Bob Chill

Don't worry about the NAO at long leads. The domain space is very small and slight variations in the upper level pattern greatly affect the calculated NAO. The predictive skill of the NAO beyond just 1-2 weeks is terrible. The AO is different as it covers MUCH more real estate. Solar mins generally mean better chances of a -AO. Sometimes that goes hand in hand with the NAO and other times they are completely disconnected. If you pick 1 index to focus on definitely stick with the AO and nothing else. It has the highest correlation (by far) as to how much or little snow the mid atlantic receives on average. Right now the AO looks favorable through most of Nov. If that carries into Dec then we can start drawing some conclusions as a Dec -AO of -1.2 or lower has like an 80% predictive skill of above normal snow. The NAO acts more like a traffic cop and is much more unpredictable and volatile. Our biggest storms happen with a -NAO relaxing towards neutral or positive (Archambault event). That's for bigger storms though. The AO controls our snow chances in general. The only thing that can easily override a -AO is a tragic Pacific. 2012 is a great example of the way we can fail even with a favorable AO. If you want to focus on the NAO then you want it to be very volatile with periods of deep negative followed by relaxations repeatedly. A stout -NAO park in place kinda sucks here. The SE loves it but not us. The AO is different in that we just want a stable -AO for as long as possible.

agreed. Especially early on as wavelengths are still transitioning. We can get some nasty warmth/ridging in Dec. It gets much harder in Jan/Feb but Dec has no problem turning on the heater. Dec 2013 hit 80 right? I remember it being insanely warm for a time. Had the windows open and it was too hot in the house.

One thing we prob all suspect and agree on is a stout relaxation of the current very anomalous Nov cold is coming. I'm sure either late Nov or early Dec ends up being pretty warm for a time. Which is totally normal and happens like every single year and stuff. lol Dec 2013 was interesting. Cold early, down right hot, and then the hammer. I don't mind December having a sig warm period but I do mind it when it's all the eye can see for 2, 3, or even 4 weeks. I really have no idea what's in store for Dec but I know what to look for. If Dec goes end up cold or at least has a decent duration period of real winter wx in the east then some of the seasonal forecasts aren't going to look so good.

@frd That JMA height plot implies favorable conditions to continue pushing the pdo positive. Iso's winter forecast is extremely well thought out and articulated but imho the potential trouble spot is his -pdo influence/forecast. We'll know in a month or 2...

We've had quite a few of these types of deals over the last 4 winters. There are numerous threads started with d5 waves in a progressive pattern that ended up being no event at all. Lol

Each year always has a bit of its own personality regardless of all the good and bad signals. Since our winters are so short it can be devastating to end up with a hostile pattern for 4-6 weeks. I'd like to think our base state features a pattern that isn't a shutout in general. I really hate when there's literally no chance for weeks on end. The most reliable indicator for good snowfall (other than enso) is a Dec -AO of at least -1.0 or lower. Data shows that -1.2 or lower is like an 80% chance of at or above snowfall. The streak of big +AOs has to end eventually. We haven't had a neg AO in Dec since 2012 and it didn't even matter that year because the Pac decimated our hopes and dreams. All the -AO did was deliver Pac maritime air out of Canada. lol.

That's interesting... My guess is the simple fact that temps are warmer and we're losing on the margins. Could be decrease in seasonal precip but I doubt that's the case.

Basic stats on enso neutral winters favor sub climo snowfall so that may be tough to overcome. The stark reality here is all ENSO winters favor below normal snowfall except for a mod Nino. I'm not thinking this will be a big winter (yet) although any winter can work out. What worried me in early fall was the potential for another hostile Pac year and god knows when we ever get blocking help again... That risk appears to be declining. Based on everything I've looked at it's looking more and more like we won't have a warm door to door winter and I'm starting to like what I see in the npac. I don't make seasonal forecasts but gun to head guess... 10-15" at DCA and somewhere around 20" at places like IAD is what I think is most likely. With the exception of mod Ninos I never have any confidence in anything until Dec starts. That's typically the earliest we'll get a glimpse at what might be the predominant pattern in the conus. Cruising towards mid Novie and not seeing hostile patterns or glaring problems is never a bad thing. Nov can be brutally deceptive though. If early Dec features a displaced trop PV and extensive ridging centered around the west coast of NA then I'll start to get a little more excited about the potential. The only thing that would deflate me is a strong consolidated +AO to kick off Dec. That's an omen that has proven to be a reliable indication that we're in for some trouble. Sure, we can use 13-14 as an example of defying that type of problem but that year was a statistical anomaly on so many levels...

