My Winter Outlook 2017-18 - VERIFICATION

[Isotherm]

11th Annual Winter Outlook can be read at the following link. Historical accuracy for long term outlooks has been 81% since the outset in 2006, which can be seen in my website.

Comments and questions appreciated!

http://www.lightinthestorm.com/archives/1108

 

 

Overview:

The past year has been characterized by an atypical amount of global heat, as the Earth continues to recover from the positive ENSO extremum of 2015-16. The vestiges of the warmth significantly impacted the winter of 2016-17, producing a top 10 warm winter in innumerable regions. The ENSO extremum acted adjunctively with a retracted Pacific jet and abnormally potent stratospheric vortex to yield a tropospheric reflection featuring widespread ridging across the continental United States. Surface temperatures responded unsurprisingly as a consequence. During spring and summer 2017, the weak La Nina of winter 2016-17 transitioned into a preferentially neutral ENSO phase; however, this period turned out quite ephemeral as La Nina conditions reemerged in the autumn of 2017. Over the past couple of months, the thermocline structure in the Pacific has become increasingly suggestive of a La Nina – an east based La Nina – with deepening cold sea surface temperature anomalies in the eastern tropical Pacific. The orientation of the La Nina event has ramifications as far as the global walker cell circulation pattern, which governs upward motion/subsidence and concomitant tropical convection dispersal. Furthermore, Rossby waves emanating from tropical convection can modulate extra-tropical ridge/trough action centers. As such, mid-latitude weather is often a function of tropical phenomena, which is invariably the case given the enormous energy storage and production in the tropical latitudes. With that being said, high latitude oscillations will dampen or enhance signals such as ENSO depending upon the geographical region under consideration. As we move forward into winter 2017-18, the weak, east based La Nina should persist. Since ENSO is not overpowering, other variables must be assigned more weight. Northeast US and continental US weather is multifactorial, and thus, myopic analyses will indubitably fail. In the following, a cursory explanation of methodology is provided, followed by index expectations, and finally, forecasted pattern progression.

Methodology [Examination of Integral Factors]

• Geopotential height anomalies near the Taymyr Peninsula and Barents-Kara Seas in the autumn season have been shown to portend wintertime northern annular mode modality and thus the overall strength of the polar vortex. High geopotential height signatures have a distinct proclivity to engender enhanced vertical wave driving into the stratosphere which can positively feedback with a weakened tropospheric vortex. The geopotential height signature for this autumn has generally resembled that of a negative northern annual mode (Arctic Oscillation) precursor.
• Various indicators were utilized to diagnose the polar night jet / stratospheric vortex strength; stratospheric temperature profile, zonal mean winds, as well as the active ozone transport associated with the Brewer-Dobson Circulation; certain proxies were used to ascertain the relative strength of this circulation. A stronger BDC implicates greater ozone transport from the tropical stratosphere into the polar regions, which aids in producing stratospheric warming, and thereby usually resulting in a weaker stratospheric vortex. These signals – overall – for the month of November were suggestive of slightly stronger than average stratospheric vortex, which would argue for an ensuing winter slightly positive Arctic Oscillation.
• Snow cover advance in the northern hemisphere was less impressive than previous years; however, the extent of snow cover ended up being at the highest levels of the past 12 years in late October / early November. This – incontrovertibly – will positively feedback and aid arctic air reservoirs in the northern hemisphere. It is hypothesized that this might have a slight to moderate effect on the Arctic Oscillation, tilting it more negative.
• Proxies for solar activity were analyzed and compared with prior years since 1950 in order to determine tendencies with NAM/NAO covariation. Solar flux levels, geomagnetic activity, solar cycle duration, intensity, and trends were included in the analysis. The current solar cycle continues to head toward overall minimum. Research revealed that the probability of protracted blocking episodes this winter is not as high as one would have expected upon perfunctory glance at the rapidly declining sunspot numbers. With that being said, the combination of suppressed solar parameters yields a fairly auspicious signal for blockiness in the northern hemisphere.
• Precursor sea surface temperatures were analyzed in the Atlantic since 1950; this signal produced success 77% of the time in prognosticating the DJF NAO modality, and success 88% of the time when extracting strong ENSO years (thus, even more applicable for the current year). This indicator suggested a mean positive NAO for the upcoming winter.
• Another NAO indicator developed has shown very high predictive ability, analyzing data in the September-early November period. Retrospectively, since 1950, the method failed only 9 times out of 66 years, yielding success in accurately predicting the NAO modality for DJF 86% of the time. Over the past 20 years, the indicator has only failed in 1 year. The signal for this autumn suggests a mean positive winter NAO, concurring with the aforementioned correlation.
• The QBO has entered a strongly negative tendency over the past few months, with rapidly neutralizing values at the 50mb atmospheric level as well. This increasing easterly shear stress in the stratosphere will destructively interfere with vortex intensification events, especially in the early part of winter.
• ENSO and associated tropical forcing patterns were analyzed to ascertain walker cell behavior and potential extratropical influence
• Global atmospheric angular momentum this autumn was suggestive of a retracted Pacific pattern and overall La Nina atmospheric propensity; analog years were evaluated on the basis of similarities in AAM mean patterns as well as poleward transport tendencies. A highly retracted jet is likely to be the dominant pattern in the Pacific with mid-level ridging aligned near the longitude of the Aleutian Islands/Dateline.
• The October inverse NAO correlation rule was utilized as a tool; this specific correlation indicated a mean negative NAO winter
• 500mb geopotential heights were noted during the October-early November period and juxtaposed retrospectively with years since 1950.
• PDO and AMO trends were used adjunctively with sea surface temperature anomaly profiles to determine potential feedbacks on the atmospheric circulation for the cold season. The analyses corroborated the notion that the mid latitude jet would likely be stronger over the north Atlantic and weaker over the north Pacific.
• Recent hemispheric and global warmth – due to its anomalous nature – was taken into account in terms of adjusting the analog year output and final outlook numbers.

