April 2020 Weather discussion for the PNW

[TT-SEA]

I guess one thing that’s flown under the radar is that the midweek airmass has been gradually trending a little less impressive, in terms of warmth.

It's the result if less troughing dumping down on us from the north late next week... so less of an amplified ridge ahead of it.

 

Sustained warmth is much preferable in my opinion... rather than heat spikes followed by cold and miserable weather. But that is just me.

[Jesse]

Meanwhile today is on track to get a lot warmer than progged. With sunny skies, the low well to our south and offshore flow in place, 62-64 wouldn’t surprise me.

 

It’s already 56 here.

[TT-SEA]

Just a short period of some rain around next Tuesday per the 12Z ECMWF... day 9. This is consistent with the 00Z run but it shows less rain on this run.

[ShawniganLake]

Might be a return to winter for the Midwest and NE.

 

5-10 day period...

 

 

 

10-15 day period...

 

Makes sense. It’s been chilly out west for awhile.

[Jesse]

Makes sense. It’s been chilly out west for awhile.

How far behind is your area for rainfall year to date? Seems like the recent cool pattern wasn’t all that wet up there either.

[TT-SEA]

Here is where it's been wetter than normal over the last 2 weeks... as usual that includes the area to the north and east of Seattle.

 

[TT-SEA]

Here is where it's been wet this year... note the area between Seattle and Olympia has also been wetter than normal.

 

[Deweydog]

Ben a cold April.

 

In more depressing news, the average high at PDX reached 60 today and MAY not fall below that until late October.

[TigerWoodsLibido]

How far behind is your area for rainfall year to date? Seems like the recent cool pattern wasn’t all that wet up there either.

 

Not sure about that part of Vancouver Island but in the south valley we are close to 8" below normal rainfall so far.

[Jesse]

Ben a cold April.

 

In more depressing news, the average high at PDX reached 60 today and MAY not fall below that until late October.

The first four days have been cold. Looks mostly near to above average going forward.

 

And that's not a depressing stat. That's just seasonality. I like seasons.

[Jesse]

Not sure about that part of Vancouver Island but in the south valley we are close to 8" below normal rainfall so far.

I would guess something similar up there. Although I know they had an extremely wet January to offset things a bit.

[TT-SEA]

12 EPS out through day 9... slight eastward shift compared to 00Z run. Looks really cold in the Midwest and NE.

 

[Cloud]

12 EPS out through day 9... slight eastward shift compared to 00Z run. Looks really cold in the Midwest and NE.

 

Hope this isn't the start to the blob re-developing for the summer. 

[TigerWoodsLibido]

What's y'all's weed burner of choice? I cant afford anything too outlandish.

[TT-SEA]

Hope this isn't the start to the blob re-developing for the summer. 

 

 

That is not water temps.   

[Jesse]

[Jesse]

What ever happened to all of that blob part II (son of the blob) hullabaloo, btw. Wasn’t that last fall?

[Jesse]

What's y'all's weed burner of choice? I cant afford anything too outlandish.

Drought.

[TT-SEA]

There are some here who love the blob.

 

But yeah persistent ridging directly offshore is what seems to help it along.

 

 

Jim's absolute favorite pattern... GOA ridging.

[Phil]

That GOA ridge is stuck stuckitty stuck, as has been the case for much of the last 12 months. That means lots and lots of troughing over the West Coast until the 4 Corners High builds by late June or early July.

I’ve had more time on my hands of late, so I’ve really dug into the details of the evolution in the tropics/subtropics and what the 4CH might look like this summer.

 

Safe to say I definitely fear a large 4CH this summer, as the signal is almost universal in IPWP-PMM-KW cycle analogs, but the placement is key. There are a lot of 2010/11/12 looking tendencies with the E-IO/Indo-China region emerging as the IPWP hotspot, with the SW/Southern US in general trending very warm, while the PNW trends dry to very dry (regionally..might be different on the west side) but avoids significant heat in that scenario.

 

So I guess that’s where I’m leaning for now. Opposite of last summer in some ways..cool/dry air masses in the PNW region, instead of mild/wet like last summer, and hot/dry in the SW US/4-Corners region, compared to last summer’s relatively weak 4CH.

