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Isotherm

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    Winter Outlook 2018-2019

    in Weather Forecasting and Discussion

    Posted

    @40/70 Benchmark - this is a great, highly detailed essay, and you did a very good job re explaining the various apposite factors. Our index forecasts are also quite similar, in fact, the only difference appears to be that I expect the positive geopotential height center to be centered more toward the NAO region rather than the north pole in the means  but I am anticipating both a weakly neg AO and weak to mod neg NAO. Other indices are similar to yours as well. Earlier this month, there were actually some conflicting factors which IMO made this winter harder to call than most realized, but now, my confidence is fairly high on our forecasted outcomes.

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    My Winter Outlook 2018-19

    in Weather Forecasting and Discussion

    Posted

    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.

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    My Winter Outlook 2018-19

    in Weather Forecasting and Discussion

    Posted

    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! :)

    My Winter Outlook 2018-19

    in Weather Forecasting and Discussion

    Posted

    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. 

    • Like 2

    My Winter Outlook 2018-19

    in Weather Forecasting and Discussion

    Posted

    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. 

    • Like 4

    My Winter Outlook 2018-19

    in Weather Forecasting and Discussion

    Posted

    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 -

    aY0BAdI.png

    9zLMqLq.png

    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.

    jt0FzB0.png

    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.

    YixFG6l.png

    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.

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    My Winter Outlook 2018-19

    in Weather Forecasting and Discussion

    Posted

    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.

     

    ENSO

    1. 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.
    2. 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.
    3. 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.
    4. 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.

     

     TAMYR REGION

     

    1. It follows that my anticipation is for a largely negative East Pacific Oscillation, and positive Pacific North American Index.
    2. 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.
    3. 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.
    4. 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.
    5. Geomagnetic activity is very low, with the 30-day running value around 7, indicative of a steep decline from previous autumns.
    6. 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.
    7. 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.
    8. 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.
    9. 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.
    10. 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.
    11. 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.
    12. 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

     11j6e5h.png

     

    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.

     

    DJF HEIGHT ANOMALY FCST

    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”

     

     DEC 2018 GENERAL PATTERN

     

    JAN 2019 GEN PATTERN

     

    FEB 2019 GEN PATTERN

     

     

    DJF TEMP DEPARTURE FCST

     

    WINTER 2018 19 SNOWFALL

     

     

     

     
     

     

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    Griteater's Winter Outlook (18-19)

    in Weather Forecasting and Discussion

    Posted

    Great, well-researched winter outlook as per usual, @griteater! Good luck with verification. I agree with some of your reasoning/conclusions and disagree with others; you'll see where those differences lie soon.

    Any thoughts regarding precipitation and snowfall departures? My only minor nit-pick is I prefer using the 1950-2010 as a base comparison period; I think the 1980-2010 base tends to overestimate cool anomalies somewhat. But very good job on your outlook last winter.

    September 2018 Discussions & Observations Thread

    in New York City Metro

    Posted

    6 hours ago, NewYorkweatherfan said:

    Tough question. I’d say in between. But it’s neither.

     

    The most precise answer to the inquiry is that NYC is in the Northeast, and also Mid-Atlantic, which partially overlaps the Northeast (think of it as a Venn diagram). Every definition I have seen indicates PA and NJ northeastward are Northeast. However, states like DE, MD, and more often, Virginia, are sometimes not considered Northeast, but they are Mid-Atlantic. I've seen some classify VA as Southeast (if so, VA is Mid Atlantic and Southeast). Regardless, these are strictly geographical designations. Our region is both Mid-Atlantic (northern) and the Northeast, as the larger umbrella region. 

    • Like 4

    Long Range Winter Speculation 2018/19

    in Tennessee Valley

    Posted

    16 hours ago, Carvers Gap said:

    The drop during the fall season (where it goes negative) is a pretty good signal for blocking IMO.  Last couple of winters it has been pretty good tool, but like most wx tools it does not work well without other metrics.  I do think there are some winters where it is not a good signal, and indeed this one might be iffy.  Whether it had anything to do w the strat split last spring is open for debate.   @Isotherm has used the QBO(in his seasonal forecasts) before which is where I learned about the tool.  I will tag him and see if he cares to comment.  The QBO rise during winter can be a good sign for a flip to warming temps.   To me the trajectory seems to signal/not signal blocking.  I don't really see it as determining intensity of the overall winter.  Blocking in the eastern valley, especially NE TN, can be a big player where we Atlantic storms do pump moisture over the mountains.  That said, I will always agree that ENSO is a major trump card.  I do think the optimum set-up for snow is slightly different in NE TN when compared to the northern Plateau as we just don't get the forcing that you all do - which is why Atlantic systems that throw moisture back over the Apps are prime for big snows here.  Middle and west TN have very different setups unless we all manage a slider.  As for the rising QBO, it does not necessarily mean that the winter is warm...just means that a quick flip to spring is possible (again, off the top of my head).  I "think" 84-85 actually had that flip.  Just saying that the when the QBO begins to have a strong positive trajectory, things can flip warm suddenly.  I will do some more digging.  Hopefully, Isotherm will stop in and add his two cents.  He has forgotten more than I will ever know.

