My Winter Outlook 2018-19

[Isotherm]

Any comments or inquiries are appreciated!

 

http://www.lightinthestorm.com/

 

Prior Forecasts: Past years’ winter and summer outlooks are maintained on my website: http://www.lightinthestorm.com/  Since the outset in 2006, the verification has been 82%.

Abstract: After multiple, successive winter seasons typified by negative ENSO conditions in the Pacific, a material alteration in the thermocline structure, walker-cells, and concomitant pressure pattern has occurred. The progression toward El Nino has been quite mercurial in that westerly wind bursts, surges of positive frictional torque, mountain torque, and angular momentum have generally been rapidly countervailed by diminutions in those values. This atmospheric warfare may persist to a certain extent, but eventually Nino-esque predilection will predominate. Global temperatures have cooled in comparison to prior years; although, anomalies are still modestly warmer than normal in the northern hemisphere. We continue our descent into the minimum of solar cycle 24, with a significantly reduced output of geomagnetic activity compared to the past few years; solar flux is suppressed quite low, and sunspot activity has been diminutive. The Atlantic sea surface temperature structure remains redolent of a warm Atlantic Multidecadal Oscillation, and the Pacific is likewise, in a warm phase. Going forward into the ensuing cold season, one of the most salient variables, invariably, will be the accurate prognostication of the tropospheric polar vortex intensity, proxies for which are the Northern Annular Mode / Arctic Oscillation and North Atlantic Oscillation. El Nino winters wherein the North Pacific and North Atlantic operate adjunctively with dual favorability feature much different sensible weather results than El Nino winters of only single domain favorability. Hence why it is highly salutary to accurately predict NAO behavior at longer lead times if possible, particularly in terms of Northeastern US winter weather. Contemporaneously, of course, it would be apocryphal to assert that the Pacific pattern is comparatively less important. It is axiomatic that the north Pacific atmospheric structure strongly modulates downstream weather, and weak-moderate El Nino north pacific patterns feature quite a bit of heterogeneity, historically. Specifically, Alaskan-low/British Columbian trough years induce largely warm CONUS patterns whereas Aleutian Low/E Alaskan ridge patterns produce the converse: colder CONUS. The discourse herein will expound upon these topics with the sensible weather prognostications thereupon.

Methodology [Examination of Integral Factors] and Key Assumptions

1. The genesis of a weak El Nino event has occurred, and accordingly, the sea surface temperature anomaly profile in the central Pacific is highly reflective of a positive/warm ENSO event. SOI values have been redolent of neutral ENSO, as the 30 day running SOI value is around 4.7, and October’s mean SOI value was 2.61, following September’s -8.5 (more indicative of El Nino). It is possible to have spasmodic SOI fluctuations such that some months are Nino-esque while others are not; however, the totality of the oscillations suggest very strongly that the ONI (Oceanic Nino Index) is unlikely to exceed low-end moderate El Nino status. I expect that the ONI peak will fall within the range of +0.8 to +1.0c, with low probability of exceeding +1.0c.

The following is the IRI model output which accords with my postulated peak numbers.

 

2. Atmospheric angular momentum (AAM) has generally been running on the negative side from late summer 2018 through mid-autumn 2018, suggestive of greater easterly wind stress in the atmosphere. While this is a La Nina signal typically, AAM can be negative through El Nino winters, wherefore, the resultant sensible weather patterns are quite different. However, westerly momentum has increased in recent weeks, in response to more frequent positive frictional and mountain torque event propagating poleward through the atmosphere. These westerly additions have begun to alter the hemispheric and global flows. Concordantly, an El Nino-esque z500 pattern will continue to develop down the road. It is also salient to note that many of the moderate to strongly negative AAM El Nino winters featured much colder Pacific SSTA (sea surface temperature anomalies), as negative/cold PDO (Pacific Decadal Oscillation) have been shown to retard westerly wind flows, concomitantly enhancing base state easterlies.
3. Accordingly, a positive/warm PDO will aid in obviating persistent, deeply negative AAM periods over the coming months. Furthermore, the velocity potential z200 structure is redolent of a west based El Nino event. This will be one of the most west-based Nino events in database, not insofar as the putative “modoki” SST calculation, but pertaining to the actual walker cell orientation and concomitant uplift zones. Intermittent westerly wind bursts and attendant enhanced convergence near and west of the international dateline are likely over the coming months. There may also be significant off-equator forcing in the sub-tropical areas near/south of Hawaii, extending a bit eastward. The sub-tropical jet should be activated compared to normal.
4. MJO cycling, as reflected by autumn analogs, sea surface temperature anomaly trends, and anticipated physical forcing, will produce conditions felicitous for MJO phases 7-8-1-2 in particular.
5. The sea surface temperature structure; the precursor tropical forcing pattern; and British Columbian “correlate” as I term it, all indicate increased probability for higher than normal geopotential heights in British Columbia, eastern Gulf of Alaska, eastern Alaska and western Canada, in concert with an Aleutian Low feature, displaced slightly west of normal. Geopotential height patterns near British Columbia in late autumn have yielded approximately a 0.7 correlation with ensuing winter geopotential heights in that region.

