psuhoffman

Seriously, with everything ambiguous it’s hard to see any one thing that is the biggest threat. I guess if a few factors like the pdo shifted the wrong way. Imo the biggest threat is simply that we don’t know what this exact combination of factors will do and if it’s slightly worse than we guess, and we have the typical December torch, then get unlucky with a couple threats, we could be staring a dud in the face.

I’m worried about the hemispheric energies.

Can’t imagine why you would be having problems

Here are my winter thoughts for better or worse. EVERY seasonal forecast is low confidence since we are making predictions based on predictions and using analogs when rarely is there a large enough sample of years with totally similar variables to draw solid conclusions...but this year especially is a crap shoot. There are conflicting signals and not really a lot of years that share similar signals to look at. So basically this isn't worth much. That said, given the lack of really strong analogs I tried to limit things to just a few important variables to try to come up with some "decent" analogs. The main factors I looked at were the Pacific basin SST including enso and north PAC PDO domain. The Atlantic SST patterns. The QBO and the prevailing fall patterns. I came up with a few analogs, but none were A level, so even the best analogs would be weak in a typical year. I tried to avoid using really old analogs as I have had no success using years from the 1950's and 60s, I think the climate has changed too much for them to be of much use unless we can accurately adjust for the changes and I cannot so I left them out. Also, before people chime in with reasons one year or another isnt a great analog...as I said NONE of these are great. They all have some deficiency. The QBO wasnt a match, or enso, or the PDO...something. So yes I know they all have some flaw but I tried to rank them based on what I thought was most important. Typically the Pacific SST anomalies outweigh other factors if its close. Based on current conditions and expected evolution of the pattern (that one is tricky I know) I came up with an analog set that included 1969-70, 1981-82, 1989-90, 1993-94, 2002-03, 2004-05, 2013-14, 2014-15, 2018-19. There were 3 outliers in the group wrt snowfall, and frankly they were not near the top if I had to rank those years so for my prediction I excluded 2002/3, 2013/14, and 2014/15 however the fact they are there means there is some upside I suppose. But taking those years out we get a mean snowfall for the remaining years of 15.7" at DCA, 19.5 at BWI, and 25.4 at IAD. One thing I found very encouraging when looking at various variables was the lack of dud winters. Just filtering the QBO and North PAC SST for instance you get a larger data set but none of the years in either set were all that bad. Most werent great either. Just average to good. Putting all that together, and with my "gut" feeling...I expect a near normal winter (which is pretty rare) in the region. Somewhere between 12-18" at DCA, 16-22" at BWI and 18-25" at IAD. Around 30-40" for areas up along the PA border and out in the NW areas of our region. Basically something between median and mean snowfall for most locations. BUT...I think there is a greater chance we beat average, than we don't make median snowfall. I am not going to waste time trying to guess exactly how each month plays out since a 1-2 week anomaly can totally flip the numbers month to month. For temperatures I would guess somewhere from normal to slightly above normal for the winter with high variability. Many of those years featured some real cold periods and some torches also. Well...that's it...near normal snow, near normal temps. Slightly better chance to boom than bust. My best guess. Good luck everyone!

Was 1989-90 in your analogs?

Only thing shattered here is your grasp on reality

Don't worry, you aren't.

@frd @Bob Chill I had already looked at the PAC SST patterns from similar fall seasons in preparing my "thoughts" for the winter so it was easy to go back and look at some of the data I saved after that post last night regarding the EOF2 VMI. Often its difficult to differentiate, its not always linear in progression and often the SST anomalies are ambiguous and not purely in a classic PDO or VM state. It can also be difficult if you look at the whole basin and every little anomaly, but if we only look at the locations of the greatest warm and cold anomalies and adjust for the warmer base state of the whole pacific today, the 6 closest matches to the fall pacific SST pattern since in the last 35 years are 1986, 1989, 1993, 2002, 2004, and 2013. All of them had a period in either October or November where the central and north pacific SST pattern looked very similar to now wrt the location of the warm and cold pools. 1986 and 2002 evolved into a more classic +PDO look by January. 1989, 2004, and 2013 remained in a EOF2 VM state through winter. 1993 evolved into an ambiguous look somewhere in between the EOF2 and PDO SST pattern for January/February of 1994. Here is the thing... both sets are too small to draw concrete conclusions...but both contain blockbuster winters and more mundane ones. But neither of those sets contains a dud crap winter. So I am not really sure what application we can even use from this war over exactly what classification the PAC base state is right now. Frankly the outcomes of a fall EOF2 VM state are BETTER than the ones for all the fall +PDO years. There are some blockbusters there also but there are some really awful crap years in that set as well. So Furtado is correct the current PAC SST is technically a EOF2 VM NOT a +PDO however he seemed to be using that fact to argue against DT about a cold winter coming and I see nothing to support that application. Overall, and I hope to have my thoughts finally written up today or tomorrow, one common theme I am finding as I identify sets of "similar" years based on different factors...is a lack of total dud years. They definitely aren't all good/great but the range on most of these factors seems to be between a mediocre near normal year and a good year...not a lot of examples of bad crap years in the sets of similar years based on Pac SST, QBO, and Atlantic SST patterns. There are also not a lot of good comp years to compare this year too with the same combo of factors so there is a lot of uncertainty and so we could have a crap year...but right now I feel comforted a little by the fact there there are not a lot of really bad winters in the different analog sets I have put together.

