Re: Long Range Thread 13.0

[Guest]

I know it's only 1 day of posts, but I'm not liking what I'm reading today at all. Date of pattern change might be pushed back......maybe a warming trend for4-5 days in early Feb.....Talk of storm for 27th-28th time frame is gone, when it was once a supposed "lock"

Hopefully this is only a blip. because with all the hype about the 27th going forward, coming on the heels of missing out on an epic blizzard with this Monday's monster would be crushing to say the least!

[Isotherm]

Pattern update:


The anticipated wave-1 increase via the tropospheric precursor pattern and concomitant MJO propagation support has led to an enhanced convergence of energy at the vortex, resulting in sufficient forcing to temporarily displace the stratospheric vortex from the center of the pole. The vortex will be pushed toward Greenland at 50-10hpa by D 10. However, after which, wave-1 convergence begins to decline, and with no follow-up wave-2 assault, and so the resultant outcome may be a near miss; namely, the reduction of zonal winds at 60N/10hpa to weakly positive levels (no reversal). Right now, it appears the wave driving will be sufficient to induce a mean zonal wind reversal at the top of the atmosphere (1hpa), but not further down. Even in the case that zonal winds are temporarily reversed at 10hpa, there are a couple of significant issues: 1) This potential displacement event will likely not be one which results in the subsequent destruction of the vortex, but rather, a rapid reconsolidation and intensification of the PNJ; and, 2) Even if a SSW event were to occur, based upon my research, this would likely be an ineffectively propagating SSW event. In other words, the significant warming at the upper levels of the atmosphere will not induce meaningful alterations of the z500 northern annular mode.

What the near miss/borderline displacement will effectuate is a weaker stratospheric vortex, making it more susceptible to future assaults. The evolution of the tropospheric pattern is such that wave-2 should begin to increase by day 10, with potentially a robust spike by 2/10. Given an expected weaker vortex, a potent wave-2 attack could possibly induce a more meaningful stratospheric reversal toward mid February. However, of course, at that point, we are approaching late winter, and the effect of stratospheric warming events tends to be less dramatic. But there are examples in the data w/ analogous background conditions to this year which featured mid/late Feb SSW events. And I currently favor late winter (later in Feb into March) for the best opportunity for a genuine negative AO pattern in the troposphere. However, this is only one possibility. If the wave driving doesn’t progress, we could run the early February regime through March.
Now, what is the early February regime? The MJO aided ephemeral alterations with PNA spike and concomitant downstream trough in the East will rapidly transition into a retracted jet / Aleutian ridge / NW US trough pattern by early February – classic La Nina regime.

There will be a transient window 1/28-2/3 for a deep coastal storm on the east coast which could produce snow, when the PNA is conducive. If we do not capitalize on that period, all hope is not lost. I think poleward ridging will develop in the Aleutians given tropical forcing progression and AAM/GWO tendencies. This will force the return of a NW US trough, but if there’s sufficient geopotential height rises extending into the Arctic and/or northeast Greenland from the Scandinavian side, the baroclinic gradient would be sufficiently suppressed to permit a wintry event down to our latitude. If there’s insufficient extension of the poleward ridge, the pattern will be similar to December with February climatology: a snowier pattern for much of New England but not necessarily that good from coastal SNE southward. Overall, Feb 1-15 looks normal to warmer than normal, but not blowtorch. There will be possibilities of snow, but it isn’t a great looking winter pattern. I do believe we will achieve at least one moderate or greater snow event in the 1/28-2/12 period.

Beyond that time, the determinants of a blocky pattern will be contingent upon MJO aid, stratosphere, and other factors. At this point, I would lean toward a continuation of the largely +AO/NAO regime with an initial +PNA transient, leading toward a –EPO/-PNA for most of the first half of February. The weakened state of the stratospheric vortex should permit the neutralization of geopotential heights in the Arctic such that the upcoming few weeks is more favorable than the winter thus far for the possibility of snow. It will favor the Lakes, New England and interior however.

A resurgence of wave-2 in early-mid February could eventually lead to genuine AO/NAO pattern for later Feb-March but that is still highly speculative, and I am not willing to attach significant confidence to the idea just yet.

In sum: it appears to be the type of pattern which will gradually inch us close to my seasonal numbers of 20-26" for NYC. It's not a great pattern for NYC but it could be occasionally "serviceable" with opportunities, given February climatology and sufficient poleward ridging. That's the type of regime which will continue to favor the northern tier / New England. Temperature wise, it looks near normal to above at times at our latitude following the cold shot.

