My Winter Outlook 2016-17

[Isotherm]

10^th Annual Winter Outlook; For previous outlooks see the following:  http://www.lightinthestorm.com/

Overview of Preset Conditions

The atmospheric/oceanic state in which we find ourselves right now is multifactorial. The super El Nino event last winter aided in inducing a variety of atmospheric tendencies: surged global temperatures such that the ensuing year features an inordinate amount of residual northern hemispheric heat, largely as a function of the excessive latent heat release via prior tropical forcing; the additional, significant injection of westerly atmospheric angular momentum (corresponding to the excessive forcing) precluded the descent of easterly stratospheric winds, thus resetting the QBO into a condition of predominately high westerly shear stress. The enormous latitudinal thermal gradient induced largely by super Nino conditions drove the stratospheric vortex into an insurmountably potent state; however, upon its collapse last spring, the vortex has remained unprecedentedly weak. One may hypothesize that this implicates a repressed vortex status for the ensuing winter, but exogenous indicators suggest otherwise. The ENSO condition is cold-neutral bordering on weak La Nina, which will likely persist for the duration of the winter. SST’s and tropical forcing are reflective of a classic Nina-esque walker cell orientation. It will be important to ascertain the likely modalities and proclivities of high latitude indices, in light of the lesser ENSO forcing (though this isn’t entirely the case). The anticipated behavior of the various global oscillations and their concomitant z500 results will form the basis of this outlook.

 

Examination of Integral Factors

• • ENSO status is cold-neutral to weak La Nina. The vast majority of model guidance maintains the cold-neutral/weak La Nina regime throughout the winter. Whether the resultant situation is weak Nina or cold-neutral, the z500 and sensible weather outcome disparities would be immaterial.

• The oceanic-atmospheric coupling has been relatively weak thus far. SOI daily values have been near neutral or even negative at times – in concert with a strongly heightened angular momentum state – the resultant regime has more closely projected on the climatological El Nino z500 pattern rather than La Nina (at least in the Pacific). The extended Pacific jet is a consequence, with a flood of warm, maritime air into Canada. This regime will experience significant alterations over the coming weeks. The atmospheric coupling response will manifest more robustly as Indonesian/Maritime tropical forcing and rapidly decreasing angular momentum (that is, a removal of atmospheric momentum from the energy budget), will eventually cause the Pacific jet to retract. The more classic low-mid latitude Aleutian ridging and concomitant troughing in the eastern Gulf of Alaska and Western US will develop by late November. The momentum will decrease to such an extent that lower than normal geopotential heights will dominate the northeast Pacific. Inter-seasonal low frequency tropical forcing should congregate in the W Pacific/Indonesian region thus winter – principally within the “domain space” of MJO phases 4-5-6. Large scale subsidence should dominate the dateline and Western Indian Ocean regions, with potentially a secondary, less potent upper divergence area near northern South America. So far this autumn, the dateline eastward in the Pacific – both tropically and sub-tropically – has been largely devoid of 200hpa negative velocity potential, while the inverse has been true to the west of the dateline. All of the aforementioned has implications insofar as Rossby wave driving and mid latitude responses.

• Tropospheric boundary layer conditions thus autumn have been suggestive of a highly perturbed vortex and would – in a vacuum – portend a weak winter stratospheric (and consequently tropospheric) vortex. Both snow cover extent and advance has been quite impressive when juxtaposed with the majority of seasons over the previous 30 years. The resultant Siberian high development and concomitant Taymyr geopotential height anomalies have been robust; namely, higher than normal geopotential heights have generally persisted in that region. The development of certain tropospheric patterns is crucial as often times they will project strongly onto climatological wave 1 and wave 2. The significance of this is that a tropospheric pattern which constructively interferes with vertical wave driving will converge and perturb the vortex.

