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Isotherm

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About Isotherm

  • Birthday 09/24/1990

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    Colts Neck, NJ

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  1. Not seeing it. The NAO dipped to -1 SD a couple days ago, but will be oscillating up to +1 SD for the next week or so. By December 15th, the Dec 1-15th NAO mean is likely to be near neutral, or possibly even ever so slightly positive. So far, it's not a propitious indication of an ensuing moderate to strongly negative NAO winter.
  2. Ok, in central NJ, the numbers were as follows: Freehold/Marlboro COOP; period of record 1959-2016. 12/57 years with 1" or greater snow depth = 21% Not surprised we're identical to BDR's percentage, given both of our average snowfalls are near 30" (the 30-year running here has pushed to a little over 31" actually). The 1960s had a 50% success rate for white Christmas's - obviously a great decade with plenty of -NAO. 1959 = 4" 1961 = 6" 1962 = 1" 1963 = 5" 1966 = 6" 1969 = 4" 1975 = 3" 1980 = 1" 1983 = 1" 1995 = 5" 1998 = 2" 2009 = 7"
  3. @ORH_wxman - are T amounts typically included for the white Christmas calculation? Doing a couple COOPs around here.
  4. I went warmer than normal for both January and February in my winter outlook, with the possibility of one of those two months featuring a > +1.5 departure. Initially, I thought January had a higher probability than February of achieving that, as a mid winter SPV intensification occurs with decreasing favorability in the ATL domain and a retrogression of the NPAC geopotential heights. I'm unsure of the exact magnitude, but yes, I see no objective evidence to abandon my forecast progression right now.
  5. The longwave circulation structure is incontrovertibly auspicious for colder than normal temperatures, though, to the extent that baroclinicity will be displaced, the structure is relatively unfavorable for significant to major+ potential (not impossible, but lower likelihood). Eastern and northern New England are most likely to receive a significant event if it occurs (6" or greater) through D10. Hemispherically, mountain torque will increase, subsequently inducing a jet extension event and resultant Nino-esque regime in the medium term. Adjunctively, LF forcing will promote maintenance of poleward ridging extending into the Arctic. Stratospherically, ozone increases in critical areas and wave 1 convergence will continue to destructively interfere with PNJ intensification for the next 2 weeks at least. However, the structure will preclude significant blocking in the NAO domain. Further down the road, eastward propagating MJO will hit a wall in p7, but the upper divergence signal will traverse the EPAC and Atlantic, much like the last wave. I expect NAO domain geopotential heights will become increasingly positive again, after the ephemeral negative interlude week 2. As retrogression of the poleward ridging initiates contemporaneously with improving NAO heights, I continue to favor mid to late December for something bigger. I would narrow it further to the 18th-23rd period approximately. Prior to then, a light to moderate event is still possible for our region, with a lower likelihood of significant.
  6. -1.5 here. 12 nights sub freezing.
  7. At this point, the explosivity of the eruptions hasn't been strong enough to penetrate through the tropopause, so any climate effects will be nil, unless a stronger eruption occurs, sending the sulfates into the stratosphere.
  8. Thanks frd, appreciate it. The December pattern won't be dissimilar from 2013, but there will be higher geopotential heights over the Arctic and the NATL than we had in 2013. Thus, the Eastern trough will be more amplified / meridional w/ less SE-ridge as a consequence. I think the best opportunity for something significant will come in the second half of December, at which time, heights will be more conducive over the NATL. Prior to mid month, threats will be a function of good timing; any short wave that becomes overly amplified could be wet rather than white for the coast. The stratospheric PV will intensify after mid month, though it should remain weaker than normal for December w/ renewed wave-1 forcing by week 2, and wave-2 vertical driving by week 3. So I expect the pressure on the vortex to continue such that the stratosphere will be favorable for a blocky troposphere. I expect the SPV to wind-up/strengthen (not to the levels of the past two winters) in January, coupled w/ a pattern retrogression to more classic Aleutian ridging / RNA. The EQBO typically features disturbed stratosphere early winter and again late winter. In my winter outlook, I liked Dec 15-30 and Feb 1-15 the best for sig/major storm opportunities. Still believe perturbation will increase again by February, but in a pattern that's overall quite a bit warmer relative to the December one.
