When will the pattern change to cold occur?

[NYCSuburbs]

Not too bad looking set up at hour 240 on the 0z ECM... strong ridging near the west coast, a strong trough dropping into the central/eastern US, and a decent ridge near Labrador and the western Davis Strait. There's still a trough near the west coast, and it looks like the western ridge might them move further east, but at least there's no PV over Alaska. The set up still isn't as favorable as we'd want it to be, but at least we're slowly starting to get somewhere...

[Weathergun]

I think there will be a +PNA spike at the end of the month, with some near normal temps for us But it probably doesn't last beyond Dec. 5. The GEFS is trending towards a stronger MJO wave in phases 3-5 in early half of December:

[MJO812]

12z GFS says that we have to wait at least until midmonth for a change.

[Thunderdude]

It looks like we will have to wait for another few weeks before we get into the blocking pattern. Eventually the NAO will tank as well there will be a +PNA by mid December.

[Isotherm]

I think there will be a +PNA spike at the end of the month, with some near normal temps for us But it probably doesn't last beyond Dec. 5. The GEFS is trending towards a stronger MJO wave in phases 3-5 in early half of December:

Yes the GEFS is now trending more in line w/ the ECMWF guidance re MJO, as suspected by many of us. It looks like we'll see a transient cold shot the beginning of dec via a PNA induced trough, but with the MJO propagating into p 3-5 and the arctic/north atlantic still unfavorable, we'll return to a Pacific origin airmass for the better part of Dec 1-15. MJO wave timing is still questionable but the steps are certainly being taken, albeit slowly, to a more conducive global regime for eastern troughiness. The weakening of the Alaskan vortex is step 1, then we've got to work on the NAO and the MJO.

[NYCSuburbs]

Yes the GEFS is now trending more in line w/ the ECMWF guidance re MJO, as suspected by many of us. It looks like we'll see a transient cold shot the beginning of dec via a PNA induced trough, but with the MJO propagating into p 3-5 and the arctic/north atlantic still unfavorable, we'll return to a Pacific origin airmass for the better part of Dec 1-15. MJO wave timing is still questionable but the steps are certainly being taken, albeit slowly, to a more conducive global regime for eastern troughiness. The weakening of the Alaskan vortex is step 1, then we've got to work on the NAO and the MJO.

We'd also have to work on the EPO by then. It's still expected to remain positive for the next 15 day range, and I haven't seen any forecast showing it becoming negative yet.

[earthlight]

Agree that it's mostly transient, but you can't complain about these maps.

[TheTrials]

gefs show several strong 500 vorts at the end of the run, you can see them on the spread with the darker blues, thats good!

[Hailstorm]

We also want the PDO to be positive as well in order to help the PNA go positive.

[earthlight]

gefs show several strong 500 vorts at the end of the run, you can see them on the spread with the darker blues, thats good!

I wouldn't count out the December 3-7 period for a brief window of opportunity into something worthwhile. Afterwards, we regress slightly before the pattern (I think) shifts after Dec 15.

[earthlight]

Although it may be ugly for the time being, this is the MJO we need to get the AK vortex out of here. A propagation through phases 3-6 like the GFS is showing (some extrapolated) would help to make that a non permanent feature of the longwave pattern.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ensplume_full.gif

[Alpha5]

Although it may be ugly for the time being, this is the MJO we need to get the AK vortex out of here. A propagation through phases 3-6 like the GFS is showing (some extrapolated) would help to make that a non permanent feature of the longwave pattern.

http://www.cpc.ncep....splume_full.gif

what regions usually correlate to a vortex over AK?

[Weathergun]

I think the cold shot that comes in around Dec. 1 will be just as short-lived (out after 2 days), as like what we've seen this month. The GEFS has gone towards the ECENS for next week. It has the PNA ridge mostly out in the Pacific next week. This will cause another trough to dig into the SW US and pump up the SE ridge again. No real blocking to suppress the SE ridge either.

[nycsnow]

I think the cold shot that comes in around Dec. 1 will be just as short-lived (out after 2 days), as like what we've seen this month. The GEFS has gone towards the ECENS for next week. It has the PNA ridge mostly out in the Pacific next week. This will cause another trough to dig into the SW US and pump up the SE ridge again. No real blocking to suppress the SE ridge either.

Check out the links I posted in banter thread the LRC pattern one is good

[bluewave]

December should at least start out as an extension of the fall pattern that we have been experiencing.

The warmest temperatures relative to the means should be over Canada with the SE coming in the coolest.

[H2Otown_WX]

December should at least start out as an extension of the fall pattern that we have been experiencing.

The warmest temperatures relative to the means should be over Canada with the SE coming in the coolest.

It's pretty discouraging to go to the end of the OP GFS and not see any changes..that's when you know you're in trouble. The EC ensembles looked okay toward Day 8-10 but still have a poorly placed high height anomaly in the Atlantic. At least there are some signs of ridging out in the Pacific though even if it is short-lived, maybe we could thread the needle.

[bluewave]

It's pretty discouraging to go to the end of the OP GFS and not see any changes..that's when you know you're in trouble. The EC ensembles looked okay toward Day 8-10 but still have a poorly placed high height anomaly in the Atlantic. At least there are some signs of riding out in the Pacific though even if it is short-lived, maybe we could thread the needle.

With the exception of the end of October, the blocking has really been in a zone too far south over Canada.

[MJO812]

Check out the links I posted in banter thread the LRC pattern one is good

The LRC says expect a storm a long the coast in the middle of December.

[earthlight]

It looks like the ridging ahead of the cutoff low, which could provide a transient block, is going to develop a little too far to the east and southeast. It would be great if this could swing towards Western Greenland. Working in tandem with the ridging on the west coast, it would increase our chances of seeing something interesting in early December. As it looks now, no luck.