Index Expectations
In light of the examination of indicators, it is noted that a capricious atmospheric pattern may be a mainstay of the upcoming winter in the northern hemisphere, with significant / dramatic reversals both intra-monthly and inter-monthly. The following is forecasted for the mean values of the Dec-Jan-Feb (meteorological winter) indices:

ENSO: Weak, east based La Nina
PDO: Near neutral
AMO: Positive (strongly)
EPO: Positive
WPO: Negative (strongly)
PNA: Negative
AO: Negative (slightly negative overall, high variability, occasional deeply negative dips)
NAO: Positive (slightly positive overall, high variability, occasional dips strongly negative and strongly positive)

 

Given the anticipated teleconnection modalities, the forecasted DJF z500 pattern will be highly reflective of these circulations.

 

Forecast/Progression:

This winter will be significantly colder than the past two, but still milder than normal for a large percentage – if not majority – of the United States. The final temperature anomalies for DJF in the Northeast US will certainly feel cold compared to the past two winters, even though the numbers still average warmer than normal. The coldest part of winter relative to normal is expected to be the front third, which will be entirely antithetical to the past several winter seasons featuring 60 degree weather deep into December. While 60 degrees cannot be ruled out in a transient burst, I do not expect sustained warmer than normal temperatures to dominate the month for the Central and Eastern US, especially the Mid-west and Northeast US. Research has indicated that there is a heightened probability of stratospheric vortex perturbation in the early part of winter. While zonal mean winds are strengthening, and the Arctic Oscillation should neutralize in the longer term, upwelling wave amplification from the tropospheric pattern and down-welling effects of the easterly shear stress and largely suppressed solar activity will invite modest ozone maintenance early in the season. The vortex strength may fluctuate near normal, so I am not anticipating blocking to extent of 2009 or 2010 in terms of magnitude. It should be sufficient blocking to countervail lower geopotential heights dipping into the W Canada/NW US region, as a consequence of the retracted Pacific jet. December’s pattern should thus feature a negative NAO, negative AO, and the analogs suggest periods of positive PNA are possible as well. It therefore might be the case that the period up through the holiday season will be wintrier than Northeasterners have seen since the inflection point of the early 2010s.

As December becomes January, the NAO should become increasingly positive with a contemporaneous decrease in PNA values, yielding an atmospheric circulation more reflective of benign/mild La Nina years. This circulation could very well be the mainstay – to varying degrees – for much of the remainder of meteorological winter. Snowfall should be above to much above normal across the northern tier into northern New England this month, with precipitation running above average. The variation in the Pacific jet will continue to favor Aleutian ridging with periods of poleward ridging into the Arctic. This will permit arctic blasts to sweep through the Northeast, but the spasmodic pattern will preferentially favor warmth to the southeast of the Great Lakes.