     

    @Carvers Gap : 

    The kind words are appreciated. I would not utilize the QBO as a correlate of blocking in and of itself (the correlation is minimal in a vacuum); however, its utility increases exponentially when employed adjunctively with other indices, most notably, proxies for solar status/activity. Further, the QBO trend; positive --> negative; negative transitioning toward positive, has proven somewhat informative as to the overall nature of the winter blocking. Again though, while yes, a(n) descending (ascending) QBO would implicate heightened (decreased) blocking probability, I don't place too much weight on QBO variation singularly. Further, there are other confounding variables that can contaminate this analysis, such as upstream tropical forcing, among other factors. Sudden stratospheric warming events occur with greater frequency in the negative QBO regime, but the sun modulates this probability as well.

    Going forward into this winter, the QBO will incontrovertibly be in an ascending phase; whether it converts technically positive during winter remains to be seen. However, we know, at the very least, it will be weak (either slightly negative or slightly positive most likely). Solar activity remains in a descending phase; so superficially, the probability appears somewhat heightened for potential -NAM, but there are other modulatory factors I examine in the autumn that I inject into my, "blocking equation" so we'll see how those shake out in a couple of months. 

     

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    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    @IrishRob17 @40/70 Benchmark,

    That is correct, I am not advocating for the once per day observation -- which is much different than capturing the maximum snowfall for the 24 hour period.

    Ray, to be clear, I am merely presenting the guidelines as they currently stand, which states that non-airport measuring should be maximum snowfall for the 24 hour period. I am not advocating that the 6-hr clearing is necessarily a bad method. I just think congruence with historical records is important and we never should have added the option for 6hr clearing in the 1998-2012 period.

    Per my discussion with Matt who works with the NJ climatologist, there was extensive debate among the people on the panel for this 6hr - maximum snowfall issues. Interestingly enough, the person who pushed most for the 6-hr method was the same person who reversed his thinking and signed off on the return to the maximum snowfall method.

    Snow measuring is an inexact science; there are arguments for both methods.

     

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    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    1 minute ago, MetHerb said:

    That's the same argument I recall back in the 90s when this "standard" came into being.  Many of us argued that it would be impossible to compare systems from the past due to different measuring standards.  I, for one, started keeping records with the current standard and never adopted sweeping and measuring every 6 hours specifically so I could compare one storm with another.  Likewise, I can compare with anyone else that measures at the end of snowfall.  Personally, I think it should never have been implemented but that ship has long sailed and we have a mix now.

     

    I concur with this too, I think they should have maintained the maximum depth standard.

    • Like 1

    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    2 minutes ago, ORH_wxman said:

    Airports have 6 hour measurements going back to the 1940s even...though not all of them did.

    The 6 hour clearing method will probably be more accurate in the long run than a coop who only sticks a ruler in the ground at 7am every morning. You lose way too much snow in the latter. Most NWS people I have talked to don't enforce the changes because they are pretty subjective and sometimes impractical. Besides, there is the subjective element of "when instructed"...and the NWS people can just say they instruct them to continue measuring with 6 hour increments. What is the point now of having a homogeneous record broken if someone has been measuring snow for a decade using the clearing method? Only in storms that have a big fluff band will the differences be really obvious anyway.

     

    Agree, and I'd argue the once per day observation is the least accurate of all for sure. The clearing/vs maximum depth should be fairly similar in most storms that aren't > 32F at the surface.

    • Like 1

    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    2 minutes ago, rgwp96 said:

    Tom it seems Nj removed a report of 31 inches off their report last week because the spotter told them he used the clearing off method.  Most areas in my county got 23-25 inches and that town which borders mine came in with 31 . Some questioned it and it was taken off the report . 

     

    Correct. This is per Matt G who works with the State Climatologist.

     

    "One final thing regarding this past event. We did receive a 31.0" storm total snow report in Kinnelon (Morris County, NJ) that no doubt got at least a little attention, as it would represent, as far as I know, the largest event total in NJ from the storm. I checked in with the observer, and he confirmed that he cleared the board 3 times mid-storm to reduce the effects of compression. Unfortunately, that makes his inflated measurement invalid, at least in the context of the current guidelines (though even with the 6 hour rule, this must have been more like 1 hour clearings), so we've nixed the value. BTW, I'll personally be working on crafting a NJ snowfall map tomorrow based on hundreds of reports received. I post it here when complete."

    • Like 1

    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    8 minutes ago, CoastalWx said:

    So many rules are vague.  I wish they kept it 6 hrs since so many are used to that. Previous records are based on that. 

     

    Prior to 1998, it was max-depth unless instructed. I think max depth would maintain more congruence w/ historical record.

