December Medium/Long Range Discussion

[JakkelWx]

7 minutes ago, psuhoffman said:

But if we just want snow...a good old fashioned warning event snowstorm, a -AO and a PNA or EPO ridge are the way to go

Good thing a moderate to strong -AO like the one we have right now usually correlates to a -NAO. But sometimes even with a -NAO and 50/50, it can still fail if the block is too far north and the 50/50 low moved out too fast like this storm we just had.

Or am I wrong about the -AO/-NAO correlation?

[psuhoffman]

49 minutes ago, JakkelWx said:

Good thing a moderate to strong -AO like the one we have right now usually correlates to a -NAO. But sometimes even with a -NAO and 50/50, it can still fail if the block is too far north and the 50/50 low moved out too fast like this storm we just had.

Or am I wrong about the -AO/-NAO correlation?

There is some overlap of the domains so usually yes. This pattern we had was good enough imo.  This is kind of a perspective thing. CAPE isn’t wrong that had the block been centered further south it could have shifted the confluence south and limited the ridging and warm surge ahead of the low. But then if the system hasn’t dug so far west it also could have suppressed the whole thing!  Had we got a better mid level pass and close we would have been ok. Plus we are still suffering the effects of the November continent wide torch in that the cold was shallow. Not true arctic air. So no it wasn’t the best most perfect pattern ever but we’ve had tons of snow in worse looking patterns. I would be happy this this look keeps repeating. Especially mid winter we can do just fine with the block centered in the AO domain with some ridging extending into Greenland.  But December isn’t forgiving around here. Like I said yesterday it’s easier to snow before Xmas with a progressive wave that doesn’t pull in the warmth from the Atlantic. Amplified coastals are a really tough sell this early. 

[CAPE]

1 hour ago, psuhoffman said:

Yes this. Wes did an amazing correlation chart and DC snow correlates to the AO more then any other single factor. Adding to this...if you want a HECS then you need a -NAO. Only one of our region wide 18”+ storms in the last 50 years didn’t have a killer block and that one PD2 featured a perfectly timed Arctic high. We got kinda lucky. But that still changed to a LOT of sleet...so had timing been any less perfect...you get it. But oddly the really big ones that feature a great block also usually feature what under a non blocking regime would be a bad pacific. I talked about this some in the snow climo thread. Our HECS look is a weird combo that doesn’t work under normal circumstances. That kind of block would often suppress an event...but a trough near AK that amplified the ridge/trough downstream or a trough crashing the west that tries to ridge in the east actually helps get something to force its way up into what is likely locked in cold and a high pressure due to the confluence. It’s a weird combo that leads to those crazy anomaly storms. But if we just want snow...a good old fashioned warning event snowstorm, a -AO and a PNA or EPO ridge are the way to go. 

The primary reason a -AO is number one when it comes to DC snow is it means the PV isn't a super wound up ball of doom, with all the cold locked up in the high latitudes. When there is a real deal -AO it reverses the "natural order", and allows anomalous cold to move into the midlatitudes with relative ease. As you said, we still want some NA blocking as it greatly increases chances for a favorable storm track underneath, and it is pretty much a requirement for an HECS as it inhibits a coastal storm from flying up the coast. Ofc 2009-2010 was the classic example of  a negative AO/NAO working the magic.

[Buddy1987]

Do I really want to invest in Sun/Mon? There was a lot of exertion from last storm. Guess that’s why we all enjoy being on here. 

[BristowWx]

2 minutes ago, Buddy1987 said:

Do I really want to invest in Sun/Mon? There was a lot of exertion from last storm. Guess that’s why we all enjoy being on here. 

I would t...I see bad things happening.  Very bad things. 

[JakkelWx]

23 minutes ago, BristowWx said:

I would t...I see bad things happening.  Very bad things. 

We do bad very goodly here.

[JakkelWx]

[cbmclean]

33 minutes ago, JakkelWx said:

I am unsure how to interpret this chart.  Can you help?