I'm just warming up to the idea that this winter may not be a disaster. When I looked at things in Sept I wasn't impressed at all and figured a dud was on tap. Now that we're transitioning into colder climo it's nice to see there are some things potentially breaking in our favor. Should be fun around here when this impressive Nov cold pattern breaks down and a couple weeks of mild weather shows up on guidance.

@frd From what I've watched over the years, a -NAO is most important during Dec so if we're going to get a good blocking month let it be December. Next best is Feb. Blocking in Jan can be an easy recipe for dry and cold (SE loves this setup though). Also, if the winter's base state is a coupled PNA/EPO ridge then we probably don't want a strong -NAO at any time. SNE definitely doesn't. As always it's a balance. I'd prefer many periods of the -NAO pressing and retreating but what I prefer doesn't mean jack. lol

This setup is very similar to a number of events in 2013-14 and the one thing that is really interesting is the level of cold behind this front. That's like once in 20 year kind of stuff for the first half of November. Because the cold appears to be legit there's a case that can be made for a real shot at snow next week. What I'd like to see is the front amplify further allowing the trailing wave to lag and not run hot on the heels of the front itself. Maybe 12z leans that way...

Personally, I'm not enthused by the setup next week. It's one thing when cold HP is established but gets really tricky banking on an early season arctic front to clear in time AND have a perfectly timed wave develop and run the boundary while we're on the cold side. Climo will fight this type of event tooth and nail. I'm not saying I don't think there's a chance just that I think climo will prevail and the reality will be rain/cold front/cold dry. We'll see.

Long range forecasting outside of easy enso years has been pretty abysmal both in model land and met or enthusiast forecasts for years (I know u know this well). It usually ends up looking something like this at the end of the season: "I got the fill in the blank correct BUT....". But = the atmosphere does what it does best and does a lot of things that nobody predicted and in many cases it was never even discussed at all. I'm not trying to insult anyone because I really appreciate the effort from the skilled seasonal forecasters. It's just not possible to consistently predict weather months in advance unless enso is the primary driver so skill is at least part luck and sometimes mostly luck. I could bat .750 in our area just by saying above normal temps and below normal snow every single winter. That's not really skill. It's basic climo and sticking with simple climo is boring but effective.

I doubt solar has much to do with it. A lot of year over year variability can't be explained. It can be speculated about but often has no tangible explanation other than weather being weather. Why was 93/94 a rainy/icy/mixed mess and 13/14 a prolific snow maker? There's no real way to pinpoint why they were so different. However, up in the NE, both of those years were great but it snows a lot more up there and an amplified progressive pattern works a lot better further north. The MA is right on the edge between good and bad snow climo so the needle wavers back and forth just cuz it can. Sometimes we're on the right side and other times we're on the wrong side of marginal patterns. That's just how life is living here. No sense trying to make sense of something that can't be made sense of.

I pulled some quick data with enso neutral and +PDO winters since 1960. Can't hang your hat on a single index but the group as a whole shows the odds of a total dud are pretty low. A few of the years were solid. The takeaway is near normal snowfall is favored with a better chance at AN than a disaster. Here's DCA for the years I pulled: 1960-61 - 40.3" 1969-70 - 14" 1980-81 - 4.5" 1981-82 - 22.5" 1985-86 - 15.4" 1992-93 - 11.7" 1993-94 - 13.2" 2003-04 - 12.4" 2013-14 - 32" 2014-15 - 18" Not a bad group right? It's also notable that all the big snow nina and nino years are in the mix (82-83, 86-87, 95-96, 02-03, 15-16). It's almost a guaranty that a mod or strong nino will have a +PDO because warm enso affects the north pac basin. OTOH- nina's generally feature a -PDO but 95-96 was very positive (very unusual year with unusual results). So why does a +PDO help us? There's a chicken or egg argument on what causes what (SST or upper level patterns driving the bus?) but for our purposes it doesn't really matter. We just need to root for a strengthening +PDO and let the chips fall. From the limited data it appears that a strengthening +PDO is better than a weakening one and that makes sense because the pattern that drives a strengthening PDO features a trough in the wpac, ridge in the epac/north america, and trough in the east half of the conus. The correlation has far too small of a sample size though so no spiking footballs on whether or not a strengthening +PDO is better. Logic says it is but this stuff is too complicated for a narrow focus like that. Right now the PDO is mostly neutral but the upcoming pattern over the next 2 weeks will likely shift things enough to push the PDO positive. If it does then just keep watching for a continuation of the +PDO and let the chips fall. It could be an important signal as we head into Dec.

