frd

Looking forward to the afternoon Euro op run today to see whether there is consistency with the robust -EPO forecast. Again, this is in the time frame of interest near Jan. 9 th.

From Ventrice regarding the high amplitude ridge set to build over the North Pac into the Aleutians. Keep in mid this development, and the progression from there is way out in time.

Will be very interesting to see if we get the afternoon Euro run to maintain the -EPO signal. As Don posted recently, we really need to see either a -EPO to develop in early to mid Jan., or a more favorable MJO progression. However, modeling has been struggling with the MJO progression for weeks. Seems this winter so far is following the variability theme, just when you think you have it figured it only changes again.

Some good mets and pros are thinking we really do not achieve any long lasting + PNA from here on out. As 40 70 Benchmark points out he feels it is mostly -PNA tendencies. That might work for areas North of us in a cold gradient pattern but I don't put much faith into snowfall for my area in a pattern such as that. One could speculate, with everything evolving we could morph or transition into a better Pac pattern with corresponding tendencies for a period of a +PNA, but my guess would be later versus soon. Any favorable window for cold and snow most likely would be transient in early Jan. One concern at the moment is figuring out the MJO progression for later in the month. That and the EPO will most likely guide the sensible weather here in the East after Jan 17 th in my opinion. If we were hoping for a strong West based NAO that has a real impact in our area, I would think later in the season. We may see a convoluted North Atlantic, along with continued wave breaking, but based on the NH pattern I simply feel a true West based block is a better bet in Feb. or even later. We still have a ways to go to get any cooperation from the descending QBO as well. New data will be out early next month that may shed some light on how quickly it is descending. .

Well, two things I came across that you are aware of, but cool to mention, per BAMWX. 1 GEFS is too robust in its HDD forecast at the end of its runs, at least in the last couple weeks. 2 EPS has forecasted a declining EPO several times in varying degrees, but corrected back.

It is a proven fact the EPS first identified this warm-up evolution a while back. Some thought the EPS might have been incorrect this go around, as it had previously reversed course to a colder GEFS outcome earlier in the Fall. However, the GEFS, CFS and other American models all trended to the warmer EPS solution. No surprises here, as alluded to by psu and others.

Thanks for the clarification psu. I would love a blizzard though .

Two years in a row it has been there I believe, or at least in the December to Feb months ...... You agree ?

I may be wrong with the date but one analog tossed out was 69 -70. Was that the winter which did not produce until March ? Maybe there was a blizzard in early March that year, whether we shared in it I am not sure, recall reading a post from Uncle in the NY forum.

Possibly, but we have had periods where it appeared the blocking would couple and did not, or we would experience a longer cycle of a -NAO and then it became only transient , or the MJO would proceed more normally and not spend more time in the warmer phases and then rapidly pass the colder phases. Ah, but what you said does have merit , because if everything lined up perfectly all the time our average snowfall climo would be much higher. The general warming base state the last few decades is also a bummer as well. And for the record, my perception is also clouded somewhat by frustration at times.

Exactly, keeping in mind this is my personal perspective, but have you noticed how difficult it has become the last several years in achieving a state of cooperation between the indices. You see it in the West Pac with the MJO, you see it in the Pac and the Atlantic where they never work together, you see it in the high latitudes when we do not achieve coupling. Either a string of random bad luck, or a change in things, where everything is out of alignment .

Interesting post by Simon :

Of course seasonal models looking correct at the current time, in regards to the HL. Courtesy 33andrain - I enjoy Snowy's post, here is a little regarding EAMT and the Siberian High . Snowy's thoughts seem to echo the modeling at this time. << Posted 12 hours ago Just a few notes about the East Asian Mountain Torque, we will start with the current status. We are currently in a negative EAMT. I expect a positive EAMT to develop in the next few days to counter the current negative trend for a brief moment. This would add some momentum for the first 10 days of January for the PNA domain. But it won’t last. However from about the 1st to 3rd of Jan, we will see another -EAMT come into play, and this one could be sustained for a while. This is going to reduce momentum in the North Pacific basin, and increase the forcing of Aleutian ridging, and therefore Western US troughing and Eastern US ridging. As you can see in the model guidance, the troughing over Siberia early in January weakens the Siberian High, which weakens our chances for a stronger North Pacific jet stream pattern, and for a strong Aleutian low. Based upon this, I’d forecast Aleutian ridging for much of the month of January, barring an extraordinary constructive interference. The weak Siberian High and Aleutian low also means that any forcing towards a SSW is unlikely in the foreseeable future. Hope everyone here had a good Christmas, and wish everyone a happy New Year. >>