In February, the pattern will be fairly similar to January, except with the potential for more negative dips in the AO and or NAO, as indicated by both research indicators and analogs. This could implicate increased opportunity for snow threats along the I-95 corridor of the Northeast, when also considering climatology peaks during this month. However, the interludes of favorability will be fairly transient, especially compared to the generally more protracted propitious period in early winter. Snowfall will be near or above normal from the Pacific NW and Rockies into the Plains, and also in the Lakes and New England. Precipitation throughout the winter will be lower relative to normal in the southern tier of the US.

 

March is outside the period of meteorological winter, and thus no confidence is expressed for this month. However, the analogs overall indicate that winter could potentially make a “comeback” in the coastal Northeast, relative to the performance of mid to late meteorological winter.

Analogs:

Based upon an examination of the multifarious variables discussed in the methodology section, the top analog years are as follows:

1. 2005-06 [first tier analog – quadruple weighted]
2. 1955-56 [second tier analog – triple weighted]
3. 1973-74 [third tier analog – double weighted]
4. 1983-84 [fourth tier analog – single weighted]

One will note that the index forecasts are fairly close to the mean of the analog seasons.

November of 2005 featured a dip of the NAO below -1.5 SD, much like this year. The mean DJF NAO was slightly positive, with a negative NAO in December.
2005-06 and 1955-56 had quite a few striking similarities to this year, and to a lesser extent 1973-74.

It should also be noted that the z500 analog composites will appear with lower heights than reality would produce due to the time period against which they’re compared (1980-2010 normals).

 

Outlook:

 

Outlook Temperatures

For the Local New York City Region

 

Dec-Jan-Feb Temperature Departure Outlook: +0.5 to +1.5; Warmer than normal

 

Expected evolution is colder than normal December (likely -1.5 or colder), warmer than normal January (likely +1.5 or warmer), and warmer than normal February (likely +1 or warmer). There is potential for one strongly negative temperature departure month; the highest probability of this occurring is in December. There is also potential for one strongly positive temperature departure month; this expectation has less confidence as far as timing, but January has a higher probability than February to see this.

Dec-Jan-Feb Precipitation Departure Outlook: Slightly above / wetter than normal

An active storm track is favored through the Ohio Valley and Northeast, with plentiful precipitation from 39N latitude northward along the East Coast.

Nov-Mar Snowfall Departure Outlook: Near normal for the PHL-NYC corridor

Due to the difficultly in prognosticating snowstorms, and possibility that one occurs in an overall warm pattern, the winter distribution of snowfall is lower confidence. However, December should produce above normal snowfall, January below normal, and February near normal. One major (12” or greater) snowstorm is possible this winter. This would likely occur between December 10th-30th or February 5th-15th.

Snowfall guesses for various CONUS locations:
Burlington, VT: 90-97”
Boston: 50-57”
New York City: 27-34”
Philadelphia: 17-24”
Baltimore: 12-19”
Washington DC: 9-16”
Richmond, VA: 3-10”
Raleigh, NC: <5”
Atlanta, GA: <2”
Houston, TX: <1”
Chicago, IL: 50-55”
Denver, CO: 60-65”
Seattle, WA: < 5”

 

Note: The analog z500 composite is reflective of high variability in the Arctic / Atlantic domains, leaning negative in the AO domain and slightly positive in the NAO domain. This will still be a noticeable increase in blocking compared to the previous couple winters. The below composite is indicative of strong poleward central Pacific ridging which will maintain the cold source in Canada throughout the winter.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[WhiteoutWX]

Very well laid out! Seasonal forecasting is not my area of expertise but it seems like you have some very solid reasoning behind your forecast. In the end though, looks like a fairly "normal" La Nina winter for most of the U.S. 

[weathermedic]

Seems to agree with what the other "big hitters" are forecasting. Thank you!

[frd]

Thanks for sharing your outlook ! I really appreciate your detailed view of the upcoming winter season as well.  

I did have a few questions, first in regards to the past year's global temps, had the globe as a whole been cooler, say neutral to only a bit over normal,  would have this changed your outlook to a large degree ?  