See the below image depicting z500 geopotential heights over the past few weeks. This pattern over W North America is likely to recur in the ensuing winter.

 

 

 

6. It follows that my anticipation is for a largely negative East Pacific Oscillation, and positive Pacific North American Index.
7. Turning to the Arctic and Atlantic, there are multifarious indicators under consideration. The Brewer-Dobson Circulation has been strengthening in recent days, as one can observe via cooling tropical stratospheric temperatures; this has shown to be an invaluable proxy which augurs polar stratospheric temperature increases as a consequence of heightened ozone concentration. Ozone has been running higher this autumn compared to the past few autumns.
8. The Quasi-Biennial Oscillation (QBO) is now solidly positive at the 30mb atmospheric pressure level – estimating between +5 to +10 (the October value was slightly negative – but it is now solidly positive). However, the 50mb QBO value is still circa -10, and will remain negative through November, December, and January, with a probable flip positive sometime in February. The 50mb QBO modality reversal typically lags the 30mb alteration by 3 months. The vestiges of easterlies in this layer are an integral difference from other winters wherein 30mb through 50mb are moderate to strongly positive. Nevertheless, the increased westerly shear stress in the upper levels will tend to enhance zonal winds 60N/10hpa at times.
9. Solar flux is running quite low, as we descend into the minimum of solar cycle 24 (which is still at least 1 year away). Flux values have generally hovered around 700 or slightly lower. Suppressed solar forcing in concert with increasingly westerly shear stress due to the positive QBO will act to stabilize the upper level stratospheric vortex, and destructively interfere with sudden stratospheric warming events.
10. Geomagnetic activity is very low, with the 30-day running value around 7, indicative of a steep decline from previous autumns.
11. Energetic electron precipitation is suppressed versus prior years, and will be below normal. Concordantly, ozone will be higher than normal in some parts of the Arctic Circle.
12. Asian mountain torque activity will be higher than normal this winter, and coupled with other propitious tropospheric factors such as MJO cycling, will aid in increased vertical energy transfer.
13. The Tamyra region, Barents-Kara Sea precursor geopotential height indicator is suggestive of a weaker than normal tropospheric vortex this winter. Higher than normal geopotential heights near this region in late autumn are indicative of heightened wave driving and negative northern Annular Mode / Arctic Oscillation approximately 70% of the time. See above z500 image for higher heights over the aforementioned region Oct 17-Nov 8; the coming weeks will feature a similar z500 pattern.
14. My NAO, “Formula” which I developed several years ago and incorporates 4 main sub-components. Its retrospective success in forecasting the modality of the ensuing DJF NAO since 1950 has been 87%; and, since utilizing it prospectively, it has verified accurately in the past 4 winters as far as prognosticating the DJF NAO modality. The past several autumns, the NAO formula has strongly indicated a winter-time positive NAO. This year, for the first time since the beginning of this decade, the formula indicates that the NAO will average negative for the DJF winter season; not strongly so, but weakly negative to potentially moderately negative. Compared to the positive NAO dominance of the past several winters, it will be a material alteration.
15. Aforementioned conducive variables, with favorable wave driving, tropospheric forcing, among other factors will produce a negative Arctic Oscillation (AO) for DJF, though not strongly so. There will be some destructive interference from attempted down-welling of a stronger than average upper stratospheric vortex. However, significant perturbation is expected from the mid/lower stratosphere through the troposphere. So while zonal winds at 60N/10hpa may run above normal, zonal winds at 70hpa may run near normal or below normal, and at 150hpa below normal.
16. In light of the combination of factors discussed, tropospheric blocking will be greater than normal, but I anticipate that there will not be a technical sudden stratospheric warming event in the meteorological winter. However, this will be immaterial insofar as the impact on the tropospheric sensible weather pattern.
17. Analogs were exceedingly sparse this year; the highly heterogeneous nature of this season’s indicators is such that sufficient commonalities were limited. The only analog that attains my threshold of featuring sufficiently high similarities is 1963-64, which is my primary and only analog for this winter. The AO average for DJF in 1963-64 was -0.46, and the NAO average was -1.43. The PNA averaged +1.06 and the EPO averaged +0.69. The primary disparity I anticipate here is a more negative EPO and a less negative NAO, compared to the 1963-64 values. The ridge/trough orientations in the mid-latitudes will be retrogressed westward somewhat compared to 1963.

