October 2017 PNW Discussion Thread

[Jesse]

Some cooler ensemble members showing up between the 29th and 31st.

 

[Jesse]

Noticed on the way in to downtown the Willamette is noticeably higher than last week.

Even the Columbia is noticeably higher. We were crossing the Glenn Jackson yesterday and I noticed that a lot of the sand bars that were visible on the south side of Government Island the last few months are now submerged.

[Phil]

You wonder if this ridge is just going to be persistent through the winter?

It won't last. This ridge is an intraseasonal response to tropical forcing associated with the MJO and diabatic heat release over the NPAC, and their combined influence on the NH wave train.

 

Eventually the background state will re-assert itself, and there will be a discontinuous retrogression next month, into a -EPO style circulation with cold air returning to the west given sufficient NATL wavebreaking as a predecessor boundary condition.

 

...Until the next MJO/strat-attack, rinse, repeat.

[Front Ranger]

Looks like the greatest cold this month has been focused in the Great Basin, with some places in NV still running more than -8 below normal.

 

[Front Ranger]

It won't last. This ridge is an intraseasonal response to tropical forcing associated with the MJO and diabatic heat release over the NPAC, and their combined influence on the NH wave train.

 

Eventually the background state will re-assert itself, and there will be a discontinuous retrogression next month, into a -EPO style circulation with cold air returning to the west given sufficient NATL wavebreaking as a predecessor boundary condition.

 

...Until the next MJO/strat-attack, rinse, repeat.

 

-EPO/-NAO already imminent. With this round favoring cold in the Midwest/East.

 

[Phil]

-EPO/-NAO already imminent.

 

4indices.png

Shot across the bow? I think an even bigger -EPO (and also more of a -PNA) is possible during the middle of November, with more SE Ridge as well.

 

With a strong enough -EPO, I don't think a -NAO is necessary for the PNW to score. With a +EPO, usually -NAO/-PNA cells are both required, at least since 1950. In -QBO especially, its tougher to sustain -EPO.

 

I can't find any Arctic blasts in the PNW without a -NAO that didn't also feature a big Alaskan Ridge/-EPO, at least over the last 50yrs.

[Front Ranger]

Shot across the bow? I think an even bigger -EPO (and also more of a -PNA) is possible during the middle of November, with more SE Ridge as well.

 

With a strong enough -EPO, I don't think a -NAO is necessary for the PNW to score. With a +EPO, usually -NAO/-PNA cells are both required, at least since 1950.

 

I can't find any Arctic blasts in the PNW without a -NAO that didn't also feature a big Alaskan Ridge/-EPO.

 

Yeah, a big-time -EPO ridge will allow pretty much anyone in the CONUS to score, regardless of NAO. 

 

But as you've pointed out before, a -NAO can definitely help sustain a "blocked" pattern.

[jakeinthevalley]

And only a handful south of PDX metro. SFA and myself. There's others but they escape me at the moment. Anybody from south valley like Corvallis or Eugene here?

Live in West Salem, work in McMinnville.

 

2.6" of rain since Saturday morning

[Front Ranger]

Big time shift west with everything in the 7-10 day range on the 12z Euro. Teasing clipper-lovers again?

[TigerWoodsLibido]

Big time shift west with everything in the 7-10 day range on the 12z Euro. Teasing clipper-lovers again?

 

EC getting my hopes up? Boy I hope it holds. 1-2 more runs trending that way and I think we will see that pattern regularly assert itself trending westward as we keep moving through the fall.

[TigerWoodsLibido]

 

Hopefully will be the first of many pass-bys of that lovely big Canadian H

[ShawniganLake]

Fall colours seem pretty good around here, better than most years, IMO. Lots of bright yellows and orange on the maples. Cottonwoods are showing a lot of yellow. As for timing, seems about normal to me, a lot of the maples will be down by Halloween.

[wx_statman]

Yeah, a big-time -EPO ridge will allow pretty much anyone in the CONUS to score, regardless of NAO. 

 

But as you've pointed out before, a -NAO can definitely help sustain a "blocked" pattern.

 

From the looks of things, that's exactly what happened in Jan 1963. The monster -NAO block helped anchor the offshore ridge to our west, which persisted from January 5th until Feb. 1st. Every major Arctic outbreak that month over the conus resulted from the same stalled long-wave pattern. The historic cold waves in the West (10th-12th) and Southeast (24th-25th), the shot in between on the 18th-19th, and the outflow snowstorm around the 29th-30th in Portland were all the result of the same long-wave pattern. 

[ShawniganLake]

I don't expect anymore meaningful rainfall this month.

 

Currently at 8.90", average here for the month total is 6.20" so it will end up above average for the month. 2016 and 2012 were wetter in October here.

Sitting at 5.05” here, much drier than last October, when we measured 12.5”.

[TT-SEA]

Big time shift west with everything in the 7-10 day range on the 12z Euro. Teasing clipper-lovers again?

 

No rain... but marine layer locks in beginning Sunday in the 12Z ECMWF.

[Kayla]

Big time shift west with everything in the 7-10 day range on the 12z Euro. Teasing clipper-lovers again?

 

Most likely yes. 12z EPS does show some retrogression but doesn't dig nearly as much as the operational in the long term. 

[Phil]

From the looks of things, that's exactly what happened in Jan 1963. The monster -NAO block helped anchor the offshore ridge to our west, which persisted from January 5th until Feb. 1st. Every major Arctic outbreak that month over the conus resulted from the same stalled long-wave pattern. The historic cold waves in the West (10th-12th) and Southeast (24th-25th), the shot in between on the 18th-19th, and the outflow snowstorm around the 29th-30th in Portland were all the result of the same long-wave pattern.