[sroc4]

Really nice post Tom

[Guest]

Yes. Great post. Informative. Unfortunately it reinforces my post from last night where I was concerned that the incredible optimism and downright giddy posts about the long range pattern change which we've been reading about for over a week are being SIGNIFICANTLY TEMPERED DOWNWARDS

[Isotherm]

Thanks guys. I think we may have a better opportunity rolling the dice with a southwest flow event as geopotential heights decrease in the West and the baroclinic zone lifts northward. The progged orientation of the PNA ridge in the 1/26-2/2 period is not conducive for tucked in coastal storms. We need it more Meridional and less SW-NE oriented, the latter of which tends to suppress / force short waves offshore. I'm not too optimistic about the 1/26-2/1 period. The gradient regime may give us a better shot, but I'm also worried about our area being too far south w/ SE Ridge issues in February.

[Guest]

........and the beat goes on and on in a downwards fashion.

[devsman]

I've already told people at work I believe a groundhog day storm is coming. So a groundhog day storm is coming.

[CPcantmeasuresnow]

I've already told people at work I believe a groundhog day storm is coming. So a groundhog day storm is coming.

If only it could repeat over and over again just like the Bill Murray Movie.

[Frank_Wx]

Nice post Tom. I do think there is a ton of short waves coming out of the PJ between the 27th and 5th, and model handling of upper energy coming out of Canada this year has been pretty poor. So if a storm were to happen I wouldn't expect models to pick up on it until 6 or 7 days out. The baroclinic zone will be S&E because of PNA ridge orientation, but I've seen instances where a strong enough STJ vort travels north enough to force a phase with northern energy. I'm a big believer in +PNA patterns so we'll have to see. Regardless of storm or not storm, this is most definitely a pattern change compared to the mild weather we're seeing now.

I do disagree about temperature departures though. It does not look above normal the 1st to 15th in my eyes.

Average 2M temp anonalies first 5 days of February



Then beyond the 5th depends on the strength / orientation of the WPO/EPO ridge. If strong enough, it will force the baroclinic zone to remain just S&E of our area while muting the SE ridge. We've seen this happen a couple of times already this winter. The EPS maintain colder than normal weather beyond the 5th.

I'm thinking normal to below normal through the 15th.

[sroc4]

This looks incredibly promising.

[Armando Salvadore]

To back up the stratospheric warming, here is your second wave 1 warming at 10mb come early Feb thanks to an ignition of the MJO. It does appear we're going to have the tilt needed (indicated by the ECMWF) to get this to really weaken, but how much does it down-well and if that is the case, what precursor effects does it have on the troposphere? Big battle between the GEFS and EPS for the 11-15. Given the pattern, i probably would buy a blend of the two because it appears we have a transient MJO wave before yet another wave forming in the western hemisphere, so it makes sense to see a jet retraction and -EPO/-WPO Aleutian ridge complex setup. I've noticed that there is more poleward heights with the ensembles this time around and also a more noticeable Scandinavian ridge that'd allow the TPV to push further south thus forcing the baroclinic zone further south. Still think we see something between 1/28-2/2. GEFS tried hinting at something around the 1st.

[Isotherm]

I think the 1/26-2/2 period has been trending worse every day, and the more likely time frame for something would be the following week, if the gradient is sufficiently south via pressing from the TPV.

The strat progression doesn't impress me yet. I think what may occur is a near miss - maybe - brief zonal reversal before reconsolidation with this attempt, followed by a stronger hit of wave-1 or potentially wave-2 via the tropospheric precursor pattern as we approach mid Feb. That may be the attempt to fully destroy or split the vortex and induce more effective downwelling. The coupling right now is rather poor, and I see no indication of a tropospheric NAM reversal through early February. The second half of February could see changes in the AO if we succeed in a more effective downward propagation.

This initial attempt looks very borderline to me, and based upon my research, the conditions are unfavorable for quick and efficient downwelling. Still uncertain whether we officially achieve the 10hpa/60N zonal wind reversal with this first attempt 2/1 as well.

[Isotherm]

The key will be achieving sufficient height rises across the pole which, consequently would force the TPV further south and thus the baroclinic zone. The second week of February is the period I am cautiously optimistic about (producing "something", possibly in the form of a SWFE as I mentioned yesterday's post). It will be a close call because the pattern clearly favors the interior. I am slightly more inclined to believe Arctic height rises on model data this time around due to the much weaker stratospheric vortex. Not a real negative -NAO/AO pattern but closer to neutral would at least permit some opportunity, with a concurrent poleward ridge.

[Frank_Wx]

The GFS shows abundant opportunities for snow events between the 29th and 8th. Temps are normal ttoo below normal (mainly below).

[Guest]

Any early indications as to what type of events? Not Godzillas and such, but clippers, Miller B's etc.

[Frank_Wx]

Any early indications as to what type of events? Not Godzillas and such, but clippers, Miller B's etc.

The potential exists for Miller A and redeveloping Alberta Clippers.

[Frank_Wx]

Check out the progression of the 10hPa Strat PV on the GFS OP:

Current - PV over the Pole:



January 27th - Wave 1 warming event underway and beginning to weaken / displace PV toward Europe:



February 8th - PV is still intact but remains displaced off the North Pole. Positive geopotential heights encompass the Arctic.



