Moving this to a new thread to not clog the tropical thread.
It seems like the expectations of late, at least in winter months, have been for tropical forcing to evolve/behave a certain way, and that doesn't seem to materialize.
When was the last favorable setup for cold in DJF maybe 2018? The last few March and/or April's have shown we can still do well on the cold side. The more we do this the more I realize the nao is great at giving us suppression but if the pattern in the west into polar Canada stinks it'll just be mush events. I personally think guys like Cohen and ventrice are in the right arena with regards to the pv, siberia, epo regions and how much they really are more of a driver but that gets to be chicken and egg with regards to forcing and other global factors
In a global or hemispheric sense we should have similar results within a few years of each other but the local effects are what changes right? I just don't think we change that much on a global scale. The atmosphere has some stability
Agreed. I think we are just now starting to really look under the hood. Back when we started this it was -nao yay +nao boo!! Now it's ok the nao is positive but the epo ridge is into siberia and we are going to have 2 weeks of cold bc the strat pv has fallen apart and the mjo is in p7
Right, I guess my point was how do we know if an analog from a cold/snowy decade (say in the 70s) that failed to produce now, didn't also fail to produce 500 years ago? Maybe because there are other factors, maybe even factors yet to be determined? Maybe it's the sequence of those global factors, not even sure that makes sense? Lol No doubt the atmosphere has some stability and factors on the global sense could be "relatively" small but have huge implications at the local level, thus why so many bash analogs when they don't produce in their backyard.
I agree. We will never know past what we know. Looking at sea ice and tree rings is helpful but imperfect anything past written documented history is an educated guess. As we add more population and recording devices we will probably see more records on local levels since we can actually record it. But like you said the imby factor will never leave if nc doesn't take a hurricane hit this year everyone will say but you said 96, 98, 99 were analogs. Well they were at 500mb but that doesn't immediately equal outcome since hurricanes are influenced by smaller scale features just like rain snow lines and a couple of degrees of tilt on a trough that goes OTS with no snow
As far as winter as a whole goes, I don't know when the last favorable setup for a generally enduring cold pattern was. But I have seen what look to be favorable 500 mb patterns over the course of the last few years fail to produce much more than slop, whereas in the past, similar looks have yielded bonafide winter storms. But that doesn't really tell us very much at face value. It could be that we're just dealing with warmer air overall. Or the dewpoints are generally a little higher. Or it could be (and probably most likely) that I haven't studied historic winter-time upper air patterns enough. But be that as it may, I don't think it's much of a stretch to conclude that it's been very, very difficult to get widespread cold and snow into the SE over the last bunch of years, with a couple of exceptions.
I feel, and this is just a gut feeling, that we need more extreme setups to get deep cold and widespread snow into the SE now than we did 20/30 years ago -- deeper troughs, stronger highs, etc. -- to counter the general warmer tendencies we see today. That may not be true at all, but after the last 10 years of watching things play out, it sure feels true.
I think if we’re looking at a winter set up, the key is what’s going on in the cold source regions and when do we start seeing those cool down. I couldn’t help but notice that for much of December and January, we had an 500mb that you would think would have allowed most of us in the western 2/3rds of the Carolinas to score a good snow, but most of us east of the foothills and south of I-40 were shut out. The overwhelming talk during all of that was how mild the source regions were. There just was simply no below average cold air in the Yukon or Alaska. Those areas actually last summer had bouts of record breaking heat throughout the summer and the overall pattern that was causing it didn’t really breakdown until nearly October. Anchorage had stretches of days reaching into the 90s and Barrow and the north slope were making runs at 70. It appears looking at different years that summer me that stay fairly seasonal in those areas are able to start building up cold air much quicker. This is something I am watching this summer and fall to see how things progressed. So far those areas having a below average to average summer temperature wise with Anchorage seeing highs mostly around 60 and the north slope mid 30s to mid 40s. Now being a week after the summer solstice, these area will be quickly losing daylight, and the overall pattern seems supportive of continued cool to average temperatures. If this overall pattern prevails through the rest of the summer, I believe you will see these areas begin to build up cold air much more quickly than what we’ve seen the last several years.
Yeah I just don’t think the warming explains it personally . I think it’s our short record , we have 130 years of records . How often have exact conditions repeated ? Probably not enough to be able to make a statistically significant claim that x pattern will lead to y conditions 95% of the time . Perhaps if we ran out one of the analogs in the 80s 100 times , only 30% of the time will it bring snow .
Yeah I can agree with that to a point. I was thinking of within our record keeping domain when I wrote the earlier post. I would obviously stipulate that were we able to view the entire climate record, we'd see a lot of diversity in sensible weather from similar patterns in different periods.