May 2017 Observations and Model Discussion for the Pacific Northwest

[Phil]

Almost the entire extratropical NH is colder than average on the latest 12z EPS run, centered on week two.

 

The western US is the lone exception, under the influence of the slowly retrograding anticyclone, which is riding a Pacific CCKW after the AAM maximum.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/26DAB0F4-4EF8-4DCA-A3E9-A2CC58AFD4B2_zpstitwoe5a.png

[TT-SEA]

Almost the entire extratropical NH is colder than average on the latest 12z EPS run, centered on week two.

 

The PNW is the lone exception, under the influence of the slowly retrograding anticyclone, which is riding a Pacific CCKW after the AAM maximum.

 

 

Has to be divine reward for our miserable Feb-Apr period.      

[TT-SEA]

EPS looks starkly different from the operational 12Z days 7-10.

 

 

Looks warmer than the operational run on day 7 and 8.  

 

Here is day 8 on the operational run:

 

http://www.tropicaltidbits.com/analysis/models/ecmwf/2017052612/ecmwf_T850a_us_9.png

 

 

And day 8 on the EPS:

 

http://www.tropicaltidbits.com/analysis/models/ecmwf-ens/2017052612/ecmwf-ens_T850a_us_9.png

 

 

Obviously the EPS mean will look much smoother by day 10.    I am not seeing signs of major troughing on the EPS though.  

 

Here is the day 15 EPS mean... 

 

[Phil]

Has to be divine reward for our miserable Feb-Apr period.

Haha, yeah everything has come together perfectly for this extended period of ridging. This is also the perfect background state to keep the extratropical NH in the freezer (-NAM, weak Asian monsoon). Not much poleward heat transfer right now.

 

The western ridge might last a week longer than I was originally thinking, if the modeling is correct with the CCKW enhancement of the MJO over the Pacific (which would require perfect timing, so, eh). Though if true, however, the recoil will be just as anomalous when the pair of waves cycle out, but you probably won't be in town for that anyway.

[TT-SEA]

Haha, yeah everything has come together perfectly for this extended period of ridging. This is also the perfect background state to keep the extratropical NH in the freezer (-NAM, weak Asian monsoon). Not much poleward heat transfer right now.

 

The western ridge might last a week longer than I was originally thinking, if the modeling is correct with the CCKW enhancement of the MJO over the Pacific (which would require perfect timing, so, eh). Though if true, the recoil will be just as anomalous when the pair of waves cycle out.

 

Could be.   We will see.  

 

Just enjoying it while it lasts.  

[Phil]

Could be. We will see.

 

Just enjoying it while it lasts.

It's been more persistent than I've thought so far, so take my statements for what they're worth. I'm also up in Connecticut right now so I don't have access to the data I normally do.

 

Then again, the reasons for the persistence are pretty clear, so it mostly comes down to the timing of waves.

[TT-SEA]

FWIW... the parallel 12Z GFS is also very warm for most of the next 17 days like the 12Z operational GFS.  

[Phil]

Interesting how we can directly correlate the flip to colder high latitude temperatures to the "climatological" start of Asian monsoon season. With the monsoonal circulations running weaker than normal, the cooling makes sense given how vital the monsoons are in distributing heat and moisture poleward.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/BB15FBDE-FCA3-4792-992E-34F3CBE797CE_zpsvmzrnw1y.png

[Jesse]

FWIW... the parallel 12Z GFS is also very warm for most of the next 17 days like the 12Z operational GFS.

Hoping a very warm start to summer could mean it peaks early. But it rarely works out that way.

[TT-SEA]

Hoping a very warm start to summer could mean it peaks early. But it rarely works out that way.

Mostly worked that way in 2016.

[Jesse]

Mostly worked that way in 2016.

Not even close. August was very hot. September was slightly cooler than average.

 

I think it has been 16 years since we've seen anything even approaching a cool August.

[TT-SEA]

Not even close. August was very hot. September was slightly cooler than average.

 

I think it has been 16 years since we've seen anything even approaching a cool August.

