Carvers Gap

Just toggling between the (3) weeklies (American, Euro, and Canadian)....there is blocking showing up over Greenland or slightly west of it in the Davis Straits. That is usually a pretty good sign that cold is coming. One thing to watch for is what the Pac does. If it is meh...periods of zonal flow could persist w/ maritime air flooding the continent. If the EPO or PNA fires up, then very cold air could head south. Some runs have the AN heights over the northern Hudson Bay....to me that is a crapshoot as to whether that helps us or not, and that is not a true NAO. If coupled with a good Pac, that works. Otherwise, zonal.

Just and addendum to the post above....the Euro Weeklies(control) does have a sharp downturn in terms by week 2 of November. The Weeklies ensemble has this as well. The CFSv2 yesterday morning started to show some hints of this. Let's see where this goes. Obviously, this could be a head fake at this lead time, but this fits with what we know about Nino climatology. It would not surprise me to see snow in the air by mid November, especially for foothills and mountain locations. It appears that summer is finally on the clock! I mean it has to be by mid November, right?

I strongly encourage everyone to read @John1122's posts in the winter discussion thread. Why? Because what I am gonna say next kind of dovetails into those comments. Both the 0z GEFS and GEPS are depicting a pretty significant(?) pattern reset to begin November. That kind of fits the 4-6 week pattern cycle of the past many years. Ridge slides west, and a trough develops in the central and eastern part of the United States. That could be a SHARP change in temps given the summer like temps we are experiencing right now. We are talking 20-30 degree differences in high temps. The Euro weeklies don't see this just yet, but they often get roasted during shoulder season...before often locking in the winter pattern by mid Dec. The 13-14 analog also had a sharp change in temps by November....

What was the preceding fall season like? AN temps w/ some periodic rain chances?

La Nina is just HOT in my backyard during fall. It has not been as hot as some years, but it is still very warm. Nights have been cool. It is almost like living in the desert with such low humidity. Leaves here are definitely in a state of suspended animation after some cold days in August and early September. Now, that we have switched firmly back to summer...everything is paused. Leaf season will run into early winter here. There are some hints that cooler weather is coming. The CFSv2 has an outright flip at 500 while the Euro Weeklies are typically blind to it. That said, the Euro Weeklies control doesn't have the flip. Usually if a flip is about to occur, I like to see the Euro Weeklies control and CFSv2 both showing something similar. Until we see that, I look for at least 2-3 weeks more of very warm weather...maybe longer, but that is pushing the envelope as the pattern will be due for a change sometime around mid-November. Ideally, we want the pattern to flip during the last week of November or first week of December. Then, maybe we can get 4-6 weeks of a pattern which could yield winter weather. What we don't want is the pattern to flip cold in early November. If it does that, that means it may well flip back warm by mid December and hold through most of January. That is a concern and very much on the table.

I have seen that year mentioned as well. How did that winter look?

@John1122, heavy snow warnings for the summits of Mono Co. John, who is it that you follow in Mammoth Lakes?

Powell is coming out of hibernation. Can someone unlock his account for him?

Some hints this amplified pattern flips very cold sometime in the next 3-4 weeks. Amplified patterns this early usually flip our way at some point. But I absolutely hate summer during October - just despise it.

We have a long way to go with seasonal forecast models. I honestly think human forecasters can hand develop seasonal forecasts which have equal or better accuracy, albeit with some AI help. For now, there is just too much for modeling to juggle. There is some rigor with seasonal modeling which is released at the beginning of each season, i.e. winter forecasts which are released at the end of November are an example of this. Right now, ENSO is incredibly hard to predict at range. Since so many models, as you and John note, are based heavily on ENSO....they swing w/ those ENSO forecasts. Honestly, it is probably the right way to build a model, but again...way too many other things to juggle. As Mr Bob notes, each year is its own analog. Until we have mathematics which can predict chaos at range, there are going to be limits to the power of AI modeling. A computer can easily beat a human in chess. But...climate/weather at the 9-12 month lead is like a game with nearly unlimited moves and options. The human mind is a better predictive tool when it comes to seasonal modeling at the moment IMHO.

Oh yeah, seasonal maps are almost always warm at the surface. I generally just look at 500 maps and source regions - even for weeklies. The Euro seasonal and weeklies(mean) almost never see cold at range. Now, the one thing that does work is to look at the control surface and/or 850 temps on the Euro Weeklies - that gives a look under the hood so to speak. The seasonal CFSv2 looked good today. I almost posted it, but it will likely change tomorrow. The CANSIPS has shown some skill at range w/ its 500 and temps maps...but only the November run has been accurate, though October can provide some hints.

Yep. Its 500 and surface maps don't correlate to the snow maps. Temps and 500 maps correlate better than last month. Generally, a very warm pattern for most of winter. 500 is more opportune for November and December if I remember correctly. The entire winter run was a bit touchy. I was really surprised to see that snow map circulating as I am not sure that I have access to it or just haven't looked! FTR, I don't think it is right at 500. The CFSv2 seasonal has been spitting out some fun 500 runs at times.

I "suspect" we see the typical mid-late Nov cold snap which lasts into the last third of December, a BIG thaw, and maybe a return later in the winter of some cold. LR ext modeling is much less bullish on even minor cold shots for this upcoming winter - big SERs showing up on modeling. I just don't think the Nina is gonna be that strong. The CANSIPS can bust bigly at times. I do think late season heat typically signals a fairly major flip to cold at some point - like summer to winter within days. Nearly all modeling has a significant warm-up mid-winter.

Yuck. @Holston_River_Rambler, the big red ball over the Aleutians is there for three straight months. Let's hope the CANSIPS is wrong. Next month is the the one with the most skill. I don't like this at all. November looked good. October isn't a bad look, but I think it stays warm. @nrgjeff, if we are talking talking basketball....this is the equivalent of Kansas making the NIT, right?

I thought for sure we were going to miss extended summer this year. Nope. October could well be VERY warm. That does likely set us up for a very sharp flip come November if past Nina years are any clue.