Part II, Thanksgiving week transient cold shot and the pattern beyond

[Typhoon Tip]

Euro ensembles look pretty good. They are actually better looking than the GEFS now, which is an about face. Better to have the more skillful ensembles range look the best imo. They feature a strong ridge in the GOA the whole time.

We'll have to see if they hold on, but this is the best I've felt in a while. It doesn't mean shiat because the devil is in the details with any storm track. but it's getting better. Lets just hope they hold.

You snow geese should hope so - whomever you may be... Although, yesterday at this time the mean was better, the overnight GFS ensemble mean ries to tank the PNA in the longer term. If so that would suggest that these current depictions of +PNA are not truly reflecting a pattern change, but perhaps a period of pattern relaxation - after which the former predominating signal might return.

Or not ... again yesterday at this time there was a hinted NAO sell off along with a AO correction downward, and the PNA ...while not hugely positive, was static to about +.5 SD out to day 15 - it is interesting that one single run can blast an entire signal away that way, from BOTH disparate regions. Probably need to pass on that, too, pending some nightly consistency.

As to that D4 thingy... I don't really have a problem with that rising PNA entrance event being warm and rainy, and west... It's a kind of Archembault system, or one that results pretty clearly because of the background synoptic evolution drops the bottom out of the geopotential medium over the TV/N Gulf, while there happens to be a well-timed wave propagating through the field - there is nothing in the concepts of what the science means that implies snow or rain; it is all about large scale precipitation events, period.

In the details, the antecedent heights over the deep S and SE/Florida are initially not very compressible - a kind of metaphor, I liken it to a wave approaching a beach with steep drop off in water depths. The wave is rolling along and encounters the sudden rise in bottom elevations (ridging) then faces out more abruptly and curls over. You want a relaxed geopotential medium over Florida as a canvas; this business with 585-588dm heights is too high.. Another flag for less compressibility is whether the balance mid level winds are above 35kts - if so, whether "curves" in the flow show it or not, there is a ridge there that is being suppressed, causing the gradient to be too steep, such that any S/W entering the TV is less mechanically able to produce cyclogenesis (fluid dynamical discussion) ... blah blah blah, but it is true. In this case, we have the former scenario, with out and out ridging there offering a bit of resistance initially. Compressibility can be compensated for with a very powerful disturbance, or ...if the larger synoptic regime is on the move, and/or both - that is about the only hope of this system compensating for the warm wall over the deep SE initially. Otherwise the wave breaks too early so to speak.

[Clinch Leatherwood]

Who has moved the goalposts? The modeling has been pretty stable and the pattern change shouldn't begin for real until 12/10. It's pretty rare to get decent snow prior to 12/15 if you go back through the past 50 years clime records.

Pattern doesn't look really any different in real terms. It'll be cooler in terms of positive departures, but there's still lows piling into AK, and there's still a high to our south.

Parade of storms aiming right for AK....still with the jockstrap ridge off the west coast.

[OKpowdah]

Pattern doesn't look really any different in real terms. It'll be cooler in terms of positive departures, but there's still lows piling into AK, and there's still a high to our south.

Sometimes you're smart ... and other times you post the 384hr op GFS

[CoastalWx]

I'd be careful using an op run to figure out the pattern beyond 7 days. Just too much variability for an op run to handle. On the ensembles, it appears the parade of storms will be aimed more at the Aleutians instead of the southern coast of Ak and nw Canada.

[weathafella]

Pattern doesn't look really any different in real terms. It'll be cooler in terms of positive departures, but there's still lows piling into AK, and there's still a high to our south.

<img src="http://mag.ncep.noaa.gov/GemPakTier/MagGemPakImages/gfs/12/gfs_namer_336_1000_500_thick.gif" />

Parade of storms aiming right for AK....still with the jockstrap ridge off the west coast.

<img src="http://mag.ncep.noaa.gov/GemPakTier/MagGemPakImages/gfs/12/gfs_npac_384_1000_500_thick.gif" />

But 12/10 is the signal. Anything before that is noise. One thing is apparent, this weekend is the high water mark of the torch. Parade of AK storms is often the seed for us. The key is whether or not the pv is there vs split. AK isn't going to be fair and mild in too many Decembers.