[Jesse]

I’ve had more time on my hands of late, so I’ve really dug into the details of the evolution in the tropics/subtropics and what the 4CH might look like this summer.

Safe to say I definitely fear a large 4CH this summer, as the signal is almost universal in IPWP-PMM-KW cycle analogs, but the placement is key. There are a lot of 2010/11/12 looking tendencies with the E-IO/Indo-China region emerging as the IPWP hotspot, with the SW/Southern US in general trending very warm, while the PNW trends dry to very dry but avoids significant heat in that scenario.

So I guess that’s where I’m leaning for now. Opposite of last summer in some ways..cool/dry in the PNW, instead of mild/wet, and hot/dry in the SW US/4-Corners region, compared to last summer’s relatively weak 4CH.

Yeah, I was gonna say. A strong 4CH doesn’t always necessarily mean a hot summer here. Especially if it’s centered a little eastward, a strongish one can actually help draw more onshore flow into our region.

 

Summers 2010-12 were cool, but they weren’t necessarily dry. At least outside of the heart of summer.

[Phil]

Jim's absolute favorite pattern... GOA ridging.

Aleutian Low builds the blob (or +PDO depending on the season), because it slows the NPAC eastern boundary current and produces downwelling in the GOA/along the west coast. Seems counterintuitive but that’s the case.

 

Aleutian High produces the -PDO/cold phase type configuration, with coastal upwelling along with a more vigorous eastern boundary current.

[TT-SEA]

The July - September period in 2011 and 2012 was extremely dry here.   It rained on just handful of days in that 3 month period each of those years in my area.

 

That was the opposite of last summer when there was measurable rain on over 40 days in the July - Sept period.  

 

My area is more indicative of the overall pattern since we are rarely shadowed here.   It takes a very different pattern to produce 10 days of rain from July - Sept compared to over 40 days.

 

The summer of 2012 was probably my favorite summer in our time here.

[Jesse]

Aleutian Low builds the blob (or +PDO depending on the season), because it slows the NPAC eastern boundary current and produces downwelling in the GOA/along the west coast. Seems counterintuitive but that’s the case.

Aleutian High produces the -PDO/cold phase type configuration, with coastal upwelling along with a more vigorous eastern boundary current.

Yeah. The pattern that creates the blob is obviously a lot different than the pattern Jim likes to see. That was just a weak troll attempt.

[TT-SEA]

Yeah. The pattern that creates the blob is obviously a lot different than the pattern Jim likes to see. That was just a weak troll attempt.

Not trolling at all. I am aware that Jim specifically cheers for non-blob forming patterns and I know ridging offshore does not build the blob.

[Phil]

Yeah, I was gonna say. A strong 4CH doesn’t always necessarily mean a hot summer here. Especially if it’s centered a little eastward, a strongish one can actually help draw more onshore flow into our region.

 

Summers 2010-12 were cool, but they weren’t necessarily dry. At least outside of the heart of summer.

FWIW, reanalysis for 2010-12 has much lower PWATs and drier conditions overall in WA/OR/ID with some wetter spots near the terrain and coast? Seems like some marine air since it gets warmer/drier relative to average inland those years.

 

Last year, there was plenty of large scale moisture transport available (and it was clear early on it’d be available) but that wasn’t a cool pattern. So mild/wet was an easy call.

 

This summer is hard. Dry is a safe bet (I think?) and for now I have to lean cool. The extremely warm E-IO/120E portion of the IPWP strongly correlates to -PNA during the warm season, but that’s often a dry pattern too, especially with the wide ITCZ/Hadley Cell going into it (typical coming out of a super +NAM/+PMM but exaggerated in our current multidecadal regime).

[TT-SEA]

FWIW, reanalysis for 2010-12 has much lower PWATs and drier conditions overall in WA/OR/ID with some wetter spots near the terrain and coast? Seems like some marine air since it gets warmer/drier relative to average inland those years.

 

Last year, there was plenty of large scale moisture transport available (and it was clear early on it’d be available) but that wasn’t a cool pattern. So mild/wet was an easy call.

 

This summer is hard. Dry is a safe bet (I think?) and for now I have to lean cool. The extremely warm E-IO/120E portion of the IPWP strongly correlates to -PNA during the warm season, but that’s often a dry pattern too, especially with the wide ITCZ/Hadley Cell going into it (typical coming out of a super +NAM/+PMM but exaggerated in our current multidecadal regime).

