SnowGoose69

December 1990 also...honestly the pattern right now at 500 over the US is pretty close to what it was in December 1990, the NAO/AO was strongly positive that month though

FWIW the 18Z NAM is taking a step towards the 12Z Euro with that 12/24 event

Thats about right...its more or less the same for summer. If you don't see a pattern change by mid July its fairly rare August turns around...oddly enough both 2001 and 2002 saw exactly that with a full scale turnaround for August but you don't see it much

Its really hard to get shutout. Many think the 72-73 record is pretty close to untouchable for NYC although we did come really close in 97-98 and 01-02 to breaking it. I think its just remarkably difficult though to avoid 1 or 2 events even in bad winters and that usually pushes you over 2.8 inches

Yeah 93-94 was like 13-14 (I believe I have the year right on that) where the NAO was positive and even the AO for periods but the EPO was insanely negative.

The last couple of El Ninos in essence acted like La Ninas...even the 15-16 El Nino the December pattern was nothing like 83/97...it was sort of more like 72...I believe for sure that in a -PDO regime that even in a Nino you risk having a SE ridge pattern if you cannot get other things to line up for a +PNA

The -NAO is less effective earlier in winter...I posted in the MA forum that this same pattern 6-8 weeks from now with differing wavelengths probably results in the SER being non existent or way flatter. The good news is that historically in a small sample size that -NAO/-PNA patterns that have set in around 12/15-12/20 have tended to result in a -NAO for the rest of the winter.

Ultimately if this same pattern was around in 8 weeks I think the MA and north MA have better success. The NAO effectiveness, maybe due to shortening wavelengths has always been shown to be way more at beating down a SER in a lousy pattern the later you get in winter, December is the month with the worst AO/NAO correlation for sure. We could have used this setup 6 weeks from now

The CFS occasionally has runs inside 30 days where it nails the pattern but the last year or so its been bad even inside of 30 days

Its also questionable how much the MJO influences things anyway...many mets claim unless its in a highly strong amplitude it likely has way less influence than we think it does and its more like cold SSTs/caused by/a result of the ridge or trof not the cause of the ridge or trof. Joe D'Aleo did a writeup in spring 2002 showing that despite a raging MJO in phase 3-4-5 all of the 01-02 winter the ultimate PV strength would have resulted in probably the same pattern if the MJO was a in 8-1-2 all winter.

I told someone yesterday this is about the ideal snow storm you're gonna get in this pattern...NYC got 5-7 inches with this. The -NAO was fake here as it was basically a bootleg -NAO as a result of a low that bombed offshore a day or two prior, otherwise this wave probably would not have sheared or dampened and cut north. http://www.meteo.psu.edu/fxg1/NARR/1989/us0106.php

The problem in the last decade now is that it seems everything DOES phase. I cannot count how many times down here we've had a setup where I said if this was 1990 this would be a big front end snow but the system became a 985 low over Missouri whereas 25-30 years ago it would not have...whether this is in part due somehow to the crazy NATL SSTs I don't know but it seems we don't get as many dampening shortwaves in these patterns anymore

It’s not over yet but it does look maybe the threat for Minnesota won’t be as bad as initially expected

Honestly don't recall ever seeing that type of pattern for any duration longer than a few days...usually that sort of RNA setup in the EPAC/W Coast occurs in regimes where your NAO/AO is positive 9 out of 10 times...

This has been a dirty SE ridge to a degree...the ridge has been there in the means but the axis of it has been centered W or even NW of the SE US and we've had Canadian highs skirting by to the north and the W Canada source region has been good vs previous years where Canada has been torched...as a result many areas in the SE have largely underperformed except those days immediately ahead of the front and we've seen areas keep getting semi wedged. Saturday will be another day like that but I'd bet Friday high temps in NC/SC/TN/GA generally are way lower than modeled now and what was modeled 2-3 days ago.

SW flow in December, especially if its 10-20kts and you are mixing from higher than 850 pretty much any model will bust...in reality though the NAM/GFS can often be too WARM in southern parts of the US in December/January for highs at D2-3 sometimes when flow is not S'ly or you are not well mixed...the last 2 weeks the GFS has cranked highs in places like RDU/BNA/ATL to 74-78 at times 3-4 days out only for them to end up in the low or mid 60s because surface flow was either light or from the E or SE.

There are usually 2 types of bad La Ninas in this area. The one where Dec is cold and Jan/Feb torch, the other where Dec/Feb torch and Jan is cold..this year may be more or less the latter.

The average of those ensembles is very much like the first half of February in 1994, except the NAO is negative whereas it was largely positive then. I think the SE ridging is probably overdone even on the weakest members. There is always a tendency in -PNA/-NAO pattern for the models to overdo SE ridging somewhat in the longer range.

The last 5 or so years it seems 8 out of 10 times when you see the EC lagging on MJO progression vs the GFS the GFS ends up more correct in the end.

I think forky and bluewave said December phase 7 in a La Nina generally sucks relative to neutral or Nino but the ensembles seem to indicate an even worse pattern than even the straight Dec La Nina composites for 7

2015 was a straight up monster SE ridge which other than I think 2 periods of 3 days never moved..this is more in line with other top 10 Decembers which in most of the eastern US climo sites are all bunched up between 84-01-06-82-90

Yeah, this partially explains the lack of big snow events in the 70s-80s overall. The cold AMO absolutely is associated with fewer big east coast snow events

Probably a combo of climate change factors and coming off the warm AMO. I think technically we are either out of or close to coming out of the warm AMO now at about 25-26 years

Strange how again we see what is basically a -NAO late in the GEFS but it couples with that SE ridge to create a ridge that goes from Cuba to Greenland...some have speculated that is due to Atlantic SSTs but I am not totally sure that is the reason why

92-93 more so is where that happened a ton. 97-98 we had the storm track and -AO in place most of the winter but it was just too mild for any snow