Yes, I tend to agree, good observation. We really need something to re-set the entire SST pattern out there. Wonder what would happen if we had a moderate Nino or even stronger. We seem to be stuck with the recurring issues.

In a general sense, I see the same issues as last year, but slightly varied. Still Pac issues persist...... Modeling not seeing the SE ridge beyond day 6 but it shows up due to the crap Pacific pattern, as mentioned earlier today by bluewave Warm and wet then cold and dry - cutters, etc. West Pac SST structure not conducive, hence effecting the MJO behavior ( related to the study done on warmer phases lasting longer and colder phases lasting shorter time periods ) Fast Pac jet - continued records being set across NA and the NH Ridging and High pressure North of Hawaii - same as last year. Then downstream effects for us. Again, nothing new. Warmer SST profile too far off the West Coast of NA. - Never really looked that good, even earlier in the Fall. Nothing remarkable is evident so far regarding this December, except the continued above average rainfall. However, the AN precip is simply a consequence of the above factors. But, maybe things will change later in January. Not loosing any sleep about this winter, not worthwhile in my opinion, as I learned to lower expectations and be more rationale after last year. However, still feel a window of significant winter weather will occur in Feb and even March. Here is a recent post form Tom. From @Isotherm Note ozone concentration propensity, which is highly reflective/comports with the mean z500 structure hemispherically. Increased ozone residence over the WPO/West EPO domains will continue to promote higher geopotential heights, whilst lower ozone concentrations in the means near the North Pole/Greenland will promote the overall +NAO paradigm maintenance, prospectively. When one considers the forthcoming AAM cycling, that too, comports with the NWP's modeled Nina-esque z500 structure in the medium term.

Also of note, SE Canada maintains snow depth and the fantasy land GEFS does have a somewhat colder look for us originating from the extreme cold air mass pooling near Alaska and the NW territories and then SE towards the Tennessee Valley, NE and the Northern Mid Atlantic.

Was waiting on this update, released today by http://www.bom.gov.au/climate/enso/#tabs=Overview I am not an expert on this topic but I am surprised we have gone from 2.2 C. in mid-October to +0.6 C. as of December 24, 2019. Even further weakening is expected according to the various climate models. The + IOD threshold is +0.4 C. Now the question is how soon will the atmosphere react, so we can revert to a more conducive and assertive Pac forcing regime, not all of these weak, multiple areas of convection that continues to throw off the various MJO models. New release- issued December 24, 2019 Positive Indian Ocean Dipole weakens: The positive Indian Ocean Dipole (IOD) continues to weaken, while the El Niño–Southern Oscillation (ENSO) remains neutral. The IOD value has fallen from a peak of +2.2 °C in mid-October, to the latest weekly value of +0.6 °C. Warmer than average waters persist near the Horn of Africa, but waters in the eastern Indian Ocean are now near-average. While the index is still above the positive IOD threshold of +0.4 °C, most international climate models surveyed by the Bureau indicate the positive IOD will dissipate in January. The rate of current weakening would suggest a return to neutral is likely by early January. Positive IOD events in spring (as happened this year) are often associated with a more severe fire season for southeast Australia in the summer months. In the tropical Pacific Ocean, while most indicators of the El Niño–Southern Oscillation are neutral, warmer than average sea surface temperatures in the far western tropical Pacific may be contributing to some changes in local weather patterns over the region. International climate models forecast ENSO-neutral until at least autumn 2020. When ENSO is neutral, it has limited influence on Australian and global climate.

Something to keep an eye on for early 2020. The modeled storm at 917 versus the Braer storm of Jan. 1993 .