 Teleconnection Index Forecasts

ENSO: Weak to potentially low-end moderate El Nino (+0.8c to +1.0c trimonthly ONI peak)

PDO: Near neutral (warmer than normal in the NE PAC)

AMO: Positive (Warm)

EPO: Negative (weak-moderately negative)

PNA: Positive (moderate-strongly positive)

AO: Negative (weakly negative)

NAO: Negative (weakly to moderately negative)

QBO: Positive/Descending westerly, +5 to +10 at 30mb, and strongly negative, -10, eventually neutralizing by the end of the winter at 50mb

AAM: Near neutral; periods of negative and positive surges

Analogs

 

 

Forecast and Progression

This will be my first winter outlook in 5 years (2014-15) since I forecasted colder than normal temperature anomalies in the Northeastern US. The indicators are suggesting very strongly that DJF temperature departures below the mean is a high probability event. While snowfall is much more difficult to prognosticate, a snowier than normal winter is likely for much of the Northeast corridor and Mid-Atlantic. There are a minority of indicators that may obviate the putative widespread “blockbuster” winter, but regardless, the majority of indicators are suggestive of a colder and snowier than average season in much of the East. As depicted in the 500mb anomaly forecast there are two principal keys to the success of this forecast: the verification of a trough-ridge couplet in the Aleutians and E GOA respectively; and, the verification of an east based negative NAO mean signal. The AO domain blocking will not be as significant.

 

December

The exogenous indicators will evolve such that lower than normal geopotential heights / trough becomes preeminent in the Aleutians region; higher than normal geopotential heights / ridge over E GOA and W Canada and the Western US; downstream, a trough should encompass much of the area from the N-Plains through the Northeast. The PNA (EPO) will be positive (negative) and the AO/NAO will be negative.

Concordantly, for the first time in several years, a large percentage of the Eastern US should experience colder than average temperatures for the month. The walker-cell structure will be such that the mean ridge/trough action centers will be retrogressed a bit further west compared to the analog year (1963-64) and the putative “canonical” look for an El Nino; namely, cool anomalies should prevail from portions of the NW US eastward through the Northeast.

The sub-tropical jet (STJ) should become active with wetter than normal and snowier than normal conditions. Most of the Northeast corridor will have the first real chance of a white Christmas in almost a decade.

January

The data analyzed suggests, quite incontrovertibly, that a relaxation in the synoptic pattern will occur, such that the poleward W-Canadian ridging reduces in magnitude. However, there may still be some vestiges of high latitude blocking that capture somewhat stale continental polar air, precluding locations in the southern/eastern part of the nation from experiencing blowtorch departures for the month. The STJ will continue to be enhanced with respect to normal.

Temperatures should be warmer than normal across most of the Northern tier (though not blowtorch in the Northeast corridor: only slightly warmer than average), and cooler than normal across the South, wherein precipitation will be quite frequent. Snowfall will be near-normal in the Mid-Atlantic and portions of the Northeast, and above normal in interior/northern New England.

February

The data strongly suggests that February will be the snowiest month relative to normal. Whether it will be the coldest month relative to normal is more indeterminate; 1963-64, the primary analog year, featured its coldest departures relative to normal in December. The weight of other analogs indicated otherwise; however, the commonalities in those years were quite a bit less compared to 1963-64.

In light of the indicators analyzed, it is quite possible that December turns out to be the coldest month relative to normal. I am not ruling that out as a possibility. Regardless, December and February should be colder than normal in the Northeast corridor.

Snowfall and precipitation will be above normal in areas that normally receive snow in the East. This month (Feb) has the highest probability of a major or greater magnitude event.

March (not included in the temperature outlook)

The trough should retrogress into the W/Central US with normal to warmer than normal temperatures returning to the Eastern US. Blocking should begin to decrease adjunctively with lowering geopotential heights in Western North America. Snowfall should be below average in the Northeast corridor and Mid-Atlantic (much different than last winter) and above normal in northern New England, as the storm track retrogresses farther west.

Thus, I am anticipating the majority of winter’s snowfall to occur within actual “meteorological winter” this year. The months of December and February should be the snowiest, and coldest with respect to normal.

 

Outlook Specifics

 

Outlook Temperatures

 

For the Local New York City Region

 

Dec-Jan-Feb Temperature Departure: Colder than normal; -0.6 to -1.6

 

Monthly Breakdown:

 

December: -2 to -3

January: +1 to +2

February: -2 to -3

 

A colder than normal December is likely, followed by a warmer than normal January, and colder than normal February. The provenance of this outlook’s reasoning emanates from the factors delineated heretofore. Snowfall will be above normal in December. Prodigious amounts are not expected, but a major event cannot be ruled out. January will feature a more tepid atmospheric structure with lower-end snowfall potential. February is anticipated to feature the highest probability of a high-end snowfall event. The winter’s meaningful snowfall opportunities should dwindle rapidly following the end of February.

 

The expectation is that this will be a winter with frequent Miller B events, and to a lesser extent Miller As. Concordantly, locations north of Philadelphia will be most favored with respect to maximum snowfall anomalies. Snowfall forecasting is inherently mercurial and lesser confidence than temperature forecasting. The ranges provided below are best, educated guesses given the expected physical forcing. The take-away message here should be a solidly snowier than normal winter, probably significantly so, for most of the Northeast corridor.

