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Winter 2021/22 December Thread


AMZ8990
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22 minutes ago, Carvers Gap said:

Thanks, man.  Hope you and your family are doing well.  Is Nina expected to last through winter or move to neutral?

The current La Niña is expected to persist until late summer or early autumn 2022. However, there are reasons to expect that this La Niña will not be as disruptive as the exceptionally strong event of 2010-12, including the fact that the 2010-12 La Niña coincided with a negative phase of the Indian Ocean Dipole.

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3 hours ago, Carvers Gap said:

Thanks, man.  Hope you and your family are doing well.  Is Nina expected to last through winter or move to neutral?

Doing ok,had a stroke in my left eye,hard to read but its getting better,docs said it will take months to heal,other that everything is ok.,hope all is well with you

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1 hour ago, Carvers Gap said:

12z GFS is a complete pattern reversal.  Its ensemble, while not a pattern reversal, is winter.

Yeah,kicks the Aleutian "H" out and a +ve PNA for a change,but to far out to believe.Even if it does work out probably just transient,but who knows.SPV is shown to be getting attacked as well

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General trend across the board today(operational and ensembles) is to weaken, severely displace, or completely remove the Aleutian high.  Opens the door for cold if true.   A true MJO 7 would allow for that.  As John noted, the atmosphere has been more a 6.  Generally speaking, seeing a large area of BN temps slide eastward and expand between the Rockies and the Apps.  In between Christmas activities, so hopefully this post hasn’t missed something major!  LOL

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The 18z GFS again flips the pattern...just switch the blues and reds on Tropical Tidbits over the US in the LR.  Basically, the Jan 3 cold front begins the flip w a transient ridge after that cold front.  No idea if that verifies, but impressive nonetheless.     If a pattern change does a occur, the CMC and CFSv2 score the coup.

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9 hours ago, jaxjagman said:

Doing ok,had a stroke in my left eye,hard to read but its getting better,docs said it will take months to heal,other that everything is ok.,hope all is well with you

Really sorry to hear this Jax.  I hope you have a full recovery.  Never heard of a stroke in eye.

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Oddly, the problem this run is that the NAO is so strong(big change since 18z and maybe not a great change) is that the NAO just bottles up the flow.  I think it still gets to where 18z did but a day or two later.    The mid continental ridge feeds into the NAO in a pay me now or pay me later pattern regarding cold.  That big ridge is a tell tale sign of an SSW that would almost certainly disrupt the TPV and SPV.  

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When I talk about pay me now or pay me later with that big ridge hooking into the NAO....If memory serves me correctly, the reaction during past years has been quite abrupt regarding the TPV - not the usual waiting game for an SSW to propagate downward.  Now, I am not sure this run is even realistic given the aforementioned feedback, but in the off chance this is even closely correct....cold air would likely be jettisoned towards the mid latitudes quite quickly.

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Indeed post 300, the GFS again simply gets rid of the Aleutian ridge.  The gradient between Kansas and northern Montana would something like 80F to sub zero - very sharp.  Trough likely goes into the east again as it did at 18z, but just a bit later.  Just one run and likely will be different at 6z.  

It is now officially Christmas!!!  Merry Christmas to the best wx forum in America.  Hope everyone has a great day.  I will try to post some, but tomorrow will be busy.  Keep the home fires lit.  

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Hate to gum up the thread with a million posts about LR modeling...but the Canadian is about to go bonkers in terms of cold.  Will simply post my comments here int this post so as not to add 10 more posts.

If the 0z GFS had not feed back into that trough, this is likely what would have happened.  No idea which one is right, but that looks an awful lot like what happened last February.  Wow.

Likely too cold, but the CMC has single digits over northern portions of the forum area with no snow on the ground which is impressive.  

We have seen these types of looks before....Head fake?  Plausible scenario.  Extreme swings?  Also a plausible scenario.  We have seen both head fakes and wx extremes during the past two winters.  If the elimination of the Aleutians high is legit, we could see a November-esque pattern develop but I am way ahead of myself with that.  

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Couple of general and finer points this morning in no particular order:

1.  The Aleutian high is weaker, displaced from its current location, or completely gone in the LR depending on your model of choice.  

2.  The EPS teleconnection for the PNA goes from extremely negative to nearly neutral - positive on the control.

2.  Pattern itself may become one dominated by -AO.  Maybe the -NAO for at time as well.  EPO showing some signs of cooperation.

3.  Tough right now to say whether we are looking at a pattern reversal, a temporary relaxation, or simply 4-5 days of cold.  If we hold to patterns lasting 4-6 weeks as a general rule, the current pattern is due to change during the first two weeks of Jan. That doesn't mean the new pattern is any better.  I think it is possible on modeling that we are seeing the beginnings of that shake-up.  Just tough to know where all of the pieces end up once the current pattern begins to erode.  

4.  The first cold front to set this in motion may well be Dec 31st.  It is not overly powerful, but could potentially knock down the much above normal temps behind it.  The Jan 3rd front could be fairly strong, but that is not a given.  

5.  Lots of things in motion this AM.  Truly those have been seen on modeling for about a week, but we can "see" those changes now on operational modeling.  Word of caution is that the base pattern seems to really be a trough in the Mountain West.  However, the cold temps being modeled at times is just insane.  There is a mid-1060s hp at the end of the 6z GFS run over MT and the front range of southwest Canada.  That will change, but it shows the extremes on modeling right now.  So, lots of stuff to get worked out.  

6.  Big takeaway is that extremes are on the map.  If the Aleutian high weakens which in turn will weaken the monster -PNA...the cold has a legit chance of coming eastward - likely in waves with very warm temps between waves of very cold air.  ALL OF THAT IS SPECULATION RIGHT NOW IN TERMS OF THE LR PATTERN.

7.  addendum:  The MJO is just crawling across 7...it is in no hurry.  Several of the maps look a lot like 8.  But work remember what John noted about low amplitude 7 a few pages ago...that is a cold signal for Atlanta.

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