December 2019 Weather Discussion for the PNW

[Timmy Supercell]

The WRF is showing a good hard frost Christmas night and the next night.  It's going to be a nippy week.  I'm glad we got the heavy rain out of the way when we did.

 

My rain event has not even started yet, at least not on this side of the cascades. I hope I can squeeze out at least a half inch from this.

[snow_wizard]

The EPS is heading somewhere very good.  The run isn't done, but just after day 10 the mean and control both look very promising.  The cold in AK is shown to be ridiculous.  We have a lot to work with.

[Phil]

The 2D presentation offered by the model sites leaves much to be desired IMO, since phenomena like a wound up PV/TPV has an important vertical structure and it is not captured at all by just looking at one pressure level like 500mb.

 

The polar vortex is really nothing more than a large, tall, photochemically-modulated tornado. It draws in and maintains within it a load of frigid, O^3-depleted air. That airmass will *not* leave the vortex unless it’s perturbed thermo-mechanically.

 

Note the stability of the TPV (north of Alaska) from the 500mb perspective on the 12z Euro. This is a different feature than your typical polar low or winter trough..it’s a stacked, vertically-coupled chemical tornado that has the coldest air walled off within it.

 

 

This is a machine. It contains the lowest (relative) pressures despite the “dense” frigid air thanks to these vigorous dynamic processes sustaining it. Will this machine, all by itself, release the airmass within and/or wander southward without being bombarded by wave activity fluxes? Of course not. The stability speaks for itself.

 

Any model solutions (in the absence of sufficient wave driving/amplification or well-timed resonance) which indicate this deep, stacked feature plowing southwards or behaving erratically are likely incorrect. A “flatter” offshore ridge is absolutely 100% NOT going to drive that airmass into the PNW.

[Gradient Keeper]

The EPS is heading somewhere very good.  The run isn't done, but just after day 10 the mean and control both look very promising.  The cold in AK is shown to be ridiculous.  We have a lot to work with.

As far as the source origin for the cold air mass it doesn't get any better than this. Well, a very few rare times in the past.

[snow_wizard]

Queue the Jaws music!

 

 

 

 

[snow_wizard]

As far as the source origin for the cold air mass it doesn't get any better than this. Well, a very few rare times in the past.

 

This is at 1989 levels.  They also had wicked cold in 1947 which also got down to us.

[Frontal Snowsquall]

The 2D presentation offered by the model sites leaves much to be desired IMO, since phenomena like a wound up PV/TPV has an important vertical structure and it is not captured at all by just looking at one pressure level like 500mb.

 

The polar vortex is really nothing more than a large, tall, photochemically-modulated tornado. It draws in and maintains within it a load of frigid, O^3-depleted air. That airmass will *not* leave the vortex unless it’s perturbed thermo-mechanically.

 

Note the stability of the TPV (north of Alaska) from the 500mb perspective on the 12z Euro. This is a different feature than your typical polar low or winter trough..it’s a stacked, vertically-coupled chemical tornado that has the coldest air walled off within it.

 

 

This is a machine. It contains the lowest (relative) pressures despite the “dense” frigid air thanks to these vigorous dynamic processes sustaining it. Will this machine, all by itself, release the airmass within and/or wander southward without being bombarded by wave activity fluxes? Of course not. The stability speaks for itself.

 

Any model solutions, in the absence of sufficient wave driving/amplification, that indicate this deep, stacked feature plowing southwards are likely incorrect. A “flatter” offshore ridge is absolutely 100% NOT going to drive that airmass into the PNW.

I liked this post until I saw your last sentence.

[MossMan]

Queue the Jaws music!

She’s a beaut!!!

[Phil]

I don’t want to be a debbie downer, and I still think the odds are high for a cold January when that TPV departs the Beaufort Sea/Alaska.

