12/20-12/21 Moderate/Intense Clipper Event?

[baroclinic_instability]

Next significant weather threat looks to come the beginning of next week as a large Pacific cyclone/occlusion breaks down over the West Coast and ejects an intense and energetic low amplitude shortwave into the plains and OV.

Here is the Pacific cyclone in question, as forecast by the 12/16/10 0Z GFS @ 81 hours:

The ejecting shortwave into the plains at 108:

This system has a lot of potential and the GFS is progging a 160+ knot upper tropospheric jet streak with this system.

A couple noteworthy items.

First, models will likely flip-flop quite a bit with this system as the "break-down" of a cyclone into an energetic baroclinic wave is often not well modeled by numerical guidance and the timing and strength of the eventual wave will likely change quite a bit run to run for the next 3-4 days. Also, the current 0Z GFS does show a potential partial phase with the Canadian retrograding cyclone with a direct connection to some relatively cold arctic air. GFS develops this "clipper" into a full fledged cyclone as it passes into the OV as deeper cyclogenesis develops. Current CMC isn't quite as impressive and doesn't phase the two systems and suggests the system remains a "clipper"/weak low amplitude upper level wave into the OV.

0Z ECMWF is not so impressive and sends a much weaker and low amplitude wave that eventually phases with the east coast cyclone. 12/18Z GFS ensembles have a myriad of solutions ranging from a large plains cyclone to weak clippers. We shall see...

[Thundersnow12]

Was just looking at this on the 0z GFS....lets see how well your snow thread luck is

[baroclinic_instability]

Was just looking at this on the 0z GFS....lets see how well your snow thread luck is

Haha, I didn't even think about that. Yeah hopefully my storm thread luck starts well.

[cyclone77]

The GEM has been featuring this system off and on for the last two or three days. Last night's run was relatively impressive with this system. The 12z and new 00z not so much. The flip-flopping nature of the handling of this system is to be expected at this range I guess. For example, last night's op GFS barely showed this feature. Tonight it's considerably more dynamic with it.

With such a powerful mid-level jet punching in, it looks like Baroclinic has a good shot at a successful thread evolution.

[Thundersnow12]

pretty interesting loop of the H5 vort on the 0z GFS

[Moneyman]

Euro says what storm?

It shears the system out as it approaches the MW. The system in the NE sheared it out.

[baroclinic_instability]

Euro says what storm?

It shears the system out as it approaches the MW. The system in the NE sheared it out.

ECM sends a much lower ampitude wave through more inline with NOGAPS. It is there though, just a lot harder to see in its 24 hr panels.

I did edit the title though lol. We will see. Models stink big with the break down of these cyclones.

[trapperman]

LOL. If this were to pan out, Roger Smith comes out smelling like a rose... after all the crap he's taken...

link

[BowMeHunter]

I give this system about the same 5% chance as Baroclinic gives SNE for their upcoming event.

[baroclinic_instability]

I give this system about the same 5% chance as Baroclinic gives SNE for their upcoming event.

I think 5% may be a tad too low.

I think there is a relatively high probability (greater than 60%) that a low amplitude wave passes through the plains and into the OV. The amplitude is a big if. 10-20% this develops into a well developed lower/mid tropospheric cyclone with a better probability of a clipper/low amplitude weaker wave. Snow threats for someone are decent though...although they may not be signficant hits.

[baroclinic_instability]

LOL. If this were to pan out, Roger Smith comes out smelling like a rose... after all the crap he's taken...

link

Weird. I saw something in there about a "December Full Moon". Stopped reading there.

[msp]

mpx bumping pops

BY EARLY NEXT WEEK...THE LATEST EC/GFS HAS A SLIGHT BUCKLE IN THE

FAST WEST TO EAST FLOW ACROSS THE UPPER MIDWEST TO ALLOW FOR LT

SNOW TO DEVELOP LATE SUNDAY AND MONDAY. CURRENT TRENDS AND

ENSEMBLE FORECAST INDICATE THAT MEASURABLE SNOWFALL IS AGAIN

POSSIBLE EARLY NEXT WEEK...BUT TIMING AND THE AMOUNT OF MOISTURE

REMAINS IN QUESTION. HOWEVER...I DID INCREASE PERCENTAGES DUE TO A

TREND TOWARD STRONGER LIFT DURING THE MONDAY TIME FRAME

[BowMeHunter]

I think 5% may be a tad too low.

I think there is a relatively high probability (greater than 60%) that a low amplitude wave passes through the plains and into the OV. The amplitude is a big if. 10-20% this develops into a well developed lower/mid tropospheric cyclone with a better probability of a clipper/low amplitude weaker wave. Snow threats for someone are decent though...although they may not be signficant hits.

