Bob Chill

AO is the key and not the NAO for longer term stable winter patterns in the east. NAO domain space can make numerical readings muddy. Focusing on the NAO is 2 weeks out tops (imo only). AO is the granddaddy beyond that. I found an old attachment in my files. This isn't the better stuff I put together but it's a great snapshot. Basically, a Dec ao reading below 1.5 pretty much locks in more blocking. Pretty classic look rn and a lot of classic data to get excited about. At least for being squarely in the game. Actual production has less to do with the AO and more to do with our dicey location.

If the block overperforms first half of Dec, I'll prob be staying at smith mtn most of the month

Rule of thumb with Nina's and favorable patterns is having the npac ridge axis aligned further east than classical placement. 95-96 really shows this as. When the top of the ridge allows "downhill flow" in Western Canada, it keeps our cold air source intact. Cold continental air flows down into the rockies and bleeds/moderates eastward. More laterally than usual with blocking too instead of digging and releasing. Our best storms have "wide and thin" high pressure to our north aka "banana high" because its shaped like a banana. We rarely or never get that even with a block when the npac ridge is in a more classic Nina position. The trough in the western conus is very hard to fight back enough for easy wins unlike people north (as close as philly). The margins here are always a razor edge in any and all setups. We have always and will always be more prone to fail that win here. That part sucks. What doesn't suck is we do get flush hits with the most powerful winter storms in the eastern half of the continent. Places as close as Ohio would kill for a coastal they can't get. I focus on the good and we have it pretty good with continental weenieism

We worry about mids with a 1028 over lake placid in the middle of Jan during a good winter It's obviously not happening but I did like the look of a TN vly overrunner last week on ens guidance. That type of synoptic can do a foot+ without any kind of modest or strong slp pass. That's the killer here. Easterly flow in the mids is no Bueno. Overrunners have SW flow in the mids. Just need to be on the right side. Simple right! It's always easy here!

Personally, I'm rooting for something bootleg or sheared or trailing thru mid month. Climo highways with big synoptic storms are really hard to skip lanes from the MA southward. Blocks alone can't stop an ocean air vacuum coastal from being to warm here. The surface is hard enough with early season climo. Mid levels with a storm off the coast are even harder. SNE or even Philly may be looking for a big wound up event. I'm not. We never get big snowstorms in early Dec even when the h5 maps say we might

We been on this ride a long time friend. I used to get head over heels with the prospect of a long range west based block and what it can mean. Time and time again I was taught to be patient. Lol I do think this one will verify and that's prob all that matters in model land. "Build it and they will come" is a good analogy where my head is at. I'm down at smith mtn for a week. Hoping trackable threats are inside of d15 by the time I get back

A very reliable rule of thumb in the MA with a real/stable block is we get our chance later. Usually after peak neg NAO anomaly on the relax. Makes logical sense as we often need a series of carves to finally start getting sprawling cold. Super slim odds in Dec with any hit and run cold. If the -nao starts pinning banana like highs in good places it's off to the races for tracking. It's going to take some time before things are favorable here imho

If the EPS version is correct, this is not a hit and run imo. That is basically the entire northern hemisphere linking up with a prime anomalous and displaced winter pattern. That is winter from San Fran to Raleigh to London to Eastern Siberia lol. Something strong will have to break it down. ,

I must be really awake or something. 3 legit wx posts in a row... my intuition must be kickin'... In a vacuum of reasons why, it's still pretty obvious we are losing on the margins and borderline setups due to warmer winter temps. It's been raining when it shouldn't. Don't want to dig any deeper than that. The NAO can really help with marginal events just because of common mid level flow under a block. We get the cold dry feed pushing back against storms instead of running away. Still doesn't win the game exclusively because sometimes the "cold dry feed" is straight out of unusually warm New England. Blocks aren't everyone's friend either. The further north you get the less you want to see a big red monstrosity over Greenland or Baffin. You also don't want to see nasty 50/50s spinning in place. But that's there and this is here. If we start seeing banana like highs sliding across to our north in mid Dec, it's prob only a matter of time b4 the shovels get dusted off and oiled up. ETA: @CAPE see if u can find the 2012ish article from Wes. He used my AO data. Would save me a lot of time. It's been a while + several PCs since I did the research.

Whomever cracks the kinda sorta decadal cycle of the AO will become a legend. It's there somehow/somewhere. I tried to find any kind of predictor other than approx 10 years with twists and turns. Lol. You can see the groups in the 60s/70s/80s easy. Things got a little weird in the 90s thru current but it's still there and this year would be "on time" for the switch. But it's always a rear view thing.

A Dec AO or NAO in the -1.3 or lower range indicates both a -ao/nao in Jan 75-80% of the time and about 60% in Feb. One of the best long term winter pattern predictors I've found. Works in reverse quite well too. Do I need to post those stats or do the memories of the multi-year soul killing blue ball in the arctic cover that? Lol An important piece for increased winter wx odds seems to be lining up and holding in time now. If it sets up stable, this general type high latitude blocking pattern lasts on avg 30-45 days. Doesn't mean deep winter as our area always requires more than one feature lining up but the possibility of our biggest thorn not drawing blood keeps looking better I posted a bunch of data on this stuff back in 2012 or so. Might be a good time for me to dig it up. Yep, it's been that long since we've had a run of classic blocky winters. ETA: AO is the bus driver as the domain space is far larger than the NAO and affects wx flow differently. An anomalous -NAO is often an extension of a deep -AO. Either way, a deep blocking episode in Dec that makes the east cold rarely indicates a warm boring winter going forward.