@Isotherm Do you continue to favor the idea that a SSWE is not favored this winter season ? I can see a way to a better pattern without such an event, as I almost worry about the consequence should we experience a SSWE, although I put the odds of an official SSWE as rather low myself. However, outside of a SSW I would certainly like to see some disruptions to the vortex in January though, along with improvements in forcing, and as you mention above, AAM and the distribution and transport of it. Seems your progression is looking good so far Tom. Still feel we have ample opportunity later in Jan. that may go into March. Time will tell.

I am very skeptical myself. Just when I thought I had a logical progression things turn the other way. When I read about the delayed atmospheric response to the weakening + IOD I started to worry a couple weeks ago, but felt the HL may bail us out. Now that seems a no go. Until proper Pacific forcing becomes more prominent and assertive we have to wait. The opposite of last year at this time in regards to the SSWE. Several mets ( not here at American ) have reversed their position only to reverse it again and then again. Wonder what BAMWX energy clients are saying? . No one has the hot hand currently. More on topic - Another interesting long range observation, and I believe also mentioned by Isotherm, was the - NAO was verifying not as negative the past 3 to 6 weeks. When you actually look at the readings ( yes debate over what is a - NAO verus blocking acknowledged ) ) we really have not experienced a deep NAO state except on one occasion. Certainly everything has been rather progressive. The wave breaks have been beneficial and I would guess have helped those further North. Looking back a bit further, it was hard to keep the previous decent NAO drop going when we had that robust - EPO I believe. psu I also can't help but feel all our cold air outbreaks from early November to mid December were caused by mostly HL and strat related events ( wave 2 etc. ) such as displacements and elongations including one event that was barotropic related. Losing the HL and vortex disruptions and elongations are a real bummer. I felt early in the season the HL and elongations may be favoring Eastern North America but now it seems that mechanism is fading. Of course we could return to it later, as a consequence of an improving Pac and increased attempts to weaken the vortex, a.k.a the Isotherm seasonal evolution, or as is typical in some Nino years. One final note about the HL is the fact that the QBO might become a bigger player by mid Feb through March. I know folks refer to shear stress as well with the QBO at 30 and 50, but those references are above my pay grade. Hopefully an improving Pac will coincide with an improved NAM state later in the season via the descending QBO including seasonal vortex weakening. We shall see.

Looking back at the last 10 days of November for the CFS it was remarkable how it changed so quickly. I use to read it was in its wheelhouse 15 days before the start of the new month, but after looking at the past 6 months and combining that some notes posted by a couple climate/seasonal mets the CFS is not really stable and in its wheelhouse until the month is almost over. ( forecasting the next month ) So, I say what good is it ? Maybe for trends, as I have noted times that it is incorrect even when it is in the existing forecast month. I expect it to warm up for Jan in the next few days. I believe the trend to warmer has started already. Whether it is, or will be correct is difficult to determine.

Admit I am a little surprised but not totally. Yes we had the good wave 1 and 2 events but nothing timed up correctly and lasted long enough. I am sure there is more to it than than that . When the vortex was in a state more prone to further attacks , it was like , is that all you have ? And hence the bounce back.But not worth the time to even figure it out. I have not read about the latest forecasts regarding the precursor pattern that was posted last week from Ventrice. This strengthening is more camp two of Isotherm and stating the atmosphere and drivers were not conducive to weaken the vortex this season until later or not at all. If so expect the HL to continue to look poor. In terms of retrogression and blocks and just because this post by HM is interesting . He posted it just because it is cool. Seems there is always a monkey wrench thrown into the winter. Of course with the run to run changes it is silly to worry. Everyone so far has been proven incorrect at least in some form or fashion about this December, not surprising given the abundant weak signals.

Speculation could be because of the weak Enso state we remain in a rather volatile and variable pattern the duration of the winter. Speculation, of course, but until a certain pattern driver takes hold and is able to provide a repetitive pattern ( feedback loop, etc ) maybe it is more of the same. Hard to say right now. Will the driver be blocking in AO domain that goes negative for a period of 30 to 45 days, will the MJO become more prominent and work in our favor, aka the Webb progression, or will it be more of the same. Interesting times ahead.

