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Long Range Pattern Drivers & Evolution Thread


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The 33andFive...Day Outlook -- Monitor here

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I posted that the EPS after I saw the 282 had multiple chances.

I just like the multiple SWs under the block. 0029B69F-0ED8-4C98-A70D-CD6246F8C41A.png.7e3ac9483b0e33e282d773cc9656089f.png.1c9e4766d1d92c16473af1e479b9c1ce.png

 

 

Here's the 5 day mean in the 10 to 15 

20191219_192104.png.1c2c10717507229096dbcd0266879587.png

 

If we filled that gap it would come very close to the 10 day mean before one of the greatest 1 - 2 punch the MA has ever seen

 

compday_vu2ff42WGL(1).gif.0e8847a6576d5e15ceabbb88e7fc67c5.gif

 

I just ripped this from crazy Joe but man thats not too far away. 

 

 

 

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Hey Tom. I did not favor a warm Nov or Dec. I thought the effects of the NPO-induced cold would first start out West in December; and when the NAO eventually relaxes for a time, we would get some warm

The shifted west tropical forcing from traditional Niño, or even Modoki, has created a stronger Subtropical High in western Pacific / Hadley. This has promoted the return of the "Kamchatka Low" which

Back on December 26, composite date for MJO passage at high amplitude in Phase 4 and historic data associated with strong AO+ patterns in combination with a positive EPO implied that the GEFS was miss

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1 minute ago, Analog96 said:

 

I just don't like that air mass Christmas night one bit.

I think we're too warm to do anything but rain, although latest trend is a bit cooler, so we'll see.

 

Theres back side flow, the H drills in from NE.

Thar low cuts to the Delmarva,  you CAD.

 

It's a light snow chance , nothing big.

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Despite ample sunshine, most of the region saw its coldest December temperatures since December 31, 2017. Select low temperatures included:

 

Boston: 15° (lowest since March 7); Bridgeport: 17° (lowest since March 8); Islip: 17° (lowest since December 8); New York City: 16° (lowest since February 2); Newark: 16° (lowest since March 7); and, Philadelphia: 19° (lowest since March 7).

 

Beginning this weekend, a milder pattern will commence. Overall, the final 10 days of December will likely have above normal temperatures, with perhaps a few somewhat cooler days.

 

Colder air could return during the first week of January. However, some of the guidance has shifted away from that idea. The progression of the MJO in concert with the teleconnections could be crucial in determining whether most of North America's cold air stays bottled up north of the Canada-U.S. border beyond the first week of January or comes south and eastward into the region just after the start of 2020.

 

The ENSO Region 1+2 anomaly was +0.5°C and the Region 3.4 anomaly was +0.5°C for the week centered around December 4. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.05°C and the ENSO Region 3.4 anomaly has averaged +0.53°C. These recent conditions are consistent with a weak El Niño. Nevertheless, a neutral ENSO remains the base case for Winter 2019-20.

 

The SOI was -6.90 today.

 

Today, the preliminary Arctic Oscillation (AO) figure was -1.408.

 

No significant stratospheric warming event appears likely through December 28, but some warming above 3 mb could develop near the end of the forecast period. Moderate Wave 2 activity could occur after December 20, likely leading to some upper stratospheric warming. Overall, most of the stratosphere is forecast to remain cold into the closing days of December on the EPS.

 

On December 18, the MJO was in Phase 4 at an amplitude of 0.621 (RMM). The December 17-adjusted amplitude was 0.769.

 

Based on sensitivity analysis applied to the latest guidance, there is an implied 54% probability that December will wind up colder than normal in New York City. That probability has fallen sharply in recent days, as the guidance has made large adjustments to the warmer side for the final seven days of December.

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The forecast +EAMT for 24th-26th of December is not exactly that strong, and is relatively short-lived.

CB0A5E89-6F85-4F07-9D3E-4E918721E26F.gif

Watch the descending high upon the Himalayas quickly succumb to the forces of descending troughs. It will probably cause a positive EAMT, but not one that can really pack a punch.

 

We do have +FT as well, but that is of course evidence the MJO signal is rather pushing into Maritime Continent, and with a lack of pace.

F4DF6F90-DB2D-4876-9C18-E75EE18D26A8.png

 

What this means is that we are in Phase 3/4, which are destructive influences to Eastern US troughing with a lag. They are also correlated with a +NAO with a 10 day lag. Ultimately they help to fuel Western US troughing and moisture transports downstream.

 

There’s little sign of proper tropical wave forcing, beyond the flip-flops of the model RMM indexes in the Western Pacific. I’d assume these would be more potent in the middle weeks of January, probably favouring snowfall chances for the Eastern US in the second half of January.

 

For now the tropical forcing is destructive, rather than constructive to the building of Eastern US forcing.

 

As for the stratosphere, I can see where Ventrice is going, and I am interested in the prospect of a SSW, but honestly I still can’t see it happening in the first days of the New Year, without adequate extratropical forcing, with a GLAAM that is still likely to be in the negative phase at that point in time, and without constructive forcing from the QBO, etc. If you push that back say 10-20 days, then I am more interested. If it happens in the next 15 days, well honestly it isn’t in the optimal position for maximum impact.


And finally for what it’s worth, the EPS shows that the IO standing wave is only taking a break over the Christmas period:

66A3DC13-F3A7-4A2A-9894-2F760A5CA709.png
The present we have been waiting for, but unfortunately not one that lasts. 
 

At this point, I believe that the standing wave should slowly weaken over January, with more constructive tropical forcing slowly coming into the picture in the latter half of the month.

 

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20 minutes ago, antmasiello_HM said:

The actual EA MT of interest is in early Jan.

EPS isn’t a big fan.

B820BB58-1B98-4675-A3C6-22F70A632694.png

 

GEFS likes it better.