5% percent was for what the gfs has been smoking and showing.. I would agree with 60%+ of a low amp wave.. I have no interest in low amp 1-2" anyways. I want this Pattern to blow up and I don't care if we have to torch to do it. This reminds of last winter all to much and I hate it.

[baroclinic_instability]

mpx bumping pops

BY EARLY NEXT WEEK...THE LATEST EC/GFS HAS A SLIGHT BUCKLE IN THE

FAST WEST TO EAST FLOW ACROSS THE UPPER MIDWEST TO ALLOW FOR LT

SNOW TO DEVELOP LATE SUNDAY AND MONDAY. CURRENT TRENDS AND

ENSEMBLE FORECAST INDICATE THAT MEASURABLE SNOWFALL IS AGAIN

POSSIBLE EARLY NEXT WEEK...BUT TIMING AND THE AMOUNT OF MOISTURE

REMAINS IN QUESTION. HOWEVER...I DID INCREASE PERCENTAGES DUE TO A

TREND TOWARD STRONGER LIFT DURING THE MONDAY TIME FRAME

0Z GEFS has more members showing potential...better than the 12-18Z. I have a feeling not much consensus will develop for another 24 hours on the potential amplitude and another 48-72+ on track/placement.

[KokomoWX]

I have not look beyond reading the snow totals but 3 to7 inches has been thrown about by the GFS while the Euro has been much more stingy.

[A-L-E-K]

Weird. I saw something in there about a "December Full Moon". Stopped reading there.

smart man.

The good news, I'll spend most my time tracking this system on Sat/Sun, just way too much work to catch up on right now. The bad news, baroclinic paints a picture of potential sweetness but with high variability, but then again when is there ever certainty 5 days out. OT but was Baroclinic an eastern poster that moved to the MW or what?

[jhamps10]

another close call for sure, ILX mentions a bit on it in the morning AFD:

LONG TERM...FRIDAY THROUGH MONDAY...FORECAST INCREASING IN CONFIDENCE A BIT AS MODELS START TO AGREETHAT THE FLOW TRANSITIONS TO MORE NWRLY AGAIN AND OPENS UP THEMIDWEST TO MORE ARCTIC INFLUENCE AND COLD TEMPS. HAVE GONE ON THECOLDER SIDE OF GUIDANCE. INCREASINGLY NWRLY FLOW INCREASES THECHANCE FOR SMALL WAVES AND MONDAY/MONDAY NIGHT WILL BE NODIFFERENT. GOING TO PUT THE CHANCE POPS IN NOW FOR DEVELOPINGSTORM THAT IS LOOKING SIMILAR WITH AN INTERACTION WITH A WAVEMAKING IT OVER THE UPPER RIDGE TO THE WEST...AND A DEVELOPING LOWFROM THE CENTRAL PLAINS.

[Harry]

5% percent was for what the gfs has been smoking and showing.. I would agree with 60%+ of a low amp wave.. I have no interest in low amp 1-2" anyways. I want this Pattern to blow up and I don't care if we have to torch to do it. This reminds of last winter all to much and I hate it.

I am 100% with you on this. I believe it will. For a time anyways.

0Z GEFS has more members showing potential...better than the 12-18Z. I have a feeling not much consensus will develop for another 24 hours on the potential amplitude and another 48-72+ on track/placement.

I agree with this strongly. Part of the problem as always seems to be the case is how the models handle the potential eastcoast storm. Need to get this current system out of the way and the Pacific one onshore.

Hopefully the eastcoast system slides right on out to sea and not up/hugging the coast.

[csnavywx]

GEFS individual members all agree that a fairly significant wave will exist, but disagree on strength, and as a result, there's a good temporal spread of about 36 hours.

This pattern is extremely convoluted at high latitudes, with the previously progged closed low to the north now forecast to propagate directly westward for a few days under the block instead of dropping south and recirculating. The timing of this closed low in tandem with the main wave coming onshore on the West Coast is critical in determining what, if any, interaction or phasing will occur. The GFS, being one of the kings of overphasing in the longer range, has now backed away from that solution, so it seems likely that these two storms should not interact in a significant way. This does leave some room for the storm to grow as it heads east (as opposed to being exposed to a crushing confluence zone like the current one). Overall, this is a BIG change from earlier, though with the block over northern Canada, one can be assured that the jet and baroclinic zone will be forced south of its normal position and cold air for many of us won't be a big problem.... for now.