 

Precipitation: Above normal

Snowfall: Above normal

 

Select snowfall amounts for various cities:

 

Burlington, VT: 75-85”

Boston, MA: 60-70”

New York City, NY: 37-47”

Philadelphia, PA: 25-35”

Baltimore, MD: 22-32”

Washington, DC: 18-28”

Richmond, VA: 5-15”

Raleigh, NC: 4-14”

 

 

 

 

 

 

 

 

 

 

 

 

 

[Isotherm]

Knew I'd forget an image -- just a note -- I added the 500mb forecast map under "forecast and progression."

[nzucker]

Great outlook, Isotherm...in line with much of what I've read here. What do you think of 04-05 as an analog, as well? Or 68-69/69-70?

[Stormlover74]

46 minutes ago, nzucker said:

Great outlook, Isotherm...in line with much of what I've read here. What do you think of 04-05 as an analog, as well? Or 68-69/69-70?

04-05 didn't get going until 3rd week of Jan 

[frd]

2 hours ago, Isotherm said:

In light of the combination of factors discussed, tropospheric blocking will be greater than normal, but I anticipate that there will not be a technical sudden stratospheric warming event in the meteorological winter. However, this will be immaterial insofar as the impact on the tropospheric sensible weather pattern.

Isotherm thank you for your outlook. I was looking forward to it . 

Can you explain, if time permits,  why you feel a technical SSWE during the MET winter is not likely this year?  

I read this part " solar flux is running quite low, as we descend into the minimum of solar cycle 24 (which is still at least 1 year away). Flux values have generally hovered around 700 or slightly lower. Suppressed solar forcing in concert with increasingly westerly shear stress due to the positive QBO will act to stabilize the upper level stratospheric vortex, and destructively interfere with sudden stratospheric warming events."

I thought maybe the odds were higher due to the phase change with the QBO and the low solar background state. Seems we need solar forcing ?

Thanks, and much appreciated ! 

[Carvers Gap]

Outstanding.  Greatly appreciate the work and for you sharing it...

[raindancewx]

You have to be careful with 1963-64. Mount Agung in the Tropics erupted as a VEI 5 in March 1963 and completely messed up the global weather pattern in the following months. 1963-64 severely lowered the AMO from somewhat positive to pretty negative. Agung did erupt more weakly in 2017 and the AMO weakened again in a similar manner, but it doesn't seem to be impacting the global pattern the same way. If you really think 1963 is the main year, stuff like this would bother me a lot -

I think it's asking a lot for the pattern to go to the severe cold of Dec 1963 nationally given how different Oct-Nov 1963 were from 2018. If you're going to say it might be like Dec 1963 int he East, which is like the second coldest Dec in the East in like 60 years, you should probably give some kind indication about the possible severity. I don't think really think people understand how extreme 1963-64 was nationally. It isn't constantly invoked like 1976 or 2014.

In some ways, the PDO is similar, in Oct 1963 and 2018, you can have a negative PDO if the NE/NW Pacific are both similar relatively, despite different actual temps, but even so, the massive difference in heat off the East Coast has to have some kind of impact between the two years.

I'd love to have 1963-64 here, really I would - it's my coldest winter since 1892. There are pretty massive problems with it as analog, the AMO, PDO, volcanoes, the very cold water v. very warm water off the East Coast, the SOI, sea ice, QBO, etc. February 1964 was 10-15F below average (1951-2010 highs for basis) in the SW.

[Isotherm]

2 hours ago, nzucker said:

Great outlook, Isotherm...in line with much of what I've read here. What do you think of 04-05 as an analog, as well? Or 68-69/69-70?

 

Thanks, Nate. I compared the various years very strictly with respect to solar, QBO, ENSO, among many other variables. There were some differences with the years you mention that warranted exclusion from my perspective, such as descending easterly tendency or negative QBO, for example. 1969-70 was a second year Nino, which played a role in limiting its inclusion as well.

 

1 hour ago, WxWatcher007 said:

Awesome outlook. Hope it turns out right! 

Thank you!

 

1 hour ago, frd said:

Isotherm thank you for your outlook. I was looking forward to it . 

Can you explain, if time permits,  why you feel a technical SSWE during the MET winter is not likely this year?  

I read this part " solar flux is running quite low, as we descend into the minimum of solar cycle 24 (which is still at least 1 year away). Flux values have generally hovered around 700 or slightly lower. Suppressed solar forcing in concert with increasingly westerly shear stress due to the positive QBO will act to stabilize the upper level stratospheric vortex, and destructively interfere with sudden stratospheric warming events."

I thought maybe the odds were higher due to the phase change with the QBO and the low solar background state. Seems we need solar forcing ?

Thanks, and much appreciated ! 