Felt like last year generally peaked early with a second peak in August.

[Phil]

Interesting how we can directly correlate the flip to colder high latitude temperatures to the "climatological" start of Asian monsoon season. With the monsoonal circulations running weaker than normal, the cooling makes sense given how vital the monsoons are in distributing heat and moisture poleward.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/BB15FBDE-FCA3-4792-992E-34F3CBE797CE_zpsvmzrnw1y.png

In response, total NH sea ice is now the second highest on record for this date (since 2006).

 

http://www.natice.noaa.gov/ims/images/ims_data.jpg

[Phil]

Felt like last year generally peaked early with a second peak in August.

Yeah, and that August warmth was mostly confined within a two week stretch. The majority of the July-September period was troughy, albeit it didn't reflect much in the surface temperatures in some areas.

[Jesse]

Felt like last year generally peaked early with a second peak in August.

Calling that an early peak is sort of a stretch.

[Phil]

Check out the deep WPAC convection now being modeled between 150E and the dateline, thanks to the slow eastward passage of this MJO wave.

 

http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=global&pkg=chi200&runtime=2017052618&fh=0&xpos=0&ypos=339

 

Here's your forcing for the western ridging. This wave has been terribly modeled, all-around.

[Front Ranger]

Felt like last year generally peaked early with a second peak in August.

 

It was basically a back and forth summer, with the warm stretches in June and August being greater in magnitude than any cool stretches.

[James Jones]

Calling that an early peak is sort of a stretch.

 

Yeah, makes no sense to call it an early peak. It was more like a normal to slightly below average July sandwiched between two warm months.

 

Going back to 1895 June was the 17th warmest on record for the Willamette Valley, while August was 8th. For the Puget Sound June came in at 20 and August at 11.

[Phil]

It was basically a back and forth summer, with the warm stretches in June and August being greater in magnitude than any cool stretches.

Not really.

 

There were two stretches of anomalous warmth (early-June and mid-August) in a sea of modest troughing/-PNA. Through the summer, the low frequency amplitude of the -PNA/western troughing increased.

[Front Ranger]

Not even close. August was very hot. September was slightly cooler than average.

 

I think it has been 16 years since we've seen anything even approaching a cool August.

Yeah, I mentioned recently that August is the month most due to be cool.

 

However, 2010 was definitely a regionally cool August (though not significantly). And 2007 was fairly cool for most of the PNW, especially the western lowlands and WA.

 

 

[Front Ranger]

Not really.

 

There were two stretches of anomalous warmth (early-June and mid-August) in a sea of modest troughing/-PNA. Through the summer, the frequency of the -PNA/western troughing increased, as did its amplitude.

 

If the cool stretches were cooler, it would have ended up as a cool summer. They were mostly very close to normal. Like I said, the warm stretches were of greater magnitude. 

 

Seasonally, that's how it generally works. Monthly/seasonal anomalies often don't reflect the weather experienced the majority of the time. Mostly because the majority of the time, the weather experienced is fairly close to normal. So the extremes usually win out.

[Phil]

If the cool stretches were cooler, it would have ended up as a cool summer. They were mostly very close to normal. Like I said, the warm stretches were of greater magnitude.

The cool periods were more prolonged and persistent. You just had a few very hot weeks sprinkled in, thanks to intraseasonal forcings masking the background state.

 

Two brief episodes of heat, a one week heatwave in early June and a two week heatwave in mid-August, together made up over 80% of the total positive departure points from June through September @ SEA & PDX. That's actually pretty remarkable.

 

On the low frequency, the background state of western troughing strengthened linearly from April through October.

[TT-SEA]

Just a wee bit gorgeous this afternoon... 

 

[Phil]

Note how the background state evolved through the warm season last year.