• As noted prior, the westerly shear stress has persisted in the stratosphere. The westerly QBO strengthened (became more positive over the past couple months. The ensuing winter state will be strongly positive, becoming more moderate late, and likely reversing into the negative state (finally) by spring 2017. Solar conditions have been variable but largely depressed. 10.7cm solar flux values are very low; generally under 800. This will continue or decrease during the winter. Solar minimum with respect to cycle 25 will occur between 2018-2020. Geomagnetic activity (proxy: AP index) min-max cycles are typically lagging that of flux and sunspot numbers. Geomagnetic parameters suggested a decline this summer, but it has been rather active again this autumn.

 

• Precursor sea surface temperatures in the Atlantic Ocean were analyzed for specific trends/anomalies which could be relevant insofar as NAO modality trends.
• Research has demonstrated that there might be a tendency for the development of poleward Aleutian mid-level ridges under a cold ENSO/+QBO regime. The correlation is a strong one. However, I have noted disparities in the recent autumn/current pattern, in terms of atmospheric behavior and forcing which do not project onto the +QBO/-ENSO z500 result. This casts doubt on the notion for a persistent poleward ridge in the Pacific.
• The PDO has been in a predominately positive phase, though declining over recent weeks. The Gulf of Alaska has cooled dramatically due to the extended jet and low geopotential height anomalies. However, the forcing emanating from this region is immaterial, and provides positive feedback at maximum in terms of the ensuing pattern. A more interesting propensity has been the latitudinal sea surface temperature gradient with very warm waters running horizontally across the sub-tropical Pacific and cold waters immediately to the north. This will add momentum to the Pacific jet and aid in precluding, at least in a protracted fashion, significant poleward blockiness. However, the westerly shear stress via the QBO and its connection to forcing modulation may result in a period of such poleward blockiness.
• The AMO has been mostly positive with the western Atlantic warmer than normal. The feedback generated from this will be insignificant compared to the Pacific, but it could aid in intensifying extra-tropical cyclones near the East Coast. Additional available energy increases the likelihood for a reversal in the predominate precipitation pattern from dry to wet across portions of the Northeastern US.
• The sum of methodologies has included analysis of exogenous indicators such as solar, geomagnetic trends/behavior, stratospheric winds, and internal variability of the PDO, AMO, ENSO, tropical forcing, NAO, AO, EPO, PNA (including a relationship I’ve examined which – retrospectively - correctly predicted the NAO modality in 86% of seasons since 1950); prior years have been juxtaposed with the present/recent pattern in attempt to ascertain an extrapolation of this year’s regime. The totality of indicators yields the following prognostication.

Indicator Outlook for DJF mean:

PDO: Near neutral to slightly positive

AMO: Positive

EPO: Positive average; transient periods of negative

NAO: Positive (potentially strongly at times); one month of negative is possible

AO: Near-neutral; favoring early winter for the negative periods, becoming more positive

ENSO: Cold neutral to weak La Nina

PNA: Near neutral; periods of both positive and negative

AAM: Predominately negative/easterly

QBO: Strongly becoming moderately positive/westerly

Anticipated Progression:

In examination of prior years, there were innumerable disparities which made it exceedingly difficult to select analog years. However, the totality of indicators studied yielded the following for closest years:

Primary analog: 1973-74

Secondary analog: 1975-76

Tertiary analog: 1999-2000

There were some notable similarities to 2011-12 as well, though insufficient to utilize it as a higher echelon analog. One will note that all three of the analog years were actually moderate to strong La Nina’s, which differs from the current ENSO state. However, there were numerous other (arguably more important in my view) strongly similar variables. I anticipate a suppressed AAM state, a strengthening polar vortex, La Nina-esque walker and Hadley cell behavior, tropical forcing, which more closely reflects the –QBO/-ENSO years rather than the +QBO/-ENSO years.