  9. The overall progression of the near to medium term appears to be congruous with thoughts hitherto. There have been some red flags in various data that reaffirm my thinking regarding the super long-term (post December), but will eschew discussing that right now. The ostensible positive trend in the NAO proggs isn't too surprising given the stratospheric circulation structure which preferentially favors higher than normal geopotential heights from the Arctic through the NW Territories, and along the West Coast, an orientation not dissimilar from recent previous winters. The predilection for lower heights in the NATL will act to increase the probability of non-frozen events for the East Coast, if an upstream short wave were to rapidly intensify. However, the poleward extent of the NPAC ridge is such that it partially countervails the effects of a more positive (relatively) NAO, in that it suppresses the zone of greatest baroclinicity. Weak to moderate short waves which do not significantly pump geopotential heights immediately downstream are our most probable snowfall opportunities through the first half of December. I expect the NAO domain to gradually improve from the middle part of December onward, which is still the time frame I like best for something significant to major+. It's indubitably a colder than normal pattern for December, and very likely snowier than normal as well. But there are some risks still present which certainly deserve recognition as well. One of the highest confidence features, which has been explicated innumerable times in this thread, is the poleward EPAC ridging, due to the fact that multifarious forcing mechanisms support its maintenance, including CHI 200hpa progression, internal wave breaking, and downwelling. It's the best looking December pattern we've seen since 2013 and possibly since 2010. PS - official SSW likely won't occur.
  10. Wow. From 1970-present it was virtually never. Shows how difficult it is to have more than 1" on the ground Christmas morning. 1995, of course, a standout year; the 1959-1967 period was excellent, as was 1945-49, and the previous solar minimum from 1880-1920. 2009 had 7" on the ground in the morning here, following the 20"+ the week before.
  11. What are the factors that lead you to believe a long-duration event is more likely at this juncture?
  12. This study discussed boreal winter conditions subsequent to tropical volcanic eruptions preferentially occurring in the spring / summer; there were a couple cases in October, but not nearly as late as current. Further, it is much too early to ascertain VEI or stratospheric aerosol loading. Hypothetically speaking, if this eruption becomes sufficiently strong, the effects would begin manifesting in the AO by mid to late winter. All of those studied eruptions were VEI 4 or greater. We will need to monitor.
  13. Since 1958, there have been several sudden stratospheric warming events in late November-December. They were as follows: Vortex splits: 08 Dec 1987 west QBO Vortex displacements: 30 Nov 1958 east QBO 08 Dec 1965 east QBO 27 Nov 1968 east QBO 04 Dec 1981 east QBO 15 Dec 1998 east QBO 16 Dec 2000 east QBO All of these winter seasons, save for one (1998-99), featured a negative AO average for Dec-Jan-Feb. Some of the winters, particularly the El Nino's, featured strong polar blocking through late winter. However, if we extract the El Nino events -- 1987-88, 1965-66, 1968-69, 1958-59, as well as the one strong La Nina event -- 1998-99, the remaining analogs are: 1981-82 (neutral ENSO) 2000-01 (weak La Nina) Their SSW events occurred on December 4th and December 16th respectively. Hypothetically speaking, if we were to see a SSW, it would likely be wave-1 induced displacement variety (as most have been early season), and occur between December 4th and 16th. The ensuing AO propensity for those two analogs was as follows for DJF: 1981: -1.216 1982 -0.883 0.974 2000: -2.354 2001 -0.959 -0.622 The common denominator was strong AO blocking in December, less but still negative in January, and neutralizing to positive in February. The DJF means were negative AO. The ensuing NAO propensity for the two analogs for DJF: 1981: -0.02 1982 -0.89 1.15 Slightly positive NAO mean 2000: -0.58 2001 0.25 0.45 Slightly positive NAO mean The progression of those two winters - while a very small sample size - could provide a clue for the upcoming season, in the case of a SSW, which is not guaranteed. Remember that every event is unique and this is a highly non-linear process. My thoughts continue to remain the same, namely, that we are going to see a -AO/NAO first third of winter with a colder and snowier than normal December. The Dec 15th-30th period is a time frame to consider for a possible major event. The duration of the tropospheric blocking, regardless of official achievements in the stratosphere, will be highly contingent upon countervailing forces in the troposphere which destructively interfere w/ -NAM maintenance.
  14. Wonder if there is any validity to the hypothesis that the frigid nights "shocked" the trees. Most red oaks are fully leafed here, but finally brown. Latest I've ever seen by 10+ days. Normally we're 95% down by early November. @tamarack
  15. Your historical knowledge is unparalleled. Thank you for the information. Do you have a list handy of all the white Christmas years in NYC?