April 2020 Weather discussion for the PNW

[Phil]

Insane spread within the D11-15 EPS mean. There’s a cluster of insanely ridgy members, and a cluster of troughy members, however the ridgy solutions are more amplified/anomalous and are skewing the mean in that direction.

 

One of the weaknesses of ensemble means.

[Jesse]

Insane spread within the D11-15 EPS mean. There’s a cluster of insanely ridgy members, and a cluster of troughy members, however the ridgy solutions are more amplified/anomalous and are skewing the mean in that direction.

 

One of the weaknesses of ensemble means.

A huge weakness. Which is why I much prefer the “spaghetti” charts for analysis.

[TT-SEA]

Actually... the mean is a great tool. Extreme members tend to compromise eventually.

When the mean is cold then there is no need to dig deeper. When the mean is warm then its all about seeing the cold members.  

[Phil]

A huge weakness. Which is why I much prefer the “spaghetti” charts for analysis.

Definitely agree. In theory you can have 3 members out of a 15-20 members ensemble that are wildly divergent and change the entire picture. Stuff like that does happen more often than many seem to think.

 

Though it does look likely that ma’ nature will be having a hot flash out there during the 2nd week of May. The duration of which appears to hinge on the speed/amplitude of the MJO crossing the Pacific under the impending completion of this cycle of poleward -AAM transfer. There’s some disagreement on that for sure.

[Jesse]

Definitely agree.

 

Though it does look likely that ma’ nature will be having a hot flash out there during the 2nd week of May. The duration of which appears to hinge on the speed/amplitude of the MJO crossing the Pacific under the impending completion of this cycle of poleward -AAM transfer. There’s some disagreement on that for sure.

Oh, there is some ridging coming. Seems like it would be a fairly common sense call not to expect it to more or less stick around all month, but lately our climate likes to have us hold its beer when presented with these statements.

[TT-SEA]

And there could be cases where extreme members skew the mean and its wrong... but overall the mean is a great tool. Particularly the EPS mean. Not perfect of course.

 

The GEFS is pretty bad and much more variable.

[Phil]

Actually... the mean is a great tool. Extreme members tend to compromise eventually.

 

When the mean is cold then there is no need to dig deeper. When the mean is warm then its all about seeing the cold members.

The mean is a great tool, with weaknesses. It’s pretty straightforward stuff, so I don’t understand what you’re getting at here?

 

Extreme members don’t always cancel equally, IE: if the extreme members are clustered on one side of the spectrum, and/or there’s a crap load of spread such that a few divergent solutions can torpedo the picture that would otherwise be presented by the mean.

[TT-SEA]

The mean is a great tool, with weaknesses. It’s pretty straightforward stuff, so I don’t understand what you’re getting at here?

 

Extreme members don’t always cancel equally, IE: if the extreme members are clustered on one side of the spectrum, and/or there’s a crap load of spread such that a few divergent solutions can torpedo the picture that would otherwise be presented by the mean.

See above.

[BLI snowman]

Yup, I would easily be ok with seeing some spikes well into the 90s this May if it meant we saw a more dynamic wave train overall.

 

Stuck ridging has been a recurring theme in almost every warm season lately. And it’s got to be one of the most mind numbingly dull patterns possible for any weather enthusiast. It even makes the big heat numbers harder to come by. Last summer was a nice shake up with things staying changeable overall at 500mb, even though it still lead to a warm final result.

 

Last May was an oddball. Coldest in decades in the SW and completely lifeless up here. 

 

The pattern in the first week alone looks more interesting than anything we saw in 2018 or 2019.

[Phil]

And there could be cases where extreme members skew the mean and its wrong... but overall the mean is a great tool. Particularly the EPS mean. Not perfect of course.

 

The GEFS is pretty bad and much more variable.

No one said anything about this EPS mean being right or wrong..clearly you’re invested in it being right, but that’s not the point.

 

The point is, the mean is conveying a picture of the pattern that isn’t necessarily matched by the median, or majority of the ensemble members, at each time interval (or even overall as the time window narrows). That doesn’t mean it’s wrong..it could be right. It’s just not always the best way to assess the probability of a particular outcome at a given point in time.

[TT-SEA]

No one said anything about this EPS mean being right or wrong..clearly you’re invested in it being right, but that’s not the point.

 

The point is, the mean is conveying a picture of the pattern that isn’t necessarily matched by the median, or majority of the ensemble members, at each time interval (or even overall as the time window narrows). That doesn’t mean it’s wrong..it could be right. It’s just not always the best way to assess the probability of a particular outcome at a given point in time.

The maps give you a much better picture of the pattern. The charts allow you to see individual members for one specific location. But only available for the GEFS which is unfortunate.

[Phil]

The maps give you a much better picture of the pattern. The charts allow you to see individual members for one specific location. But only available for the GEFS which is unfortunate.