December should begin with a neutral to negative tropospheric and stratospheric AO due to the exceptional tropo-stratospheric perturbation. The Pacific will largely be unfavorable with a positive EPO and low geopotential heights amplifying in the Rockies/W US, indicative of a –AAM regime. The NAO could potentially trend negative for a time, combatting the poor Pacific, enabling some troughiness to develop in the C/E US. Many of the analog years featured one month of colder than normal temperatures with more conducive z500 regime. 1975-76 featured a very cold January, and 1973-74 a colder than normal February, and 1999-2000 a colder than normal January. However, there are a number of adjustments that should be performed. There is significantly greater global/hemispheric warmth compared to the 1970s analogs due to the post super Nino conditions. Secondly, the state of the stratospheric vortex is very weak right now, and projected to remain that way through November. There’s a high correlation between November and December outcomes. Thus, I think December is the month most likely to feature high latitude blocking. However, it must be sufficiently significant, especially in the NAO domain to mute +EPO induced Western troughiness. The Southeast ridge will be attempting to burgeon northward. Thus, even early winter, I am conflicted, but given signaling and analogs, December should be near normal temperature wise in the Northeast corridor, with possibly slightly above or slightly below temps. Given the precursor factors and analogs, I expect the precipitation pattern to become increasingly wet across the northern tier and Northeast. I don’t believe it will be sufficient to reverse the drought in the Northeast, but a normal or wetter than normal winter is likely with a warm W Atlantic an active Pacific stream.

January will become increasingly warm with a rapidly intensifying vortex. In the Pacific, the continuance of a low-latitude Aleutian ridge with low heights across Alaska/NE Pacific and NW US should persist. However, periods of poleward Aleutian ridging are possible, occasionally suppressing the Eastern ridge and providing wintry threats. The vast majority of the time, the Atlantic should be unfavorable. Transient blocks are not out of the question. January should be warmer than normal for most of the South and East, with colder weather confined to the Rockies and northern tier.

February should look like a classic Nina-esque regime at z500 and likely in the low levels. An active jet with numerous snow threats across the Mid-west and northern New England should dominate. A continued unfavorable Atlantic and increasingly unfavorable Arctic, coupled with an indeterminate NPAC state could yield occasionally mild to record warm temperatures in the Eastern US. Snowfall will be highly dependent upon transient blocks and baroclinic zone suppression via poleward NPAC ridging. Overall, the month looks warmer than January. Cold weather dominates the N Plains.

In sum, this winter will be colder than last year (not surprising given the record warmth), but warmer than normal across the South and most of the East. Colder than normal departures will be found across the NW US/Rockies and into the Mid-west. The most likely period for a severely cold outbreak, including the East is between December 20^th-January 15^th. If a coupling can occur between high latitude blocking and poleward Pacific ridging, the wintertime source region of cold can expand southeastward. All three analogs featured a period of colder than normal weather in the East. For the most part, the East Coast will be battling milder weather. Precip should be normal to above from the Mid-Atlantic northward, and snowfall normal to below from the Mid-Atlantic southward. There should be more frequent light-mod snows across the North with fewer large events. Bigger events are possible in the Lakes/Interior Northeast with intensifying inland lows.

 

Outlook Temperatures:

For the Local New York City Region:

Dec-Jan-Feb Temperature Departure Outlook: +1 to +2; Warmer than normal

[Expected evolution is near normal December, warmer than normal January, and warmer than normal February].

Dec-Jan-Feb Precipitation Departure Outlook: Near normal (possibly above to the north)

Nov-Mar Snowfall Departure Outlook: Near normal to the north of NYC and below normal from NYC southward

Snowfall guesses for various CONUS locations:

Burlington, VT: 90-100”

Boston: 40-45”

New York City: 21-26”

Philadelphia: 13-18”

Baltimore: 10-15”

Washington DC: 9-14”

Richmond, VA: 5-10”

Raleigh, NC: 0-5”

Atlanta, GA: <2”

Houston, TX: <1”

Chicago, IL: 45-50”

Denver, CO: 60-65”

Seattle, WA: 5-10”

 

 

 

Analogs:

 

 

Primary analog z500:

 

 

 

 

 

[michsnowfreak]

Good analysis. Whether its what i want to hear or dont want to hear, i always put more value in the outlooks based on reasoning and not gut feeling. A stormy winter looking likely in the Great Lakes.

[Met1985]

Great write up! I hope your wrong lol.