And lastly, I am always very intrigued by your thoughts on the AO and NAO domains and the strat.  Do you feel that we are still slowly going back to a multi year or decadal - NOA tendency in the years ahead ?  ( I was surprised to hear what your NAO tools are indicating for this upcoming cold season )

And, if you care to comment as well, with the solar min still coming up in the period 2018 to 2020 will we once again run the risk of severe blocking during the cold season.

 

  

 

 

 

[Morris]

Thanks!

[Wow]

Very thoughtful breakdown but since it give me above normal temps and below normal snowfall I choose not to believe it!

[BuffaloWeather]

The best in the business IMO. Always appreciate your winter forecast. 

[40/70 Benchmark]

We are very, very similar....2005-2006 is my number one analog, too......I'm also going for a bookend winter.

I'm a bit colder because of a smudge more blocking, but very similar snowfall totals.

Great work.....I look forward to your outlook the most.

[Isotherm]

Thanks everyone!

10 hours ago, 40/70 Benchmark said:

We are very, very similar....2005-2006 is my number one analog, too......I'm also going for a bookend winter.

I'm a bit colder because of a smudge more blocking, but very similar snowfall totals.

Great work.....I look forward to your outlook the most.

 

Thanks Ray, much appreciated. I will take a more thorough read through yours later today; it looks very well researched and written as per usual. I did notice that we have some differing NAO thoughts, and I think that's probably the primary disparity between many winter outlooks this year, namely, the Atlantic signaling, which will tend to modulate whether the low heights remain Mid-west/Rockies in the means or push further east. The signal I extracted from the Atlantic was one which actually favors a +NAO based upon my retrospective analysis. Both of my major indicators suggested +, but the signal overall is a slightly positive one. So I'm expecting a lot of variance.

Interesting that we both arrived at 2005-06 as the primary analog. It's always great when two different methodologies yield congruous results; one would hope that implicates we're on the correct track.

[40/70 Benchmark]

2 minutes ago, Isotherm said:

Thanks everyone!

 

Thanks Ray, much appreciated. I will take a more thorough read through yours later today; it looks very well researched and written as per usual. I did notice that we have some differing NAO thoughts, and I think that's probably the primary disparity between many winter outlooks this year, namely, the Atlantic signaling, which will tend to modulate whether the low heights remain Mid-west/Rockies in the means or push further east. The signal I extracted from the Atlantic was one which actually favors a +NAO based upon my retrospective analysis. Both of my major indicators suggested +, but the signal overall is a slightly positive one. So I'm expecting a lot of variance.

Interesting that we both arrived at 2005-06 as the primary analog. It's always great when two different methodologies yield congruous results; one would hope that implicates we're on the correct track.

I'm more confident in the AO....and the early season negative NAO.

The big question will be whether blocking re emerges late this season.

[Isotherm]

20 hours ago, frd said:

Thanks for sharing your outlook ! I really appreciate your detailed view of the upcoming winter season as well.  

I did have a few questions, first in regards to the past year's global temps, had the globe as a whole been cooler, say neutral to only a bit over normal,  would have this changed your outlook to a large degree ?  

And lastly, I am always very intrigued by your thoughts on the AO and NAO domains and the strat.  Do you feel that we are still slowly going back to a multi year or decadal - NOA tendency in the years ahead ?  ( I was surprised to hear what your NAO tools are indicating for this upcoming cold season )

And, if you care to comment as well, with the solar min still coming up in the period 2018 to 2020 will we once again run the risk of severe blocking during the cold season.

 

  

 

 

 

 

Frd - thanks - appreciate it. To respond to your inquiries - global temperatures were certainly a factor, albeit a relatively minor one, in finalizing the numbers. Hypothetically, if global temperatures were near normal, my forecasted departures would have been decreased slightly in the means, but still above normal for the majority of the country.

Regarding the AO/NAO domains, like I mentioned in the outlook, superficially one would anticipate a very blocky season given the propensity for suppressed solar activity. I do think we're looking at more NAO domain blocking than we've seen since the 2012-13 winter, but nowhere near the extent of 09-11. Going forward, I do continue to anticipate the down-up and top-down mechanisms responsible for NAO modulation to become increasingly conducive for protracted negative NAO/AO periods. In other words - yes, I do largely believe this winter is the inflection point, and henceforth, the preponderance of winters over the next handful of years could average more negative, obviously with some inter-seasonal variation still existing (every season won't be negative).