The maps don’t always give you a picture of the pattern. Especially when there’s large spread/divergent clusters, which often happens at-range and smooths/distorts the wavetrain illogically.

 

I think you really have to know what it is you’re looking at before interpreting the most likely progression of the pattern if there’s large spread in an ensemble mean and you’re near/beyond D10. You’d better have a good logical basis to argue otherwise.

[TT-SEA]

The maps don’t always give you a picture of the pattern. Especially when there’s large spread/divergent clusters, which often happens at-range and smooths/distorts the wavetrain illogically.

 

I think you really have to know what it is you’re looking at before interpreting the most likely progression of the pattern if there’s large spread in an ensemble mean and you’re near/beyond D10. You’d better have a good logical basis to argue otherwise.

 

 

Of course the mean is smoothed and gets more so as you go out in time.    Its a good guide though... particularly the EPS mean.

[Timmy Supercell]

This April definitely seems a lot drier than 2019 at least in my area. 

[TacomaWaWx]

The AFDs aren’t usually too interesting this time of year. We will see what happens this weekend.

[Frontal Snowsquall]

Viewer pic on NWS Boise's Facebook page, shelf cloud and dust storm.

 

Also a 1.75" hail report in Owyhee County out of the storms so far.

 

You ever get dust storms in K Falls? I've never experienced one but it's on my bucket list.

[Jesse]

Seems like a good rule of thumb for high temps lately is take whatever prevailing guidance is and add 3-5 degrees.

[Timmy Supercell]

You ever get dust storms in K Falls? I've never experienced one but it's on my bucket list.

 

Yes, barely once. 06/09/2015. There was enough dust ahead of a storm that I can taste it, got in my eyes, and reduced visibility.

 

Locals might not have called it a legit one, but I believe low visibility and 50-60mph would constitute at least a minor one.

 

Shortly before it reached here I took some photos. I should have taken pics when this was at the height. I couldn't see downtown shortly after these.

 

 

 

 

June 9th 2015 was also a three-round storm day. One woke me up at 4am with some of the most frequent lightning I've ever seen, then the day ended with more storms at sunset with a rainbow. 

[MossMan]

.54” on the day, 2.94” on the month.

[Timmy Supercell]

A Phoenix or Tuscon style dust storm though I'm not even sure is possible in this area. I'd like to experience one of those.

[Phil]

A Phoenix or Tuscon style dust storm though I'm not even sure is possible in this area. I'd like to experience one of those.

I’ll pass. Guess I’m lucky too, as that’s probably the one type of weather that’s actually impossible here. Never gets dry enough (though there are stories of them happening during the dust bowl years).

 

What a weird stretch..a true mega-drought pattern that mysteriously came and went within a decade.

[Frontal Snowsquall]

Yes, barely once. 06/09/2015. There was enough dust ahead of a storm that I can taste it, got in my eyes, and reduced visibility.

 

Locals might not have called it a legit one, but I believe low visibility and 50-60mph would constitute at least a minor one.

 

Shortly before it reached here I took some photos. I should have taken pics when this was at the height. I couldn't see downtown shortly after these.

 

 

 

 

June 9th 2015 was also a three-round storm day. One woke me up at 4am with some of the most frequent lightning I've ever seen, then the day ended with more storms at sunset with a rainbow.

Nice pics! Yeah, I would love to have seen video and pictures of that thing moving in. If it reduced visibility then I'd classify it as one. It's always surreal looking at these pictures and then imagining it coming right at you. Here's an article Cliff Mass wrote a couple months ago about dust storms here in the PNW.

 

https://cliffmass.blogspot.com/2020/02/dust-storm-season-begins-in-eastern.html?m=1

[Jesse]

I’ll pass. Guess I’m lucky too, as that’s probably the one type of weather that’s actually impossible here. Never gets dry enough (though there are stories of them happening during the dust bowl years).

 

What a weird stretch..a true mega-drought pattern that mysteriously came and went within a decade.

 

The 1930s through early 1940s always interest me even from a local climate perspective. A lot of times when we are flirting with a top tier warm month and/or season, and I am looking at old records to verify, years in that period will pop up and often rival the present day warmth.

 

Of course, there were also some big time cold anomalies back then too, that we haven't even come close to in recent years. For whatever reason that was an unusually dynamic period for our climate zone.

[TacomaWaWx]

59/48 0.05” today. Looks like we will finish April with 2.03” of rainfall.

[Jesse]

64/50 here today. Will end April with about 1.2" of rain.

 

Could set a midnight low if skies stay clear. Good chance it will drop into the 40s.

[Jesse]

The maps don’t always give you a picture of the pattern. Especially when there’s large spread/divergent clusters, which often happens at-range and smooths/distorts the wavetrain illogically.

 

I think you really have to know what it is you’re looking at before interpreting the most likely progression of the pattern if there’s large spread in an ensemble mean and you’re near/beyond D10. You’d better have a good logical basis to argue otherwise.