[JakkelWx]

3 minutes ago, cbmclean said:

I am unsure how to interpret this chart.  Can you help?

It looks like the SPV is going to soon downwell into the tpv. 

Its game time.

[cbmclean]

Just now, JakkelWx said:

It looks like the SPV is going to soon downwell into the tpv.

I understand what the SPV and TPV are and that they are usually distinct entities.  What happens when the SPV downwells into the TPV?

[psuhoffman]

1 minute ago, cbmclean said:

I understand what the SPV and TPV are and that they are usually distinct entities.  What happens when the SPV downwells into the TPV?

The bottom line is there are indications the PV might be a weakling this winter. That is opposite what we’ve had recently. 

[cbmclean]

2 minutes ago, psuhoffman said:

The bottom line is there are indications the PV might be a weakling this winter. That is opposite what we’ve had recently. 

Last year especially the strength of the PV was truly sickening to behold.  Perhaps the most demoralizing part was the fact that modeling picked it up so early and it advanced forward in time so remorselessly.  I am still scarred by your infamous post from December 30th of last year highlighting the historical results from past analogs to the pattern then forecast, absent extensive NA help. 

[North Balti Zen]

44 minutes ago, cbmclean said:

What happens when the SPV downwells into the TPV?

Dr. Peter Venkman: This forum is headed for a disaster of biblical proportions.
Moderator: What do you mean, "biblical"?
Dr. Raymond Stantz: What he means is Old Testament, Mr. Moderator, real wrath-of-God type stuff. Cold you can see and icebergs coming down from the sky! Rivers and the Chesapeake freezing solid!
Dr. Egon Spengler: Forty years of darkness! Ji saying it is too much snow, EJ calling "uncle"...
Winston Zeddmore: The dead rising from the grave! The panic room abandoned!
Dr. Peter Venkman: Human sacrifice, Phineas and Amped no longer trolling  - MASS HYSTERIA!

[psuhoffman]

27 minutes ago, cbmclean said:

Last year especially the strength of the PV was truly sickening to behold.  Perhaps the most demoralizing part was the fact that modeling picked it up so early and it advanced forward in time so remorselessly.  I am still scarred by your infamous post from December 30th of last year highlighting the historical results from past analogs to the pattern then forecast, absent extensive NA help. 

By mid December I knew we were in trouble...and by Xmas I knew we were completely screwed and likely headed for a total dud winter.  We were looking at a combination of the worst possible pacific pattern and NAM state possible...and judging by the onset of those two patterns combined with the typical duration of both when they present at that level of anomaly...history said both were likely to continue through the majority of our snow climo.  The history of such years with that pacific and high latitude look was really ugly. 

Right now everything up top looks more favorable.  The pacific is more murky.  The Euro weeklies resume the central pac ridge look week 3 and keep it locked in straight through...there is a -AO most of the time but mostly ruined by the awful pac.  However...the models were doing that by Xmas not long ago and then backed off.  It seems they "think" we should be going to that out in time...but like it past years when they thought things would get better, keep pushing that look out.  What has ended up the reality is a mediocre but not completely hostile pacific.  If that continues and the AO remains negative we should have a decent winter.  So far things look better then I expected.  

[Snowchaser]

Hmmm this looks very interesting for early next week. 

[Maestrobjwa]

9 minutes ago, psuhoffman said:

By mid December I knew we were in trouble...and by Xmas I knew we were completely screwed and likely headed for a total dud winter.  We were looking at a combination of the worst possible pacific pattern and NAM state possible...and judging by the onset of those two patterns combined with the typical duration of both when they present at that level of anomaly...history said both were likely to continue through the majority of our snow climo.  The history of such years with that pacific and high latitude look was really ugly. 

Right now everything up top looks more favorable.  The pacific is more murky.  The Euro weeklies resume the central pac ridge look week 3 and keep it locked in straight through...there is a -AO most of the time but mostly ruined by the awful pac.  However...the models were doing that by Xmas not long ago and then backed off.  It seems they "think" we should be going to that out in time...but like it past years when they thought things would get better, keep pushing that look out.  What has ended up the reality is a mediocre but not completely hostile pacific.  If that continues and the AO remains negative we should have a decent winter.  So far things look better then I expected.  

