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Rainshadow

Meteorological Winter Pattern Discussion, A December That Is December Or A Nino November?

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 (00z Saturday run)

GEFS  Predominately below normal 850mb temp anomalies through the 20th.  A more significant above normal spike on the 21st & 22nd.  Then non stop below normal 850mb temp anomalies until mid late May when it will be switched to constant/non stop above normal anomalies. Ok, seriously below through the end of its run on December 1st.  Looks +PNA driven, but personally this looks over the top cold.

GEPS  Above normal 850mb temp anomalies start Sunday the 17th, replaced by below normal anomalies 19th-21st, briefer above normal anomalies later on the 21st, below normal anomalies on the 22nd thru 26th.  November 27th-December 1st back and forth favoring below normal anomalies.

EPS  850mb Thermal pattern similar to the GEPS. Except non stop below normal anomalies last from the 22nd through the end of its run on November 30th.  Initial change to colder next weekend looks -NAO driven, we should be in range for it, after that it looks dollar cost average rather vanilla with a +PNA/+EPO driven air mass.

  GEFS return to cold is more stout -NAO driven,  EPS cold is more +PNA/Aleutian low driven,  GEPS -NAO is about as strong as the GEFS, but its more Pacific flow air.  -NAO is never any models strong point,  so I would wait until this gets within day 9 to know confidently.    It is hard to say about the GEFS NAO bias as it has been negative when the NAO has been positive and positive when the NAO has been negative.  So this month it has had a negative bias so far.

This morning's NAEFS 11/24-12/1 is weakly confident of below normal temperatures.  Granted week 2 especially this fall has been more la la land than usual, but that is a consistent outlook given the predicted teleconnections. 

 

 

Today  (00z Tuesday run)

GEFS  A trending more significant above normal 850mb temp anomaly spike on the 21st & 22nd.  Below normal 850mb temp anomalies thru the 25th (including the weekend system), then above normal anomalies the 26th thru the 28th.  Then persistent below normal anomalies from November 29th through December 4th (-NAO driven) The Pacific looks hostile, so good luck with that.

GEPS  Similar to the GEFS near term, but above normal 850mb temp anomalies arrive a day earlier on the 25th. Below normal anomalies on the 29th through early December 2nd and then above to the end of its run on December 4th.

EPS  850mb temp anomaly is pretty much positive from the 21st thru the 24th, the CFP hit is the most glancing of the three. Above normal anomalies on the 25th thru the 28th, another glancing cold blow.  Pretty much the story until a stronger colder anomaly arrives on December 2nd. Run ends on December 3rd.   The Pacific is hostile this is -NAO W driven.  Pattern overall looks to be more active/wetter than it has been.

This morning's NAEFS 11/27-12/4 is confident of near normal temperatures.  

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There is a significant wave 1 hit forecast by NASA.  They stop at day 10, so can't compare the uber GEFS after that. There were a pair of significant wave 1 hits late last November and again mid December.  I am no strat expert, but last year (past performance no indication of future trends) the MJO had more to do with our sensible weather than these wave 1 hits.  Beyond the wave 1 hits, if a beyond the forecast period wave 2 hit then sets a SSW in motion, go for it. 

 

1.JPG

2.JPG

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GEFS vs EPS @300 hours 

 

GEFS below have a rebuilt EPO in Alaska/western Canada. That’s a cold pattern. 579BC9F7-A541-458C-8502-EF7BCE324060.png.ce460092b00058ef9424472d43a2bb5f.png

 

Meanwhile, EPS have lower heights in Alaska and Western Canada, tainting is with more pac than Arctic air. BB7ADB81-0EAE-4E48-BD55-477F84C86CD1.png.2814848eb89e6f8cce440a35e0aca8f6.png
 

NAO domain looks solid on both. You could get away with the eps in late winter, not so much late November if you want coastal snows. Still, eps could produce interior threats.
 

lots of volatility ahead. 

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52 minutes ago, irishbri74 said:

Hm honking a little bit for early December becAuse of the NAO regime:

 

 

He's been steadfast for several days on the NAO prediction, interesting as this suggestion is the opposite of most sentiment from the forecasting community for a mild Dec as the pattern reloads

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Well from an interesting perspective there are many moving parts to the first half of December.  We (I think) can agree upon that the MJO is in phase 1 as the tropical convection is over Africa as is the strongest vel potential. From here agreement all falls apart.  The global models all outlook the MJO to go into the COD which returns the atmosphere to its base state and with that warm pool south of Alaska an outcome like Barney GFS is possible.

