psuhoffman

Whatever it takes.... I think I should be getting a pretty big commission after that post this evening...

These are some examples of warning events with a ridge bridge

I remember the exact conversation you are talking about. It is possible to get a ridge across the entirety of the EPO/AO/NAO domains...and yes that is commonly called a ridge bridge...and when it happens it is extremely good for our snow chances. But it is very rare. So the fact that there are not more snow events with both a -NAO and -EPO is simply because that combination is less common not that it isnt a good pattern. But the reason our absolute biggest storms are usually associated with a +EPO is mostly because they are also associated with the most anomalous west based NAO blocks. Typically a block that strong cut off over greenland makes it even harder to have a strong ridge in the EPO domain. Frankly if we did it would probably be too much of a good thing and might flood the CONUS with so much cold it would just be a uber cold dry look. Think January 1977 \ Brutal cold but not much snow.

Holy crap, I thought I was the doom and gloom one.... yup, I wish the powers that be would settle on one common label for a lot of these things to stop the confusion.

NAM is the Northern Hemisphere Annular Mode, or what is more commonly called the Arctic Oscillation or AO.

That wasn't the one that brought me to tears...that storm happened a little earlier in that god awful dumpster fire period but I remember it well. It certainly contributed to my buildup of misery. I was actually foretasted to get 8-14" being about 15 miles southeast of Philly and ended up with NOTHING. I went to bed and the evening news said 8-14" southeast of Philly, 12-18" at the shore. I knew something was wrong when I woke up expecting a few inches already and the sun was out and the wind was blowing. I knew before I even turned on the news it was over. Was a CRAZY sharp back edge...Atlantic City only about 35 miles southeast of me got 18". I saw the dark clouds passing by to my east all day.

Actually there was a 4 year stretch from 1949-1952 also. But...what if this is year one of a 3/4 year stretch....????

I actually remember being in tears in 1992 at the end of that stretch (living in south Jersey at the time) after we were finally supposed to get a legit snowstorm (it was predicted to be 4-8") and it ended up 1" before turning to rain. I think it was very late in that season and it had been 3 years without a decent snowfall including a few other busts where 3-6 or 4-8" forecasts the day of a storm turned into very little or nothing...and I actually cried a little bit. It was awful.

As a follow up to that last post... the reason my mood shifted suddenly about a week or so ago was due to the sudden flip of the NAM state. See back when I predicted a decent season I was relying on a similar Pacific to last year but with more high latitude blocking help. 1982 was one of my top analogs and so I was kind of expecting something like this... 1960 was also very high on the analog list 1960 took until later in winter to get good but in both cases what made it work was the HL blocking overcoming that pacific ridge. That pac look isnt the end of the world if you have AO/NAO blocking. That was what I was counting on. I guess it was really foolish to go against the long term +AO/NAO cycle but imo the north pac SST, atlantic SST, QBO phase, solar, and enso (weak warm following a nino) all argued for blocking this year. And through from November until a week ago...everything looked on track. Maybe not for the 1982 analog...I was starting to think we would have to wait until a little later in winter... but the 1960 look kind of matched what we were seeing 2 weeks ago with persistent Atlantic help being muted by the PAC. That pattern tends to get better later in winter. But the sudden reversal of the NAM state to a 2+ std dev positive really tossed that out the window. When the NAM state goes strongly positive this time of year it usually is a persistent issue. It sometimes flips but usually not until very late like 2018. Sometimes there is a fluke like 2006 where the NAM flips after being strongly + this time of year so there is always hope. But the fact is both a strong pac ridge and a strongly positive AO are both persistent features and when combined are a horrible pattern. That combination has lead to most of our epic fail dumpster fire winters. Just wanted to explain my thought process. I am not reacting emotionally to one model run. I am simply looking at the preponderance of evidence we are seeing...and I know historically that is the absolute worst pattern we could possibly see right now wrt our snow chances this winter. But there was that 1 year out of 15. And there were some other years "somewhat" similar that flipped better. If the guidance is off and that ridge ends up further northeast it throws all this doom and gloom out the window. Or if the NAO flips all bets are off.