 

Thanks, Frd. It may be somewhat counter-intuitive, but the research I've read actually indicates that descending westerly QBO/low flux couplets aid in vortex stabilization in the upper levels. It's actually the least perturbed state insofar as technical sudden stratospheric warming events. However, like I delineated in the outlook, I don't think this should be of significant concern to anyone this particular year due to other factors which suggest tropospheric blocking. The still negative 50mb QBO, conducive wave driving, torque events, among other variables such as enhanced BDC/ozone transport, will keep the lower stratosphere + troposphere more perturbed this winter.

 

1 hour ago, Carvers Gap said:

Outstanding.  Greatly appreciate the work and for you sharing it...

Thank you.

33 minutes ago, raindancewx said:

You have to be careful with 1963-64. Mount Agung in the Tropics erupted as a VEI 5 in March 1963 and completely messed up the global weather pattern in the following months. 1963-64 severely lowered the AMO from somewhat positive to pretty negative. Agung did erupt more weakly in 2017 and the AMO weakened again in a similar manner, but it doesn't seem to be impacting the global pattern the same way. If you really think 1963 is the main year, stuff like this would bother me a lot -

I think it's asking a lot for the pattern to go to the severe cold of Dec 1963 nationally given how different Oct-Nov 1963 were from 2018. If you're going to say it might be like Dec 1963 int he East, which is like the second coldest Dec in the East in like 60 years, you should probably give some kind indication about the possible severity. I don't think really think people understand how extreme 1963-64 was nationally. It isn't constantly invoked like 1976 or 2014.

In some ways, the PDO is similar, in Oct 1963 and 2018, you can have a negative PDO if the NE/NW Pacific are both similar relatively, despite different actual temps, but even so, the massive difference in heat off the East Coast has to have some kind of impact between the two years.

I'd love to have 1963-64 here, really I would - it's my coldest winter since 1892. There are pretty massive problems with it as analog, the AMO, PDO, volcanoes, the very cold water v. very warm water off the East Coast, the SOI, sea ice, QBO, etc. February 1964 was 10-15F below average (1951-2010 highs for basis) in the SW.

 

You seem to be making the assumption that analog = forecast, which isn't the case here. As I stated in the outlook, 1963 was the only year that met my threshold of sufficiently similarity for inclusion as an analog. However, that doesn't imply I'm projecting its sensible weather results directly onto this year's winter outlook. It's merely a guide. As one can see by my departure forecast, the temperature anomalies are MUCH more tempered compared to 1963, to account for the warmer globe, Agung, and expected less severe blocking in the NAO region. 

1963-63 finished with departures of -3 to -4 for DJF in much of the Northeast. I have around -1 for NYC for DJF -- substantially warmer.

[raindancewx]

It just seems there are so many years that are more similar than 1963. Oct and Nov both look a lot like 1986 and they have similar background states for instance. Last year, the years you mentioned were quite similar to Oct/Nov, so I was fairly confident you had the right idea, other than in TX. Same was true for Grit's ideas last year. But you don't really have that this year. Oct/Nov look almost opposite 1963 really, it's not even a magnitude thing which would be forgivable. I mean, 1963 is basically as warm as it gets for US Falls it isn't really similar at all.

For one thing, we have the warmest Oct SST on record in Nino 4 this year other than 2015. In 1963, it was way colder. This is the blend of the warmest Oct Nino 4 data in El Ninos for December, and the blend is not as warm as this year, its still 0.2C too cold, and that's even with a fairly cold 2009 to make the blend colder. It isn't that the correlation itself is overwhelming, but 2nd warmest + weak correlation still implies warmth to me for Dec. If you wanted the exact number for Nino 4, a blend of 2015, 2009, 2009 matches in October, but even that is still warm in the NE, as 2009 wasn't really cold in the NE. I think there is a case to be made for the middle of the US being cold in December, but I just don't see it for the NE.

Well...we'll see I guess.

[Isotherm]

It seems we're weighting variables differently for analog purposes. You appear to assign significant weight to occurent weather similarities in the preceding autumn, which I do not. I'm much more interested in comparing global pattern drivers and indices, which in my view, will prove more salutary for prognostication purposes. Along that vein, 1963 checked more of my boxes as far as analoging than any other year since 1950. 

[frd]

5 hours ago, Isotherm said:

My NAO, “Formula” which I developed several years ago and incorporates 4 main sub-components. Its retrospective success in forecasting the modality of the ensuing DJF NAO since 1950 has been 87%; and, since utilizing it prospectively, it has verified accurately in the past 4 winters as far as prognosticating the DJF NAO modality. The past several autumns, the NAO formula has strongly indicated a winter-time positive NAO. This year, for the first time since the beginning of this decade, the formula indicates that the NAO will average negative for the DJF winter season; not strongly so, but weakly negative to potentially moderately negative. Compared to the positive NAO dominance of the past several winters, it will be a material alteration.