I'll have to defer on your question. I don't know enough about the IOD and how it affects our sensible wx to give a qualified answer. I generally stick pretty close upstream with mid latitude patterns. The Pac basin is the furthest upstream I look at along with the high latitudes.

Yea, finally ready to root for cold again. Nov is snow is pretty rare in my yard. We'll see

Ha! I'm mostly done worrying about weeklies and seasonal stuff unless there's a nino or nina. Otherwise it's just not predictable enough and the only thing long range models do for us is to give us something to discuss that probably won't happen anyways. Nov is a very tricky month. Sometimes it tips the winter's hand and other times it's a complete headfake. One thing that's really grabbing my attention is the prog'd longwave pattern over the pacific. Below normal temps and heights from Japan to the aleutians. I expect the ssta plots to show a strengthening +PDO this month. I'll have to dig through the stats but if memory serves me, the majority of the +pdo winters have above normal snowfall. Get that going and odds tip in our favor.

It really doesn't matter much in Nov. Wavelengths are in transition and the climo base state of the trop pv is way up there near the pole. The fact that the trop pv is getting displaced so far south in early Nov is quite anomalous and atypical. It's either random choas or a sign that winter may in fact feature a displaced trop PV more often than one parked over santa's workshop. Won't know the answer for a while but current guidance is no doubt a net positive even if it's just a transitory shot and regression back to climo location. The strat is a different beast. You only need a SSWE when the strat PV is strong. Years that start off with a weak strat PV generally feature high latitude blocking. Not always on our side of the pole but blocking in general. 09-10 featured a very weak strat pv early and it never recovered. I believe there was also a warming event thwt year but the gears were already turning well in advance. Personally, I'll root for any disruption or degradation of the strat PV as early as possible. Weak early with no sswe > strong early with a huge warming event. That's what (imo) we should be rooting for... anything and everything that prohibits a strong and consolidated strat PV.

If you look at Nov 2013&14 npac SSTA plots they look pretty similar to this year. . This year looks like a blend of those 2 years (especially ENSO regions) and I find it encouraging. Here's current, Nov 2013 and 14 SSTA plots: Yea, 2013-15 period featured a pretty nasty +AO/NAO but the Pac doesn't really drive the high latitudes as much as it drives the longwave pattern in the mid latitudes so jumping to the conclusion that the similarities to 13&14 means the AO/NAO are going to suck is a mistake. Current ens 5 day mean height patterns look a lot like Nov 2014. I don't think all of this is coincidence. If current ens guidance is correct, at least a portion of Nov will look very similar to Nov 2014. Looking at the GEFS panel below you can see how nice the Pac is setup to continue the trend towards a +PDO. If this is the dominant pattern in Nov then the npac SSTA configuration is going to look very good. Still a month out from game time but you can't help but to think that the Pac/NA pattern will likely feature a coupled -EPO/+PNA at times this season. 2014 looked great in Nov and fell completely apart in Dec but no 2 years are ever the same. Not to mention that Dec 2014 was only a relaxation before the same pattern as Nov set up and carried through all the way into March. I can visualize the possibility of getting a favorable Pac/NA pattern similar to the 2013-15 stretch but what could really make it interesting is if the AO/NAO are also more favorable instead of the complete opposite of what we want to see. Analogs are good tools to use but where people make the biggest mistake is assuming the same outcome as a previous analog. The atmosphere is way too complex to work that way. Take 13-14 for example. The mean height pattern through met winter was uncannily similar to 93/94. But sensible wx was MUCH different in our yards. Instead of a mix/icy redux of 93/94 we ended up getting snowed on start to finish. Personally, I'd MUCH prefer NOT to get a 93/94 or 13/14 upper level pattern redux because it's not a good pattern for our region to get snowfall even though one of those years was prolific. However, give me a 13/14 or 93/94 redux with SOME semblance of a -AO/NAO and I'll root for that all fookin day.