BWI: 26" DCA: 19” IAD: 34” RIC: 14” Tiebreaker (SBY): 11”

We're pretty irregular down here with any and all sets of tele's. Our snow needs timing far more than up north. So any pattern that repeats air cold enough to snow can get it done even if jacked up. Big storms are different and Dec is not a big storm month here. We've had numerous 2-6" snowfalls splattered in all enso phases. More common in the first half of the month. It's a weird quirk in DC. Dec snow is rare except around Dec 5th give or take lol. Stats back it up.

Battle ground patterns with a block like to aim hoses at places for hot streaks. We've won some and lost more. Lol. Gotta have a chance before you can lose tho

GEFS has been consistently showing a decent TN valley overrunning setup in the 5th-7th window. The carving troughs aren't digging deep but are plenty cold. I like the breadth of the cold air. Flat and wide instead of a deep bowl.Gulf is open from what I keep seeing. Overrunning is one of the only ways for our sub to score together in early Dec. Ways out in time but it makes a lot of sense if it starts locking in next week.

@raindancewx the comparison is based on solid ensemble consensus for traditional high latitude blocking and the fact that we (in the mid Atlantic) are often dependent in that type of feature in ANY nina if we want winter at all. How long it last or even if it materializes are unknown but the look is classic. If early Dec is showing a piece of what winter has in store then mid Atlantic people will enjoy it. I have no thoughts about the west on this stuff. Nobody here broad brushes the US with winter thoughts in areas outside of "home"

Once we get finished with the 95-96 redux we can immediately jump into disco about the incoming 09-10 redux. Brooklyn is just letting us know that 09-10 is knocking at the door again real soon

There is some sort of weird decadal ao/nao cycle. I don't understand it other than it's obvious in the rear view. We've had a run of dog turd ao/nao years lately. Fluked out in 13-15 stretch. Atypical there. Last winter wasn't hostile. Almost seemed like blocking was making a comeback. Makes you wonder if this year is part of the eventual reversion. If it is then a winter with patterns like 95-96 isn't crazy talk. Snow beats to a different drum and that was a monster year. A redux there is def crazy talk haha

Man, I'm diggin the quick carve progression in early Dec. Fits into the personality of the last 1.5 months. Fast starts and good winters are rare. 2013 was the last one right?

Man, I still can't get the multiverse treble hook out of my mouth. I bit that ish hard lol.

You believe this is a hostile pac? We'd of killed for this jet structure multiple times in recent years. It's not perfect and it never is but the pac jet as depicted is slow/split/dirty with a cold air factory in Western Canada. I find that very workable

If the early Dec deep western trough rolls quick like what's been happening all fall, Dec will keep a lot of people glued to screens every 6 hours . And if a stable block sets up then 10x as many will be glued...

I'm a damn noob again lol. I forgot the CFS ran weeklies. This is a great visual of what I'm thinking (in very general terms). Uber scandy ridge rolls forward and assets itself into the NAO domain and all forces the tpv into Siberia. The last panel shows the -AO/NAO combo flipping + awful quick but thinking that far ahead is more insane than what I'm already posting. This progression kills the big cold air factory in the arctic but it also keeps the door open for western Canada to do what we need. Force seasonal cold air under a block and it works in early Dec when other features line up. I want a perfect pattern as much as anyone but the vast majority of our snow falls with a jacked up pattern. If a locked shutout pattern shows up I'll change my mind REAL quick and go dark again

Going off of intuition only (some call it a WAG lol),I feel pretty strongly against a persistent trough in the west in Dec. Climo and odds favor it so I'm thinking against the grain here. The deep western troughs have all been rolling forward quickly last 6+ weeks. Nothing is locking down yet. Oct/Nov are transitional so locked patterns are less common but even by fall standards, cold continental airmasses have preferred to roll and not sit. Dec plays by different rules because 2 week locked patterns are common. All ens are showing a potential strong western NA trough trying to load first week of Dec. If that rolls forward efficiently with successive shortwaves, I'll be pretty stoked cuz we'll be trackin legit phantoms before we know it! Eta: my thoughts above are contingent on the Scandy ridge asserting itself and the NAO domain remaining "unhostile". Or even blocked... We've been bombarded with long duration Nina troughs lately and never get anything to push back until later in the season. I may be off my rocker or too optimistic but I can't ignore the gut feel of a winter with real AO/NAO help (including Dec). We'll see soon enough

A good start no doubt. I've refined my strategy this year. In addition to shoveling all my neighbors' snow into my yard, I have a nice tilt trailer that can haul 3 tons of snow so I'll import from Smith Mtn this year. @psuhoffmanwill be very jealous of my very legit snow totals this year. Mappy will need a new color for my rockville yard. Yolo time