That epic 1968/69 Niño winter also featured that strong west based -NAO, which locked a trough into SW Canada and kept the NPAC ridge offshore, instead of over western North America.

[BLI snowman]

Fall colours seem pretty good around here, better than most years, IMO. Lots of bright yellows and orange on the maples. Cottonwoods are showing a lot of yellow. As for timing, seems about normal to me, a lot of the maples will be down by Halloween.

 

Yeah, been really nice this past week in the Portland region.

[wx_statman]

That epic 1968/69 Niño winter also featured that strong west based -NAO, which locked a trough into SW Canada and kept the NPAC ridge offshore, instead of over western North America.

 

That 1968-69 was a strange beast. The most heavily Modoki-skewed Nino in a 1950-2011 reanalysis period that I've seen. Nino3 barely toed the line around +0.6C while Nino4 was in mod-strong territory at around +1.6-1.7C. 

[BLI snowman]

From the looks of things, that's exactly what happened in Jan 1963. The monster -NAO block helped anchor the offshore ridge to our west, which persisted from January 5th until Feb. 1st. Every major Arctic outbreak that month over the conus resulted from the same stalled long-wave pattern. The historic cold waves in the West (10th-12th) and Southeast (24th-25th), the shot in between on the 18th-19th, and the outflow snowstorm around the 29th-30th in Portland were all the result of the same long-wave pattern. 

 

Which transitioned into major West Coast ridging in February while the East stayed cold. The same delicate balance displayed in 2013-14 even though that was a +NAO winter.

[Phil]

Which transitioned into major West Coast ridging in February while the East stayed cold. The same delicate balance displayed in 2013-14 even though that was a +NAO winter.

Well, I think the climatological differences in the wavetrain during February tend to complicate things. A -NAO in January actually plays very differently on the NPAC than a -NAO in February, except during volcanic years.

[BLI snowman]

Well, I think the climatological differences in the wavetrain during February tend to complicate things. A -NAO in January actually plays very differently on the NPAC than a -NAO in February, except during volcanic years.

 

Depends on ENSO as well of course. February 1956 was actually deeply -NAO but was a torch in the East. The PNW and Western Europe were frigid though.

[SilverFallsAndrew]

Sitting at 5.05” here, much drier than last October, when we measured 12.5”.

 

17.02" here last October.

[Front Ranger]

Depends on ENSO as well of course. February 1956 was actually deeply -NAO but was a torch in the East. The PNW and Western Europe were frigid though.

The NAO controls ENSO, PNA, EPO, PDO, SOI, and volcanic eruptions.

 

#masterindex

[TT-SEA]

The NAO controls ENSO, PNA, EPO, PDO, SOI, and volcanic eruptions.

 

#masterindex

 

Mt. Agung is still on high alert but seismic activity has gone down dramatically in the last few days.

[TT-SEA]

64 at SEA... 65 here.

 

Beutiful day.

[Front Ranger]

Mt. Agung is still on high alert but seismic activity has gone down dramatically in the last few days.

 

We were warned that may not happen.

[Phil]

Depends on ENSO as well of course. February 1956 was actually deeply -NAO but was a torch in the East. The PNW and Western Europe were frigid though.

Definitely. A -NAO during Niña winters tends to benefit the western/central US more than the eastern US. The -EPO is much more influential East of the Mississippi River in terms of the temperature departure during La Niña.

 

Seems the opposite is true for El Niño.

[Phil]

The NAO controls ENSO, PNA, EPO, PDO, SOI, and volcanic eruptions.

 

#masterindex

Kidding aside, what the NAO says about the system state is probably more important than any immediate effects it might have.

[TT-SEA]

Finally some snow here... its taking forever this year!  

 

18Z GFS:

[stuffradio]

18Z continues the theme of whenever lower pressure begins to reach the NE pacific, it just dies and goes towards Alaska while high pressure takes over the NE pacific instead.

[TT-SEA]

Still have nice fall color after the wind and the rain...

 

[Geos]

It's been a really nice day. Was at the coast this weekend and it rained hard all day Saturday and into Sunday morning. Some big breakers to be seen as well.

Was 45 this morning and made it to 64 this afternoon. Few more clouds now. 

[SilverFallsAndrew]

18z ensembles aren't bad. 

[weatherfan2012]

Definitely. A -NAO during Niña winters tends to benefit the western/central US more than the eastern US. The -EPO is much more influential East of the Mississippi River in terms of the temperature departure during La Niña.

Seems the opposite is true for El Niño.

yeah it's a shame this difference isn't giving more consideration in both the weenies and Mets world as it seems to many sees the nao as the all in for the eastern us when in fact it's anything but the case.but I think just like with climate the real problem is to many think in terms of simplelisem when in fact it's way more complex then most will give it credit for.

[stuffradio]

18Z GEM screws everything up by bringing low pressure to the NE pacific.

 

Edit: But the 12Z CMC ensembles doesn't have this. We'll have to see the 00Z CMC ensembles.

[snow_wizard]

18Z continues the theme of whenever lower pressure begins to reach the NE pacific, it just dies and goes towards Alaska while high pressure takes over the NE pacific instead.

 

I love it!

[snow_wizard]

The fall colors are really popping here now.  The broadleaf maples are quite vivid compared to normal and some cottonwoods look like they could turn really good this year.  Some of the non native trees are absolutely on fire.

[Guest happ]

The fall colors are really popping here now.  The broadleaf maples are quite vivid compared to normal and some cottonwoods look like they could turn really good this year.  Some of the non native trees are absolutely on fire.

 

Tim has been posting great photos of fall color.

[TT-SEA]

Tim has been posting great photos of fall color.

 

One more from this afternoon...