From my memory 2009 was a pretty neutral NAO year. It was also a weak Nina following a strong Nina in 2008. I also seem to remember some decent cold periods that winter that just didn’t produce much snow. Typical cold dry Nina stuff. But even so maybe some bad luck not to do a little better wrt snow that year.

Ugh I hate this crap. Let’s fight about exactly how to term something. Bottom line is the last few +VM winters were good pacific driven patterns so their linguistic victory of definitions seems pointless. And a +VM isn’t a -PDO more a slightly positive one. Both November 2002 and 2013 were good north pac sst matches and both features great pac driven winters following. We will see. I’m not saying that’s what’s coming just that I don’t know what Furtados point is here.

Yay you’re back...

There is still enough spread within the ensembles that it could go either way, but if the lead northern stream wave ends up dominant that is probably the inevitable result. Its coming across too far north and out ahead of the cold push for our purposes.

Not thrilled with the current look on guidance but enough time to change. It's evolving towards the lead northern stream vort being the main player, and that also is trending more out ahead of the main trough meaning the boundary would likely be north of us initially and then we are stuck with the old cold chasing precip and we all know how that works out. It had more potential when there were multiple waves riding the boundary and we could get one of them to clip us after the cold push. If the only game ends up that initial vort we are in trouble imo. But a LONG way to go with such a delicate setup. But right now its going the wrong way imo.

He said that during the solar decline before the minimum the NAO trends more positive, and if we look at the last few cycles the winters leading up to the minimum did feature mostly +AO/NAO winters.

I wasn’t kidding. I suppose I was being a bit flippant in how I said it. But if you read Isotherms winter outlook he is basically saying we will have a Nina like regime with above normal temperatures and below normal snowfall and a very hostile base state for snow here. The pattern he described was not like last year, it’s significantly worse. I suppose if you only look at the raw snowfall expected for Baltimore it’s close but Baltimore was a local snowfall minimum last year with more snow throughout most of our region north/south/west of the city. That’s just bad luck. Regionally we had a near normal snowfall winter last year. Isotherm is predicting a warm below avg snow winter for the whole east south of New England! Not the same.

Frankly I don't mind a 7-10 day warm period in ANY part of winter...so long as its not endless warmth with no end in sight as you say. Even some of the best winters had a warm period somewhere. People just don't remember the torch week that happened in between all the snow. It's extremely rare, like once every 20 years or so, that we get a winter without at least one anomalously warm period somewhere. Might as well get it out of the way early...

It's not a bad sign though imo, that even with some factors not right (like the MJO) we are still getting anomalous cold intrusions into the CONUS. In really crap years one of the telling signs that the base state is just not good is how difficult it can be to get cold.

That was my thoughts as reading it. Granted he includes some factors and influences that are above my pay grade into his calculus BUT he is going with a pacific pattern that is opposite of what it is trending towards right now. Doesn't mean it is wrong...he gives some very good reasoning as to why the current trends could be a false flag, but the bottom line is it is still a lot of guess work as to which factors and influences will be dominant absent a strong enso signal.

@showmethesnow We had a somewhat similar type wave in November 1995 put down a nice early season snowfall across the region. This looks to have an even colder air-mass to work with than that one did. ETA: on a side not though... while I think this setup has potential to put down some anomalous snowfall somewhere south of typical for this time of year... the specifics of where and how much are likely not to be resolved until late. This is a somewhat similar setup to many of the progressive waves along the thermal boundary we saw in 2013/14 and 2014/15 and if we think back on that period while it was awesome, a lot of times the "threats" at day 7 turned into nothing and the actual snow we saw wasn't even on the radar until inside 72 hours.

He isn't saying it's going to be like last year, he is saying its going to be much much worse.

Oh I am not confident we get snow. Just confident we won’t fail exactly how the guidance shows right now.

Yea at this moment the models are favoring a split with one wave riding to our nw and one se. yea I know all the typical snow hole jokes but I am not sweating that exact placement being correct from this range. If that type evolution is right then if they are off a bit in either direction we get snow. And the whole evolution might change also.

Why not now? All you have to do is extrapolate it 6 hours....about 14 times

Can't wait to read it.