Now that I am home with the data in front of me...I will answer this...but its gonna hurt. First let me start with some hope...there were some similar patterns early in winter that flipped. The best 3 examples of that are 1965/66, 1999/2000 and 2004/5. This is the 1966 example. It went from this to this and a pretty epic period in late January and then another big storm in February. However...all 3 of those examples the pacific ridge pattern set in early in December and was already breaking down in the first half of January. This time the pattern is really just locking in during the first part of January. Big difference. In those 3 examples the pattern lasted a good month and then flipped. But a pattern setting in December with the jet still going through seasonal fluctuation is much different than one setting in January when the wavelengths are broad and the jet takes on its dominant winter phase. But I don't have all the answers...maybe those 3 should be used as hope that things could flip quick...although even in those examples quick wouldn't happen until February given the length of those patterns and that the same pattern is setting in a month later this year. If you want to sleep tonight I suggest you stop reading right now and disregard everything else I have to say because the rest of this is going to give you nightmares. Still reading.... you must really want punishment Wow you really hate yourself.... ok I warned you...you asked for it, don't blame me I am NOT paying for the therapy. Ok the reality those are NOT the real comps to this current situation. There are 15 similar January months to what the guidance is projecting for the first half of January. Assuming we do not get some kind of crazy fast shift...and nothing is hinting at that...it is highly likely January will feature a strong central PAC ridge and a +NAM state. 15 previous Januarys fit that. This is the composite of those years I think we can all agree that looks familiar...and is a good match to the current projections. Here are the facts you asked for...and I warned you, you are not going to like it. These are the Februarys that followed EVERY single one of those years was below average snowfall at BWI. Only one wasnt below avg at DCA. In all 15 of those years we only had one warning level snowfall in February and that was 2006. This was the patern that February. It took a complete reversal of the NAM state and great blocking to get the only good February we had following similar Januarys. I know some don't consider that month good because it was one "fluke" storm and then warmed up...but IMO we were unlucky not to get more storms that month. I don't see that storm as a fluke, I see it as a fluke that we only got that storm honestly. But whatever... IF you subtract that one year from the 15 February looks like this... And there were no warning level snowfalls and the avg february snowfall in DC those 14 years was 1.4". And this is the February temps for those months Bottom line... if the long range guidance is correct and what they are advertising day 10+ actually is reality... pray to god we get the 1 in 15 year miracle flip to a raging -NAO because otherwise we are toast and we are looking at a year like 1950, 1989, 2002, 2008, 2012... Maybe the CFS is right and the pac ridge ends up much further east than all other guidance and the MJO would indicate it will. Hug that and pray.... and don't blame me, I just put together the data...I am not happy about it and I didn't make it be and I am praying the guidance is wrong.

That look actually isn't too far from a workable one. As is that would be mostly a cold dry look after the wet look the first week which I suspect is from a cutter to usher in the pattern. BUT...get the trough to hang back into the SW a bit more to create a positively tilted trough with just enough SE ridge and it becomes a good pattern for progressive waves. I would take my chances with that look. Its a stones throw from a workable look unlike what the Euro weeklies suggests with is pretty much a no hope shut out the lights for the entire season look. However...I am about to drop what is going to be the least popular post in americanwx history.