Of interest today I see the new UKMET seasonal was issued, and to my eyes it seems to have gone to more of a -NAO look very it's previous update. Seems to echo your forecast of the NAO to a degree.

I wanted to say your NAO forecasts are remarkable, especially in view of how difficult, if not impossible that indice is to predict on a seaonal basis.  

I include this as well for reference : 

 

 

[weathafella]

Isotherm, that’s a nice write up!  Thanks for putting the work in.  I hope you’re right (suspect you are)!

[donsutherland1]

8 hours ago, Isotherm said:

Any comments or inquiries are appreciated!

 

Fantastic discussion, Isotherm.

My thinking is a lot like yours right now. I suspect that December will have an outcome pretty similar to what happened in 2002 as Atlantic blocking tries to take hold. A pause might occur in January as was the case then, before February finished very strongly.

Overall, I believe the predominant state of the teleconnections will be PDO+/EPO-/AO-. That's a great combination with a central Pacific-based El Niño event. I'm not sure about the NAO but note your research into that index. If it continues to prove accurate more often than not, it's a great breakthrough.

Having said that, I'm a bit more aggressive with the snowfall in the Middle Atlantic region (as posted in the November AmWx contest) for such cities as Washington and New York. I currently have NYC at 50".

Good luck with the forecast. You have shown skill and I expect that you will again do well.

[uncle W]

1963-64 had a weak to moderate el nino...QBO was slightly positive...solar was low...2018 is similar and it follows two weak la nina's...63-64 followed two weak negatives...I doubt December gets as cold as 1963...but it still could be below average...

 

 

[uncle W]

 

[Isotherm]

19 hours ago, weathafella said:

Isotherm, that’s a nice write up!  Thanks for putting the work in.  I hope you’re right (suspect you are)!

Thanks!

18 hours ago, donsutherland1 said:

Fantastic discussion, Isotherm.

My thinking is a lot like yours right now. I suspect that December will have an outcome pretty similar to what happened in 2002 as Atlantic blocking tries to take hold. A pause might occur in January as was the case then, before February finished very strongly.

Overall, I believe the predominant state of the teleconnections will be PDO+/EPO-/AO-. That's a great combination with a central Pacific-based El Niño event. I'm not sure about the NAO but note your research into that index. If it continues to prove accurate more often than not, it's a great breakthrough.

Having said that, I'm a bit more aggressive with the snowfall in the Middle Atlantic region (as posted in the November AmWx contest) for such cities as Washington and New York. I currently have NYC at 50".

Good luck with the forecast. You have shown skill and I expect that you will again do well.

 Thank you very much, Don. I hope my NAO formula proves useful in the years ahead. Re snowfall, if I bust, I expect that it will be on the low side. The numbers may be slightly conservative. 

[griteater]

Enjoyed the write-up Iso.  You continue to push the science forward, kudos.  Love the NAO predictor.  I spent more time in this arena with my outlook this year as well, looking for more clues.  If we do in fact see a 10mb SPV that is stronger than normal along with a solid -NAO, that would be quite the call.  Good luck and thanks for taking the time to post it.

[Isotherm]

On 11/11/2018 at 4:54 PM, frd said:

Of interest today I see the new UKMET seasonal was issued, and to my eyes it seems to have gone to more of a -NAO look very it's previous update. Seems to echo your forecast of the NAO to a degree.

I wanted to say your NAO forecasts are remarkable, especially in view of how difficult, if not impossible that indice is to predict on a seaonal basis.  

I include this as well for reference : 

 

 

 

1 hour ago, griteater said:

Enjoyed the write-up Iso.  You continue to push the science forward, kudos.  Love the NAO predictor.  I spent more time in this arena with my outlook this year as well, looking for more clues.  If we do in fact see a 10mb SPV that is stronger than normal along with a solid -NAO, that would be quite the call.  Good luck and thanks for taking the time to post it.

 

 

Thank you both for the comments!

[40/70 Benchmark]

1963-1964 is one of my top analogs, as well...agreed.

Great job....similar to my outlook, as usual....though I think I am a bit more hung ho on a HECS.

[40/70 Benchmark]

3 hours ago, Isotherm said:

 

 

 

Thank you both for the comments!

Your outlooks are the best that I have ever seen, and the reward at the end of my research is reading your's.

Thank you.

[40/70 Benchmark]

7 hours ago, Isotherm said:

Thanks!

 Thank you very much, Don. I hope my NAO formula proves useful in the years ahead. Re snowfall, if I bust, I expect that it will be on the low side. The numbers may be slightly conservative. 

Agree..especially across SNE and maybe NYC.

[Isotherm]

11 hours ago, 40/70 Benchmark said:

1963-1964 is one of my top analogs, as well...agreed.

Great job....similar to my outlook, as usual....though I think I am a bit more hung ho on a HECS.

 

11 hours ago, 40/70 Benchmark said:

Your outlooks are the best that I have ever seen, and the reward at the end of my research is reading your's.

