August 2017 PNW Discussion Thread

[Jesse]

06z GFS has to be off its rails. No day cooler than 96º and 6 days above 100+ over the next 10 days at PDX. Would put this month in the record books that's for sure whether or not they beat the all-time high. 

 

Believe it or not, ensemble support isn't terrible. 

[Kayla]

Believe it or not, ensemble support isn't terrible. 

 

The good news is the 00z Euro and EPS are not on board. Still above average through the period but it's a lot more reasonable.

[Phil]

The -QBO is now taking over in the tropics down to 50mb, for the first time since 2014 with proper shear stress. Though technically, the tropical tropopause has been trending progressively higher/colder since May, when the QBO30 integral first flipped negative/easterly.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/20C47E21-1DFC-4F16-990A-D0496BA540EF_zps4qjhnqty.jpg

[Timmy]

The -QBO is now taking over in the tropics down to 50mb, for the first time since 2014 with proper shear stress. Though technically, the tropical tropopause has been trending progressively higher/colder since May, when the QBO30 integral first flipped negative/easterly.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/20C47E21-1DFC-4F16-990A-D0496BA540EF_zps4qjhnqty.jpg

you are so smart!

[Jesse]

The -QBO is now taking over in the tropics down to 50mb, for the first time since 2014 with proper shear stress. Though technically, the tropical tropopause has been trending progressively higher/colder since May, when the QBO30 integral first flipped negative/easterly.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/20C47E21-1DFC-4F16-990A-D0496BA540EF_zps4qjhnqty.jpg

Nice.

 

A) Do you expect anyone to understand this?

 

B ) What does it have to do with our weather?

[Geos]

Smoke really rolled into after 6pm around here. By 7pm I couldn't see the Cascades whatsoever. 

 

Low went down to 63 here.

[Phil]

you are so smart!

If I were smart, I would have recognized my strengths and weaknesses, and stuck with my large scale predictions, instead of trying to make a seasonal forecast just for the PNW.

 

I'm actually happy with my planetary-scale forecast. My trimmed quotes from back in June:

 

Once into August/September, the system state starts looking a lot like 2014, with the strong WPAC convection/-QBO, which was the theme back in 2014.

 

I don't see sustained ridging until August, or maybe late July if everything synchronizes perfectly/early. Big western ridges occur under a certain set of boundary conditions, most of which are not present yet but should be present within two months or perhaps a bit less. When the next MJO moves out of the IO/EHEM, the warm IPWP/WPAC area will be very enabling for convection. Could very well be enough to force some degree of low frequency coupling.

This would fit with the idea of an (almost) inverse low frequency pattern progression compared to 2016, with most of the troughing focused during the early and middle summer, and more ridging developing towards the end. Though, the progression of the background state is weaker this summer compared to 2016, so we might see a highly variable mid-latitude circulation and a dormant ENSO.

 

An August heatwave is also starting to look more likely now, in my opinion, though it's still questionable whether it persists into/through the autumn, or merely passes with the intraseasonal forcing. The warming dateline/WPAC waters don't bode well for a cool autumn, though.

Like last summer, when I try to forecast beyond my area of expertise, I tend to make mistakes.

[Front Ranger]

I don't remember the last time I saw just "Smoke" for the daily forecast from NWS.

 

NWS Portland going with the less ominous sounding "haze".

 

[Front Ranger]

SEA may have set the record for warmest August low this morning. Record is 68 from 1981, and lowest ob this AM was 69.

[Phil]

Nice.

 

A) Do you expect anyone to understand this?

 

B ) What does it have to do with our weather?

On the large scale, the -QBO is associated with more vigorous and equatorward convection with the cooler/raised equatorial tropopause (an overall reduction in tropical static stability).

 

Given SSTAs and solar forcing, this favors enhanced WPAC forcing as we move into the autumn, which is actually fairly reminiscent of 2014, 1985, 1981*, 1976, 1960, etc (solar starts to matter more by November and beyond). So, the circulation might follow a +WPO/west-shifted +PNA in S/O/N, which is actually the classic -QBO wavetrain.

 

This is assuming we continue the +IOD/+IOWP/dormant ENSO regime and avoid geomagnetic storms. If we somehow flip into a more -ENSO/Indo forcing state, the picture changes significantly in October/November.

[Kayla]

12z GFS ups the ante to 100+ on 7 of the next 10 days at PDX. 

 

Does anyone know what the record number of 100+ days is for PDX in a season? Isn't it only like 5-6 days?

[Geos]

On the large scale, the -QBO is associated with more vigorous and equatorward convection with the cooler/raised equatorial tropopause (an overall reduction in tropical static stability).

 

Given SSTAs and solar forcing, this favors enhanced WPAC forcing as we move into the autumn, which is actually fairly reminiscent of 2014, 1985, 1981*, 1976, 1960, etc (solar starts to matter more by November and beyond). So, the circulation might follow a +WPO/west-shifted +PNA in S/O/N, which is actually the classic -QBO wavetrain.