EPV is forecasted to get more poleward the end of this month. The forecasts keep getting bullish by the day. Reminder that a longer EPV means stronger vertical forcing going from the Trop to the Strat, while an arrow pointing toward the North Pole is more favorable for PV weakening. Also notice how 1hPa mean zonal winds are expected to go negative (easterly) suggesting the very top of the PV will get into an extremely weak state.



At Day 10, the EURO is VERY close to a technical SSWE at 10hPa/60N mean zonal winds.



As stated, I think the warming event will be significant enough to bring changes to our pattern, but it does not look like we'll achieve a SSWE that follows through from the mid to lower levels of the Stratosphere. It will be GREAT if models begin showing another Wave 1 to follow up from the one that will take place this weekend, or a Wave 2. Ultimately, I think that will destroy the PV.

[Frank_Wx]

And then look what the GEFS do by Day 12. -AO/-NAO with continuing -WPO/-EPO conditions. The progression on the GEFS is exactly how I felt the pattern change would go. Starts in the Pacific, works its way into the Arctic, then hope these higher heights begin showing up over the NAO domain.

Day 12



Day 16

[Frank_Wx]

Today's LR 12z GFS gives me a tingly feeling inside.

[nutleyblizzard]

Today's LR 12z GFS gives me a tingly feeling inside.

The GEFS is looking great for cold and snow too!

[Armando Salvadore]

Good agreement between the GEFS and EPS for this upcoming weekend into early next week. GEFS and EPS hinting at something diving south from western Canada and trying to redevelop a wave off the mid-atlantic coast. So, it appears we enter into a clipper pattern with a +PNA at hand. However, not the most ideal because +AO/NAO, but sufficient to produce at least something wintry.







I took the 12z GEFS and 0z EPS and took their respective tropical forcing forecasts because their is some discrepancy between the GEFS and ECMWF. Most likely, we see more of what the GEFS has, and that is we go from a weak phase 2 into a transient base state MC wave, then an initialization of a MJO wave back into the western Hemisphere.



Now check this out, if we look at the 12z EPS, we now see the EPS latching onto the 12z GEFS idea and that is a much poleward and stronger ridge centered over the Aleutians down below!By the way, we do see a jet retraction as Tom alluded too and pacific wave break which will cause the anticyclone over the west coast and Alaska domain to retrograde. Ensembles are hinting at that connection of the Aleutian ridge and Scandinavia ridge, which would direct the TPV further south. Already have changes on the 12z EPS.

[billg315]

So does that mean we're going into an MJO phase 8 and 1 around this time frame, and is that what we're looking for in terms of a better chance at east coast trough/storms? (sorry if this is a dumb question, I'm trying to learn more of these long-range factors that we watch, so I may occasionally ask dumb questions).

[Armando Salvadore]

So does that mean we're going into an MJO phase 8 and 1 around this time frame, and is that what we're looking for in terms of a better chance at east coast trough/storms? (sorry if this is a dumb question, I'm trying to learn more of these long-range factors that we watch, so I may occasionally ask dumb questions).

Don't be sorry for asking! Currently, we're in a phase 1 signal and soon to be in phase 2 (indian ocean). Hovmollers and RMM indices indicate that we see a transient MJO wave disperse before igniting again in the western hemisphere and west pacific by the first week of Feb. Sometimes, the forecasts on those RMM plots may be wrong because of the destructive interference from the la Nina maritime continent standing wave. Any propagation of the MJO in the west pacific supports a poleward Aluetian ridge to extend and if it can punch into the Arctic circle, we'd see more influence of the polar vortex to push further south thus pushing the baroclinic zone south as mentioned several times.

[billg315]

So does that mean we're going into an MJO phase 8 and 1 around this time frame, and is that what we're looking for in terms of a better chance at east coast trough/storms? (sorry if this is a dumb question, I'm trying to learn more of these long-range factors that we watch, so I may occasionally ask dumb questions).

Don't be sorry for asking! Currently, we're in a phase 1 signal and soon to be in phase 2 (indian ocean). Hovmollers and RMM indices indicate that we see a transient MJO wave disperse before igniting again in the western hemisphere and west pacific by the first week of Feb. Sometimes, the forecasts on those RMM plots may be wrong because of the destructive interference from the la Nina maritime continent standing wave. Any propagation of the MJO in the west pacific supports a poleward Aluetian ridge to extend and if it can punch into the Arctic circle, we'd see more influence of the polar vortex to push further south thus pushing the baroclinic zone south as mentioned several times.

Got it (in the big picture sense, haha) Thank you!

[Snow88]

18z GFS shows 2 little disturbances to watch

168 hours

222 hours

[jmanley32]

Frank 12z 31st system thats just to south and bombs a little late?

[aiannone]

TWC's Tom Nizol just said, winter weather lovers in the east and especially Northeast should stay tuned to this pattern change. He likes clippers turning into Northeast snowstorms as they hit the coast.

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