Thank you.

 

Very much appreciate that, Ray - thank you for the great compliment! It looks like you've produced an exceedingly fastidious disquisition there - I have not had an opportunity to read it yet, but will provide feedback after doing so. On first glance, it appears our conclusions are quite similar which is good to see. I believe strongly that the NAO will average negative for the first time in quite awhile. Latest data continues to give credence to the colder December.

[Met1985]

Isotherm another excellent winter write up. Thank you for the info and well thought out explanation for your basis.

[LibertyBell]

On 11/11/2018 at 12:04 PM, nzucker said:

Great outlook, Isotherm...in line with much of what I've read here. What do you think of 04-05 as an analog, as well? Or 68-69/69-70?

For snowfall I think we have to remember that we are in a much much wetter climate now than we were in the 60s or 70s for that matter.  Looking at the past decade or two massive uptick in precipitation and big precipitation events I think that while using them to describe general patterns may be correct, that actual snowfall amounts could be much higher, in line with our new normals.

[Isotherm]

On 11/15/2018 at 10:57 PM, Met1985 said:

Isotherm another excellent winter write up. Thank you for the info and well thought out explanation for your basis.

 

 

Thank you!

[Isotherm]

1. Near-term tropospheric precursor pattern will continue to enhance vertically propagating wave-1 energy which will peak at the z10 vortex in about 10-12 days.

 

2. Medium term burst of wave-2 energy is likely to initiate in early December, peaking close to December 10th. This burst will not be as intense as wave-1, and thus, while the concerted assault is unlikely to destroy the upper stratospheric vortex, it will weaken in substantially. This notion is reflected in the medium term z10/60N zonal wind forecast, redolent of rapid deceleration by the second week of December

 

3. The Brewer-Dobson Circulation continues stronger than normal w/ enhanced ozone transport into polar regions

 

4. MJO wave and its concomitant udiv signal will propagate ewd through the EPAC, Atlantic, and toward Africa by D7 (reflective of p8-1 passage). The rossby wave dispersion attendant will act adjunctively in northern stream deceleration and aid in the incipient HLB signal.

 

5. The synergistic forcing of the above quite nicely coincide on the December 8th-10th period for the rather rapid redevelopment of higher than normal geopotential heights in the east based NAO region, which will gradually retrogress in the second week of the month.

 

6. Angular momentum removal in the sub-tropics via the MJO and GWO progression into suppressed AAM octants (as indicated by udiv propagation into Indian Ocean) will ultimately lead to a jet retraction event by week 2, following this current jet extension. The present negative FT will eventually manifest in the mid-latitude pattern in about 10 days. Implications are that the Pacific wave-train and jet configuration will acquire a somewhat Nina-esque appearance in the first 10 days of December. Blocking will be developing over the NAO/AO domains contemporaneously with a wavier/Aleutian ridge regime in the Pacific in the December 1st-10th period. Colder weather will return to the Northeast in the means by the second week of December due to the amelioration in Arctic/Atlantic signalling; however, the Pacific will be less auspicious initially.

 

7. Once the intraseasonal forcing signal fades -- which, I expect the MJO will progress to phase 2, thereupon, weakening into the null phase by the second week of December -- the predominance of the lower frequency forcing signal will reemerge, and about one week following, I anticipate the Aleutian Low/E GOA High Nino-esque regime to return. This -- by my estimation -- will occur sometime around the middle point of December +/- a few days. 

 

8. In light of the above, the large scale pattern indicators are such that: a) December 1st-5th is likely unpropitious in the means, b) December 6th-12th - becomes more conducive as NAO/AO begins to respond to vertical wave driving and tropical forcing c) middle of December onward through the second half of the month (the cycle probably lasts until early January) becomes even more favorable as the Pacific rearranges and resumes a more Nino-esque structure

 

9. By extension, I anticipate angular momentum in the sub-tropics will increase as we approach mid December. Countervailing easterly momentum deposits will likewise increase in the mid latitudes and reinvigorate blocking.

 

 

To me, I'm not expecting the low-AAM mini cycle (As Tam refers) to be destructive to Atlantic/Arctic blocking prospects. It will result in a Nina-esque Pacific pattern, possibly for 10 or 12 days, before the interseasonal signal returns and MJO forcing is dampened. 

 

By the time the large scale variables reshuffle again, i.e., possibly a more robust sub-tropical momentum loss, we should be into January and thus would coincide with anticipated pattern break period.

 

Overall, everything is going as planned so far. I think the "best" part of the month for snow potential is toward mid December and onward, which is more congruous w/ improved climatology anyway. However, "best" potential doesn't preclude a threat prior. I wouldn't be surprised to see something in the 7th-11th period.

[frd]

12 hours ago, Isotherm said:

Overall, everything is going as planned so far. I think the "best" part of the month for snow potential is toward mid December and onward, which is more congruous w/ improved climatology anyway. However, "best" potential doesn't preclude a threat prior. I wouldn't be surprised to see something in the 7th-11th period.