4BC69F96-DCC9-4699-AABB-59C7F64DC3C4.png

The positioning of these things are important.


It could work out, but given the progression of the GSDM and the cycle of it, I’d assume it to be a bit earlier. A late torque is better, but it doesn’t really change the narrative. Might improve the short term outcome though, it depends on the strength of the +EAMT of course and how that interacts with the PNA domain 5-10 days downstream.
 

The progression of a gradual change to colder risks in the Eastern US, doesn’t involve a sudden flip to deep cold in Early January IMO.

 

One thing it would help more is to increase the likelihood of that SSW that is making the rounds. Which would help us down the line.

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2 hours ago, antmasiello_HM said:

 

The RMMs are reacting to higher frequency waves and multiple areas of forcing. This is why they sort of cut through the middle and eventually emerge into W. Pacific. The lower frequency signal will reach the central tropical pacific in the second week of Jan probably. I agree with Eric on that.

 

Use Roundy's statistical guidance for a visual: http://www.atmos.albany.edu/facstaff/roundy/waves/ and more specifically: 2020.png

We don’t enter the colder phases  to after the 10th on those correct? 

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1 hour ago, Snowy Hibbo said:

EPS isn’t a big fan.

B820BB58-1B98-4675-A3C6-22F70A632694.png

 

GEFS likes it better.

4BC69F96-DCC9-4699-AABB-59C7F64DC3C4.png

The positioning of these things are important.


It could work out, but given the progression of the GSDM and the cycle of it, I’d assume it to be a bit earlier. A late torque is better, but it doesn’t really change the narrative. Might improve the short term outcome though, it depends on the strength of the +EAMT of course and how that interacts with the PNA domain 5-10 days downstream.
 

The progression of a gradual change to colder risks in the Eastern US, doesn’t involve a sudden flip to deep cold in Early January IMO.

 

One thing it would help more is to increase the likelihood of that SSW that is making the rounds. Which would help us down the line.

 

The EPS is signaling it. I disagree that it is not.

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17 minutes ago, antmasiello_HM said:

 

I'm not a fan of calling phases warm or cold. I'm also not a fan of isolating a region and treating as if it's the only region, like we've seen in some recent posts this evening. After all, the MJO explains like 25% of the variance. But anyway, the warm pool gets excited during the second week on those charts.

Why aren’t you a fan of that? Wouldn’t p6 be unfavorable for sustainable cold in the east? 

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1 minute ago, antmasiello_HM said:

 

Well, for starters, the time of year matters for the wave train response and what is statistically likely over the US. Being solely in a phase says nothing about the inertial state or changing state since the wave itself, its interaction with other forces, and its influence around the globe all can alter from event to event. Background states affect the way the MJO affects the wave trains and their influence on our weather. 

Very informative. Thank you. So we could be going back to the base state we had in early November? 

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4 hours ago, antmasiello_HM said:

 

This signal has been on the last few runs and fits with the classic tropospheric precursor pattern. It also fits with a classic Niño progression for a mid winter disturbance. The entire evolution with the TPV and this reminds me of 1987.

1986-87 analog showed up a lot in the fall. I did not use it for bad qbo values. But it was definitely there.

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27 minutes ago, Webberweather said:

As the VP200 hovmoller below shows, this is a classic example of multiple higher frequency circulation signals competing for dominance in RMM phase space, hence the dampened/weak MJO. What we're seeing right now is not an MJO in the classical sense but rather a mattering of convectively coupled Kelvin waves (k = 3) projecting onto low frequency modes, which oftentimes occurs in cases like these there's an effective hand-off between lower frequency variability (in this case +IOD >>> +ENSO) and the subseasonal circulation leaves the antecedent dominant forcing signal (I.e. the MJO leaving the Indian Ocean & +IOD). Subseasonal tropical forcing being composed of multiple, fast-moving convectively coupled kelvin waves which are coupled to the extratropical circulation means there really is no single, confined area of the global tropics contributing to the total forcing from the tropics as we try to idealize w/ the MJO. Anthony has said (& noted in the classic Wheeler & Hendon (2004) paper), the RMM MJO only explains 25% of the total variance of U850, U200, & OLR in the 30-80 day band & it's worth noting that the 3rd EOF (via Kessler (2001) & Roundy (2014)) actually explains the advancement towards El Nino conditions which is probably happening at the moment. While some coherent features remain analogous between the composites and the forthcoming pattern, since more variance is being partitioned outside the temporal band (30-80 days) where these filtered U850, U200, & OLR anomalies are frequently associated w/ the MJO, this is going to significantly alter the downstream response over North America the next several weeks & forecasters + weenies/enthusiasts alike should be aware of it.

 

Even though the RMM Index will show the MJO approaching the West Pacific, it's really not that simple in this case.

 

vp200_GFS_anom.KELVIN.5S-5N.png.31aa087d42de9c1b47f2aadf23f0f28b.png

 

 

 

PC 1-3 power spectra from Wheeler & Hendon (2004)

 

RMM Power Spectrum EOFs 1,2, & 3.gif

Which leads to what?

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2 minutes ago, 33andrain said:

That's the setup for our 1/3 storm. I really like that date. And, yes, I realize there are a couple other chances before then. :) 

 

I do agree that once after N/Y we are tracking.

 

The one on the 26th has a slight chance at something light, I like it better for N/E, but I think we have a few days to see where that SW is going to cut S/E.

 

But once into the New Year we may get busy. 

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11 minutes ago, PB GFI said:

This deserves more attention in here.

 

ecmwf-ens_z500a_namer_11.png

I would like to see the ridging get better in Ak for the Early January threat. The +AO and +epo could make it difficult along the coast for snow. We will have threats and it’s early January(not December) but that makes me uneasy 

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