Phil

Arctic temperatures typically bottom out around February 1st, +/- 10 days. NH SSTs above 40N bottom out in early March. This is prime time. The higher Sun angle does lead to a tighter N/S temperature gradient over the mid latitudes as the tropics/subtropics begin to warm, coinciding with the maximum average spacing between planetary waves. If events are rare in the PNW after February 5th, it has little to do with the Sun.

This run isn't as good as the 12z for the PNW, but continues the theme of modified arctic air.

Putting it simply, breaking down the PV releases the shackles holding the coldest air up at the pole. Flow turns increasingly meridional in nature, and cold air spills into the mid latitudes. The PV is being bombarded by wave breakers and the shifting stress fields associated with the QBO, which is in a declining state. The cooling of the equatorial Strat is slowly igniting the MJO, further amplifying the Rossby wave train. A weaker/disrupted stratospheric PV increases vertical shear on zonal flow below and reduces downward transport of frigid gases from the polar mesosphere, hence you break down the vortex column and often fall into a -NAM/-EPO dominated regime.

Crush job and bifurcation: 1mb http://img822.imageshack.us/img822/3540/hpda.jpg 10mb http://img194.imageshack.us/img194/4586/kbig.jpg

The Euro loves to hang vorticity back around meridional flow..so you get a lot of pseudo cutoff lows. I wouldn't worry about it..

Oh you lucky dog. My wife refuses to even consider Montana. Don't be surprised if I pop by with some cuban sticks and moonshine.

Not to be rude, but weren't you downplaying the whole event last night based on a few bad GFS runs? I'm rooting for you guys. If anyone deserves to score at this point, it's the PNW.

This is crazy. Winter Storm Watches in: New Orleans LA Gulfport MS Tallahassee FL Savannah GA What has the world come to when coastal FL is colder and snowier than parts of coastal Alaska?

West coast ridge dominates until the Feb 7-8 on this run. Brutally cold for the Midwest and East.

Arctic blast after hr 300, pushed back a day compared to 18z

The 1600s/early 1700s were obscenely cold. There has been a ton of paleoclimatological research done on this matter..so when I get home I'll try to dig it up.

It would require a lot of writing and linking. I'm on my IPhone so when I can get back to a PC I'll put something together in the climatology forum. I'll just say this and shut up. There's a reason the most intense winters in North American history occurred during the prolonged solar minimums..and tended to be warmer during the decades featuring an active Sun, specifically a strong solar wind. Looking at the isotope history in the GISP/Vostok ice core data, the transition we're about to go through may very well be the most dramatic in several thousand years. I personally know a few Danish scientists who do the analysis on the ice cores, and they've confirmed my suspicion. The winters during the Dalton Minimum during the 1800s were extreme..NY harbor froze over on numerous occasions, as did the Chesapeake Bay. If you think that's impressive, look at Native American tales of winters that occurred during the Maunder Minumum. We'd be scared s**tless if that were to occur now. I'll have to dig up the research/history on this. But I'll say, it's nothing short of fascinating.

Even if this winter doesn't pan out for the west, you've gotta feel good about the return to extreme mid-winter cold over much of the US. History clearly tells us that when we see numerous cold winters on a decadal/multi-decadal timescale, everyone ends up hitting the jackpot eventually. I've been seeing some good signs on a global scale, which started back in 2012. We're quickly leaving the 1998-2012 regime which was marked by broad, poleward-migrating Hadley Cells and a significant drying of the tropical atmosphere above 600mb. The circulatory system is in a transition state..once we leave the current solar maximum, the dominoes should begin to fall.

Uh, who hacked Tim's account??

Arctic blast on the GFS beginning around 276-288hrs.

That ridge over AK is pure insanity on the 18z GFS.

Actually, thus far it's been the other way around. The ECMWF has been trying to pop a SE ridge since early January, which has failed to verify. The Pacific block is a near certainty. The SE-ridge would be a downstream response and it's existence will depend on a number of factors that are difficult to determine right now.

Honestly I think (for now) we should have 4 pinned threads on one forum. - NW US - SW US - Central US - Eastern US This way the community is not divided and will have more opportunity for inter-forum communication and growth. This is how EasternWX got so big. Only when the forums were large enough to warrant subforums, were they implemented over there.

Not true at all, from a 500mb perspective. Shortwave activity will usually not be picked up on from this stage anyway, especially post-truncation. Not to be rude, but I can't believe you're saying it will be a "bone dry" event 10+ days out, when just 1hr ago you were claiming the GFS was smoking pot with it's entire solution. Make up your mind, dude.. On a lighter note, when did you fly back to BC from Ontario? Sounds like a lot of back & forth.

Wow @ the 12z GFS ensemble mean. I've never seen a signal this strong @ hr 300+ before..ever. Only now, we don't have to deal with the giant PV over Greenland. So this is a better setup than December, assuming it verifies. http://img713.imageshack.us/img713/3379/76dh.jpg

Yeah, you don't want the block too far offshore or flow will turn onshore and snow levels will rise. Northerly/NNW flow in the upper levels is the best, especially in Oregon. That's what allowed a shortwave to deepen into "Storm King" in 1880. It's also what produced December 2008.

I disagree. The chances of a 4"+ snowfall go up dramatically in the PNW lowlands with arctic air around. Shortwaves producing precipitation won't be picked up well (if at all) out at this range..we need to focus on getting the cold air in. This isn't Minnesota, where arctic air is nearly irrelevant to snowfall.

The good news now is the PV is nothing like the giant black hole it was back in December/early January. The vorticity maximums are un-stacking as we speak due to continued bombardment from an upward propagating train of wave-breakers. So given the chaotic nature of the Rossby train and tropical response to the cooling Eq/Strat, this window should be harder to predict than the event back in December, yet offers much more potential as well.

The pattern change is not too far off to be taken seriously. Whether it not it leads to an arctic blast in the PNW remains to be seen..but the likelihood of a blast during the window of interest is probably 50/50..in other words, above average.

12z GFS splits the PV from 1-10mb with a significant perturbation below 10mb. This can only help things.