August 2016 Observations and Model Discussion for the Pacific Northwest

[Front Ranger]

I don't think anyone forecasted that.

 

The consensus was for a generally warm/ridgy spring (overall) and a cool/troughy summer (overall), with a particular emphasis on J/A/S in regards to the latter.

 

This has verified for the most part, localized/microscale anomalies aside. The mean 500mb height anomalies and full-column temperatures will reflect a trough in the PNW for J/A/S.

 

More and more riding on September...

[Front Ranger]

For PDX based on 1981-2010 normals, September is warmer with an average high of 75.8. For June it's 73.5. Our biggest swing is the Sep to Oct period, followed by the Oct to Nov period. There is a big pattern change here that occurs. Autumn comes fast here in the PNW and you can feel it. In about 2 months our normal highs here will be in the low 60s.

 

Cooler lows in September, though. Much shorter days, too - less summery.

 

And for the Puget Sound region, where Tim lives, September temps average almost the exact same as June.

[Phil]

More and more riding on September...

Isn't October supposed to determine the fate of everything?

[TT-SEA]

Yeah but just barely. 53.6 for June and 53.1 for September. What's interesting is that the mean maximum for PDX in June is 91.3 and in September it's 90.6 even though September averages +2.3 degrees warmer overall. So one would think June has a better chance for the hottest temperatures but that's not the case. September has reached 105 here and in June it's only 102.

 

 

Seasonal lag?

[James Jones]

Cooler lows in September, though. Much shorter days, too - less summery.

 

And for the Puget Sound region, where Tim lives, September temps average almost the exact same as June.

September is usually sunnier, though, so it feels more "summery" in that way, but yeah, the lower sun angle is very noticeable. As far as averages:

 

BLI: 66.6/50.3 in June, 66.9/47.6 in Sep

 

SEA: 69.9/51.9 in June, 70.5/52.1 in Sep

 

OLM: 70.6/47.6 in June, 71.8/46.0 in Sep

 

PDX: 73.5/53.6 in June, 75.8/53.1 in Sep

 

SLE: 73.9/49.3 in June, 76.8/48.4 in Sep

 

EUG: 73.2/47.6 in June, 76.9/47.0 in Sep

 

 

So the farther south you go, the warmer September is in comparison to June. I'd say September is clearly a bit more "summery" in the Willamette Valley than June, while it's about the same for the Puget Sound (with an advantage to June when you get up to Bellingham). September also has less precip days than June at all stations other than Bellingham.

[Deweydog]

Interesting air mass change already in progress with dew points into the low 30's in Eugene.

[Jesse]

Interesting air mass change already in progress with dew points into the low 30's in Eugene.

Yeah, this is a pretty fascinating setup overall.

 

They are -4 compared to yesterday also. May break the 90+ run.

[Jesse]

We'll be camping near Mount Adams again Thursday and Friday night. This is a big group trip with friends we've planned all year. Expecting the winds to get pretty crazy at points. Wonder if the Gifford Pinchot will be putting out a campfire ban.

[Front Ranger]

Isn't October supposed to determine the fate of everything?

 

October is the single most important month for providing clues for the following winter. All others pale in comparison.

[Jesse]

Gotta say, today is absolutely stellar.

[Front Ranger]

Yeah but just barely. 53.6 for June and 53.1 for September. What's interesting is that the mean maximum for PDX in June is 91.3 and in September it's 90.6 even though September averages +2.3 degrees warmer overall. So one would think June has a better chance for the hottest temperatures but that's not the case. September has reached 105 here and in June it's only 102.

 

Like I said, it's a bit different when you get further north.

 

And there's no doubt in my mind June is capable of September's warm extremes...the 102 record at PDX is one of their weaker monthly max's. And Sep 1988 was easily the top end of what can historically occur in September. No other historical event in September has really come close (1944 was the closest). If that extreme of a pattern occurred in late June, I think it would produce very similar temps.

[Deweydog]

Gotta say, today is absolutely stellar.

Kinda hazy.

 

F--

[Jesse]

Kinda hazy.

 

F--

No haze here.

 

Breezy and the sky is very blue.

[Jesse]

Like I said, it's a bit different when you get further north.

 

And there's no doubt in my mind June is capable of September's warm extremes...the 102 record at PDX is one of their weaker monthly max's. And Sep 1988 was easily the top end of what can historically occur in September. No other historical event in September has really come close (1944 was the closest). If that extreme of a pattern occurred in late June, I think it would produce very similar temps.

Thing is, airmasses as warm as September 1988 are generally harder to come by in June. As well as deep offshore flow driven by surface high pressure in the basin.

[Deweydog]

Thing is, airmasses as warm as September 1988 are generally harder to come by in June. As well as deep offshore flow driven by surface high pressure in the basin.

 

Yeah, it seems 20c+ is generally a little easier to come by in September, as is offshore flow.  Onshore flow in general tends to be weaker as the typical summertime thermal gradients begin to wane.  The biggest equalizer in September is the fact subsidence inversions become a real factor and without offshore flow a considerable amount of energy is spent breaking them despite the warmer air masses overall.

[Deweydog]

Meteorologist Mark Nelsen updated his forecast. He's going 7 degrees warmer now on Friday. He went with Friday being the coolest day to it now being the hottest day.

 

http://lmgcorporate.com/kptv/weather/ibs_web_7-day.jpg

 

Friday turned into a real wild card.  Went from looking to be the hottest day to looking to struggle to get much above 90 with an incredibly well-mixed air mass.  Now it's back to looking like the peak of the event with again the possibility of a perfect storm.  

[GobBluth]

Friday turned into a real wild card.  Went from looking to be the hottest day to looking to struggle to get much above 90 with an incredibly well-mixed air mass.  Now it's back to looking like the peak of the event with again the possibility of a perfect storm.  

NWS is still forecasting Friday as having the strongest winds, but we get to 103. The well mixed air mass is hot top to bottom.

 

Nights around 60 should feel like a pleasant reprieve.

[Front Ranger]

Thing is, airmasses as warm as September 1988 are generally harder to come by in June. As well as deep offshore flow driven by surface high pressure in the basin.

They're very hard to come by in September. Which is why 1988 blows away any other event after Aug 17 in the airport era.

 

That event was as extreme and rare as they come. Look at it this way: PDX has hit 100 twice in September: 1988 and 1944. They've hit 100 six times in June.

[Deweydog]

NWS is still forecasting Friday as having the strongest winds, but we get to 103. The well mixed air mass is hot top to bottom.

 

Nights around 60 should feel like a pleasant reprieve.

A set up like this can bring about a gap wind as well, basically a hot version of a backdoor cold snap. The models edged away from that scenario but a very well mixed air mass from start to finish on Friday would take a little edge off the highs in the metro area.

[Deweydog]

Looks like the new cold phase told Eugene's streak to go **** itself.

[Trainwreck]

Looks like the new cold phase told Eugene's streak to go **** itself.

Eugene just hit 90.

[Deweydog]

Eugene just hit 90.

On some hippie's Prius car thermometer?

[snow_wizard]

Love the roller coaster coming up.  I don't mind extreme quick hitting heatwaves that crash and burn as fast as they arrived.   The WRF shows it going from 90s in the lowlands around Seattle on Saturday to freezing nighttime temps in the North Cascades by Monday morning!

 

Meanwhile very pleasant here with a temp of 79.

[Trainwreck]

 

On some hippie's Prius car thermometer?[/quot

 

Actually it was on his favorite modest mouse cd/thermometer. Granola anyone?

[Phil]

October is the single most important month for providing clues for the following winter. All others pale in comparison.

I've personally found higher correlations/anticorrelations in November.

 

Also, there are many years where October provided no predictive value for DJF whatsoever.

[TT-SEA]

Love the roller coaster coming up.  I don't mind extreme quick hitting heatwaves that crash and burn as fast as they arrived.   The WRF shows it going from 90s in the lowlands around Seattle on Saturday to freezing nighttime temps in the North Cascades by Monday morning!

 

Meanwhile very pleasant here with a temp of 79.

 

 

Big roller coaster.   

 

A couple very warm days... then back to maybe a little above normal... and then probably a little more above normal.   

 

Doesn't it normally stay in the mid to upper 90s for all of the second half of August and September?  

 

And remember... this climate sucks beyond comprehension.  Loathe it right?       Don't be praising anything here.   

[Jesse]

Looks like the new cold phase told Eugene's streak to go **** itself.

Same with our 85+ stretch!

[Jesse]

18z doesn't think the cooldown will be short lived....

[Deweydog]

Same with our 85+ stretch!

It's the kind of thing cold phase dreams are made of.

[Jesse]

It's the kind of thing cold phase dreams are made of.

[Front Ranger]

I've personally found higher correlations/anticorrelations in November.

 

Also, there are many years where October provided no predictive value for DJF whatsoever.

 

No month is perfect. But I've shown my work before...October is the best bet overall, at least for the PNW/West.

 

The last couple Octobers certainly did nothing to disprove this hypothesis. 

[Front Ranger]

Big roller coaster.   

 

A couple very warm days... then back to maybe a little above normal... and then probably a little more above normal.   

 

Doesn't it normally stay in the mid to upper 90s for all of the second half of August and September?  

 

And remember... this climate sucks beyond comprehension.  Loathe it right?       Don't be praising anything here.   

 

Classic Tim. Just can't resist.

[Front Ranger]

Same with our 85+ stretch!

 

SEA managed to scrape 80, keeping that streak alive.

[Jesse]

Yeah, it seems 20c+ is generally a little easier to come by in September, as is offshore flow. Onshore flow in general tends to be weaker as the typical summertime thermal gradients begin to wane. The biggest equalizer in September is the fact subsidence inversions become a real factor and without offshore flow a considerable amount of energy is spent breaking them despite the warmer air masses overall.

Indeed. I know September gets a lot of flack for being boring, but I find it to be a fascinating month because of dynamics like this. Summer's ghost.

[James Jones]

18z doesn't think the cooldown will be short lived....

Ensembles aren't nearly as promising. 

 

http://i.imgur.com/SQMZEGW.png?1

[Timmy Supercell]

Indeed. I know September gets a lot of flack for being boring, but I find it to be a fascinating month because of dynamics like this. Summer's ghost.

 

September on the east slopes is much like May, without the storms.

[Jesse]

Ensembles aren't nearly as promising.

 

http://i.imgur.com/SQMZEGW.png?1

Things are in flux. Based on the Euro ensembles I could envision them trending cooler.

[Jesse]

September on the east slopes is much like May, without the storms.

There are many other aspects of weather that I find interesting besides thunderstorms.

 

Don't get me wrong, they're cool and all...

[TT-SEA]

Classic Tim. Just can't resist.

Ha! He goes on a typical Jim rant and then the next day is praising our weather. I would say he welcomed some ridicule.

[Timmy Supercell]

I hope we get another Indian Summer in early October. Really looking forward to a few days I jump from 28 and freezing fog to 80+ and clear.