     I've previously provided reference to the current NWS guidelines. I checked with the NJ State Climatologist, who specializes in snow cover and was very much involved in the crafting of the guidelines. What he was able to explain to me was that traditionally, the six hour option has only been available to professional observers at airports. However, back in about 1998 the NWS rules were revised and the six hour option was added for Coop observers*.

    • Like 2

    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    1 minute ago, CoastalWx said:

    I thought OceanSt was saying many first order stations clear the board or what have you, every 6 hrs.  And what the heck defines intermediate depth measurements? every hr? every 6 hrs? 

     

    Per the NJ state climatologist: "When things were reconsidered in 2012, the 6-hour option was removed except for "when instructed."

    Now, I'm not sure of the frequency of this usage, but apparently the 6-hour option is not in use, only when instructed to do so by the NWS (usually airport).

    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    7 minutes ago, CoastalWx said:

    Don't first order stations clear the board every 6 hrs?

     

    They're not supposed to as per official guidelines. They should be taking intermediate depth measurements to capture maximum depth. Unfortunately, there is a ton of miscommunication on this issue. NWS airports do use it sometimes when advised (See last post).

    • Like 1

    March 12/13/14 Blizzard/Winter Storm/WWA etc

    in New England

    Posted

    Just as an FYI, the latest NWS/COOP guidelines for measuring snowfall are to take the maximum accumulation of new snow in a 24 hour period. The 6 hour clearing method is no longer in effect, unless specifically instructed to by a NWS office (airports sometimes).

     

    See the following: section 3.1 and onward

    http://www.nws.noaa.gov/os/coop/reference/Snow_Measurement_Guidelines.pdf

     

    The following is courtesy of Matt G. who operates with the New Jersey State Climatologist, regarding the official guidelines:

     

     I've previously provided reference to the current NWS guidelines. I checked with the NJ State Climatologist, who specializes in snow cover and was very much involved in the crafting of the guidelines. What he was able to explain to me was that traditionally, the six hour option has only been available to professional observers at airports. However, back in about 1998 the NWS rules were revised and the six hour option was added for Coop observers*. This was despite the protest of several people on the committee, as a higher up (I won't name names, but any snow weenie will know the name well) overrode them. When things were reconsidered in 2012, the 6-hour option was removed except for "when instructed." The same fellow who brought about the 6-hour allowance, oddly enough, signed off on the removal of the 6-hour option. All that said, the biggest debate on the committee related to the snow->melt-> snow in a single day situation, the same occurrence that has been argued about here. Ultimately, the compromise was made to simplify the guidelines and call daily snowfall the maximum accumulation achieved during a day, period. There's arguments to made both ways (and it sounds like there were among the experts on the committee), but ultimately, the guideline is objective, consistent, and most in line with historical practices. 

     

    All that said, from what I've seen as a heavy user of Coop data and a state coordinator for CoCoRaHS, far and away the most common "problem" with snow measurements is that many observers (and from what I've seen, perhaps the majority of non-airport Coop) take their measurements once daily at ob time without making any attempt to capture the maximum accumulation. This is probably not a new issue, as I bet it's been relatively common through the years. But sometimes the differences between maximum accumulation and ob time measurement can be significant, so this is something I gently remind volunteers about, with the understanding that many are unable (e,g., at work or sleeping) or unwilling to take these extra measurements (some Coop sites, for instance, are businesses or municipal operations centers, thus not manned all day). It sucks, but we live with it. As for frequent board clearing, I suspect it's a relatively rare occurrence, though people still assert that the 6-hour clearing rule is the standard. I would not be surprised if even some NWS employees are not aware of the current guidelines (hopefully most are). It just won't die. 

     

    One final thing regarding this past event. We did receive a 31.0" storm total snow report in Kinnelon (Morris County, NJ) that no doubt got at least a little attention, as it would represent, as far as I know, the largest event total in NJ from the storm. I checked in with the observer, and he confirmed that he cleared the board 3 times mid-storm to reduce the effects of compression. Unfortunately, that makes his inflated measurement invalid, at least in the context of the current guidelines (though even with the 6 hour rule, this must have been more like 1 hour clearings), so we've nixed the value. BTW, I'll personally be working on crafting a NJ snowfall map tomorrow based on hundreds of reports received. I post it here when complete. 

     

    This is a good debate to have! Thanks for sharing your thoughts. 


    * A note about Coop stations. There seems to be some confusion about what constitutes an "official" report, which is subjective in the first place. The airports are first-order stations that also double as Coop stations. The remainder of Coop sites are manned by volunteer observers, and their data also constitute "official" records in my mind, in that they make up the permanent climate record of the US and are quality controlled and archived in NOAA's NCEI GHCN-Daily dataset. For that matter, so now are CoCoRaHS data (if you are a CoCoRaHS observer, your data are a part of the weather/climate records archived at NCEI!). 
    • Like 2
    • Thanks 1
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