Stormchaserchuck1

50/50 low really rolls north. Almost touching southern Greenland. and the +PNA trough in the N. Pacific weakens a little moving east.. We need that Pacific piece for the trough to dig.

Looks like a nice pattern actually. Not far from having a south-of-Alaska low (+PNA modeled) and 50/50 low. Then it's a matter of how wet the system is.

The 3-8" snow event with -AO at -3 wasn't part of the cold pattern? These next 2 rainstorms are frustrating. Supposingly, we are going to get well into the 50s both times. The Pacific pattern isn't bad for these storms. Gawx did research in the ENSO thread that showed, we have a chance at having the most DJF +PNA on record [CPC]. Out of non-Nino years, he says it will be the most +PNA DJF on record (going back to 1948). We all know how -PNA has been shutout pattern as of late, so it is a little concerning that DJF +PNA this year didn't produce more snow.. we aren't going to be so cold probably in future Winters.

AO sure is rising to positive pretty fast.. Maybe it's moving from -5 to 0 so fast that we will see a snowstorm around the 20th By the way, this pattern is in the N. Atlantic for the mean of the next 15 days.. When I rolled the February analogs ahead to March, they seemed to reverse.. notice the +AO/+NAO signal for March. Notice how the most +height anomalies in the N. Hemisphere are over the Azores.

Looks like about 1.5" here

Need it to hold when the storm moves east.. I still say the pattern is colder than average and above average precip, so snowstorm is probably high probability but a Gulf of Alaska low is not there, and 50/50 low is a little more progressive for when the storm arrives. There is more spacing between waves in the mid-latitudes, vs having it all slowed down. I don't think "coming out of -AO" produces the same snowstorm window as coming out of -NAO.. but I'm not 100% sure on that. I think -AO during the pattern favors snowstorms, but when you are rising up to neutral NAO from negative that has high major snowstorms correlation, especially with 50/50 low lingering.

Nice -5 AO rainstorm, 2 weeks from the coldest of the year, tomorrow. I still contest that 90N is too far north.. >95% of classic -AO cases were further south.

Here's 20 top analogs to the Atlantic/Arctic pattern

What do temps have to be for Kuchera to work? Looks like low 30s to me.. not even 1:10 probably.

They look +NAO to me. Just confirms that our best snowstorms happen with favorable Pacific and +NAO (that's why negative heading to neutral is so strong.. -NAO is actually a very dry pattern).

NAM has had the low near Detroit.. Gfs was much furth south. Still some spread, but fwiw the 0z Hrr looked like the 18z NAM.

+NAO is a wetter pattern.. so a slightly displaced NE 50/50 low can correlate with storms.. and snowstorms if the Pacific is favorable. The pattern looks somewhat like 13-14 and 14-15, with the monster +NAO those Winter's just south this time and +ridging over Greenland and AO zone. The important point about 50/50 low though is where it is when storms are coming.. because it shifts around a lot.. is it a south-based +NAO for the storm, or an ideal 50/50 low? I was just pointing out that the map brooklynwx posted, it's not a slam dunk for arctic air.. an Atlantic SLP gradient in that spot actually has a slight correlation with SE ridge... doesn't mean it can't snow. Again, +NAO like that one, with a favorable Pacific is a snow pattern. precip is +0.50 correlated to +NAO, which in this case may slightly overlap 50/50 low some of the time.

0z Hrr.. then the 2nd storm is trending toward rain

Be aware of this pattern though... But the Pacific side is favorable, so it should be cold enough

It does moderate a little at 84hr, with the 925mb low up near Lake Eerie. Rain except in the mountains.

CAD is holding surprisingly strong for the storm after it.

It's also a bit odd to have another strong storm right on its tail like that.. there is usually more spacing between waves.

We are failing though because there is +NAO tendency this season. I posted it on the last page, this connection is a little warmer. Because we are at 40N, south of 45N, what happens in the mid-latitudes is actually more important for us than what happens at 90N.

NAM is north but it is the horrible NAM.

Block at 90N has only sustained though for more than a few days maybe 4-7 times since 1948 (I've gone through and looked at the data on daily - came up with 7 main index regions in the N. Hemisphere, and North Pole was not one of them). It's because of this a super strong low is now projected to form just south of Greenland. It's too bad it's not 5 degrees south, because that would have been an awesome 50/50 low. But the H5 change between projected time and day-of is not big, because the CPC calculates NAO error, and it has like a 90% chance in that graph of verifying positive. It's because of this slight displacement north of the 50/50 that we will now have a SE ridge! Unfortunate, but I'm saying there is a reason in this case for the -AO to link up with a SE ridge.. it's a little too far north. Now, 2017-2023, there were a lot of anomalous SE ridge's in that time (especially 22-23).

It's probably more about the Pacific pattern being good vs neutral/not.

I know you all like the Hrr at 48hr.. big storm

Before we get 1" of new snow! I would have actually favored more of a Weak Nina late season look, because I've correlated the ENSO subsurface with Pacific PNA pattern, and it actually came back with high forecasting predictability. But this season is different.. a good case study! A week ago, I wasn't thinking it would be as favorable as this.... I'm still real curious though to see if we can get solid cold in the 2nd half of Winter.. I do think that as the average temperature starts to increase, there is tendency of late to keep us warm.

I think for future reference, it's a good research to do where the block is. A lot of AO data overlaps with NAO, and a lot of times it's a Greenland block that is -AO.. but this time it's over the North Pole, so that's actually a little different. This is why I like to look at raw 500mb maps vs the actual index numbers, although you could probably look at AO vs NAO and get a good analog system from that.

Yeah I think it's a pretty legit shot at something good. Hopefully storm systems keep being as strong as modeled. If that Pacific pattern that is currently modeled holds, watch out... It's a good observation too that a 90N block correlates with cold at 45N, but further south at 40N there could be a tropical ridge tendency as the 3rd wave down. Today it has evolved to look like that because of south-based +NAO though.