November 2017 PNW Discussion Thread

[Gradient Keeper]

Day 10

 

http://maps1.pivotalweather.com/maps/models/ecmwf/2017112900/240/500h_anom.na.png

[snow_wizard]

The euro is shitting on us

 

It's the same thing we've been expecting for a while now.

[snow_wizard]

You don't need (or want) to start with a flat/dirty ridge when it comes to discontinuous retrogression. In your climate, you need as much "amplification" as you can get, especially given the expanded EPAC Hadley Cell (for now).

 

The ridge will retrograde offshore eventually. It's going to require a significant amount of time, though. It probably won't happen until sometime around New Years.

 

It seems hard to believe it could go a solid month right over us though.  

[Phil]

I've been watching the cam off/on. Too cloudy to see anything really now

 

Yeah, they're in the rainy season there. Hard to see with the antecedent convection but it just threw up a giant mushroom cloud.

[Gradient Keeper]

6z GFS in 2 hours 24 minutes!

[snow_wizard]

Another thing I would like to point out is the only La Nina winters where we really do terrible is when there is little or no amplification.  If things remain amplified our turn will come.

[Phil]

It seems hard to believe it could go a solid month right over us though.

I don't know how long it's going to stay right over you, but I don't expect anything interesting out there until Christmas at the earliest, and the first week of January at the latest.

[Jesse]

PDX has been sitting at 44-46 for basically the last 27 hours.

[Phil]

Another thing I would like to point out is the only La Nina winters where we really do terrible is when there is little or no amplification. If things remain amplified our turn will come.

Yep. People are forgetting 1999/00, 2007/08, etc. All of which were disasters, considering their potential (on paper).

[TT-SEA]

I think the first freeze here will be on Monday night (12/4)... despite the east wind that the ECMWF surface map shows.

 

Ironically the first freeze here last year was also on 12/4... following a good snow event and with the ground covered in snow.  

 

This was sunset on 12/4/16...

 

 

[snow_wizard]

Yep. People are forgetting 1999/00, 2007/08, etc. All of which were disasters, considering their potential (on paper).

 

Also ones like 1975-76 and to a lesser extent 1973-74.

[snow_wizard]

PDX has been sitting at 44-46 for basically the last 27 hours.

 

It's been the same here except the range has been 42-44.

[Phil]

Also ones like 1975-76 and to a lesser extent 1973-74.

I thought it was 1974/75 and 1975/76 that were the crappy ones?

[SilverFallsAndrew]

38 here with some lingering light rain. Early Sunday morning I could see a few flakes here.

[TT-SEA]

It's been the same here except the range has been 42-44.

 

 

But its been dumping snow at Snoqualmie Pass since this morning and still going... hopefully getting close to opening.

 

[SilverFallsAndrew]

But its been dumping snow at Snoqualmie Pass since this morning and still going... hopefully getting close to opening.

 

 

If not the weekend trough will definitely do the trick.

[BLI snowman]

The East was way overdue for a cold December. December has been as horrific back there as January has been here for the most part.

[VancouverIslandSouth]

You don't need (or want) to start with a flat/dirty ridge when it comes to discontinuous retrogression. In your climate, you need as much "amplification" as you can get, especially given the expanded EPAC Hadley Cell (for now).

 

The ridge will retrograde offshore eventually. It's going to require a significant amount of time, though. It probably won't happen until sometime around New Years.

 

Our last decent Arctic blast in Feb 2011 start off very suppressed. 

 

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20170215.gif

 

The run up to the Nov 2010 blast was also pretty flat:

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20101112.gif

 

Same with the run-up to the Dec 2008 blast.

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20081209.gif

 

It may be possible but I haven't see any recent examples of major amplification over the PNW transitioning into a blast within a couple weeks of it happening. It's certainly possible it could retrograde offshore later in the month, but I'll be looking for something more like the above 3 images before I get excited.

[Phil]

The East was way overdue for a cold December. December has been as horrific back there as January has been here for the most part.

D**n straight. The last time I saw a snowflake in December was four years ago. I've seen more snow in April than I have in December over this timespan.

 

Not that it matters to me personally...I just count December as yet another "autumn" month now. March is more wintry than December nowadays.

[snow_wizard]

I thought it was 1974/75 and 1975/76 that were the crappy ones?

 

Dec 1974 had a big snowstorm in this area, but it was fairly lame other than that.

[snow_wizard]

Our last decent Arctic blast in Feb 2011 start off very suppressed. 

 

 

 

The run up to the Nov 2010 blast was also pretty flat:

 

 

Same with the run-up to the Dec 2008 blast.

 

 

It may be possible but I haven't see any recent examples of major amplification over the PNW transitioning into a blast within a couple weeks of it happening. It's certainly possible it could retrograde offshore later in the month, but I'll be looking for something more like the above 3 images before I get excited.

 

A flat ridge centered off the CA coast is a good setup.  On the other hand Jan 1985 had an extreme western ridge that later retrograded.  It's a viable option.