The general idea that run to run model changes would be frequent, and at times significant, is really holding true so far. I would not want to issue a 30 day forecast because the swings in modeling are really extreme. I really feel many mets are even at a loss. Of note, the same theme the last two weeks, pretty subtle yet significant changes on the modeling, ie. the -NAM state for example. Overall trends up top in the last 72 hours are not very good as you know. A lack of cooperation in the drivers at play, maybe the seasonal models had a clue, although that determination is still yet to be determined. I really don't like the looks of the TPV and its location out in fantasy land. Unfortunately I believe the progression to a more conducive winter pattern that can reload and has real snow potential will have to wait possibly, although there is a window as the PNA goes + near days 8 to 12. Funny thing is with the reasoning of the two camps , as we discussed before, one warmer less snow and then the other more seasonal and maybe snow potential, well the momentum seems to change with the modeling. There have been some set backs in terms of real threat window, and so far Philly and the surrounding areas have had multiple low end snow events, but every one has under-performed. Certainly not a positive trend, even HM admits to the trace phenomenon. Another thing I was looking for was the occurrence of a "significant "snow event prior to December 15th to aid in providing some support for an above seasonal snowfall potential. These may or may not be clues as well as to the future. Another observation from the NE forum, from Tip. He mentioned how cold air was not holding on and was surprised how certain events up North trended warmer. Sounds like our area right, LOL . He posted that he felt we needed to establish deep cold air source with a -EPO and then intervals of + PNA. ( Of note on or near Jan 2nd to the 4 th we do enter a forecasted period of + PNA. ) I like to see what happens then. Wondering if the best pattern does go down in the second part of the winter. There are several analogs/outlooks that support that idea, along with a few Nino winters starting after Jan 15th in terms of snowfall and colder outcomes. Whether they prove useful in this day and age and background state , hard to say. Things are still progressing in terms of forcing and continued developments up top. Bottom line, very hard pattern to predict and just enjoy the holiday season and treasure those in your life Very bottom a post by Don S courtesy 33andrain - my take away (I think we all know this , but ) from it is the importance of a - AO and a + PNA. Those are your clues to Jan to March IMHO. Some interesting posts below regarding the IOD and the HL. From Don S courtesy 33andrain Dreams of a white Christmas for the Middle Atlantic and southern New England regions will have to wait for at least another year. Milder air is now pushing into the region and will likely predominate through the much or all of the remaining days of December. Through December 21, snowfall amounts for select cities include: Allentown: 2.1" (1.6" below normal) Atlantic City: 0.5" (2.1" below normal) Boston: 11.5" (4.9" above normal) Bridgeport: 5.5" (1.9" above normal) Harrisburg: 0.2" (3.5" below normal) Hartford: 21.1" (14.8" above normal) Islip: 4.3" (1.7" above normal) New York City: 2.5" (0.5" below normal) Newark: 4.2" (0.7" above normal) Philadelphia: 0.1" (2.1" below normal) Providence: 8.0" (1.0" above normal) Worcester: 25.3" (13.5" above normal) Despite the warmth, which could take monthly departures toward and perhaps even above normal across many parts of the region, dreams of a snowy January persist. Perhaps a key to whether those dreams are realized will be the state of the Arctic Oscillation (AO) and Pacific North America (PNA) pattern. Since 1950, 52 snowstorms brought 6" or more snow to at least one of the following cities: Boston, New York City, or Philadelphia. 60% of those storms had an AO-, 64% had a PNA+, and 38% had an AO-/PNA+. From among the 18 storms that brought 6" or more snow to at least two of those cities, 83% occurred with an AO-, 83% occurred with a PNA+, and 67% had an AO-/PNA+. From among the 11 storms that brought 6" or more snow to all three of those cities, 91% occurred with an AO-, 91% occurred with a PNA+, and 82% had an AO-/PNA+.

To go with the above from @Bob Chill this is a another fascinating animation regarding the NW Atlantic, Check out the second image loop from Anthony.