But, we have seen the global models constantly sell a COD similar to the GFS forecasting 90s in the summer, yeah it eventually will come, but you are not telling us anything by forecasting your bias.  Both the MikeV and Roundy (he is back!) is outlooking a healthy MJO at least into Phase 3.

twc_globe_mjo_vp200.png.a312ee826f9415302b0716d44fcd9a06.png

Red ellipses for MJO

mjo.JPG.040728b94740c09d4ad28f413ae93427.JPG

 

I don't know the accuracy of this site, but at least it is capturing the current 500mb pattern pretty well and I am selling on a COD MJO.  Its progression would support a colder pattern post Thanksgiving, but then would sell a -NAO after that.  Again global model NAO skill scores go to zero after day 8, so you might as well take my dead figs opinion on the state of the NAO after that.  They would be as accurate as the GFS.

gfs-ens_z500aNormMean_nhem_1.png.21fdfdbf99aecde5af0595948b7b0cd7.png

nada_1_dic_low.png.937ee0b01cb8e8a2abf04747da8c8680.pngnada_2_dic_low.png.2ffc4d7565c5329daea53a81a2886254.pngnada_3_dic_mid.png.f45a619f5171959d14dbfd034feea724.png

 

Going forward and assuming the MJO is viable, these are confidently warm phases for the first half of December

combined_image.png.65aedea7ce4607bee7e1c6ae40f0f00d.png

Now can causes in the mid and polar latitudes negate this.  Yes.  It did in mid November.  There is an ongoing Wave 1 hit, but would need another, or a wave 2 hit to pick up the slack.  This is not a bad thing as Charlie pointed that a strong MJO phase 3(?) could initiate a SSWE.  But I really would be highly skeptical of these la la land cold hits for now.  My skepticism meter would be much lower in the second half or final third of December.

 

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12 hours ago, irishbri74 said:

Hm honking a little bit for early December becAuse of the NAO regime

Reading between the lines he is saying that we have entered another NAO- regime like 60s (mentioned in his tweets) and the last solar min around 2010.

nao.timeseries.gif

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4 hours ago, Rainshadow said:

Well from an interesting perspective there are many moving parts to the first half of December.  We (I think) can agree upon that the MJO is in phase 1 as the tropical convection is over Africa as is the strongest vel potential. From here agreement all falls apart.  The global models all outlook the MJO to go into the COD which returns the atmosphere to its base state and with that warm pool south of Alaska an outcome like Barney GFS is possible.

But, we have seen the global models constantly sell a COD similar to the GFS forecasting 90s in the summer, yeah it eventually will come, but you are not telling us anything by forecasting your bias.  Both the MikeV and Roundy (he is back!) is outlooking a healthy MJO at least into Phase 3.

 

Red ellipses for MJO

 

 

I don't know the accuracy of this site, but at least it is capturing the current 500mb pattern pretty well and I am selling on a COD MJO.  Its progression would support a colder pattern post Thanksgiving, but then would sell a -NAO after that.  Again global model NAO skill scores go to zero after day 8, so you might as well take my dead figs opinion on the state of the NAO after that.  They would be as accurate as the GFS.

 

 

 

Going forward and assuming the MJO is viable, these are confidently warm phases for the first half of December

 

Now can causes in the mid and polar latitudes negate this.  Yes.  It did in mid November.  There is an ongoing Wave 1 hit, but would need another, or a wave 2 hit to pick up the slack.  This is not a bad thing as Charlie pointed that a strong MJO phase 3(?) could initiate a SSWE.  But I really would be highly skeptical of these la la land cold hits for now.  My skepticism meter would be much lower in the second half or final third of December.

 

I think the RMM models are jumping on the standing wave which is around phase 1 or 2. Can see it here. Question is, whether the standing wave is the primary forcing or is it the robust mjo wave??/

 

chi200.cfs.eqtr.png

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Here are the 11-15 day looks form each of the ensembles. GEPS by far look the best in the pacific. They all have the -nao, and you def will need it with the -pna look out west. You lose the nao and up goes the se ridge. The problem I see with the gefs and eps is the pacific pattern. You have an Aleutian ridge which drops the trough in the rockies areas. That is going to promote storms to try and deepen in the middle of the country and want to cut to our west. That is where the -nao hopefully will help keep heights at bay. If we lose that though, it's cutter, cold shot, then warm up and cutter again, rinse and repeat. The geps and gefs both have a -epo look forming so it should send south some legit cold into the center of the country then start to spread out. If the -nao is legit that the models are showing, it could be a fun start to December. You have cold pressing and fighting se ridge, could lead to some nice storms.