 

This is assuming we continue the +IOD/+IOWP/dormant ENSO regime and avoid geomagnetic storms. If we somehow flip into a more -ENSO/Indo forcing state, the picture changes significantly in October/November.

 

So in the case of a +WPO/west shifted +PNA that would mean a trough in the West. Maps show that the west is cool in about every month with that type of pattern.

http://madusweather.com/teleconnection/wpo_pos.php

[James Jones]

12z GFS ups the ante to 100+ on 7 of the next 10 days at PDX. 

 

Does anyone know what the record number of 100+ days is for PDX in a season? Isn't it only like 5-6 days?

 

Pretty sure it's 5 in 1941 and 1977. Might be missing another year in there.

 

Looking at the 12z reminds me of the 2010 Russian heatwave. That thing blew the doors off of any previous heatwave on record, and if the 12z verified August would be well on its way to do the same with any previous record warm month around here, though odds are strongly against it.

[TT-SEA]

Smoke is drifting more to the west off Vancouver Island compared to yesterday when it was moving more to the SSW.  

[Phil]

So in the case of a +WPO/west shifted +PNA that would mean a trough in the West. Maps show that the west is cool in about every month with that type of pattern.

http://madusweather.com/teleconnection/wpo_pos.php

It depends, but those maps are missing a ton of years/dates.

[Jesse]

12z Canadian looks to generally agree with the GFS.

[DareDuck]

BTW, I goofed on this. RDM hit 100 on 7/29/2016. I got lazy and only checked Jun & Aug when I made the post.

 

So, RDM has actually seen triple digits every summer in recent years.

Ah very interesting. This my 3rd summer here and they've all been pretty warm. I wonder how unusual reaching 100 5 straight summers is for RDM.

[TT-SEA]

81 at SEA at 11 a.m. despite the smoke/haze.

[Front Ranger]

BLI reporting just 3 mi visibility with smoke.

[Deweydog]

97 at Larch.

[Timmy]

scappoose is running +6 from yesterday. 90 at 11:05

[ShawniganLake]

BLI reporting just 3 mi visibility with smoke.

looks like the Fraser valley is in the 2.5 to 3mi range as well.

 

You can definitely smell it here today.

[Jesse]

I wonder if there have been other periods in the last several hundred years where our area experienced hot summers/long duration heatwaves with the frequency we have been seeing over the last decade +.

 

Seems like you might have some good info on this sort of thing, Dmitri, regarding the tree ring studies and whatnot. I would assume perhaps the medieval warm period saw similar spells?

[Phil]

I wonder if there have been other periods in the last several hundred years where our area experienced hot summers/long duration heatwaves with the frequency we have been seeing over the last decade +.

 

Seems like you might have some good info on this sort of thing, Dmitri, regarding the tree ring studies and whatnot. I would assume perhaps the medieval warm period saw similar spells?

I'm not Demitri, but it's well known that the four corners high was amplified (during boreal summer) from ~ 900AD to ~ 1300AD, which lead to frequent megadroughts and heatwaves across the western US.

 

From Cook et al 2010:

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/C17EAD35-55F1-466B-A0A9-B1D9F2F06504_zpsov88yxrx.jpg

[Jesse]

Pretty murky here in Eugene, which is what, 500 miles south of where the fires are?

 

 

You must be in the hills south of town judging by this picture. Pretty area.

[Phil]

Just for the west coast states, using borehole sea salt ratios near the ocean. The transition into the little ice age circulation is particularly abrupt around 1250AD.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/E08F0AB8-388C-4CB5-99D8-FF874C31A7A4_zpsyfs0jfex.jpg

[Geos]

80 at home and 83 down here in Bothell. Definitely some haze in the air still.

[Jesse]

I'm not Demitri, but it's well known that the four corners high was amplified (during boreal summer) from ~ 900AD to ~ 1300AD, which lead to frequent megadroughts and heatwaves across the western US.

 

From Cook et al 2010:

 

 

I am definitely aware of the megadroughts that purportedly affected western North American in that era. Apparently anthropologists believe these frequent droughts may have played a role in the collapse of several native civilizations in the American southwest, such as the Anasazi and Pueblo.

 

It would be interesting to see what kind of warm spells the area that is now Portland was capable of stringing together back then, and how it compares to now. Although obviously proxy data is probably the best we have for that sort of thing.

[TT-SEA]

Really active fire down in the Oregon Cascades just SE of Andrew.  

 

http://weather.cod.edu/satrad/exper/?parms=pacnorthwest-02-48-0

 

Click 'Play' in the lower right corner.

[Jesse]

My signature confirms your guess, but it's a good one nonetheless.  Yes, it's a pretty area, although I was just looking at photos from 2003 when I bought the property and marveling at how much greener and lusher it was then.  5 years of hot, dry summers will do that.

 

A slow transition to a Grants Pass or Roseburg like vegetation pattern for you guys.

[Jesse]

Really active fire down in the Oregon Cascades just SE of Andrew.  

