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Winter Speculation 17/18 -December Thread


AMZ8990

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16 minutes ago, *Flash* said:

I thought that was a GFS bias more than Euro but could be wrong. My default is to lean Euro (4 Corner issues aside) as GFS sorts itself out in the mid range, but I can’t remember where I got that from. Honestly, Carv, I’m getting more nervous about middle Tennessee getting shut out while areas that have already seen snow this winter get a second helping. Would be thrilled for East TN members who missed out last time. 

Still about a week out...I think the conversation as expected will move to which piece of energy the Euro tries to jump on as the main piece.  I still think an overrunning wave event has high potential.  These models are struggling. Those big highs are finally being “seen” by the models.  Now, that energy from the previous runs did not disappear IMO.  Maybe something like a wave event followed by a storm on the EC?  Until they get the pattern...tracking will be tough.

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5 minutes ago, Carvers Gap said:

Still about a week out...I think the conversation as expected will move to which piece of energy the Euro tries to jump on as the main piece.  I still think an overrunning wave event has high potential.  These models are struggling. Those big highs are finally being “seen” by the models.  Now, that energy from the previous runs did not disappear IMO.  Maybe something like a wave event followed by a storm on the EC?  Until they get the pattern...tracking will be tough.

I agree,  it's gonna be hard to track anything until we get a few kinks ironed out.  We've got plenty of solutions on the table though,  I wouldn't put to much weight into anything just yet.  I think everyone in the forum is still in play though, with what we've seen the previous 3 days, anything is possible.

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I think there was better agreement last night among the ensembles.  But the models have been washing away trends like footprints on the seashore.  Some consistent features have been very cold Arctic air into the entirety of the Plains, a SE ridge prior to Christmas that is tough to budge, cold moving East out of the northern Plains, and precip out of the GOM originating in TX.  I might add the trend of making the cutoff more progressive out of the SW and making the East colder from Christmas Day and after...but would like a couple of more runs before locking those trends in.... I still think this is a pattern that produces ice on the southern fringes.  The EPS had decent snow means for all of KY.  What does that mean for those of us to the south of that mean?  Anyway, put those ingredients together...and it would take serious work not to get at least 2-3 events to track for the forum area.  Don’t forget that the cold will be attacked as it leaves.  Just a ton of moving parts w very cold air factored into the equation.

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It seems the 12z GFS is overamping the EPO ridge.  When it does that, the trough hangs back West.  I think it is an error.  Looks like feedback.  Terrible run-to-run continuity for an event (trough placement for the entire NA pattern) that is five days away.  It is struggling with the entire NA pattern where changes begin on Weds.  I can understand struggles past d7.  It is swinging wildly w a pattern evolution that begins in 48 hours.

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This is 0z on December 25th.  The left is the current run at 12z.  The right is 6z.  The changes that begin this pattern begin on Wednesday...and look at the massive differences the GFS is producing in the Pacific from run to run.  It is replacing troughs with ridges.  No continuity.  Big time consequence downstream with each of these changes.  The 12z GFS overamps the EPO ridge allowing it to undercut and really just becomes high latitude blocking and not an EPO ridge.    Looks like feedback to me.  But that feedback is allowing the ridge to be undercut.  If the Euro is consistent at 12z...time to give the GFS much less weight.  The GEM is also doing something similar at 500.  Both do not look resonable (edit....might happen but ensembles disagree) given neither model is being consistent.

IMG_1213.PNG

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Both the GEM and GFS at 12z are backing cutoffs westward across the Rockies and cutting them off over San Francisco.  When has this actually happened?  I can't really say they are reverting back to a particular solution because they have cycled through so many possibilities.  When the entire circulation pattern of NA is changed every run, the model cannot be trusted. 

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Interestingly....the crazy runs of the GFS and CMC both seem to move to cold in the East around Dec 26th as Powell mentioned.  What concerns me is how they get there.  But they do get there.  I suspect the energy coming into Seattle gets kicked along.  If so, the trough and winter weather arrive 48 hours earlier.  Let us see what the Euro does and the ensembles.  Both the GFS and CMC do hint at ice around that time.

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Sorry...meant Wyoming....I have fished there a ton.  I should know better.  -51F at 234.  While unreal, and I do think very cold air will arrive on Christmas or after.....that is a great example of feedback.  It could happen, but likely won't.  Models are really like extremes during the past several runs as evidenced by the wild shifts.

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3 minutes ago, 1234snow said:

I think all models are in agreement that first wave will kick out around the 22-23rd and be a cutter bringing us a rainstorm. What happens next is some of the biggest run to run inconsistencies I’ve ever seen at that time range.

Agree.  The 12z GEFS looks very consistent to 6z.  That is a massive step in the right direction.

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The differences are slight at 144 on the GFS and Euro, but that slight difference may be enough to make a big difference here. The Euro has the high closer to the coast and doesn't push the trough as far west as the 12z GFS did, which had the trouch aligned off shore of Washington State. Still all that needs to be a few hundred miles east to match the epic GFS run from last night.

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