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Isotherm

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About Isotherm

  • Birthday 09/24/1990

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  1. Thanks for these daily updates. This winter is about as volatile as one can get - from record cold in early January to record warmth now. But overall, the warmth will have won out, and it will be remembered as a fairly classic Nina progression: cold/snowy first half, warm/essentially snowless second half. March isn't included for meteorological winter temperatures, but March will be snowier than February.
  2. The higher geopotential height induction over the EPO domain occurs fairly rapidly (circa March 1st) and consequently, 850mb temperature anomalies respond over the Northeast. So this does not look like a stale/mild airmass to me. It's not severe cold but it will be more than sufficient. The mid level flow is emanating from the NW territories, even though the trough buckles near the West Coast (it's not significantly modifying the downstream airmass). The GWO collapse and concurrent MJO/GWO pulse 1-2 is reflective of a severe retraction event driven by momentum removal, tropical forcing, and torques. Poleward AAM transport has initiated and will encompass the higher latitudes for the first half of March.
  3. RMM diagrams continue to lag the true u-div forcing progession at z200. The MJO signal has entered phase 1 (skipped over phase 8) as expected, as one can see by the -VP signal over Africa. This will operate adjunctively with the downwelling circulation anomalies and tropospheric wave break to tank the NAO in about 7-9 days.
  4. The 10-day window of Feb 29-Mar 10 produces more 6"+ snow events in NYC than any 10 day period from Dec 1-Jan 20, except ties Dec 20-30. So Feb 29-Mar 10 is a snowy period climatologically; to assert otherwise is patently false.
  5. The models are a little overzealous with dumping the lower geo-potential heights in the W USA. A few points: [1] CHI 200HPA ostensibly indicates the propagation of u-div signal through phase 8 and already going into phase 1. The RMM diagrams are lagging here. Further, the convective signal becomes less coherent, but the upper level signal does not as significantly. [2] The coupled alterations with poleward -AAM propagation and GWO/MJO contemporaneous circulation into lower-Mr state, E-Hemisphere based forcing, will initiate a jet retraction process. [3] Late December-early Jan we cycled through a deamplified 8-1-2, and the W US signal was not as suppressed as modeled. [4] The -PNA troughing should retract sufficiently such that heights rises in the Central US and fall near the East Coast, due to shorter wavelengths. This is the MJO Z500 composite anomalies for phase 2 in March. The NATL will be wrong due to the severe stratospheric downwell, but I expect this appearance in the W USA. If we retract the trough sufficiently, a West Coast based trough is favorable in March.
  6. Yes. See my latest post in SSW thread.
  7. Wave-1 and 2 are distinct atmospheric circulation patterns whereby we have "one" notable ridge and trough signal, or "two" ridges and troughs throughout a given spacial domain. Certain tropospheric patterns constructively interfere or enhance wave-1 resonance by nature of the fact that they project upon the climatological wave-1 or wave-2 circulations. This has been almost a perfect progression for a major SSW, and we're seeing that. Wave-1 preconditioning/displacement and elongation with a follow-up wave-2 split with ridges pressing on the Atlantic and Asian sides. The current SSW is one of the most severe we've ever experienced due to it's zonal mean wind reversal and duration (7-10+ days). The upwell of the wave-2 implicates strong coupling w/ the stratosphere and downwell feedback will be rapid. Thus, as MJO continues, u-div through the E hemisphere, and the circulation anomalies propagate downward, the AO/NAO will reverse by late February, and the Pacific should improve. Late feb (last week) into march will produce a snowstorm in my opinion.
  8. February is upon us - pattern change is in order

    Agree. Back in mid January, we thought there would be a protracted break and most were interested in the pattern, and now it's reversed going forward. I am confident the ideas postulated are correct, but we'll see. It's going to take at least 10-14 days to reshuffle hemispherically. But one can see the resultant NAO/AO decline on the latter part of the EPS. This is a legitimate response to the downwelling, as well as GWO and MJO alterations. Yes, that brings us to about 3 weeks of conducive snowfall climatology for many, but all that is really needed is one good event or two to push totals near normal for most on the coast (speaking NYC centric).
  9. February is upon us - pattern change is in order

