December 2012 Pattern Analysis

[earthlight]

That strong block helps to keep that 50/50 in place also increasing the confluence over southeastern Canada. I would think the Euro will start to catch on to this strong blocking and confluence and shift the storm threat east in the coming runs.

Agree, although I'm not sure if we can stop the primary surging decently far northwest with the ULL cutting off a little too far west before it hits the confluence and is forced to redevelop the surface low.

This block will stick around too...and with the potential for a split flow out west I'm becoming pretty confident we'll see another winter storm threat by Jan 2-4.

[Weathergun]

That strong block helps to keep that 50/50 in place also increasing the confluence over southeastern Canada. I would think the Euro will start to catch on to this strong blocking and confluence and shift the storm threat east in the coming runs.

The Euro guidance has been behind the GFS guidance on the blocking developing this week. The GEFS was the first to show a block cutting off from the Aleutian ridge.. However, both models and their ensembles, break down the Rex/Omega block in the long term, with the new PV forming near Scandanavia. The Euro does this quicker than the GFS. Which causes this 26-27th storm to track further west than the GFS. But I think both models and their ensembles, could wind up be too fast breaking down the Rex/Omega block.

[Neblizzard]

The Euro guidance has been behind the GFS guidance on the blocking developing this week. The GEFS was the first to show a block cutting off from the Aleutian ridge.. However, both models and their ensembles, break down the Rex/Omega block in the long term, with the new PV forming near Scandanavia. The Euro does this quicker than the GFS. Which causes this 26-27th storm to track further west than the GFS. But I think both models and their ensembles, could wind up be too fast breaking down the Rex/Omega block.

That could ultimately destroy the cold pattern if they are correct?

[nzucker]

That could ultimately destroy the cold pattern if they are correct?

The ridge building over AK should preclude the breakdown of the cold pattern into early January. With the EPO going negative, we should get more arctic air in here for the next 2-3 weeks.

[Weathergun]

That could ultimately destroy the cold pattern if they are correct?

Well the 12z GFS & GEFS is showing more blocking developing in 300hr+. So I think not. It's the final outcome with 26-27th storm, that gets affected.

[nzucker]

Well the 12z GFS & GEFS is showing more blocking developing in 300hr+. So I think not. It's the final outcome with 26-27th storm, that gets affected.

18z GFS continues the theme of the coldest air of the season arriving after the 12/27 storm. Looks cold all the way until the end of the run with 850s down around -15C after that storm heading towards New Year's.

[NYCSuburbs]

The 0z ECM finally gets the Pacific to change with a monster ridge out west and a huge trough covering the entire eastern half of the US. We lose the -NAO but make up for it with the more favorable Pacific:

While it's still in its 240 hour fantasy range where it has also shown this coming week to have an arctic outbreak, this time it coincides with the time period towards early January that has been pointed out by some to have a better chance of a colder pattern. The CFSv2, for what it's worth, has also been showing a sustained cold outbreak starting around the end of the month/early January, and it has nailed the December coast to coast warm pattern. With this week looking uglier than first thought, hopefully early-mid January still holds promise.

[earthlight]

Split flow developing on the west coast, plenty of cold air dumping into Canada and the CONUS by 150 hours on the GFS.

[earthlight]

Lets take it a little further...winter is here without a doubt if the GFS is correct. Classic.

[CooL]

If that cutoff energy gets ejected we could be looking at some awesome potential

[nzucker]

If that cutoff energy gets ejected we could be looking at some awesome potential

The 18z GFS finally ejects it as an overrunning event at 264 hours, which gives us a moderate snowfall and very cold air in its wake. Looking before the fantasy range, however, there is a strong signal for a Miller B around Day 9 as a Manitoba Mauler moves in and the PNA spikes with a falling EPO due to a strong Aleutian low. This is right after the 12/30 system we are watching as a potential Miller A Nor'easter.

The pattern appears very favorable going forward with VERY cold air on the table. GFS tanks our 850s several times down to -15C with the polar vortex lurking just to the north. It's also a stormy pattern due to two things:

1) energy diving down the northern stream due to the strong block over Alaska, causing clippers/maulers

2) the eventual ejection of the trough in the Southwest/California which could produce an overrunning event

Here is the potential Miller B threat at Day 8 as a Manitoba Mauler moves southeast: