September 2023 Weather in the PNW

[Cascadia_Wx]

14 minutes ago, SilverFallsAndrew said:

I'm calling for an average to slightly above average month temp wise. Precip near to slightly below normal.

Seemz reasonable.

[TT-SEA]

12Z EPS going with a western ridge and eastern trough scenario starting in a week like its 00Z run showed.

[Chewbacca Defense]

Very nice fall morning, got down to 52, and very foggy out in the county.  Sky is clear, but the horizon looks a little smoky.

 

Sounds like they are getting the Lake Whatcom Fire under control.  It got up to 45 acres, and the the crews are making a lot of headway despite very steep, rugged terrain.  They have a helicopter up there now mainly just dumping on hot spots.  They still have the level 2 evacuation in place for the homes close by, but hopefully they can take that down in the next couple of days.  They are warning people to stay clear of the water just below the fire, they still have boulders and trees falling down the hill and into the water.

[RentonHill]

I know its common knowledge but feels crazy that we havent had a below average summer since 2012. 

[Rubus Leucodermis]

1 minute ago, RentonHill said:

I know its common knowledge but feels crazy that we havent had a below average summer since 2012. 

[TT-SEA]

12Z EPS really likes the idea of warmth building out west.

[MossMan]

5 minutes ago, TT-SEA said:

12Z EPS really likes the idea of warmth building out west.

Going to be snowing in 11 short weeks! 

[TT-SEA]

Just now, MossMan said:

Going to be snowing in 11 short weeks! 

Yes... and Phil will remind us soon that the ridging coming up with only last for a few minutes like all ridging around here.   

[Phil]

16 minutes ago, RentonHill said:

I know it’s common knowledge but feels crazy that we havent had a below average summer since 2012. 

The PNW region’s dust bowl decade.

Good news is the step change in 2013 was driven by a change in circulation (internal variability) related to the IPWP structure. As was the 1930s dust bowl. So, at some point this interdecadal state will change/revert back, maybe sooner than we think. Or maybe later. Who knows.

We’ve had at least 2 false alarms in recent years, so keep your expectations in check, but I think this backwards-evolving El Niño (inception via costero to EPAC-canonical mode) could mark the end of the post-2013 base state. It’s the best chance we’ve had so far.

Time will tell, but the LP emergence is external to the WPAC for the first time in over a decade. And upon termination of the niño there will likely be a residual EPAC/WHEM rising cell but this time without the dateline convection. Which would not only be pre-2013, but pre-1998 in W2 structure.

[Phil]

The bugs are screaming outside, sounds like something out of the rapture. As if nature knows the heat is coming back.

[Phil]

13 minutes ago, TT-SEA said:

12Z EPS really likes the idea of warmth building out west.

5+ days without an EPS map from you. First sign of red paint you’re all over it.  

If/when this disappears, you’ll disappear with it.

[RentonHill]

13 minutes ago, Phil said:

The PNW region’s dust bowl decade.

Good news is the step change in 2013 was driven by a change in circulation (internal variability) related to the IPWP structure. As was the 1930s dust bowl. So, at some point this interdecadal state will change/revert back, maybe sooner than we think. Or maybe later. Who knows.

We’ve had at least 2 false alarms in recent years, so keep your expectations in check, but I think this backwards-evolving El Niño (inception via costero to EPAC-canonical mode) could mark the end of the post-2013 base state. It’s the best chance we’ve had so far.

Time will tell, but the LP emergence is external to the WPAC for the first time in over a decade. And upon termination of the niño there will likely be a residual EPAC/WHEM rising cell but this time without the dateline convection. Which would not only be pre-2013, but pre-1998 in W2 structure.

Basically its all solar cycle???

[RentonHill]

7 minutes ago, Phil said:

5+ days without an EPS map from you. First sign of red paint you’re all over it.  

If/when this disappears, you’ll disappear with it.

When does our raging jet start again? right after this coming ridging episode?? I could have sworn someone said beginning of September but I'm not going to go back and look

[RentonHill]

SSW?

[T-Town]

Back in T Town. Was raining hard on the top of Santium Pass when we went over about 9 am. One of the few times I’ve left gray skies on the east side for sun on the west. 

[Anti Marine Layer]

Welcome to meteorological fall. Hope everyone enjoyed the rain yesterday.  

[TT-SEA]

51 minutes ago, Phil said:

5+ days without an EPS map from you. First sign of red paint you’re all over it.  

If/when this disappears, you’ll disappear with it.

Exactly! 

And you are literally the exact opposite.   You only post cold maps for out here and completely ignore any trends away from troughing.   We balance each other and together provide full information.     

[Phil]

45 minutes ago, RentonHill said:

Basically its all solar cycle???

I wouldn’t say that. There are a myriad of push/pull factors within the system as it attempts to equilibrate to both external forcing(s) and internal structural instability. Hence the resonant and state dependent nature of its behaviors.

You have GHG/solar radiative forcings which can be considered “external” in terms of emergence, then you have quasi-chaotic, inertially-resonant tendencies in heat/mass exchanges that are integral to the system and how it responds to said external forcings, and modulate the degree to which said external forcings are expressed.

[Front Ranger]

2 hours ago, SilverFallsAndrew said:

I'm calling for an average to slightly above average month temp wise. Precip near to slightly below normal.

Recent September history favors this.

[MossMan]

1 hour ago, Phil said:

The bugs are screaming outside, sounds like something out of the rapture. As if nature knows the heat is coming back.

I hear some wind blowing through the trees and some birds. 

[ShawniganLake]

51 minutes ago, RentonHill said:

When does our raging jet start again? right after this coming ridging episode?? I could have sworn someone said beginning of September but I'm not going to go back and look

Probably around the time our global cooling kicks in.  Was supposed to be in 2017/2018. Still waiting  

[TigerWoodsLibido]

Phil and Tim playing a forum debate ballgame before College Football starts tonight!

[Phil]

10 minutes ago, Phil said:

I wouldn’t say that. There are a myriad of push/pull factors within the system as it attempts to equilibrate to both external forcing(s) and internal structural instability. Hence the resonant and state dependent nature of its behaviors.

You have GHG/solar radiative forcings which can be considered “external” in terms of emergence, then you have quasi-chaotic, inertially-resonant tendencies in heat/mass exchanges that are integral to the system and how it responds to said external forcings, and modulate the degree to which said external forcings are expressed.

But these internal variables (IE: albedo and heat fluxes modulated by variability in large scale circulation/convection) import significant structural changes to radiative budget, exceeding that of both GHG and solar/aerosol forcing(s) combined. At least on intra/interdecadal timescales.

And because this is inherently unpredictable, it poses the greatest threat to humanity. All “abrupt” climate change scenarios (both GHG/anthropogenic and natural) rely on this internal augmentation/amplification.

The paleo data makes clear the degree to which said internal instability/red noise may be expressed, often with global consequences. Thankfully, as of now, we have not encountered high amplitude internal variability since the end of the Holocene thermal maximum.

But given the growing anthropogenic/GHG forcing(s) on/within the system since the end of WWII, I question how long this will hold true. Doesn’t necessarily mean rapid warming/cooling, but a significant reorganization of the global circulation patterns and seasonality is well within the realm of possibility (and is inevitable at some point as obliquity continues to decline and the Holocene interglacial destabilizes, though hopefully that’s at least a few thousand years away).

[Phil]

7 minutes ago, TigerWoodsLibido said:

Phil and Tim playing a forum debate ballgame before College Football starts tonight!

I’m probably in much better shape than Tim.  

[TT-SEA]

3 minutes ago, Phil said:

I’m probably in much better shape than Tim.  

No doubt... just based on age alone.   

[Phil]

21 minutes ago, ShawniganLake said:

Probably around the time our global cooling kicks in.  Was supposed to be in 2017/2018. Still waiting  

Looking more closely, the EPS seems too slow in propagating the MJO/CCKW east of the dateline, starting around 9/10. Either that or there’ll be more bifurcation between the CCKW and LP. We’ll see if this changes as we get closer, but that’s my opinion as of now.

Jet extension would begin when anomalous subsidence transits the IPWP, which (should be?) sooner than currently advertised by the EPS. Sometime in mid-September, I think?

[Christensen87]

D**n, 18z pretty much says bye bye to the rain altogether on Sunday. 

[Phil]

1 hour ago, RentonHill said:

When does our raging jet start again? right after this coming ridging episode?? I could have sworn someone said beginning of September but I'm not going to go back and look

Did you mean to say troughing episode? The only ridging I see on guidance is ~ 10 days away.

I think that GOA trough will build in mid-September, even if not advertised right now. We’ll see, I could be wrong.

[Phil]

The stratospheric polar vortex has formed! Net cyclonic anomaly as of 8/27.

The descent into winter 2023/24 has begun.  

[the_convergence_zone]

Back after a week, wasn’t it supposed to rain while I was gone??? It’s warm and smoky and bone dry. Still looks like summer to me. 

[seattleweatherguy]

Rain for Labor Day weekend? Some forecasts show some, others show none

[TT-SEA]

9 minutes ago, the_convergence_zone said:

Back after a week, wasn’t it supposed to rain while I was gone??? It’s warm and smoky and bone dry. Still looks like summer to me. 

AQI is in the 30s... its not really smoky.   And its only in the mid 70s so its not that warm.  Its actually a gorgeous day.   

And we did have a regionwide rain event!  

[TT-SEA]

3 minutes ago, seattleweatherguy said:

Rain for Labor Day weekend? Some forecasts show some, others show none

Very little rain... but Sunday and Monday should be quite cloudy with persistent marine layer both days.    Could be marine layer drizzle in the morning hours too.  

[TT-SEA]

A bit of an over-performance at SEA today.   ECMWF showed 73 but its 77 on the hour.    ECMWF shows 82 tomorrow so maybe mid 80s particularly on the east side... perfect lake day.

[TT-SEA]

GFS was more accurate for today... and don't think we are done with summer-like weather.    Also sure the 95 is wrong.   

 

[Tyler Mode]

1 hour ago, Phil said:

The stratospheric polar vortex has formed! Net cyclonic anomaly as of 8/27.

The descent into winter 2023/24 has begun.  

What is the typical date?

[ShawniganLake]

48 minutes ago, TT-SEA said:

AQI is in the 30s... its not really smoky.   And its only in the mid 70s so its not that warm.  Its actually a gorgeous day.   

And we did have a regionwide rain event!  

83 here today.  Pretty nice day. 

[Phil]

https://x.com/climatologist49/status/1697714105627603452?s=46&t=656Z973wLtGKaIyhhq_7QQ

[Phil]

25 minutes ago, Tyler Mode said:

What is the typical date?

8/26 average but always happens in late Aug/early Sept (since it’s solely driven by insolation).

[TT-SEA]

78/60 on the day at SEA.   That is summer perfection in fall.