[Phil]

Our last decent Arctic blast in Feb 2011 start off very suppressed.

 

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20170215.gif

 

The run up to the Nov 2010 blast was also pretty flat:

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20101112.gif

 

Same with the run-up to the Dec 2008 blast.

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20081209.gif

 

It may be possible but I haven't see any recent examples of major amplification over the PNW transitioning into a blast within a couple weeks of it happening. It's certainly possible it could retrograde offshore later in the month, but I'll be looking for something more like the above 3 images before I get excited.

Uh, this is very incorrect. Here's the pattern observed back in January of 2011, which preceded the blast in February 2011.

 

Very similar to the upcoming pattern:

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/2531329F-538B-4656-9355-5466BFB1D681_zpsn4lbi26a.png

[Gradient Keeper]

Our last decent Arctic blast in Feb 2011 start off very suppressed. 

 

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20170215.gif

 

The run up to the Nov 2010 blast was also pretty flat:

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20101112.gif

 

Same with the run-up to the Dec 2008 blast.

 

http://www.wpc.ncep.noaa.gov/dailywxmap/htmlimages/dwm500_test_20081209.gif

 

It may be possible but I haven't see any recent examples of major amplification over the PNW transitioning into a blast within a couple weeks of it happening. It's certainly possible it could retrograde offshore later in the month, but I'll be looking for something more like the above 3 images before I get excited.

Late January 2014 huge block over us very similar to the upcoming pattern. It then retrograded sharply giving us an arctic blast early February.

[Phil]

Uh, this is very incorrect. Here's the pattern observed back in January of 2011, which preceded the blast in February 2011.

 

Very similar to the upcoming pattern:

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/2531329F-538B-4656-9355-5466BFB1D681_zpsn4lbi26a.png

Heck, even I'm surprised how amazing the match is.

 

I'd suggest avoiding the use of 500mb isobars to interpolate the nature of the wavetrain. You'll miss the forest through the trees unless you know exactly what to look for.

[Phil]

A flat ridge centered off the CA coast is a good setup. On the other hand Jan 1985 had an extreme western ridge that later retrograded. It's a viable option.

A flat ridge is a terrible setup in a Niña/-QBO winter. That gets you another 2007/08.

[Phil]

The d11-15 EPS shows the western US ridge coupled all the way into the stratosphere, supplementing the wave-1 wavebreak that shoves the PV into Siberia and begins tearing it apart.

[Brian_in_Leavenworth]

Sometimes before an arctic blast, it seems the ridge will temporarily flatten and a allow a system in, then it will re-amplify and retrograde.

[Phil]

Man, the CFS really is a piece of s**t.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/824DD794-EF21-4989-B48B-89844F465CD9_zpsumyuhswr.jpg

[SilverFallsAndrew]

LOL

[Gradient Keeper]

Man, the CFS really is a piece of s**t.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/824DD794-EF21-4989-B48B-89844F465CD9_zpsumyuhswr.jpg

 

C F S

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[Gradient Keeper]

6z GFS in 1 hour!

[Phil]

The long period cooling of global SSTs/surface temperatures has continued over the last year. We've lost almost 0.2C since last November (2016).

 

[BLI snowman]

Heck, even I'm surprised how amazing the match is.

 

I'd suggest avoiding the use of 500mb isobars to interpolate the nature of the wavetrain. You'll miss the forest through the trees unless you know exactly what to look for.

 

Would be nice to just have the timing of everything in 2010-11 moved up a month. 

[snow_wizard]

A flat ridge is a terrible setup in a Niña/-QBO winter. That gets you another 2007/08.

 

I meant a flat ridge right off the CA coast that ends up retrograding and amplifying in the sweet spot.  That scenario brings a fair number of our cold waves.

[Phil]

Would be nice to just have the timing of everything in 2010-11 moved up a month.

So far, that's what looks to be happening.

[Phil]

I meant a flat ridge right off the CA coast that ends up retrograding and amplifying in the sweet spot. That scenario brings a fair number of our cold waves.

That doesn't happen in -QBO/Niña winters. You need the ridge amplified during the discontinuous retrogression, otherwise you're left with a +EPO hose job.

 

Different story in +QBO/Niña.

[snow_wizard]

Would be nice to just have the timing of everything in 2010-11 moved up a month. 

 

I was sort of thinking of the Jan 1985 ridge happening in December and then the good Feb pattern happening in Jan.  It remains to be seen if this block will rival Jan 1985 or not.

[snow_wizard]

The ECMWF control model shows one retrogression step happening late in week two.

[snow_wizard]

The d11-15 EPS shows the western US ridge coupled all the way into the stratosphere, supplementing the wave-1 wavebreak that shoves the PV into Siberia and begins tearing it apart.

 

What little PV there is.

[Phil]

What little PV there is.

There's a healthy PV in the stratosphere. Dismantling it would go a long way to further destabilizing the global tropics and maintaining a blocked NPAC/-PNA/-EPO in January, when the large scale forcings become much more favorable for western troughing.