[WEATHERBUFF]

My thinking also. I think conditions favor areas further north and a little above temps won't hurt there but may hamper areas from NYC south.

[ldub23]

I hope you are right.

[griteater]

Iso - excellent work as usual.  You did a good job of describing how you see the winter playing out.  I enjoyed the read and thanks for posting.

[OHweather]

Awesome job, Isothem. Although perhaps a little bit unconventional, I really enjoyed that you didn't just use a SST analog method and copy/paste the results into your forecast.

You went with a warmer look overall than I did, but I can't find strong reasons to disagree with your reasoning and outlook. I think this winter will be a very interesting case study on the stratospheric PV, as early and persistent attacks have kept the vortex very weak thus far, with a potential split coming up again soon. As I mentioned in my outlook, some weak fall PVs (especially in +QBO winters) ended up recovering during the winter; this one looks to remain weak into December. I suspect that some of the upward transfer that has been weakening the PV has to do with the Nino-like north Pac low that has been rather persistent for the last several weeks, and if that area shifts to a more typical Nina look moving forward (which you seem to suggest happening, and as some of the longer range models are hinting at) the upward transfer into the strat may weaken, allowing the vortex a chance to re-intensify for January and February. The tropospheric indications, especially the SAI, which do suggest a -AO/weak strat PV this winter, typically go for the vortex weakening later in winter. It will be interesting to see if those theories hold, or if the Pacific pattern potentially becoming less favorable, along with the +QBO background state, do allow for the PV to intensify through January and February. It will be interesting to see what "wins out" if you will this winter.

I also think your comments about the N. Pac and lack of ridging that you expect are interesting. Typically, +PDO, +QBO, and +AMO La Nina winters (especially the La Nina/+QBO combo) favor a more poleward ridge there, as you said. It will be interesting to see if the cooling of the waters there that has recently occurred does contribute to a stronger jet there later in winter; my one thought is the SST gradient is a little far south, close to 30N or so, which is a little farther south of where you'd expect the polar jet to be sitting in the Pacific in a La Nina year...meaning it will be interesting to see if there is the SST gradient enhancement to the jet as you mentioned. Jets are driven by temp gradients, so it's an interesting idea. Although the QBO is still positive, do you think that perhaps the current weak state of the PV may weaken the correlation for more poleward Pac ridging? Or do you just think the hemispheric pattern as a whole just won't support persistent ridging there for the other reasons you mentioned?

All in all, although we came to different conclusions in our outlooks, I can't say your reasoning is wrong, because it is backed up by solid meteorology and you have a track record for producing accurate winter outlooks. I think it will be very interesting to see how some of the "conflicting" signals pan out during the winter. Verbatim, your forecast probably wouldn't be a snowless disaster IMBY, so I guess I'll take it either way

[Isotherm]

22 hours ago, OHweather said:

Awesome job, Isothem. Although perhaps a little bit unconventional, I really enjoyed that you didn't just use a SST analog method and copy/paste the results into your forecast.

You went with a warmer look overall than I did, but I can't find strong reasons to disagree with your reasoning and outlook. I think this winter will be a very interesting case study on the stratospheric PV, as early and persistent attacks have kept the vortex very weak thus far, with a potential split coming up again soon. As I mentioned in my outlook, some weak fall PVs (especially in +QBO winters) ended up recovering during the winter; this one looks to remain weak into December. I suspect that some of the upward transfer that has been weakening the PV has to do with the Nino-like north Pac low that has been rather persistent for the last several weeks, and if that area shifts to a more typical Nina look moving forward (which you seem to suggest happening, and as some of the longer range models are hinting at) the upward transfer into the strat may weaken, allowing the vortex a chance to re-intensify for January and February. The tropospheric indications, especially the SAI, which do suggest a -AO/weak strat PV this winter, typically go for the vortex weakening later in winter. It will be interesting to see if those theories hold, or if the Pacific pattern potentially becoming less favorable, along with the +QBO background state, do allow for the PV to intensify through January and February. It will be interesting to see what "wins out" if you will this winter.