1) that will be easy. I’ll work on that either tonight or tomorrow. The hard part was compiling the data set and examining the pattern for each one. You can’t just look at the numerical indexes. Often an important feature is hidden. A Hudson Ridge often wont show up. Some west based NAO blocks don’t really show up well if the eastern NAO domain near Iceland isn’t impacted or there is a trough near the Azores. An east based epo ridge can sometimes show as neutral if there is an Aleutian low encroaching on the western epo domain. There could also have been blocking days before the event that by the time of the snow relaxed and the NAO flipped positive. Only looking at the day of the storm you would miss it. Now that I have that data sorting it in different ways is easy. 2. I can easily do that but the day of a snow will obviously show a correlation to cold since it has to be below avg to snow. During the storm it’s very likely near or below freezing. A better study would be to look at temps the day before and after. That would be harder. I would have to go back and look it up. I could give you the dataset and you could do it. But even then you will clearly see a correlation to cold. What you might not see is a high correlation to arctic cold. A lot of the events had temps near freezing. A lot were mixed events where 1.3 QPF lead to 6 or 8” of snow with a high of 34. That was a pretty common thing in the set. Pure snow warning events were rare. But that’s not shocking. The all snow zone on a lot of storms is relatively narrow. And most storms in the mid latitudes ride the boundary between warm/cold. We aren’t far enough north to often get a storm that’s riding the arctic boundary or a storm that’s late in its cycle and no longer pressing WAA north. You have to either have elevation or more latitude to get a lot of those.

This....but I’d favor “head out west and hit the powder”

That’s somewhat closer to the analogs of PNA only snows. There were only 6 in 70 years so still not a great snow look but it’s the first time I saw a realistically workable look on the ensembles.

January 1960 1964 and 2000 also had similar pacific patterns early and went on to an epic period. But all features blocking. As did 87 and 96. So again we can recover from this but the path is clear.

With a strong +NAM I didn’t see many that showed significant improvement. Part of that is because with a strong TPV over the pole it’s difficukt for that pac ridge to press into western north Am like we need. The strong NAM state naturally resists that. The years where that pac ridge migrated east also tended to have a - NAM along with it. Anything can happen but by far our best way out of this mess later in winter is through a flip in the NAM state.

This is the key imo. Looking at all the analogs to a strong central pac ridge in January, most had that feature persist at least to some degree into Feb and March. The only years that went on to a snowier outcome had significant NAO help to mitigate its impact. Absent that...the comp years that the NAO remained positive were pretty awful here. Some had better outcomes NYC north. Hopefully we see signs of a reversal of the NAM by mid January.

Dude.... do you know how many storms youre describing? I remember the February 1987 storm the day after I had to go to Harpers Ferry WV from NJ for a baptism. We had about 12” in NJ and there was 16” at Harpers Ferry and by the time I got to the Christiana Mall in Delaware almost all the snow was gone. By WV nothing but piles. So do we toss that storm? Feb 2006 was gone 48 hours later. Toss it. The only good snow we got in Feb 1997 was gone the next day. Tossed. Careful. Soon our average of snowfall you approve of will be about 2”.

Thanks for your thoughts. Love when you pop in.

The IOD was keeping the convection centered in phase 2. That’s not ideal but not that hostile either. Kind of a wash. I’m not an mjo expert so I didn’t add much but the whole last month while people were rooting on the IOD demise to release the mjo once the IO standing wave weakened I was thinking “but are we sure once released it’s not going to just rush back into warm phases like last year”. The sst profile in the mjo regions except for the IOD was a little too similar for my comfort level.

Climo beats op runs at range. The pattern never really supported a snowstorm. Epo ridge is too far west without NAO support. Of the 88 snowstorms I looked at none were remotely like the pattern shown next week. And that was before it degraded further the last 24 hours.

Ummm. Ironically the people wanting the IOD to release its grip on the mjo got their wish. And the minute it did the mjo rushed right to the warm phases just like last year. Be careful what you wish for! And even assuming the wave progresses thats still 2 weeks away from getting to cold phases at day 15 and the last attempt at that feat died. I guess you just have to laugh. This is like a horror show in every way right now.

There were a couple random runs. It’s better to take ensembles over several days to avoid the one day blips. But over the course of days they have pretty much been warning us this was coming for a long time.

If that upper low pass on the gfs is correct we would likely have at the least some bands of snow showers in the area. But that’s a big if.

Your coating is more like...