Isotherm, great update, thanks !

If I may ask a quick question, recent modeling in the last 24 hours, ie., EPS and even the GEFS , also the Euro weeklies, have some folks concerned about December as a whole, ( warm vs cold )  with weakening of the -EPO and changes over Alaska. 

Is this to be expected and it seems that the models have been having a hard time recently. 

So, I guess what I am asking is don't worry about the models ? 

The colder/ snowier second half of December is still a outcome to consider ? 

[Isotherm]

On 11/24/2018 at 11:14 AM, frd said:

Isotherm, great update, thanks !

If I may ask a quick question, recent modeling in the last 24 hours, ie., EPS and even the GEFS , also the Euro weeklies, have some folks concerned about December as a whole, ( warm vs cold )  with weakening of the -EPO and changes over Alaska. 

Is this to be expected and it seems that the models have been having a hard time recently. 

So, I guess what I am asking is don't worry about the models ? 

The colder/ snowier second half of December is still a outcome to consider ? 

 

Thank you, frd. And yes, I wouldn't be concerned with the weeklies, and high model volatility is expected, especially in the Atlantic. Note the large error bars on ensemble means for the NAO/AO D10-15, similar to what we experienced in November. The vertically propagating wave energy via wave 1 initially with some subsequent augment from wave 2 will reinvigorate the -NAO in the second week of November. The pattern progged is actually similar to what I forecasted for December w/ PAC NW-NE US colder than normal pattern courtesy of a -NAO and Nina-esque Pacific/Aleutian ridge. The Pacific will begin to transition more Nino-esque in mid month.

 

 

 

[frd]

1 hour ago, Isotherm said:

Thank you, frd. And yes, I wouldn't be concerned with the weeklies, and high model volatility is expected, especially in the Atlantic. Note the large error bars on ensemble means for the NAO/AO D10-15, similar to what we experienced in November. The vertically propagating wave energy via wave 1 initially with some subsequent augment from wave 2 will reinvigorate the -NAO in the second week of November. The pattern progged is actually similar to what I forecasted for December w/ PAC NW-NE US colder than normal pattern courtesy of a -NAO and Nina-esque Pacific/Aleutian ridge. The Pacific will begin to transition more Nino-esque in mid month.

Thanks Isotherm! 

[Isotherm]

When one steps back and poses the inquiry: if I were to remove the modelled EPS z500 progression from the equation, and the GEFS for that matter, how would I anticipate the hemispheric/global pattern to progress in light of the apposite physical forcing mechanisms; namely, AAM tendency progression, GWO/MJO, among other factors, etc.? For those who believe a protracted pattern break-down is ahead, ask yourself: am I thinking this principally because a volatile snapshot on the day 15 EPS suggests so, or is the belief grounded in reasons separate from modeled z500 pattern? 

 

Given the relevant factors to which I allude, I wouldn't alter anything regarding my pattern post several days ago. The BDC continues to intensify, quite strongly actually, as ozone transport increases; angular momentum is falling, and the MJO will cycle through 8-1-2, thereafter becoming incoherent and dampened by the resumption of low-frequency forcing which will reinvigorate the Nino-esque WGOAK/Aleutian Low signal. The follow-up wave 2 hit to which I've mentioned in past days is now being detected on the guidance; notice the progged wave 2 geopotential heights forecasted to increase rapidly by day 10, concordant with the auspicious tropospheric precursor regime. So we have a potent wave-1 peaking now, and will follow up w/ subsequent wave 2 around December 10th. Thus, again as noted in the post several days ago, while the Pacific jet retracts, reflective of the ephemeral suppression of angular momentum, the Arctic/Atlantic signal will countervail with a prevalence of higher geo-potential heights. This pattern will be imprinted most notably in the December 10th-16th period, wherein the Pacific has lower than normal favorability while contemporaneously, the Arctic/Atlantic have higher than normal favorability. The result will be a muted, short-term warm-up in the Northeastern US. The Pacific thereafter, improves, in concert with the weaker than normal tropospheric vortex, as we move into the second half of December. The snap-shot one sees at the end of guidance, once it comes into view, will be more accurately reflected as the short term alteration that it is. I will not use the words "Relaxation" or "pattern break" because those are subjective, imprecise parlance depending upon one's viewpoint. But more accurately, the Pacific will temporarily worsen while the Atlantic improves (Dec 8th-15th), followed by an improving Pacific and continued conducive Arctic/Atl. 

 

The Euro guidance is over-weighting and too aggressive with the MJO impact.

 

 

Below -- the 00z ECMWF and 12z ECMWF valid 00z December 7th. Notice the significant alterations in the NAO domain especially. There are changes in the NPAC, too. This is what I'm referring to regarding the undermodeled Arctic/Atl response in the extended.

 

 

 

 

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