[CoastalWx]

It's in La La Land, but for the heck of it.....the ensembles sort of show signs of a potential storm over the east near the 6th. There seems to be a big cold push south across the Plains with some sort of s/w moving through the Midwest. Both the EC and GFS hint at it. Even the euro op has been hinting at it. It looks like it could be a cutter, but perhaps after the low moves through...that's when the colder air comes in.

[Clinch Leatherwood]

Sometimes you're smart ... and other times you post the 384hr op GFS

below

I'd be careful using an op run to figure out the pattern beyond 7 days. Just too much variability for an op run to handle. On the ensembles, it appears the parade of storms will be aimed more at the Aleutians instead of the southern coast of Ak and nw Canada.

below

But 12/10 is the signal. Anything before that is noise. One thing is apparent, this weekend is the high water mark of the torch. Parade of AK storms is often the seed for us. The key is whether or not the pv is there vs split. AK isn't going to be fair and mild in too many Decembers.

I'm not using the OP GFS as anything but a rough guesstimate. Many of the models have signaled changes longer term only to mute some of those changes as we get in closer (remember we were certain cold air was coming late november for weeks). I think the OP is doing that again at 12z.

Two chances potentially 12/3 and 12/6 and then towards 12/10 it looks to me like the pattern is reloading. It won't be the same torch we've had now, but it's still going to be above seasonal as it looks right now to me. Doesn't mean it cannot snow.

[QVectorman]

Talking about the MJO, do the different phases of the MJO produce different patterns in the 500 mb level depending on if it's an mod/strong la nina vs. mod/strong el nino or are the anamolies for each phase fairly identical for la nina/el nino years?

[Logan11]

I'm not too impressed with the cold air supply in Canada - source region musn't be good....homegrown stuff. Take this GFS run with the vodka stuff spilling over the pole and it would be yielding cold temps.

Also the mean ridge position to our south is particularly bad for us at this early point in the season with the simmering Atlantic Ocean yet. It's never great to have that ridge there per se, but in January/February maybe we are far enough north to still be cold while the MA and SE is mild and cash in along that boundary.

It's in La La Land, but for the heck of it.....the ensembles sort of show signs of a potential storm over the east near the 6th. There seems to be a big cold push south across the Plains with some sort of s/w moving through the Midwest. Both the EC and GFS hint at it. Even the euro op has been hinting at it. It looks like it could be a cutter, but perhaps after the low moves through...that's when the colder air comes in.

[OKpowdah]

below

below

I'm not using the OP GFS as anything but a rough guesstimate. Many of the models have signaled changes longer term only to mute some of those changes as we get in closer (remember we were certain cold air was coming late november for weeks). I think the OP is doing that again at 12z.

Two chances potentially 12/3 and 12/6 and then towards 12/10 it looks to me like the pattern is reloading. It won't be the same torch we've had now, but it's still going to be above seasonal as it looks right now to me. Doesn't mean it cannot snow.

Use the ensemble mean if you want to make any sort of argument.

I think that we nailed late November from weeks out. I don't know what you're remembering, but it was always going to be transient cold followed by the torch. If anything, the warmth we anticipated will be a little less. We even got a decent sized snowstorm

[Clinch Leatherwood]

below

below

I'm not using the OP GFS as anything but a rough guesstimate. Many of the models have signaled changes longer term only to mute some of those changes as we get in closer (remember we were certain cold air was coming late november for weeks). I think the OP is doing that again at 12z.

Two chances potentially 12/3 and 12/6 and then towards 12/10 it looks to me like the pattern is reloading. It won't be the same torch we've had now, but it's still going to be above seasonal as it looks right now to me. Doesn't mean it cannot snow.

Obviously last nights Euro was totally different. It begins to nip the parade of storms out in the PAC and by about day 5 looks much different. That said if I had to make a prediction 12/10 to 12/25 at or above normal temps in Boston/PVD.

[weathafella]

Ensembles are totally in opposition of the op run long term. Around 12/10 there is very cold air (498 thickness) pushing down into Hudson Bay and racing SE. Gradient pattern signal with SNE solidly on the colder side. We'll see.

[Clinch Leatherwood]

Use the ensemble mean if you want to make any sort of argument.