I also think your comments about the N. Pac and lack of ridging that you expect are interesting. Typically, +PDO, +QBO, and +AMO La Nina winters (especially the La Nina/+QBO combo) favor a more poleward ridge there, as you said. It will be interesting to see if the cooling of the waters there that has recently occurred does contribute to a stronger jet there later in winter; my one thought is the SST gradient is a little far south, close to 30N or so, which is a little farther south of where you'd expect the polar jet to be sitting in the Pacific in a La Nina year...meaning it will be interesting to see if there is the SST gradient enhancement to the jet as you mentioned. Jets are driven by temp gradients, so it's an interesting idea. Although the QBO is still positive, do you think that perhaps the current weak state of the PV may weaken the correlation for more poleward Pac ridging? Or do you just think the hemispheric pattern as a whole just won't support persistent ridging there for the other reasons you mentioned?

All in all, although we came to different conclusions in our outlooks, I can't say your reasoning is wrong, because it is backed up by solid meteorology and you have a track record for producing accurate winter outlooks. I think it will be very interesting to see how some of the "conflicting" signals pan out during the winter. Verbatim, your forecast probably wouldn't be a snowless disaster IMBY, so I guess I'll take it either way

 

 

Thank you everyone for the comments! 

OHweather - thanks for your detailed response! I'm happy that you noticed that the forecast methodology was slightly unconventional. To address your inquiries -- my research indicated that there is a propensity for VI following autumn weak vorticies. If we experience a sudden stratospheric warming event later this month [or near zonal wind reversal], there aren't many examples. However, Nov 30 1958 featured a displacement event, and the AO was negative for Dec and Jan, with strongly positive Feb AO; however, the QBO was in an easterly phase. Early Dec 1981 displaced, with a -AO Dec/Jan, and +AO Feb, but again, easterly QBO. The only Nov-early Dec warming event I can find under a +QBO regime was early Dec 1987, though it was Nino, so not a great comparison. The AO in that particular season was negative Dec, then jumped positive in Jan, before heading negative again in Feb. The tropospheric boundary layer indicators are fairly impressive this year, but other exogenous ones as mentioned are poor. My thinking is December could be pretty blocky as I noted in the forecast w/ a -AO and -NAO, and best case scenario, we're able to stretch the blocky period through early/mid January before we break down. Even if we were to achieve a SSW in late November, the typical 40-60 day rule would support the notion of an early/mid January period reversal. Re the Pacific, when I was examining the tropical forcing pattern this autumn, the behavior actually seems to align more closely with the forcing tendencies of autumns preceding -QBO/-ENSO winters with low latitude Aleutian ridging. This seems to be an important factor from what I've researched. It's possible we see changes during the winter which yield a more conducive pattern for poleward ridging. And yeah - I think that hypothesis could have merit as well - namely, the stratosphere and troposphere being rather decoupled right now. There were 3 separate indicators I monitor for the NAO (one of which has worked 85% of winters retrospectively to 1950), and they were suggestive of a +NAO mean for DJF. So I would be rather surprised if we see a -NAO DJF. For the AO, the indicators I use were split down the middle, with some suggesting negative, and others positive. So tough call, which is why I'm erring neutral, with early winter favored negative.

Another curveball is some of the latest seasonal modelling seems to be suggesting a colder mid rather than early winter, which I think, contradicts current stratospheric signals. Not too concerned at this point; I didn't use seasonal modelling at all for my outlook and don't really have much faith in them.

And yeah, your area should do much better this year (hopefully)! Your outlook had very robust scientific reasoning as well, and there's a part of me that's hoping yours will be closer to reality!  Good luck to us both! 

[Chinook]

On 11/12/2016 at 3:28 PM, Isotherm said:

significant injection of westerly atmospheric angular momentum (corresponding to the excessive forcing) precluded the descent of easterly stratospheric winds, thus resetting the QBO into a condition of predominately high westerly shear stress. The enormous latitudinal thermal gradient induced largely by super Nino conditions drove the stratospheric vortex into an insurmountably potent state; however, upon its collapse last spring, the vortex has remained unprecedentedly weak.