[BxEngine]

Im thinking the middle to the end of december to actually get something that resembles a good winter pattern of cold and stormy for us

Those that predicted a cold stormy December are possibly headed for a severe bust.

http://www.americanwx.com/bb/index.php/topic/30019-nyc-banter-and-bs-thread-part-iv/

[TheTrials]

strong alaskan ridging on the euro starting around 200 hours. That's nice to see.

[TheTrials]

really nice pattern showing up on the euro. Ridging takes over alaska and the atlantic ridging starts to build towards greenland.

[Neblizzard]

really nice pattern showing up on the euro. Ridging takes over alaska and the atlantic ridging starts to build towards greenland.

Yup the EPO goes negative, encouraging signs..

[Weathergun]

This is laughingly bad, even for the GEFS.

Last week:

This week:

[uncle W]

The AO was at its highest point since August a few days ago...The AO was at its lowest point last year on this date...

Top five warmest 11/26 all had slow starts to winter...1946 and 1895 had great endings...1979, 1988 had little snowfall while 1999 had light amounts also...

67 in 1946

66 in 1895

66 in 1979

66 in 1988

63 in 1999

[MJO812]

12z GFS has transient shots of cold air. I think we have to wait till the middle of the end of December for a prolonged shot of colder air.

[Sundog]

12z GFS has transient shots of cold air. I think we have to wait till the middle of the end of December for a prolonged shot of colder air.

I think we have to wait until next winter to see a prolonged shot of cold air.

[MJO812]

12z GFS ensembles are colder in the long range than the op run.

[Isotherm]

Figured I'd throw my post from the banter thread into here as its applicable. Main points to take away - the first 10 days of December aren't all that bad, and we are experiencing a pattern change to colder than normal temps in the Northeast. However, we all know excellent PNA ridges cannot last forever in a Nina regime, and tropical forcing, NAO, AO will still be unfavorable for the mid dec period. the MJO should propagate into more conducive octants by Dec 20 and I still believe blocking will follow suit shortly thereafter. So colder than avg for early Dec, probably back and forth mid dec, but the pattern likely is fruitless in terms of significant snows....until we get into the final 1/3 of the month.

18z GFS ensembles valid 168hrs for the opening of December. I can paint a much uglier map than this.

The PNA ridging is very nice, and will get December going on the colder side of normal.

Scroll out through 384hrs and the Northeast stays out of the orange (warm).

The arctic looks terrible as does the atlantic, and the PNA is morphing into a more typical nina RNA position by December 10th as notedin my last post. However, we can count on Dec 1-10 being colder than normal. Thereafter, it's looking more likely we'll see a back and forth or pacific orgin airmass period (aka not favorable) for Dec 10th-20th. The MJO will either be in phases 4-6 or not giving much help in the COD during this time frame. I still believe much better prospects lie ahead snow potential wise particularly for the last 1/3 of Dec. December does not look like a blowtorch or even warm month to me.

Also - like last December - who cares if most of the month doesn't produce snow wise if we get a SECS or MECS in the final week? (or sure, HECS)

[SnowGoose69]

Figured I'd throw my post from the banter thread into here as its applicable. Main points to take away - the first 10 days of December aren't all that bad, and we are experiencing a pattern change to colder than normal temps in the Northeast. However, we all know excellent PNA ridges cannot last forever in a Nina regime, and tropical forcing, NAO, AO will still be unfavorable for the mid dec period. the MJO should propagate into more conducive octants by Dec 20 and I still believe blocking will follow suit shortly thereafter. So colder than avg for early Dec, probably back and forth mid dec, but the pattern likely is fruitless in terms of significant snows....until we get into the final 1/3 of the month.

18z GFS ensembles valid 168hrs for the opening of December. I can paint a much uglier map than this.

The PNA ridging is very nice, and will get December going on the colder side of normal.

Scroll out through 384hrs and the Northeast stays out of the orange (warm).

The arctic looks terrible as does the atlantic, and the PNA is morphing into a more typical nina RNA position by December 10th as notedin my last post. However, we can count on Dec 1-10 being colder than normal. Thereafter, it's looking more likely we'll see a back and forth or pacific orgin airmass period (aka not favorable) for Dec 10th-20th. The MJO will either be in phases 4-6 or not giving much help in the COD during this time frame. I still believe much better prospects lie ahead snow potential wise particularly for the last 1/3 of Dec. December does not look like a blowtorch or even warm month to me.

Also - like last December - who cares if most of the month doesn't produce snow wise if we get a SECS or MECS in the final week? (or sure, HECS)

It still looks bad overall to me outside of the Day 5-12 period where I think there could be some decent cold, and by that I mean marginally below normal. There is no question the GFS has been consistent on about 14 of its last 16 runs since Thursday in showing some sort of hint of that W trough coming back by say 12/10-12/15 or so. I would not be surprised if we get a massive SE ridge again sometime between 12/15-12/25...after that maybe, MAYBE we see the big pattern change, if we don't get it though by late December this is quickly turning into 1999-2000 where I'm sure we'll get a 3-4 week period where its very cold some time in January of February and thats probably where the big storm happens. Remember, even 1988-89 had a period of brutal cold, it just so happened it setup in the nation's mid section and nowhere near us here on the East Coast, even the poorest La Nina winters tend to have that 3-4 week cold snap. The NAO has not surprised me so far, I'd been quite skeptical of the negative forecasts since September because I did not like the water temp profile in the Atlantic, the anomalies had been running a bit too mild between 35 and 50N and now they are virtually entire near or slightly below normal near Greenland, at this point I'd expect we'll see at most a 3 week period this winter with a -NAO and we may not even get that, its the EPO and AO that may ultimately go into favorable regimes and give us that period of winter.