I think that we nailed late November from weeks out. I don't know what you're remembering, but it was always going to be transient cold followed by the torch. If anything, the warmth we anticipated will be a little less. We even got a decent sized snowstorm

And transient cold is the only thing on the horizon right now which is the point I'm making, ensemble or no. There are those that think bumble the snowmonster comes in on the 545 train early December. I just don't see it happening.

When I see guys like Mitch V and others now curtailing cold/snow predictions for December I take notice. I suspect by 12/1 we see a sleu of "adjustments"

Doesn't mean it cannot snow. We had plenty of brtual cold 2 winters ago and all it did was shun storms south.

Even seasonal will bring snow as we get into the right climo later in December and January down here.

[CoastalWx]

I'm not too impressed with the cold air supply in Canada - source region musn't be good....homegrown stuff. Take this GFS run with the vodka stuff spilling over the pole and it would be yielding cold temps.

Also the mean ridge position to our south is particularly bad for us at this early point in the season with the simmering Atlantic Ocean yet. It's never great to have that ridge there per se, but in January/February maybe we are far enough north to still be cold while the MA and SE is mild and cash in along that boundary.

I don't think it looks bad for early December. The models show eastern and southern Canada becoming below normal. The amount of Pacific taint is becoming less and less on the models. Now maybe it goes back the other way or the se ridge is strong, but Canada looks ok to me, at least through the 1st week.

[weathafella]

Ensemble mean d15 has ridging up into AK with Cahirs ridge sending cross polar over the pole. I'm sure it will be much colder here about 10 days beyond that point....around 12/21.

[CoastalWx]

Talking about the MJO, do the different phases of the MJO produce different patterns in the 500 mb level depending on if it's an mod/strong la nina vs. mod/strong el nino or are the anamolies for each phase fairly identical for la nina/el nino years?

I know Allan did some research regarding some of the phases and the MEI state.

http://raleighwx.ame...wx.com/MJO.html

I'm sure if the ENSO state was weak or strong, it may effect the regions where the MJO wave is likely to hang out. wxwatcher91 might be able to explain more.

[OKpowdah]

Definitely a little rough right now, but this will change

[Clinch Leatherwood]

Ensemble mean d15 has ridging up into AK with Cahirs ridge sending cross polar over the pole. I'm sure it will be much colder here about 10 days beyond that point....around 12/21.

Ensembles look better than the OP for sure. The question becomes....and still is today, where is the pattern going after 12/10. We still don't have the answer. To me we look to be setting up a track for storms to head west which may be good for nothern areas, not so much here with a high to our south....but it's forever away.

[QVectorman]

I know Allan did some research regarding some of the phases and the MEI state.

http://raleighwx.ame...wx.com/MJO.html

I'm sure if the ENSO state was weak or strong, it may effect the regions where the MJO wave is likely to hang out. wxwatcher91 might be able to explain more.

Thanks! I was looking around on Allan's earlier but didn't see any classification by MEI except one section that stated the MEI<.5 for the month. Hopefully wxwatcher can chime in.

[Ginx snewx]

Ensemble mean d15 has ridging up into AK with Cahirs ridge sending cross polar over the pole. I'm sure it will be much colder here about 10 days beyond that point....around 12/21.

[/pattern]

[weathafella]

Ensembles look better than the OP for sure. The question becomes....and still is today, where is the pattern going after 12/10. We still don't have the answer. To me we look to be setting up a track for storms to head west which may be good for nothern areas, not so much here with a high to our south....but it's forever away.

The key in the pattern depicted is to have an even stronger high to the north so cold air can press.

[OKpowdah]

And transient cold is the only thing on the horizon right now which is the point I'm making, ensemble or no. There are those that think bumble the snowmonster comes in on the 545 train early December. I just don't see it happening.

When I see guys like Mitch V and others now curtailing cold/snow predictions for December I take notice. I suspect by 12/1 we see a sleu of "adjustments"

Doesn't mean it cannot snow. We had plenty of brtual cold 2 winters ago and all it did was shun storms south.

Even seasonal will bring snow as we get into the right climo later in December and January down here.

Nobody ever called for December to be an I95 month. Never was going to be.

We agree on the first round of below normal temperatures and possible snow threats.