You nailed the wet aspect of last summer way ahead of time... it was frequently wet. A better "moisture transport" as you called it. Way more days with rain than normal here. Some of the shadowed areas got missed and people said you were wrong. But you got the pattern right.

 

It was the first summer in 15 years when we never had to water anything.

 

Also why the fire season was basically non-existent.

[Jesse]

FWIW, reanalysis for 2010-12 has much lower PWATs and drier conditions overall in WA/OR/ID with some wetter spots near the terrain and coast? Seems like some marine air since it gets warmer/drier relative to average inland those years.

 

Last year, there was plenty of large scale moisture transport available (and it was clear early on it’d be available) but that wasn’t a cool pattern. So mild/wet was an easy call.

 

This summer is hard. Dry is a safe bet (I think?) and for now I have to lean cool. The extremely warm E-IO/120E portion of the IPWP strongly correlates to -PNA during the warm season, but that’s often a dry pattern too, especially with the wide ITCZ/Hadley Cell going into it (typical coming out of a super +NAM/+PMM but exaggerated in our current multidecadal regime).

 

This part is usually just code for global warming right?

[Phil]

This part is usually just code for global warming right?

Lol.

 

Well, there’s certainly a correlation between global temperature and cycling of the structure/seasonality of the Warm Pool/Hadley Cell/ITCZ. But it’s a chicken egg paradox at best..and these variations have been ongoing throughout the Holocene. Climate models generally cannot simulate more than 30-40% of the Hadley Cell/ITCZ broadening via temperature increase/radiative forcing alone (and actually tend to invert the observed changes in the seasonal cycle..and can’t project changes to the climatological latitude of the warm pool until the divergence has already begun). There’s very likely to be something else going on here that we don’t understand yet.

[ShawniganLake]

How far behind is your area for rainfall year to date? Seems like the recent cool pattern wasn’t all that wet up there either.

About 5” above for the year. January was historically wet. Like 10” above average

[Phil]

Definitely a signal for retrogression on the 12z EPS.

 

A lot more members went that way D11-15.

[Omegaraptor]

FWIW, reanalysis for 2010-12 has much lower PWATs and drier conditions overall in WA/OR/ID with some wetter spots near the terrain and coast? Seems like some marine air since it gets warmer/drier relative to average inland those years.

 

Last year, there was plenty of large scale moisture transport available (and it was clear early on it’d be available) but that wasn’t a cool pattern. So mild/wet was an easy call.

 

This summer is hard. Dry is a safe bet (I think?) and for now I have to lean cool. The extremely warm E-IO/120E portion of the IPWP strongly correlates to -PNA during the warm season, but that’s often a dry pattern too, especially with the wide ITCZ/Hadley Cell going into it (typical coming out of a super +NAM/+PMM but exaggerated in our current multidecadal regime).

 

Do these summers tend to produce thunderstorms, or are we in for a boring summer after a boring winter?

[Timmy Supercell]

Heavy rain! Just 10-15 degrees warmer and it's froggy weather. 

[Jesse]

About 5” above for the year. January was historically wet. Like 10” above average

That’s what I remembered. Probably a different story for water year though considering how dry October/November were.

[Jesse]

Do these summers tend to produce thunderstorms, or are we in for a boring summer after a boring winter?

I will make a BOLD prediction. Whatever ends up happening you probably won’t like it.

[Jesse]

Definitely a signal for retrogression on the 12z EPS.

A lot more members went that way D11-15.

Hoping so. Maybe this period of MJO enhanced ridging will end up a little shorter than anticipated.

[Omegaraptor]

PDX up to 63. Beautiful sunny day today!   

[MossMan]

PDX up to 63. Beautiful sunny day today!

Up to 52 at MMH. (MossMan’s House)

[Jesse]

PDX up to 63. Beautiful sunny day today!   

Water worries out the window for the next few hours?

[Omegaraptor]

Water worries out the window for the next few hours?

Not much reason for the Willamette Valley to worry about water supply right now. Also the Sierras are currently getting dumped on. Tahoe snow cams look wonderful.