    Weeklies look excellent in the NAO/AO domains, and that's all that matters to me. Even given a less than ideal Pacific, heights should be more suppressed over NE US. I also think the p8 MJO will yield a bit better result in terms of those upstream W USA heights. Due partially to the fact that this MJO pulse is extremely amplified/coherent and protracted duration in phase 7, I think there will be at least a several day lag as far as downstream NPAC alterations post propagation into p8. Thus, that may allow some vestiges of lower geopotential heights in the NW US in the Feb 17-21 period, before we begin shifting significantly thereafter. The GWO/AAM looks much more auspicious to me once beyond D10, as FT/MT will be decreasing coupled w/ initiation of -AAM poleward propagation. I still like Feb 23-Mar 10 approximately. I think there will be a 6-10" event minimum in that period, somewhere along I-95.
  10. The etiological factors of this resultant SSW event are of course numerous, from previous tropospheric precursor, wave 1 preconditioning, to MJO forced rossby wave dispersion - but typically with these events, even wave 2 upwells, the feedback in terms of downwell is progressive/gradual. So while the polar cap heights will be conducive rather rapidly in the troposphere, I think the -NAO/AO signal will continue to strengthen with time, as we head into the 20th-25th period and even beyond. The LR ensemble variance is muting the severe negative decline. I'm not sure that the pattern will be sufficiently favorable for us by the 17th-18th, as the Pacific is still responding to poor MJO forcing, and the -NAO block won't yet be west based enough to countervail that upstream signal. IMO, as the lagged MJO response phase 8 manifests by 20th-25th, in conjunction w/ continued downwell of positive circulation anomalies/propagation southwestward, the synoptics become much, much better into the last week of the month. The NAO may not peak until the very end of month or beginning of March. But regardless, after the 20th-22nd is when I am most interested. Credit: AER (polar cap) Note upwell and then subsequent 'dripping paint' downwell. This will intensify the -NAO as we move through the last 1/3 of the month, progressively.
  11. We should have a typical February/Nina warmer than normal departure. NYC's trend will be upwards through the meteorological winter: cold Dec, near normal/slightly below Jan, and probably warmer than normal Feb. Should be interesting to see if we can make a run at 0 for the DJF departure, but that would require a solid +3 month or greater.
  12. February is upon us - pattern change is in order

    It's a w2 upwell split (after w1 downwell preconditioning already) so the coupling is quite a bit stronger here. It's not so much temperatures; geopotential height alterations are more important. I think we'll see a fairly rapid response aided partially by MJO and AAM changes later this month, such that cooler air relative to normal begins returning toward the last week of Feb. I'm very much interested in the last week of Feb into early March. I've been on the +NAO winter train from the start, but I do believe we'll induce a legitimate -NAO signal beginning late month. The next 10-15 days will be on the warm side to occasionally torch IMO.
  13. For most in the PHL-NYC contingent, I am fairly confident the largest snowfall event has not been experienced yet. I like the last week of February or first week of March for this potential. MJO+Strat lag coupled with GWO alterations and increased -AAM transport should kick in Feb 21-25. Not sure yet about specific windows, but I think the overall configuration rapidly improves in those final 8 days of the month.
  14. Stratospheric vortex splits tend to preferentially induce much more rapid transitions to wintry weather in Europe, while conversely, displacement events tend to be less auspicious for Europe, and better for the United States. Initially, the southwestward propagation of the daughter vortex will be counterproductive as it acts to suppress the poleward reach of the NPAC ridge, yielding a fairly zonal flow across the US for several days. However, once the warming event occurs, it will feedback and quite literally aid in reinvigorating the MJO pulse into phase 8 as we reach the Feb 16th-18th time frame. That will further aid in shuffling the rossby wave train and subsequently eliciting a legitimate -NAO by about Feb 20th-22nd in my opinion. Concurrently, GWO/AAM alterations will occur as MT/FT decreases and forcing continues circulating. So, my thinking is that Europe's probably into winter by circa February 14th, we're probably waiting until the last week of the month for the real step-down into wintry weather. It will come, but I think this month is probably going to look like what happened w/ a lot of prior SSW in the books -- namely, that the SSW month actually features warmer temp departures than the month prior (January). These are very early thoughts - though it would be congruous with most of the analogs in my outlook - March could be the much colder month relative to normal. After we reset the global pattern AAM/GWO wise by late Feb, and a genuine -NAO initiates, in concert with MJO u div signal persistent into p2-3, could mean a potentially cold/active front 10 days of March. To sum up, I still think we begin the transition as we approach the 18th-20th, but I'm most interested in wintry weather further into the last week of Feb and first half of March.
  15. At the very end of the EPS, we see the first legitimate indication of a -NAO initiation of the winter to date. I think the prospect of an interesting Feb 20th-Mar 10th period look good right now, given coupled AAM/MJO and stratospheric alterations (even if the NAM isn't in the tank). The tropospheric vortex has essentially vaporized by the end of the EPS, reflective of the decimated stratospheric vortex. The initial positioning will be poor mid month (TPV), but eventually, I think it'll simply become overwhelmed by the higher geopotential heights propagating southwestward, and we do achieve a legitimate -NAO for the last week of Feb into March. The ewd propagating MJO will operate adjunctively as well in engendering this response.
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