From Russia with Love

850 mb analysis from 12z 12/31 centered over North Pole. Note position of -35°C cold pool over Asia and -20°C cold pool INVOF the Hudson Bay.



12z analysis @ 100 mb from 1/1 ECMWF shows warm temperature anomaly over Asia INVOF the -35°C pool @ 850 mb. This anomaly has been nearly stationary for weeks. It may have played a role in sustaining the persistent jet anomaly across the PAC by enhancing the thermal contrast with the warming contributed by the on-going +ENSO.



D+8 ECMWF forecast from 1/1 shows warm stratosphere anomaly has propagated E to a position INVOF Hudson Bay. This is where the cold air...currently positioned over Asia will set up next week and take the place of the 'warmer' -20°C pool.



The arctic airmass forecast to enter the lower 48 next week had its origins over the snow fields of Siberia.

Public Enemy #1

Another week of obsessive / compulsive anticyclogenesis from the ern PAC.

Preliminary SOI - December '06

(Updated below)

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.

Time for a Change

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.

Retro

Does Thursday/s 5H NHEMI T chart -- with its depiction of three distinct waves --suggest a looming pattern change via retrogression.

Back up a few of the main ftrs @ 5H and see if you don/t see winter in all the right places.

12/26 Storm - Contest Worthy?

Most likely not.

All guidance strongly suggests this is a synoptic-scale rain storm with the potential for mesoscale snowfall along the comma head/s SW to NE axis.

Barring significant changes in tomorrow/s NWP solns...this storm is not in play.

dModel / dT

An animation illustrating how the forecast atmosphere is influenced by initial conditions.

All panels have a VT @ 12z on 12/26.

Click to animate. Loop speed = 3 sec. / frame

Heat ridge...open waves...closed waves...phasing...amplifying...deamplfying...Newfoundland LOW...or no...all forecast to happen at the same time.

Implications of Region 3.4/s Latest SSTA - Is el Nino Fading?

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.

Waiting for -AO -- Stratospheric Warming

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.

1. Lower tropopause ==> falling / colder geo-heights
2. Lower heights ==> colder air
3. Colder air ==> builds hi-lat anticyclone
4. Hi-lat anticyclone ==> hi-lat blocking
5. Hi-lat blocking ==> -AO
6. -AO ==> Trof E
7. Trof-E ==> strong outbreaks of arctic air in the E
8. Strong outbreaks of arctic air in the E ==> increased chances for storminess
9. Increased chances for storminess ==> snowfall forecasting contests

Is there really evidence of a warming event?

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.

Year to Date

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.

The period-of-record (PORN) average gives all forecasts stations at least a little something through the end of December...with snowfall ranging from 0.8" @ RDU to 25.6" @ CAR.

More than half the stations (13) have not recorded any measurable snowfall so far this winter. Deficits at the other stations range from 70% (PWM) to 99% (ALB).

What about '06 YTD compared to last year?

It/s even worse b/c last year was so good. December '05 in NYC was 480% of PORN. EWR just above 400%. BDR almost 300%.

Some comparisons to '05 were not possible b/c NWS does not publish '05 data in their F6 bulletins.

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.