I'm very interested about the prospects of the subsequent winters for sure, and would certainly love to forecast a blockbuster winter one of these years.

 

[frd]

33 minutes ago, Isotherm said:

 

Frd - thanks - appreciate it. To respond to your inquiries - global temperatures were certainly a factor, albeit a relatively minor one, in finalizing the numbers. Hypothetically, if global temperatures were near normal, my forecasted departures would have been decreased slightly in the means, but still above normal for the majority of the country.

Regarding the AO/NAO domains, like I mentioned in the outlook, superficially one would anticipate a very blocky season given the propensity for suppressed solar activity. I do think we're looking at more NAO domain blocking than we've seen since the 2012-13 winter, but nowhere near the extent of 09-11. Going forward, I do continue to anticipate the down-up and top-down mechanisms responsible for NAO modulation to become increasingly conducive for protracted negative NAO/AO periods. In other words - yes, I do largely believe this winter is the inflection point, and henceforth, the preponderance of winters over the next handful of years could average more negative, obviously with some inter-seasonal variation still existing (every season won't be negative).

I'm very interested about the prospects of the subsequent winters for sure, and would certainly love to forecast a blockbuster winter one of these years.

 

Thanks Isotherm, hopefully in the next few years we get a blockbuster season. Appreciate your thoughts as always. 

    

[Paragon]

1 hour ago, Isotherm said:

Thanks everyone!

 

Thanks Ray, much appreciated. I will take a more thorough read through yours later today; it looks very well researched and written as per usual. I did notice that we have some differing NAO thoughts, and I think that's probably the primary disparity between many winter outlooks this year, namely, the Atlantic signaling, which will tend to modulate whether the low heights remain Mid-west/Rockies in the means or push further east. The signal I extracted from the Atlantic was one which actually favors a +NAO based upon my retrospective analysis. Both of my major indicators suggested +, but the signal overall is a slightly positive one. So I'm expecting a lot of variance.

Interesting that we both arrived at 2005-06 as the primary analog. It's always great when two different methodologies yield congruous results; one would hope that implicates we're on the correct track.

Make that 3/3 as far as going for bookend winters goes ;-)  Interesting in using 2005-06 as an analog, I see how we could bust both positive or negative as far as snowfall goes. A colder version of December 2005 (or a colder November that results in an early season snowfall this year- or both!) could result in more snow in the early part of the period.  December 2005 was very close to being a much snowier month for us.  Then again, we got a big anomalous snow event in February 2006, so we could easily go the other way there.  I remember there were predictions of a snowier and colder March 2006 that didn't really materialize (if that had worked out we could have gotten something similar to your 1955-56 analog, March 1956 was BIG), though we did get an inch of snow in early April to make it to 40" in the city (for the fourth consecutive winter!).  Large gradient that winter (chiefly because of the December 2005 and February 2006 event- Long Island got rain in the former and we were east of the best forcing with the latter.)- NYC had 40" of snow while JFK barely had two feet- 27" for the season I think (same as the total NYC got in the Feb 2006 storm!)  NYC had 6" in the December 2005 event, while JFK got zero, and NYC had 27" in the February 2006 event, while JFK had just 13"!  Do you see a similar gradient this year in the same area?

 

*note, another winter which bears some similarity to what you've forecasted (at least for our area) is 2008-09.

 

 

 

 

[AfewUniversesBelowNormal]

Classic La Nina probably doesn't work in 2017. The 10-year La Nina average is already much different from 50s-80s. 

[40/70 Benchmark]

58 minutes ago, Paragon said:

Make that 3/3 as far as going for bookend winters goes ;-)  Interesting in using 2005-06 as an analog, I see how we could bust both positive or negative as far as snowfall goes. A colder version of December 2005 (or a colder November that results in an early season snowfall this year- or both!) could result in more snow in the early part of the period.  December 2005 was very close to being a much snowier month for us.  Then again, we got a big anomalous snow event in February 2006, so we could easily go the other way there.  I remember there were predictions of a snowier and colder March 2006 that didn't really materialize (if that had worked out we could have gotten something similar to your 1955-56 analog, March 1956 was BIG), though we did get an inch of snow in early April to make it to 40" in the city (for the fourth consecutive winter!).  Large gradient that winter (chiefly because of the December 2005 and February 2006 event- Long Island got rain in the former and we were east of the best forcing with the latter.)- NYC had 40" of snow while JFK barely had two feet- 27" for the season I think (same as the total NYC got in the Feb 2006 storm!)  NYC had 6" in the December 2005 event, while JFK got zero, and NYC had 27" in the February 2006 event, while JFK had just 13"!  Do you see a similar gradient this year in the same area?