 

It was indeed an "early peak", by all rationally-derived seasonal scale indicators. Facts are facts.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/9BFB72C9-193A-4E59-8B98-76C4A779266A_zpsmupmqs20.png

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/01958C6B-DB3B-48D2-8F29-FDEA8125F7AD_zps7qr0i7vp.png

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/B98CFE84-CB4A-4B34-9216-84F2056BD2CF_zpsxkry4dnw.png

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/4E8B43D3-A758-4F1C-A709-5EFCAFF5B5B8_zpskmj41dmg.png

[Front Ranger]

The cool periods were more prolonged and persistent. You just had a few very hot weeks sprinkled in, thanks to intraseasonal forcings masking the background state.

 

Two brief episodes of heat, a one week heatwave in early June and a two week heatwave in mid-August, together made up over 80% of the total positive departure points from June through September @ SEA & PDX. That's actually pretty remarkable.

 

On the low frequency, the background state of western troughing strengthened linearly from April through October.

I disagree that it was remarkable. See the second part of my post above.

[Front Ranger]

If you include spring, no doubt 2016 peaked early. But the discussion was about summer.

[Phil]

I disagree that it was remarkable. See the second part of my post above.

Statistically, it is remarkable. Over 80% of the positive departure points from 6/1 to 9/30 occurred just in 3 weeks at both locations. There are ~ 18 weeks between 6/1 and 9/30.

[Front Ranger]

Statistically, it is remarkable. Over 80% of the positive departure points from 6/1 to 9/30 occurred just in 3 weeks at both locations. There are ~ 18 weeks between 6/1 and 9/30.

You'll find something similar a lot of summers in the PNW. Same thing with cool anomalies in the winter.

[Phil]

You'll find something similar a lot of summers in the PNW. Same thing with cool anomalies in the winter.

I can't find anything like it, at least back to 2003. I admit I haven't looked back farther than that yet, but I will when I have more time.

[Jesse]

Check out the deep WPAC convection now being modeled between 150E and the dateline, thanks to the slow eastward passage of this MJO wave.

 

http://www.tropicaltidbits.com/analysis/models/?model=gfs&region=global&pkg=chi200&runtime=2017052618&fh=0&xpos=0&ypos=339

 

Here's your forcing for the western ridging. This wave has been terribly modeled, all-around.

Retracting your cold June call? Or just pushing back timing?

[TT-SEA]

SEA had way more positive departures than negative departures last summer... same with BLI.

 

If you look at those stations... it was mostly above normal with short periods of below normal spread out through the JJAS period.

[Front Ranger]

SEA had way more positive departures than negative departures last summer... same with BLI.

 

If you look at those stations... it was mostly above normal with short periods of below normal spread out through the JJAS period.

Near normal counts as below normal.

[Phil]

Retracting your cold June call? Or just pushing back timing?

Might need to push everything back by about a week. The MJO (climatologically) speeds up and shallows once at/beyond the dateline, but this one isn't modeled to do that. Sometimes constructive interference w/ CCKWs can deepen/slow it down until it reaches the EPAC, which might be the case here.

[Front Ranger]

I can't find anything like it, at least back to 2003. I admit I haven't looked back farther than that yet, but I will when I have more time.

I bet 75-80 percent of the departure points in summer 2008 came in about 3 weeks.

[Jesse]

SEA had way more positive departures than negative departures last summer... same with BLI.

 

If you look at those stations... it was mostly above normal with short periods of below normal spread out through the JJAS period.

Sounds like a classic early peaking summer.

[Phil]

SEA had way more positive departures than negative departures last summer... same with BLI.

 

If you look at those stations... it was mostly above normal with short periods of below normal spread out through the JJAS period.

For J/A/S? No way, dude.

 

PDX averaged -0.1C during that time period, and OLM/EUG were all within a fraction of a degree of normal.

[Jesse]

18z ensembles still drop to near normal by next week. Could be a lot of nice days in the 70s coming up.

[luminen]

73F here currently. Feels a bit hot to be honest. Dam(n), we need some thunderstorms to liven things up though...

[Jesse]

73F here currently. Feels a bit hot to be honest. d**n we need some thunderstorms to liven things up though...

Yeah. The weather sure looks to lose a pulse going forward. More t-storms would be much appreciated.

[Deweydog]

Memorial Day weekend sucks balls without a chance of thundersnow.