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December/January 2019/20 Winter Speculation Thread

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Figured we could have a separate thread dedicated strictly to December.  Should be helpful when looking back on the discussions in the future.  Hope everyone is doing well, and I hope we all have a December to remember!  

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GFS(12z and 18z) and CMC(12z) are both hinting at a fairly strong upslope event beginning late Thanksgiving Weekend.  12z Euro is not too far off from that...looks a bit too wound up.  Strong NW flow coming in nearly perpendicular to the mountains.   

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0z Euro looked even better for that. Would be a nice atmosphere for setting up Christmas decorations! 
giphy.gif&key=eec1d159d648a95547a41569349a9602c8eb39ec242ef01b5cc344ead8ece438 
 
 
You mean you aren't like everyone else and have had your tree and other decorations up since November 1st???

Sent from my XT1710-02 using Tapatalk

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Pretty strong warm signal for mid-December with that CPC forecast for the AO...the MA forum has been discussing it today.  So, I went and looked for myself.  If that verifies...going to be some very warm air east of the Rockies somewhere.  But hey, maybe this is our year to buck the indices.  We will see.  My guess is the SSW situation is triggering some crazy stuff at high latitudes.  Everything(Modeling, indices, etc) went pretty wonky during the last two events.  Not sure this one leads to a split...but it might as the PV looks fairly elongated on the 12z Euro d10 map at 10mb.  I think we have a good window during that first week of December.  Last year, basically same deal occurred.  Great window and the models flipped almost concurrently to a less than favorable pattern towards the end of December.  Only good thing about that...I don't think lightning will strike twice in the same place.  Really don't want to see the AO go that positive...that would be a long term problem I think.  I think Bob Chill in the MA forum compared it to an AK vortex.  Don't want to see a big +AO or an AK vortex as the break down very slow many times.  Again, a warm December is very plausible given the cold pattern that preceded it and that it is a Nino-ish ENSO set-up.  Fingers crossed for Jan/Feb 2020 as last year it just went warm and never looked back.  Hopefully, many of the models are on "mayhem mode" as this SSW and seasonal transition is probably making a mess of things.  That said, we can definitely see into early winter now on modeling...not sure I am a fan at this point of what I see for early winter.  But it is still early.

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1 minute ago, Carvers Gap said:

And sure enough the 18z GEFS goes stone cold in the LR.  Seriously, it is like washing your car thinking it is not going to rain.  

Carver, i posted this in the mid Atlantic forum, that i heard when the ao goes very positive like indicated, it means that a SSW is underway and the ao should respond accordingly. Im probably crazy for saying that, but i heard it about 9 years ago but can't remember who told me. I know its a different pattern and year, but dec 1984 was really warm with raging ao and nao and end of December, things changed dramatically. If you have any ideas on what could be going on, let us know.

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8 minutes ago, Daniel Boone said:

Hm replied to my tweet regarding this and said he expected this to happen but, it should be short lived. 

When did HM respond to that Daniel? Just curious. 

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47 minutes ago, Mr. Kevin said:

Carver, i posted this in the mid Atlantic forum, that i heard when the ao goes very positive like indicated, it means that a SSW is underway and the ao should respond accordingly. Im probably crazy for saying that, but i heard it about 9 years ago but can't remember who told me. I know its a different pattern and year, but dec 1984 was really warm with raging ao and nao and end of December, things changed dramatically. If you have any ideas on what could be going on, let us know.

Yeah, pretty significant warming at 10mb being modeled.  What we don't know and what models don't model well...is where the blocking sets up after the SSW event.  Last year, when the SSW was being signaled in mid-lat December(actually split in early Jan) seems like much of the modeling signaled a cold mid-Jan into Feb.  Obviously, the cold unexpectedly dumped west(unexpected relative to it being shown to go elsewhere from about 2-3 weeks out...If I remember correctly).  I definitely buy the SSW throwing the indices into extremes.  And I also think there will be some surprises(relative to what we are seeing and not seeing in modeling right now).  

The 12z EPS didn't look to bad BTW.  18z GEFS looks similar.  Seems like the morning model suites have been warm and afternoon/evening suites have been cooler.  

 

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40 minutes ago, Daniel Boone said:

Hm replied to my tweet regarding this and said he expected this to happen but, it should be short lived. 

Strong work.  I hope it is short- lived.  Always seems like strong blocking events decay slowly...unless of course it is blocking favoring the East coast.  LOL.

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Teleconnections look real ugly upcoming,Starting into the first  week of Met winter.Really a huge uptick of the AO tho there are a some ensemble members don't show this while with a -PNA /+NAO.EPS really wants to build an strong Upper Level Ridge into the Valley,have to wait and see there ,looks to be a trough right now going through East Asia next Sunday,But either way we are going to seemingly warm up into the first week of Dec. seemingly,but i dont think it  is as bad as what the EPS is showing

ao sprd2 gif  618×800  (1).png

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1 hour ago, Daniel Boone said:

Hm replied to my tweet regarding this and said he expected this to happen but, it should be short lived. 

You have to remember when you look at peoples tweets on twitter are they talking about IMBY.We live in another warp zone to where they live at,just saying.