From there... we had better hope that the N. Canada block stays put and holds a bit longer or the Bering ridge breaks and rolls over to the east, otherwise that monster GoA/EPAC trought spells trouble for here (in the form of a torch or very dry N-NW flow aloft).

[jhamps10]

Looking at the GFS it looks like a good hit for most north of I-70, and not too bad of one even down here.

[Harry]

GFS shows the problem well and thus the eastcoast potential. Need to lose that and have it go out to sea.

My goodness i would sell my soul to get rid of this damn block once and for all or shift it further east and for the rest of the damn winter. The -NAO west can blow me.

[buckeye]

ggem now shows a 978 low off cape cod...

if that's the case our lil storm ain't got a chance in hell

[baroclinic_instability]

GGEM shows the difficulty models have in breaking down these large cyclones. It is the same issue but opposite of low amplitude phasing. Models suck with it. GGEM breaks the cyclone down into two weaker baroclinic waves instead of one distinct shortwave like the GFS.

[buckeye]

ggem now shows a 978 low off cape cod...

if that's the case our lil storm ain't got a chance in hell

good lord...boston CRUSHED

i'm jealous

[buckeye]

GGEM shows the difficulty models have in breaking down these large cyclones. It is the same issue but opposite of low amplitude phasing. Models suck with it. GGEM breaks the cyclone down into two weaker baroclinic waves instead of one distinct shortwave like the GFS.

baro, would you agree regardless that it's all moot for us if that coastal materializes in front of it and pumps the n.e. vortex

[baroclinic_instability]

baro, would you agree regardless that it's all moot for us if that coastal materializes in front of it and pumps the n.e. vortex

Good question. The solutions are still all over the map. Models have gone from a southern stream shortwave over the SE states ejecting over the Gulf Stream to a really late hook near New England. The latest GFS op run has a very tight cyclone over SNE off the coast and remains somewhat progressive with the overall vortex. CMC, besides already being less favorable with the breakdown into two waves, shows a larger vortex that partially retrogrades E over the Lakes. That solution would be partially reminiscent of this this current storm for some. As Cs said, a partial phase would be good with the retrograding Hudson Bay upper low over Canada, and the GFS still has a favorable interaction with that system in terms of low level cold air. GFS, in other words, right now is pretty much the most ideal solution. Probability wise it is still looking low (less than 20-25%) that the GFS operational solution verifies since it is best case with every scenario right now.

[baroclinic_instability]

baro, would you agree regardless that it's all moot for us if that coastal materializes in front of it and pumps the n.e. vortex

I will add, from experience with the CMC and looking at it close operationally, the CMC has some weird tendencies in terms of wake breakdown and it struggles more than other operational models. It does seem, far enough out, at times to send "diffuse" energetic waves over the intermountain W and "disintegrate" the energy into almost nothing and/or send a ton of weak waves through the flow. Honestly those solutions don't verify well unless the baroclinic zone over the region in question is very weak and/or non-existent. For now I am not finding the CMC solution into two weak waves very valid at this point in time.

[Harry]

For those in Se WI, S.MI, N.IN, N.OH etc..

We CANT have that block/system ANYWHERE inside the red box for this storm to work out for us. Outside of the red box in the green would be great/much better.

And the way to avoid the red box is to have the eastcoast system go right on out to sea and not swing up into New England. If there is a god in this universe it will go out to sea.lol

If baroclinic wants to elaborate further feel free to do so. I am just giving the dirty/quick and easy to understand version of what needs to happen.

[snowstormcanuck]

For those in Se WI, S.MI, N.IN, N.OH etc..

We CANT have that block/system ANYWHERE inside the red box for this storm to work out for us. Outside of the red box in the green would be great/much better.

And the way to avoid the red box is to have the eastcoast system go right on out to sea and not swing up into New England. If there is a god in this universe it will go out to sea.lol

If baroclinic wants to elaborate further feel free to do so. I am just giving the dirty/quick and easy to understand version of what needs to happen.

Agree 100% Harry. The problem is we've seemingly had that vortex over the W. Atlantic for a couple of weeks now, and as s/ws rotate around it and amplify, they re-inforce it. Pattern changes usually happen slowly so I'm not too optimistic that gyre is going to scoot out into the middle of the Atlantic in time for early next week.

I'm not giving up on this one, but I'm realistic, especially as far N & E as I am. The period between Christmas and New Year's is piquing my interest a bit though.

[The_Global_Warmer]

Looks like a good hit for the guys around I-80...no way this gets down here.

more cold to warm then cold again with nothing.