Seattle Snow Failures vs Successes At 500mb Level

[snow_wizard]

It's pretty easy to see from these composite maps the difference between the 500mb anomalies that cause either success or failure for snowfall. Map number one is a composite of early Dec 2013, early Feb 2014, and early Jan 2017. Map number two is a composite of the Nov 2010 cold wave, Jan 2007 cold wave, and the New Years snowfall of January 1950.

 

It's easy to see on the favorable setup how we are able to tap into cold directly north of us instead of from the NE.

[MossMan]

It's pretty easy to see from these composite maps the difference between the 500mb anomalies that cause either success or failure for snowfall. Map number one is a composite of early Dec 2013, early Feb 2014, and early Jan 2017. Map number two is a composite of the Nov 2010 cold wave, Jan 2007 cold wave, and the New Years snowfall of January 1950.

 

It's easy to see on the favorable setup how we are able to tap into cold directly north of us instead of from the NE.

Why is it so hard to get the map #2 setup anymore?

[Jesse]

Why is it so hard to get the map #2 setup anymore?

Too many warm summers.

[Deweydog]

A lack of warm summers.

Fixed!

[Jesse]

Fixed!

Tell yourself what you want. There were some summers in the 1950s that would have driven MossMan up the wall. Amazing winters then though.

[Deweydog]

Tell yourself want you want. There were some summers in the 1950s that would have driven MossMan up the wall. Amazing winters then though.

Colder climate period = consistently colder weather*

[Jesse]

Colder climate period = consistently colder weather*

 

Yup. I would have been in heaven back then. Muddy dogs in July but an army of snowmen in January. Sometimes you gotta make the hard choices!

[Deweydog]

Yup. I would have been in heaven back then. Muddy dogs in July but an army of snowmen in January. Sometimes you gotta make the hard choices!

Rock the vote!

[snow_wizard]

Why is it so hard to get the map #2 setup anymore?

Let's hope it can figure out how to do it again....and soon.

[Black Hole]

Let's hope it can figure out how to do it again....and soon.

This winter is totally different than the repetitive pattern we have seen the last 5 years or so with a resilient giant west coast ridge. Hopefully this means that we will see more winters like this in the years to come. If so, you will definitely score sooner or later. 

 

Seeing this change gives me hope that at a minimum we will see some more variety. 

[Brennan]

Positive PDO cold waves compared to negative PDO ones? Hmmm

 

I say this because I know the 80s in general featured a lot of dry cold spells. 1992-93 was positive PDO as well if I'm not mistaken.

 

I'll check it out more closely later. Might be something to it

[MossMan]

Too many warm summers.

I want warm summers and cold winters. That is why I will eventually be moving to a place that will feature both...but is still only about 2hrs away from my current location.  

[Brennan]

Ok just some small stuff I looked through today. I looked at Sea-tac's top 10 snowfalls since 1948 to compare snowfalls to monthly PDO. I added the previous month's PDO number following the month of the snowfall. I'm not saying there is a direct correlation or that the PDO is the driving factor. And yes I realize HALF of the top 10 snowfalls are from the same 2 winters.  . Had we scored a huge snowfall at sea-tac this year (over 7" in one calendar day) it would have been completely unprecedented in terms of snowfalls during POSITIVE PDO winters. I also looked at SEA-TAC's top 16 snowiest winters, and all but two featured a NOV-FEB MINUS PDO average. The two that didn't fit were 1985-86 which averaged +0.59 and 1979-1980 which averaged +0.31... So as you can see, we shouldn't have expected widespread large snowfall totals in Western Washington this year going in... Just based on the fact that our PDO was obviously going to be positive. I'M NOT SAYING THE PDO IS A DRIVING FACTOR. 

 

1/13/50: PDO: -2.13, -0.80

1/27/69: PDO: -1.26, -1.27

1/26/50: PDO: -2.13, -0.80

12/31/68: DO: -1.27, -0.44

12/23/65: DO: +0.06, -0.59

12/26/74: DO: -0.12, +0.43

1/25/72: PDO: -1.99, -1.87

11/21/85: DO: -0.75, +0.29

1/29/69: PDO: -1.26, -1.27

2/28/62: PDO: -1.15, -1.29

[IbrChris]

This winter is totally different than the repetitive pattern we have seen the last 5 years or so with a resilient giant west coast ridge. Hopefully this means that we will see more winters like this in the years to come. If so, you will definitely score sooner or later. 

 

Seeing this change gives me hope that at a minimum we will see some more variety. 

Ridiculously resilient west coast ridge just a bit late to the party this year. Looks like a good 10+ days of ridging coming up though.

[IbrChris]

It's pretty easy to see from these composite maps the difference between the 500mb anomalies that cause either success or failure for snowfall. Map number one is a composite of early Dec 2013, early Feb 2014, and early Jan 2017. Map number two is a composite of the Nov 2010 cold wave, Jan 2007 cold wave, and the New Years snowfall of January 1950.

 

It's easy to see on the favorable setup how we are able to tap into cold directly north of us instead of from the NE.

Pretty small sample size...would be useful to include some other dates. The main thing of note IMO is the differences in potential over-water trajectory. It would be useful if you not only included 500 mb height anomalies but also plots for the same days of zonal wind at 300 mb. It's nice to see where the jet is located, although we get an idea from the 500 mb maps snowfall in Seattle is too nuanced for me to be convinced this is the main culprit.

[snow_wizard]

Pretty small sample size...would be useful to include some other dates. The main thing of note IMO is the differences in potential over-water trajectory. It would be useful if you not only included 500 mb height anomalies but also plots for the same days of zonal wind at 300 mb. It's nice to see where the jet is located, although we get an idea from the 500 mb maps snowfall in Seattle is too nuanced for me to be convinced this is the main culprit.

 

I think that feature is dead.  We almost always get a ridge sometime during the winter.

[Black Hole]

Ridiculously resilient west coast ridge just a bit late to the party this year. Looks like a good 10+ days of ridging coming up though.

True, but models already hinting at a return to cooler troughy weather in early Feb. 

[snow_wizard]

Pretty small sample size...would be useful to include some other dates. The main thing of note IMO is the differences in potential over-water trajectory. It would be useful if you not only included 500 mb height anomalies but also plots for the same days of zonal wind at 300 mb. It's nice to see where the jet is located, although we get an idea from the 500 mb maps snowfall in Seattle is too nuanced for me to be convinced this is the main culprit.

 

I've done it with larger sample sizes before.  It comes down to very subtle differences in blocking position and shape.

[snow_wizard]

True, but models already hinting at a return to cooler troughy weather in early Feb. 

 

Yeah...it's obvious the mean pattern has changed.  Need to look no further than CA for that.