I haven't paid much attention to long range this year honestly. Since there's no obvious "easy signal" so far I'm not into winter mode yet. First good looks at reasonable leads will get me back into it Yea, we can luck into a big storm any year but no reason to think we'll have a juiced stj and blocking yet. This year seems kinda boring leading in. I don't have high expectations. Would like to see the atlantic behave better early on. It's been what... 9 years since had a persistent favorable atlantic in DJF?

Hey weenies, figured it would be exceptionally strange for me to not post in the winter thread during Oct so.... TL:DR: Favorable enso is close to off the table. I have no ides if the AO/NAO will cooperate. The north Pac ssta's are moving in the direction of what we want to see but plenty of work to do over the next month. This could be a sign that the Pac jet won't destroy our hopes and dreams and there's no reason at all to think we're F'd yet. My confidence in any outcome is very low still. I have no opinion on QBO/blocking/strat PV etc yet but I am warming up to the idea that this winter may not be a total disaster. Enso probably won't drive the bus as it's pretty late and the enso regions are ambiguous imo. Numerical data for region 3.4 looks ok but I'm more of a visual person when assessing the influence of the eq Pac and right now it just doesn't look all that great. Region 3.4 warmth seems more of a byproduct of the pac having expansive warmth north of the equator in general and not due to circulation patterns responding to nino forcing. In early Sept I thought the pac nino and pdo regions looked like trash. This is not a ssta map that inspires confidence in a good winter in the mid atlantic: I havent been paying much attention to what others have been saying but if enso isn't going to do much then the next best thing is to have a +PDO. The PDO is what helped make the 2013-16 winters favorable. It may have been the primary reason. Hard to say. It's also what made 95/96 a prolific nina. A +pdo during a nina is very uncommon. Especially a mod+ Nina. When I looked at the ssta map in early Sept my first thought was the PDO region looked like crap. Not as bad as a -pdo but pretty bad. Over the last 2 months the PDO region has improved. Not as fast as I'd like but it's better. The area off the coast of Japan needs to cool down but you can see the expanding region of BN ssta's in the western pac compared to early Sept. Hopefully that keeps building eastward. It could be the first clue as to what the predominant pac jet structure ends up being this winter. We only have 14 real weeks of winter and it goes quick. As we've seen recently and countless times in the past, the pac jet is a big deal here and get it wrong for a month and you can kiss half or more of winter goodbye regardless of all other indices. The problem is there is no way to know what the jet is going to do weeks or months in advance. Especially during transition months like Nov and early Dec. However, if Nov features a trough in the west pac and a ridge in the east pac centered near the west coast it's going to push the pdo region into a configuration that can be really friendly here. It would also increase our chances of getting off to a good start in early Dec. If there is a persistent good pac pattern in Dec it's entirely possible it will recur throughout met winter. It's a chicken or egg argument though just like "the blob" in 2013-15. What causes what? Do the ssta temps force the troposphere or does the trop force the ssta's? IMO it's a little bit of both. Weather patterns force the ssta's and once the warm and cool anomalies are well established they can assist with persistance. Gun to head this winter will be close to average in both temps and snowfall and the odds of +climo snowfall are slightly higher than an epic fail. I'm expecting the -EPO to flex at times and I doubt we'll get SE ridged to death.

BWI 11/11 IAD 10/31 DCA 11/17 RIC 11/11 Tie Rainfall 10.10"

I never expected much snow but I didn't really anticipate this much cold rain. What a miserable muddy mess. I'm in full on root like F for warm and dry mode.

Grass is trying to cave. Not expecting much. Too close to mix line and too warm to start but I expected that for days so not a bummer. If I get an honest inch I'll be satisfied. Watching snow fall never gets old though