 

But to those thinking the Alaska TPV *itself* is going to deliver the goods (especially with building dateline convection and +AAM in the subtropics) I’d keep expectations in check. Anything can happen I guess, but that would be extremely difficult to pull off. A vortex/low tends to draw in/bottle up cold. A blocking high often does the opposite.

[Guest CulverJosh]

I liked this post until I saw your last sentence.

And it will evolve and not stay as your animation suggests. You are acting like Tim.

[MossMan]

I liked this post until I saw your last sentence.

Phil says no. Looks like we should all go back to being in a bad mood.

[snow_wizard]

The EPS is clearly better than the 0z which was clearly better than yesterday's 12z.  The control gives us a shot of impressive martime polar air and is poised to drive the main cold in here at the end of the run.  I would sure like to see the EPS spaghetti.  There have to be some killer members.

[Front Ranger]

Phil has always misunderstood the flat offshore ridge pattern progression. SW was not saying that in itself would drive the cold air south, he clearly explained how it is often part of a pattern progression capable of that - when there is a big ridge merger upstream.

[snow_wizard]

I liked this post until I saw your last sentence.

 

He misunderstood my post.  I said a flatter ridge around New Years would lead to a better outcome for us a few days later because it allows a future high pressure cell to piggy back over it which causes an amplified offshore block.  Phil knows I'm not that dumb.

[snow_wizard]

Phil has always misunderstood the flat offshore ridge pattern progression. SW was not saying that in itself would drive the cold air south, he clearly explained how it is often part of a pattern progression capable of that - when there is a big ridge merger upstream.

 

Well said.  That flat ridge progression plays into many of our all time greats.  The upstream ridge literally sucks the juice out of the flat ridge and causes an explosive offshore block.

[snow_wizard]

I am 100% stoked now!

[ShawniganLake]

Well said. That flat ridge progression plays into many of our all time greats.

I agree with this. I think Phil’s view is that given the background state we would be better off with an amplified pattern and then look for retrogression of a -EPO. Phil? Am I close?

[snow_wizard]

While I don't have access to EPS spaghetti Weatherbell does show the spread on the PNA and EPO indices so that will give some clue as to how wild some of the EPS members might be.

[snow_wizard]

I agree with this. I think Phil’s view is that given the background state we would be better off with an amplified pattern and then look for retrogression of a -EPO pattern.

 

You are probably right.  That is another viable way we can score.  I have always found the flat ridge play to be a better outcome for us.  Usually colder and snowier.  That is doubly true with the extreme cold progged in AK.  If this plays out like Feb 1, 1989 we will be doing back flips!

[Frontal Snowsquall]

As far as the source origin for the cold air mass it doesn't get any better than this. Well, a very few rare times in the past.

Queue the Jaws music!

That's big league stuff!

[Phil]

Phil has always misunderstood the flat offshore ridge pattern progression. SW was not saying that in itself would drive the cold air south, he clearly explained how it is often part of a pattern progression capable of that - when there is a big ridge merger upstream.

You’re talking out of your butt.

 

This isn’t a Niña/+QBO/dateline subsidence state that can amplify a dirty Aleutian Ridge/RWD regime into a legitimate GOA block/-PNA and drive the vortex south. Even 1989 had a massive SSW to pull it off.

 

You’re assuming the pattern will progress a certain way based off parameters that don’t exist this year.

[snow_wizard]

Another thought I have is Phil might not be wild about the flat ridge scenario, because the East doesn't get nailed nearly as hard as they would with a more amplified Western or just off the coast ridge like earlier runs showed.

[ShawniganLake]

You are probably right. That is another viable way we can score. I have always found the flat ridge play to be a better outcome for us. Usually colder and snowier. That is doubly true with the extreme cold progged in AK. If this plays out like Feb 1, 1989 we will be doing back flips!

Yea. I agree the amplified retrogression route often times seems like we end up with backdoor cold. Drier outcomes.

[GHweatherChris]

Oh boy, here we go...

[MossMan]

Oh boy, here we go...