 

http://weather.cod.edu/satrad/exper/?parms=pacnorthwest-02-48-0

 

Click 'Play' in the lower right corner.

 

Yep, one of my favorite hiking spots on Mount Jefferson.

[jakeinthevalley]

Pretty murky here in Eugene, which is what, 500 miles south of where the fires are?

 

Most of the smoke in the valley today is from the Whitewater Fire, near Mt Jefferson. Wind shift last night brought it westward

[TT-SEA]

Yep, one of my favorite hiking spots on Mount Jefferson.

 

I was watching some news reports... that is west of the crest right?   Scary.  

[Jesse]

I was watching some news reports... that is west of the crest right?   Scary.  

 

Yes.

 

The whole Oregon side of the Gorge is on the verge of burning, too. Also west of the crest.

 

https://inciweb.nwcg.gov/incident/article/5403/37289/

[wx_statman]

Ah very interesting. This my 3rd summer here and they've all been pretty warm. I wonder how unusual reaching 100 5 straight summers is for RDM.

 

I just checked. Looks like they never (since 1948 anyway) had 5 straight summers reach 100 until reeling off 9 straight from 2002-2010. Then a couple year break in 2011-12, followed by the current 5 year streak. 

[wx_statman]

I wonder if there have been other periods in the last several hundred years where our area experienced hot summers/long duration heatwaves with the frequency we have been seeing over the last decade +.

 

Seems like you might have some good info on this sort of thing, Dmitri, regarding the tree ring studies and whatnot. I would assume perhaps the medieval warm period saw similar spells?

 

Your guess is as good as mine on that. I don't think tree ring data can reconstruct heat wave tendencies. It's difficult enough to tease out the precipitation signal from the temperature signal as it is, since cambial growth in trees responds to a combination of the two (and at different times of year depending on species, location, microclimate, etc). Having said that, I'm no expert in tree ring studies. 

[Phil]

I am definitely aware of the megadroughts that purportedly affected western North American in that era. Apparently anthropologists believe these frequent droughts may have played a role in the collapse of several native civilizations in the American southwest, such as the Anasazi and Pueblo.

 

It would be interesting to see what kind of warm spells the area that is now Portland was capable of stringing together back then, and how it compares to now. Although obviously proxy data is probably the best we have for that sort of thing.

Interesting info. I wasn't aware the of the droughts' impact on the early natives. I guess it does make sense, though.

 

And yeah, while proxies (usually) provide decent large scale pictures of dominant climate state(s), the picture is more muddy on decadal/subdecadal scales, and especially on seasonal timescales. Their resolution isn't great for the most part.

 

I have a paper bookmarked somewhere on my PC that specifically discusses the PNW and SW US climates from 1000AD to 1950AD. It doesn't target seasonality, but I'll post it here if I can find it on my phone. I can still summarize the findings as the following:

 

1) Warm/dry from 1000AD to around 1235AD, with the warmest and driest years usually clustering together in 30yr to 70yr stretches. The warmest/driest years were up to +2 standard deviations above the current +2SD threshold, which is pretty remarkable. Some of the glaciers that currently exist in the Olympic mountains did not exist during this time frame.

 

2) Climate shift to cool/dry PNW and cool/wet SW from 1250AD to 1450AD, with approximately 80% of the cooling occurring in two abrupt step changes lasting under a decade each. There was a sustained transition into a +PDO during this timeframe.

 

3) Shift to wet/slightly warmer everywhere from about 1470AD to 1580AD under a very strong +PDO. The wettest conditions relative to average also shifted from the far SW into the middle latitude western US.

 

4) Very cold period from 1600AD to 1700AD, with moderate drying in northern zones and further wettening in the SW. The cooling occurred within 20 years, and was the most significant temperature swing in this proxy record.

 

5) Warming/drying from 1700AD to 1950AD, with the changes occurring in three step changes lasting about 20 years each. There was a brief colder/wetter period from 1800 - 1845AD that corresponded to the Dalton minimum and a period of enhanced volcanism.

[Deweydog]

PDX's 89 at noon running three degrees behind the 7-28-09 noon temperature. Four degrees behind 7-29-09.

 

#pedestrian

[wx_statman]

Just for the west coast states, using borehole sea salt ratios near the ocean. The transition into the little ice age circulation is particularly abrupt around 1250AD.

 

http://i724.photobucket.com/albums/ww243/phillywillie/Mobile%20Uploads/E08F0AB8-388C-4CB5-99D8-FF874C31A7A4_zpsyfs0jfex.jpg

 

This shows that the 1850-1900 pluvial along the west coast was a unique occurrence over the last 300 years. Something I've read about or seen referred to in other studies. Events like the Willamette Valley flood of 1861 or the California flood of 1862 were most likely not representative of late-LIA conditions, and may have been unique occurences going back several centuries prior.

[wx_statman]

PDX's 89 at noon running three degrees behind the 7-28-09 noon temperature. Four degrees behind 7-29-09.

 

#pedestrian

 

We're in a drier airmass though. We're +1 on 7/21/2006 with similar dp's.