 

*note, another winter which bears some similarity to what you've forecasted (at least for our area) is 2008-09.

 

 

 

 

March 2006 got cold, but it also got dry.

Its actually 4/4 regarding bookend...as Homenuk went in that direction, as well on NYmetrowx.

[griteater]

Iso - first off, your vocabulary is loaded!  Excellent analysis.  Thanks for posting the outlook.  It looks like you had the same 'problem' as I did in that your forecast this year is very similar to last year's version. 

Your AO/NAO indicators are interesting.  There are a lot of those hidden indicators out there.  We just have to work to find them and utilize them properly.  I found it interesting that your SST indicator was showing +NAO, while Chuck's SST indicator was showing -NAO.

It's going to be interesting to see how Dec kicks things off.

[tamarack]

17 hours ago, Wow said:

Very thoughtful breakdown but since it give me above normal temps and below normal snowfall I choose not to believe it!

Given my ignorance of the science, that's what I look for as well. 
That said, very thorough and interesting write-up, though (nitpick alert) the above average snowfall forecast for my particular little area (western Maine foothills) is far different than the weighted analogs, which work out to 65" while our average is 89".  We certainly don't want another 05-06, the year of no snowpack (and almost no snow at all after Jan 31), but I can weenie on the snowfall map. 

[NEWeatherWx]

Sent from my iPhone using Tapatalk

[Isotherm]

8 hours ago, Paragon said:

Make that 3/3 as far as going for bookend winters goes ;-)  Interesting in using 2005-06 as an analog, I see how we could bust both positive or negative as far as snowfall goes. A colder version of December 2005 (or a colder November that results in an early season snowfall this year- or both!) could result in more snow in the early part of the period.  December 2005 was very close to being a much snowier month for us.  Then again, we got a big anomalous snow event in February 2006, so we could easily go the other way there.  I remember there were predictions of a snowier and colder March 2006 that didn't really materialize (if that had worked out we could have gotten something similar to your 1955-56 analog, March 1956 was BIG), though we did get an inch of snow in early April to make it to 40" in the city (for the fourth consecutive winter!).  Large gradient that winter (chiefly because of the December 2005 and February 2006 event- Long Island got rain in the former and we were east of the best forcing with the latter.)- NYC had 40" of snow while JFK barely had two feet- 27" for the season I think (same as the total NYC got in the Feb 2006 storm!)  NYC had 6" in the December 2005 event, while JFK got zero, and NYC had 27" in the February 2006 event, while JFK had just 13"!  Do you see a similar gradient this year in the same area?

 

*note, another winter which bears some similarity to what you've forecasted (at least for our area) is 2008-09.

 

 

 

 

 

I wouldn't read too much into the analogs. I utilized them significantly for z500, to a lesser extent temps/pcpn, and to a much lesser extent snowfall distribution. With that being said, I think there will probably be two noticeable gradients this season; one of which serves as the demarcation between normal snows and below to much below normal snows, which I expect to set-up very close to 40N; the other gradient will separate near normal from above to much above, probably aligned in interior SNE.

[Isotherm]

4 hours ago, tamarack said:

Given my ignorance of the science, that's what I look for as well. 
That said, very thorough and interesting write-up, though (nitpick alert) the above average snowfall forecast for my particular little area (western Maine foothills) is far different than the weighted analogs, which work out to 65" while our average is 89".  We certainly don't want another 05-06, the year of no snowpack (and almost no snow at all after Jan 31), but I can weenie on the snowfall map. 

 

Thanks, as I just posted, I didn't weight the analogs w/ snowfall as I did with z500 and temperatures. Since snowfall is much more non-linear / chaotic, I thought it more prudent to forecast based upon mean storm tracks and alterations expected throughout the season. I leaned more toward the 1955-56 totals for Northern New England.