Phil says no.

[snow_wizard]

You’re talking out of your butt.

 

This isn’t a Niña/+QBO/dateline subsidence state that can amplify a dirty Aleutian Ridge/RWD regime into a legitimate GOA block/-PNA and drive the vortex south. Even 1989 had a massive SSW to pull it off.

 

You’re assuming the pattern will progress a certain way based off parameters that don’t exist this year.

 

We shall see.  I'm going by my gut on this.  The boxes have all been checked for a great outcome for us this winter.  Obviously it never a 100% thing.  Do you happen to know much about 1947?  That year had a similar situation to 1989 as far as cold in AK ending up here outcome.  That was Jan 1947.  Interestingly 1946 was one of the Octobers this one was similar to as well.

[snow_wizard]

Phil says no.

 

I think he was referring to the difference of opinion going on.

[Phil]

Another thought I have is Phil might not be wild about the flat ridge scenario, because the East doesn't get nailed nearly as hard as they would with a more amplified Western or just off the coast ridge like earlier runs showed.

Haha. I’ll actually be in Miami, so I don’t care either way.

 

But I don’t want to miss snow. So I guess if anything I’d prefer a torch when I’m gone.

[GHweatherChris]

I think he was referring to the difference of opinion going on.

Yep

[Winterdog]

Things are finally starting to look up! DJ and Jim are back, and Jake is feeling it as well!!

Currently 39 with a few peeks of the sun.

Whoops. I thought my platitudinous post would be taken more tongue in cheek. I see no reason whatsoever to be excited over today’s models.

[BLI snowman]

You are probably right.  That is another viable way we can score.  I have always found the flat ridge play to be a better outcome for us.  Usually colder and snowier.  That is doubly true with the extreme cold progged in AK.  If this plays out like Feb 1, 1989 we will be doing back flips!

 

We're not in a deep -ENSO state though, which is when we usually see that progression work out for us (1955-56, 1964-65, 1988-89).

[Phil]

I think he was referring to the difference of opinion going on.

To be clear, I didn’t say winter cancel. I just don’t think the Alaska vortex pattern will deliver the goods. At least not in this particular case.

 

And though models are insistent, I’m going to be stubborn and insist that the vortex will not stick around for too long and things will improve with time.

[MossMan]

Whoops. I thought my platitudinous post would be taken more tongue in cheek. I see no reason whatsoever to be excited over today’s models.

D**n...I was hoping that was the new and more optimistic Jake!

[Jesse]

d**n...I was hoping that was the new and more optimistic Jake!

Just start looking at the models yourself. It’s empowering.

[MossMan]

Just start looking at the models yourself. It’s empowering.

I don’t want to.

[Phil]

I agree with this. I think Phil’s view is that given the background state we would be better off with an amplified pattern and then look for retrogression of a -EPO. Phil? Am I close?

Yes. Or at least more amplified wave activity attacking the TPV in Alaska. A legitimate SSW could obviously do it singlehandedly. But *something* has to dislodge that airmass..it absolutely will not wander south on its own accord. There’s no low frequency predisposition towards an amplified Aleutian High with a +ENSO lean/E-IO subsidence as the dominant background state.

[Jesse]

[Front Ranger]

We're not in a deep -ENSO state though, which is when we usually see that progression work out for us (1955-56, 1964-65, 1988-89).

 

I believe it also played out that way in 1990 and 2008, though.

[Deweydog]

In all honesty, I hope people are taking today’s discoveries with a big grain of salt. There’s really nothing at the moment which shows much of any shift from what looks like a teleconnective disaster.

[Phil]

Phil says no. Looks like we should all go back to being in a bad mood.

I’m not saying no. The EPS is.

 

But I think the EPS might be wrong this time. Historically it has struggled with the maritime/WPAC gradient both during MJO transits and low pass changes. Just so happens that domain is central to the shifting low pass signal in J/F/M.