I had wondered what had made the QBO rebound this summer to positive (westerlies) when it should have gone into negative values.

[Isotherm]

VERIFICATION:

 

FORECASTED:

 

 

 

 

 

 

ACTUAL:

 

DJF 500mb pattern:

DJF Temperature anomalies:

DJF Precipitation departures:

Central Park DJF temperature departure: +4.1

Most of the tri-state area finished between +3.5 and +4.2 for temperature departures.

Snowfall: 30.2″

Snowfall Forecast versus actual totals:

Burlington, VT: 90-100” 91”

Boston: 40-45” 45.8”

New York City: 21-26” 30.2”

Philadelphia: 13-18” 15”

Baltimore: 10-15” 2.9”

Washington DC: 9-14” 3.4”

Richmond, VA: 5-10” 7.1”

Raleigh, NC: 0-5” 0.8”

Atlanta, GA: <2” T Houston, TX: <1” 0 Chicago, IL: 45-50” 26.1” Denver, CO: 60-65” 19.3” Seattle, WA: 5-10” 11.2”
VERIFICATION DISCUSSION:

Based upon the forecast maps from late November, the z500 pattern quite closely paralleled the outlook expectations. Troughiness preferentially favored the NW United States while concurrently, ridging predominated the Eastern US. Occasional poleward ridging near Alaska/Dateline permitted periodic cold blasts into the United States, but for the most part, the Pacific remained unfavorable. Additionally, the NAO was strongly positive as anticipated, with a largely inauspicious AO regime as well (both were positive).

In terms of the sensible weather, December verified as the coldest month of the winter with slightly warmer than normal temperatures in the East as forecasted, with January and February featuring well above normal temperatures.

Dryness dominated the South and East while a wetter than normal preferentially favored the West and northern tier.

Snowfall was very close to reality, with below to well below normal snowfall from 40N southward, and near or above normal snowfall from NYC northward. The slight flaw here was that the above normal snowfall extended a bit further south than expected into portions of the NYC area/Long Island. Furthermore, DCA/BWI area featured even less snowfall than forecast, and Denver into portions of the Mid-west (Chicago) received very little snow relative to normal. Seattle’s totals were close to forecasted, as were totals in the Southeast US and New England.

Overall, considering the lead time of the long range forecast and the nature of the record warmth in January and February, the outlook for solidly warmer than normal temperature departures across the vast majority of the United States worked very well in my opinion. Hindsight is 20/20, and certainly I would have gone even warmer, but given some conflicting signals (a few suggestive of cold) last autumn, the magnitude of the forecasted warmth was slightly tempered. Even still, the general ideas and progression verified, and this winter forecast will be considered a success. This will bring the long range success rate up to 80% since initiation of long range summer/winter outlooks in 2006.

Overall Winter 2016-17 Grade: A-

[binovc]

Great forecast, but an "A", thats 100%

[nzucker]

19 hours ago, binovc said:

Great forecast, but an "A", thats 100%

Well, he did miss the magnitude of the warmth, and he also had the Great Lakes snowier than normal which didn't verify. Additionally, the NYC metro finished with above average snowfall, a continuation of the warm, snowy pattern of 2015-16.

I think in today's climate (warm background conditions), it pays to go very warm in non blocking patterns. With global temps running 1C above the 1950-1980 mean, our winters should be about 2C above that mean. Also, we have not seen a -NAO since March 2013, so that limits any cold in the East.

Isotherm, the biggest disappointment for me this winter was how quickly the favorable SSW/warm strat conditions in early Nov faded. Although the pattern was decent from Nov 20-Dec 20 with a moderate snowfall 12/17 and a significant cold shot, it quickly evaporated and Dec 20-31 torched. December had way more potential. Also, the models teased us with a -NAO induced cold pattern in the 1/5-1/20 period, the one PB hyped, but then backed off. 

Why do you think we can no longer see a sustained NAO block? Any chance that "comes back" next winter?