 

Agree with all of the above. At a certain range it just becomes a meaningless blob of comforting colors. All the details of differering solutions are lost. You could technically have 24 colder ensemble members and 26 warmer ones and the mean maps would probably spit out a wash of light orange over the west that looks sort of like a ridge if you don't know what you're looking at.

 

Also, SIDE NOTE, I believe Euro spaghetti charts for particular locations are available somewhere. I've seen Mark Nelsen post them before, and even other members here.

[TT-SEA]

I think the charts have some value... its not all or nothing.    Always have to paint the other side as extreme.  

 

But the long range mean maps are not always just a meaningless blob.    The 12Z EPS today is a good example.   This is a pretty strong signal for western warmth and eastern cold.    That is meaningful.     It goes both ways.   Its just as meaningful when it shows western cold and we have seen that many times.

 

And yet things can change and sometimes it does not end up that way.   That is true with all weather models.

 

[BLI snowman]

The 1930s through early 1940s always interest me even from a local climate perspective. A lot of times when we are flirting with a top tier warm month and/or season, and I am looking at old records to verify, years in that period will pop up and often rival the present day warmth.

 

Of course, there were also some big time cold anomalies back then too, that we haven't even come close to in recent years. For whatever reason that was an unusually dynamic period for our climate zone.

 

That +PDO period between 1920 and 1945 was pretty dynamic everywhere. Like recently, we had a very rapidly warming global climate but it was still a lot colder than it is today. Also fairly neutral ENSO much of the time. Led to lots of volatility and some big extremes that haven't been approached since. 

[GHweatherChris]

I see post shuffling happening...

[Jesse]

I see post shuffling happening...

I went to edit mine and accidentally deleted. Not sure what the other one was all about...

[Jesse]

That +PDO period between 1920 and 1945 was pretty dynamic everywhere. Like recently, we had a very rapidly warming global climate but it was still a lot colder than it is today. Also fairly neutral ENSO much of the time. Led to lots of volatility and some big extremes that haven't been approached since.

Yeah, that seemed to be the period where the global climate really turned the corner away from the 19th century/LIA hangover regime.

 

Then of course there was another relative cool down from the mid 1940s thru the 70s. Followed by the current modern warming regime. Part of me wonders if we could ever see another couple decade bump down at some point, even with a multi-decadal warming trend continuing in the background, but the 2007-12 negative PDO period was sadly the best we have been able to muster thus far.

 

The generally +PDO and weak ENSO forcing with a rapidly warming globe does sound an awful lot like the last 6-7 years, though. Just oscillating about what is now a much warmer mean than 80-100 years ago.

[GeorgeWx]

I think the charts have some value... its not all or nothing. Always have to paint the other side as extreme.

 

But the long range mean maps are not always just a meaningless blob. The 12Z EPS today is a good example. This is a pretty strong signal for western warmth and eastern cold. That is meaningful. It goes both ways. Its just as meaningful when it shows western cold and we have seen that many times.

 

And yet things can change and sometimes it does not end up that way. That is true with all weather models.

 

Right but the signal for eastern cold is stronger than western warmth. More of a dirty ridge out west.

[Phil]

The 1930s through early 1940s always interest me even from a local climate perspective. A lot of times when we are flirting with a top tier warm month and/or season, and I am looking at old records to verify, years in that period will pop up and often rival the present day warmth.

 

Of course, there were also some big time cold anomalies back then too, that we haven't even come close to in recent years. For whatever reason that was an unusually dynamic period for our climate zone.

Yeah, the seasonal cycle was unstable but quite pronounced during that period. The winter circulation often resembled LIA type years but the summers were anything but. The summer ITCZ/z-cells were very far to the north until the 1950s.

 

Those seasonal extremes technically began muting/canceling out starting in 1947, which continued through the 1950s before a “cold era” seasonal circulation briefly returned during the 1960s/70s, and debatably, the early/mid-1980s as well. But I’d argue against that.

[Phil]

That’s a lot of cold across the country on the 00z GFS. Now continuing through at least May 7th in the PNW.

 

[TT-SEA]

That’s a lot of cold across the country on the 00z GFS. Now continuing through at least May 7th in the PNW.

 

 

 

Not cold at the surface on May 7th on the GFS... northerly flow and sunshine can be quite mild out here at this time of year.

 

 

 

Also... Tuesday is warm on this run.

[Phil]

This is insane for mid-May. YEAH BABY!

 

[Phil]

[Jesse]

[TT-SEA]

It’s a below average day. Even at the surface.

 

 

 

Its a warm, sunny day per the GFS.     The high temps are above normal that day.   

[TT-SEA]

Was sort of hoping Phil would respond to the interesting climate discussion that was going on, rather than weakly trolling the King troll of this forum. It’s just too easy dude.

 

 

He is way more interesting when he is serious and desperately trolling.  

 

But I think he is genuinely excited about the pattern on the GFS... which is fair.    That same pattern would also be beautiful out here.