Beyond that, ridging in the east Pacific is projected to retrograde toward the Aleutians. Depending on if that ridge can amplify, we would achieve the more permanent pattern change everyone is looking for, in which we have more Nina-esque ridging across the North Pacific and lowered heights dropping down into western Canada. At the same time, the troughs impacting the east will break cyclonically over the North Atlantic, pumping up ridging over western Europe. This trough-ridge couplet continues to deform and retrograde ... we end up with the +NAO lowered heights backing into eastern Canada and New England. This is an excellent set up for snow here ... a la 2007 like Will was saying.

[Clinch Leatherwood]

The key in the pattern depicted is to have an even stronger high to the north so cold air can press.

I think a key will also be to get the eastern PAC high further east. I don't like where it's sitting now, little too far west in this model which to me would favor a track too far west to help the CP. Again at rough glance 12/10+

There is going to be 2 or maybe what'll end up being one significant shot of cold storminess in that 12/3 to 12/8 period. We need to make one of those work.

[OKpowdah]

I think a key will also be to get the eastern PAC high further east. I don't like where it's sitting now, little too far west in this model which to me would favor a track too far west to help the CP. Again at rough glance 12/10+

There is going to be 2 or maybe what'll end up being one significant shot of cold storminess in that 12/3 to 12/8 period. We need to make one of those work.

Disagree. We need the east Pacific high further NORTH. Right now, that high acts as ONE thing for us: a ridge for RWD to place a trough in the east. We need it to do one MORE thing: block the Pacific flow. This it is not quite accomplishing, and is the reason why it is able to be flattened and pulled back west

[Clinch Leatherwood]

Disagree. We need the east Pacific high further NORTH. Right now, that high acts as ONE thing for us: a ridge for RWD to place a trough in the east. We need it to do one MORE thing: block the Pacific flow. This it is not quite accomplishing, and is the reason why it is able to be flattened and pulled back west

http://raleighwx.americanwx.com/models/gfsensemble/12zgfsensemble850mbTSLPNA384.gif

If both highs shifted north all we'd have is a storm track running into the Lakes. We need the EPAC high both east and north. That's JMHO but moving it north sure will cool things and cut some of the inflow of warmer air but it won't do much to help set the trough.

It's way beyond worth talking about at this range. But aside of those few days in the 12/3 to 12/8 range so far we're still a little off.

Going outside to enjoy the 65 degree torch.

[CoastalWx]

Disagree. We need the east Pacific high further NORTH. Right now, that high acts as ONE thing for us: a ridge for RWD to place a trough in the east. We need it to do one MORE thing: block the Pacific flow. This it is not quite accomplishing, and is the reason why it is able to be flattened and pulled back west

I think Scott is thinking more of a +PNA pattern, but I don't see that happening in the classic +PNA form that we all know. Instead, we'll need the amplitude way up there into AK, like you said.

[CoastalWx]

http://raleighwx.ame...mbTSLPNA384.gif

If both highs shifted north all we'd have is a storm track running into the Lakes. We need the EPAC high both east and north. That's JMHO but moving it north sure will cool things and cut some of the inflow of warmer air but it won't do much to help set the trough.

It's way beyond worth talking about at this range. But aside of those few days in the 12/3 to 12/8 range so far we're still a little off.

Going outside to enjoy the 65 degree torch.

Well wait a sec, Sam is referring to H5 anomalies....not necessarily surface high pressure. When we say ridging in AK, we are thinking the mid levels at 500mb.

[ctsnowstorm628]

Man, some are so bitter about the upcoming pattern...its a shot of some decent cold air and possible winter threats. Take it for what its worth. We haven't had any shots recently and this should be greatly welcomed to say the least.

Meanwhile, 61/40

[Clinch Leatherwood]

Well wait a sec, Sam is referring to H5 anomalies....not necessarily surface high pressure. When we say ridging in AK, we are thinking the mid levels at 500mb.

Oh I know, I'm paiting with a broad brush because we're talking about 300+ hours on the GFS. I'd like to see that classic west coast high east coast trough that allows a major storm to develop but that's probably not in the cards at least yet.

[CoastalWx]

Euro says if you're walking in Memphis, you may be walking with flakes flying onto Beale.