[tamarack]

5 minutes ago, Isotherm said:

 

Thanks, as I just posted, I didn't weight the analogs w/ snowfall as I did with z500 and temperatures. Since snowfall is much more non-linear / chaotic, I thought it more prudent to forecast based upon mean storm tracks and alterations expected throughout the season. I leaned more toward the 1955-56 totals for Northern New England.

I missed that caveat, which makes all kinds of sense, for the reason you gave.  Of course, all 4 of the analog years were BN for snow here, though 55-56 was only about 7" shy.

[Isotherm]

6 hours ago, griteater said:

Iso - first off, your vocabulary is loaded!  Excellent analysis.  Thanks for posting the outlook.  It looks like you had the same 'problem' as I did in that your forecast this year is very similar to last year's version. 

Your AO/NAO indicators are interesting.  There are a lot of those hidden indicators out there.  We just have to work to find them and utilize them properly.  I found it interesting that your SST indicator was showing +NAO, while Chuck's SST indicator was showing -NAO.

It's going to be interesting to see how Dec kicks things off.

Thank you very much Grit, appreciate the kind words. I noticed that too - the forecasts aren't too dissimilar from last year. The differentiation is that I expected last winter to be much warmer overall (I went +1 to +2 for NYC), but as you know, with LR forecasts, it's generally unwise to forecast much, much above or much, much below, unless your confidence is extremely high, since that will increase your probability of busting. This winter, I'm anticipating much more blocking than last year, although, still not sufficient to tilt the NAO negative in the means for DJF. Speaking of which, I did find that interesting too. The SST methodology I employ is different as far as time period analyzed among other things. Both of my indicators which have been performing very well (and retrospectively) suggest +NAO, so we'll see. As mentioned, I think it won't be far from neutral on the + side.

 

Agree, very interested to see how things progress this winter. Monthly timing is always tough, invariably seems that one month delivers a curveball, but we'll see. Good luck to you and all who forecasted!

[Isotherm]

8 hours ago, StormchaserChuck said:

Classic La Nina probably doesn't work in 2017. The 10-year La Nina average is already much different from 50s-80s. 

Could you elaborate with less equivocal parlance? A 10-year La Nina average is a small sample size and definitely insufficient to base a forecast upon, in my view.

[TugHillMatt]

Very good read! I am definitely hoping for a more "normal" winter here in the Great Lakes after the past 2 horrible ones. Thanks for your post.

[Isotherm]

12 hours ago, blackrock said:

Very good read! I am definitely hoping for a more "normal" winter here in the Great Lakes after the past 2 horrible ones. Thanks for your post.

 

Thanks!

[Paragon]

16 hours ago, Isotherm said:

 

I wouldn't read too much into the analogs. I utilized them significantly for z500, to a lesser extent temps/pcpn, and to a much lesser extent snowfall distribution. With that being said, I think there will probably be two noticeable gradients this season; one of which serves as the demarcation between normal snows and below to much below normal snows, which I expect to set-up very close to 40N; the other gradient will separate near normal from above to much above, probably aligned in interior SNE.

I'm also noticing a resemblance to 1993-94 in these steep gradients.  That year the below normal snowfall radiant was south of Philly and the above/well above normal gradient started near the mid-Jersey shore.  Also a predominantly +NAO winter (it shows we can get a big snowfall season without a predominantly -NAO.)  Based on your ideas, I'm thinking you believe the gradients will be further north this year.

 

[michsnowfreak]

After our historic winter in 2013-14 & a tundra 2014-15, the last 2 winters were very mild. Still plenty of snowfalls but the mild temps were irritating. Temps still seem a wild card but I can't believe how overwhelming the forecasts have been this year for above avg precip in the Lakes!

[Hoosier]

11 minutes ago, michsnowfreak said:

After our historic winter in 2013-14 & a tundra 2014-15, the last 2 winters were very mild. Still plenty of snowfalls but the mild temps were irritating. Temps still seem a wild card but I can't believe how overwhelming the forecasts have been this year for above avg precip in the Lakes!

It would take a lot of you know what to not go with above average precip in our region in a Nina year.

Excellent writeup, Isotherm.

[Isotherm]

Thanks, Hoosier!

[Stebo]

Yeah I really love this outlook, great work and I hope it verifies, would be a nice roller coaster ride for this region.