 

cmc-ensemble-all-avg-namer-z500_anom_5day-5547200.png.217a7ccdfecc20de9905a0a9474682b2.pngecmwf-ensemble-avg-namer-z500_anom_5day-5547200.png.2ba33892ae225ff9011e6c192d6c6a34.pnggfs-ensemble-all-avg-namer-z500_anom_5day-5547200.png.309b19da6cf7db2d0ec190f2c11ad08a.png

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6 hours ago, tombo82685 said:

I think the RMM models are jumping on the standing wave which is around phase 1 or 2. Can see it here. Question is, whether the standing wave is the primary forcing or is it the robust mjo wave??/

 

chi200.cfs.eqtr.png

I Seriously follow the convection. 

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20 minutes ago, tombo82685 said:

Here are the 11-15 day looks form each of the ensembles. GEPS by far look the best in the pacific. They all have the -nao, and you def will need it with the -pna look out west. You lose the nao and up goes the se ridge. The problem I see with the gefs and eps is the pacific pattern. You have an Aleutian ridge which drops the trough in the rockies areas. That is going to promote storms to try and deepen in the middle of the country and want to cut to our west. That is where the -nao hopefully will help keep heights at bay. If we lose that though, it's cutter, cold shot, then warm up and cutter again, rinse and repeat. The geps and gefs both have a -epo look forming so it should send south some legit cold into the center of the country then start to spread out. If the -nao is legit that the models are showing, it could be a fun start to December. You have cold pressing and fighting se ridge, could lead to some nice storms.

18z GEFS D12 - Bingo - Atlantic and Pacific in good shape. All the cautions about lala land modeling.

gef288.gif

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57 minutes ago, Chubbs said:

18z GEFS D12 - Bingo - Atlantic and Pacific in good shape. All the cautions about lala land modeling.

 

if that occurs, you can probably kiss the figs good bye till 2030

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Way out, but looks like there may be some building support for a wave 2 hit to the strat. 0z GEFS had 4 ens members with SSW in early December, to early. We got our strong wave 1, which is weakening the PV. Need a follow up strong wave 2 to do it in. 

latest_u1060_ens.png

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Petty cool illustration of how the PV starts off strong

gfs_nh-vort3d_20191120_f012_rot000.png

then with strong wave 1 hit, shreds a piece of it off and weakens it

gfs_nh-vort3d_20191120_f240_rot000.png

gfs_nh-vort3d_20191120_f252_rot000.png

then we go to this by end of run

gfs_nh-vort3d_20191120_f384_rot000.png

 

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11 minutes ago, Chubbs said:

 

I believe the +npo is the Aleutian low, which is more nino like and that is a better phase IMO for us. -NPO looks risky if you don't have -nao. Looks like trough dump in west and you get cutter chances. 

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5 minutes ago, Chubbs said:

 

Yes but with a raging -PNA that will just dump the cold out west and our friend the SE ridge will want to perk up, right?  It's basically last winter in the Pac with that setup.  Good news is by the time the PNA improves we're in meteorological winter

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Just now, tombo82685 said:

I believe the +npo is the Aleutian low, and that is a better phase IMO for us. -NPO looks risky if you don't have -nao. Looks like trough dump in west and you get cutter chances. 

Isn't NPO an interchangeable term with EPO?

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1 minute ago, tombo82685 said:

I believe the +npo is the Aleutian low, and that is a better phase IMO for us. -NPO looks risky if you don't have -nao. Looks like trough dump in west and you get cutter chances. 

Overrunning setup, just too early in the season at our latitude

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Just now, susqushawn said:

Isn't NPO an interchangeable term with EPO?

Yea I believe so. east pacific oscillation and north pacfic oscillation

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1 minute ago, susqushawn said:

Overrunning setup, just too early in the season at our latitude

Yup, you will def get big cold pushes, but they are most likesly to be well to our west, so you really need a -nao in this setup or it's mix at start to rain or cutter cold, cutter. 

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EPS I thought took a step back at 12z, Pacific looks worse towards the end. Can see the continued dumpage of cold into the west and we start losing the -nao look, stronger -pna look as well. Not a torch look but you can see the se ridge looming

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THere def seems to be good agreement on a nice cold shot just after thanksgiving into start of December from all ens right now. 

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