[griteater]

Isotherm - you had one of the best performing outlooks I've seen for this winter.  Excellent job on the 500mb pattern prediction. 

[Isotherm]

On 3/19/2017 at 4:54 PM, binovc said:

Great forecast, but an "A", thats 100%

 

7 hours ago, nzucker said:

Well, he did miss the magnitude of the warmth, and he also had the Great Lakes snowier than normal which didn't verify. Additionally, the NYC metro finished with above average snowfall, a continuation of the warm, snowy pattern of 2015-16.

I think in today's climate (warm background conditions), it pays to go very warm in non blocking patterns. With global temps running 1C above the 1950-1980 mean, our winters should be about 2C above that mean. Also, we have not seen a -NAO since March 2013, so that limits any cold in the East.

Isotherm, the biggest disappointment for me this winter was how quickly the favorable SSW/warm strat conditions in early Nov faded. Although the pattern was decent from Nov 20-Dec 20 with a moderate snowfall 12/17 and a significant cold shot, it quickly evaporated and Dec 20-31 torched. December had way more potential. Also, the models teased us with a -NAO induced cold pattern in the 1/5-1/20 period, the one PB hyped, but then backed off. 

Why do you think we can no longer see a sustained NAO block? Any chance that "comes back" next winter?

 

4 hours ago, griteater said:

Isotherm - you had one of the best performing outlooks I've seen for this winter.  Excellent job on the 500mb pattern prediction. 

 

 

Thank you very much for the kind words guys. Zucker - I agree. I did expect that the SSW effects would dissipate rather rapidly but it was still disappointing. As you know, probabilities are such that simply because we have experienced a stretch of +NAO doesn't increase the odds that next winter will be -NAO (independent / dissociated events). I am conflicted right now about next winter but it is very early. Additionally, if I say too much, I would divulge some of my methodology.

[nzucker]

12 hours ago, Isotherm said:

 

Thank you very much for the kind words guys. Zucker - I agree. I did expect that the SSW effects would dissipate rather rapidly but it was still disappointing. As you know, probabilities are such that simply because we have experienced a stretch of +NAO doesn't increase the odds that next winter will be -NAO (independent / dissociated events). I am conflicted right now about next winter but it is very early. Additionally, if I say too much, I would divulge some of my methodology.

BTW I was just pointing out why you didn't give yourself an A+; overall your forecast was excellent. Where you missed you didn't miss by much. Snowfall largely comes down to chance, and NYC was fortunate to benefit from the brief interludes of cold that did exist in a furnace winter.

The SSW came too early and was too short-lived for NYC metro. Interior areas had 12+ with the Nov 20th storm, but climo is just not supportive of coastal snowfall at that point; we got a dusting after heavy rain with temps in the 40s. The 12/17 storm took a poor track and changed to rain after a 4-6" front-end dump. So we largely missed the two chances bequeathed us by the strat warming/PV split. Had it happened a month later, very different story.

I also think the warm background conditions from the 2015-16 Super El Nino made an impact. 500mb heights were consistently higher than average between the 30th and 40th parallel; the flow was perennially compressed between these latitudes. The record warmth in FL proves this. A similar phenomeon happened after the 97-98 Super Nino with very little cold air the following 98-99 winter (until March, ironically).

Are global temps going to spike a lot with the upcoming El Nino? Could we be dealing with the same warm background conditions again? Also, could we have the favorable weak +ENSO/-QBO/low solar combo for Winter 17-18? Thoughts?

[OHweather]

Just wanted to say that this was a fantastic forecast!  I'm still sort of shocked over how much FEB blew away the previous warmest FEB on record here in Cleveland.  I'm hoping for a colder winter coming up.

[Isotherm]

20 hours ago, OHweather said:

Just wanted to say that this was a fantastic forecast!  I'm still sort of shocked over how much FEB blew away the previous warmest FEB on record here in Cleveland.  I'm hoping for a colder winter coming up.

 

Thanks OH, appreciate it! And agreed - I think most of us would like to see an end to these record warm spells in DJF.