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Be interesting to see how this winter evolves,The  two strongest IOD events in modern day era happened into the mid 1990's into winter with no SSWE,in 2006 there was a SSWE into late Jan but the IOD peaked around Oct +1.3,but this year is the strongest event in modern day era back into 1980's,so the strronger years you wouldn't expect this to even have a SSWE,especially this year with the low solar min unlike past IOD event years  which happened more into the mid decades.

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The 0z EPS and GEFS have flipped in opposition to each other and the EPS is in eastern trough camp.  Now, the EPS has been pretty awful of late.  However, it is getting to be the time of year that we want it in our camp.  As Jeff mentioned, once we get into winter proper, the LR models begin to settle down a bit.  The EPS has a very workable pattern as it rolls the ridge through and keeps neutral to AN heights in the Davis Straights regions.  We will see if it holds.  The EPS has been reasonably steady with that look for a few runs.  GEFS is bouncing around.   It is really easy to get fooled at this time of year.  Last year modeling(edit) looked cold - went warm.  This year, the look has been cold...and now warm...and now one model back to cold.  Going to take a few days to work this out I think.

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8 hours ago, jaxjagman said:

Teleconnections look real ugly upcoming,Starting into the first  week of Met winter.Really a huge uptick of the AO tho there are a some ensemble members don't show this while with a -PNA /+NAO.EPS really wants to build an strong Upper Level Ridge into the Valley,have to wait and see there ,looks to be a trough right now going through East Asia next Sunday,But either way we are going to seemingly warm up into the first week of Dec. seemingly,but i dont think it  is as bad as what the EPS is showing

ao sprd2 gif  618×800  (1).png

Thought the EPS was to warm 

11.png

22.png

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Check that...now the 6z GEFS has joined the EPS in continuing the block over Greenland along with a trough east of Hawaii in the LR.  Way out there, but good to see a continuation of the evening runs yesterday with the exception of the 0z GEFS.  The 0z GEPS(edit) also looks workable.  Maybe that Greenland block is doing some work.  Might it also be that modeling is beginning to get a handle on the SSW event.  I would definitely keep one eye over my shoulder with this...probably going to be a lot of movement.   Even though I wave December warm...part of my gut thinks this December is going to buck some trends.   As someone noted, the West is due for a warmer winter...and the East is due a cold one.  Sometimes the law of averages comes into play if that makes sense.  

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And hey, we even have a d10 storm on the 6z GFS.  It progressive bias makes that unlikely, but it does phase that system.  Maybe something to keep an eye on is the upslope event still being advertised for next Monday.  That has been a fairly consistent feature for a few days now.   You know if your area is favorable for that,  but wouldn't surprise me for northwest facing slopes above 2,500'' to see measurable snowfall early next week with that.  If that storm cuts and is as powerful as advertised....going to drive some cold air with latent moisture in it.  Wouldn't be surprised to see areas on the Plateau, places like Max Patch, Roan Mt, and areas of western NC receive some snow from that.  Thankfully we are not in a dry pattern.  If there was one concern that I had during early-mid fall is that we were in a dry pattern.  Keep the current pattern, and we should have our chances at some point just due to precip being in the pattern.  Think it was 2017 that had that crazy cold shot in December where we had exceptional cold but no precip as the mega-EPO ridge was so tall that it had no precip.   

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10 hours ago, jaxjagman said:

You have to remember when you look at peoples tweets on twitter are they talking about IMBY.We live in another warp zone to where they live at,just saying.

He was talking about the advertised +AO. 

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Nice PNA pops on the long range 12z GEFS.  Probably would depend on NW energy for winter events, but not a bad pattern for December.  And definitely better than what is was cooking-up for the past few days.

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12 EPS doubling down on a very stout EPO/PNA ridge out west combined with a ridge in the Atlantic during the d10-15 time frame.  I would think that is setting the stage for some serious cold to swing into the pattern.  That look seems to be the SSW type block that is just crazy.  At one point the block is almost into areas well above the Arctic Circle.  The Aleutian low is impressive as well.  

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Just when you think the +IOD was going to waeken it comes back stronger.Even the strong event in 97 per Jamstec on 12-14 of that year was at+ 1.103 but this was in a Very strong ElNino unlike this year

Tropical Monitoring    North Carolina Institute for Climate Studies (1).png

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Least a minor SSW upcoming by the GEFS,have to wait and see i think.This afternoon the GEPS which was seemingly in the GEFS camp seems to have switched more to the GFS in the long range

 

Edit:Wrong about the last statemnet,GEPS has been more like the GFS not GEFS

Polar Vortex Forecasts   Simon Lee.png

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Realistic run of the Weeklies(Euro) I thought.  Pretty representative of the current pattern.  Periods of cold.  Couple of warm weeks during Christmas and right after with a return to seasonal right at the end.  Keeps pushing back the warmer pattern.

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30 minutes ago, Carvers Gap said:

Realistic run of the Weeklies(Euro) I thought.  Pretty representative of the current pattern.  Periods of cold.  Couple of warm weeks during Christmas and right after with a return to seasonal right at the end.  Keeps pushing back the warmer pattern.

Looks like the control with no blocking,more crappie west pattern,pattern would be cutter city with cold chasing moisture,we all know how that works out well here

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