LR progs continuing their depiction of high index flow across the CONUS with a strong...fast PAC jet well into Week2.
No need to panic...yet. Only five days into MET winter and there/s a whole lotta winter to go.
Monday, December 4, 2006
This just in to the NEWxSFC newsroom...November/s SOI is -1.4. Still negative but not as strong as last month/s -15.3. In any event, el Ninner is still in play.
'63...'01...'57...and '02 were the hot picks for analog years last month and there/s no change after incorporating November/s index. It comes as no surprise some of these SOI analog years ('63 and '02) are also the top picks based on the MEI.
Interesting to note...'57 shows up in the top five years for QBO...as well and the winter of '57 was a very good snowfall season across the NE and M-A.
Going back in time to the SOI/s 'Big Bang' in '76 as in 1876...the SOI YTD fits best with '11 and '25...but it/s difficult finding other tele-connected indices and snowfall data back that far such that the 'eligible' analog years begin in 1950 b/c that/s when most of the other index data begin.
SOI - '06 YTD
Sunday, December 3, 2006
Latest QBO comes in @ 10.10...hot on the heels of October/s 10.86. Top three analog years since 1948 are still 1990...1971...and 1969 based on regression and R² analysis for QBO values YTD. '90 had a neutral ENSO...'71 was cold...but '69 was warm as is '06.
1969/1970 snowfall @ RIC was 14" and near the period-of-record normal. 1957 was a good match using regresson...but the R² value didn/t make the top 10.
The winter of '69 snows were generous to interior NE stations such as BTV...ALB...BGM...BDL...and MDT but near-normal to occasionally below-normal elsewhere.
"The QBO determines the character of the early winter, leading to a colder and more stable polar vortex in December and January during the west phase of the QBO and a more disturbed and warmer Arctic during the east phase of the QBO.
The solar cycle influences the latter part of the winters when a clear difference is observed between periods of high and low solar activity. During high solar activity the winters in the west phase of the QBO tend to be disturbed and are often connected with Major Midwinter (stratospheric) Warmings." - anon
Solar activity has been anything but high for a long time...so don/t look for any dramatic height falls over the Arctic.
QBO since January '06...