Now when was the last time we actually had a great pac? Lol

[cbmclean]

12 minutes ago, North Balti Zen said:

Dr. Peter Venkman: This forum is headed for a disaster of biblical proportions.
Moderator: What do you mean, "biblical"?
Dr. Raymond Stantz: What he means is Old Testament, Mr. Moderator, real wrath-of-God type stuff. Cold you can see and icebergs coming down from the sky! Rivers and the Chesapeake freezing solid!
Dr. Egon Spengler: Forty years of darkness! Ji saying it is too much snow, EJ calling "uncle"...
Winston Zeddmore: The dead rising from the grave! The panic room abandoned!
Dr. Peter Venkman: Human sacrifice, Phineas and Amped no longer trolling  - MASS HYSTERIA!

So would the TPV be the Gatekeeper and the SPV the Keymaster?

[psuhoffman]

1 minute ago, Maestrobjwa said:

Now when was the last time we actually had a great pac? Lol

2014 and 2015 we had a lot of pac help... we have had some periods since then but nothing sustained for long stretches like that.  

[Maestrobjwa]

1 minute ago, psuhoffman said:

2014 and 2015 we had a lot of pac help... we have had some periods since then but nothing sustained for long stretches like that.  

And for 2009-10...was an awesome pac a part of that perfect setup?

[psuhoffman]

2 minutes ago, Maestrobjwa said:

And for 2009-10...was an awesome pac a part of that perfect setup?

The pac was good for the Dec storm...we really need EVERYTHING to be perfect to get a big snow in December...it was actually only EHH for the Feb snow blitz but the Atlantic blocking was perfect.  

[Ji]

Ggem with another Noreaster Monday and we get rain

[psuhoffman]

GFS really isn't far from something Monday...its got a kicker right on its tail...need that to either back off or dig more and amplify the trough.

[North Balti Zen]

12 minutes ago, cbmclean said:

So would the TPV be the Gatekeeper and the SPV the Keymaster?

That is absolutely correct. 

[Snowchaser]

Just now, Ji said:

Ggem with another Noreaster Monday and we get rain

Things can still change 

[Ji]

GFS really isn't far from something Monday...its got a kicker right on its tail...need that to either back off or dig more and amplify the trough.

Ggem does it but no cold again

[psuhoffman]

4 minutes ago, Ji said:

Ggem with another Noreaster Monday and we get rain

somewhat similar problem to yesterday...only even less cold in front and the storm doesn't develop and close off a circulation until past our latitude.  But its close and guidance is just coming around to this idea...curious to see what happens in future runs.  Still time for thermals to adjust some but it won't be an easy win.  

[psuhoffman]

2 minutes ago, Ji said:

4 minutes ago, psuhoffman said:

GFS really isn't far from something Monday...its got a kicker right on its tail...need that to either back off or dig more and amplify the trough.

Ggem does it but no cold again

Can we keep this pattern rolling into January when this would really pay off?  The worst kind of gut punch would be to largely waste this now then have it break down and resume a typical nina look when our best snow climo starts.  

[clskinsfan]

8 minutes ago, psuhoffman said:

GFS really isn't far from something Monday...its got a kicker right on its tail...need that to either back off or dig more and amplify the trough.

The Kicker has a legit chance to work out. Temps are fine. Will it be juicy enough?

There is a little clipper to watch after that as well. 

[Ji]

Can we keep this pattern rolling into January when this would really pay off?  The worst kind of gut punch would be to largely waste this now then have it break down and resume a typical nina look when our best snow climo starts.  

That's what I'm afraid of. We have seen 3 winter storms so far and DC is 0-3

[Ji]

Can we keep this pattern rolling into January when this would really pay off?  The worst kind of gut punch would be to largely waste this now then have it break down and resume a typical nina look when our best snow climo starts.  

We still have not seen any arctic air yet