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Wintry Winter 2019-20 Discussion

Rain Cold said:
One day, will you do a seminar on all of these 2 and 3 letter mysterious indexes and their values and the implications for the pattern/weather? :)
Click to expand...

In a very hand-wavy sense, think of the North Pacific Oscillation as the Sea Level Pressure component that's closely related to the Pacific North American Pattern, keeping in mind that the PNA is measured traditionally at 500mb instead of the surface. The North Pacific Oscillation variability is closely linked to the 2nd EOF of SST in the extratropical North Pacific (the so-called "Victorian mode"), the 1st EOF of SSTs is the more well known PDO.


Here's what the positive phase of the NPO looks like using SLP:

North_Pacific_Oscillation.png



ecmwf-ens_mslpaNormMean_npac_6.png



Here's what the positive phase of the NPO (or in this case North Pacific Index (they're virtually the same)) correlates to at 500mb:

152.15.113.4.315.13.41.9.gif


Looks familiar eh?

It's basically the same exact pattern as the PNA at 500mb, so in essence, you can think of the NPO as the surface pressure component of the PNA.
152.15.113.4.315.13.42.20.gif
 
Webberweather53 said:
In a very hand-wavy sense, think of the North Pacific Oscillation as the Sea Level Pressure component that's closely related to the Pacific North American Pattern, keeping in mind that the PNA is measured traditionally at 500mb instead of the surface. The North Pacific Oscillation variability is closely linked to the 2nd EOF of SST in the extratropical North Pacific (the so-called "Victorian mode"), the 1st EOF of SSTs is the more well known PDO.


Here's what the positive phase of the NPO looks like using SLP:

View attachment 25885



View attachment 25886



Here's what the positive phase of the NPO (or in this case North Pacific Index (they're virtually the same)) correlates to at 500mb:

View attachment 25888


Looks familiar eh?

It's basically the same exact pattern as the PNA at 500mb, so in essence, you can think of the NPO as the surface pressure component of the PNA.
View attachment 25889
Click to expand...
This is great. Thank you!
 
Webberweather53 said:
Fwiw, here's the JMA's latest forecast for Jan 2020. It actually isn't totally unreasonable given this pattern has reappeared on a regular basis in almost every winter since 2011-12.


View attachment 25891
Click to expand...

I would take that, showing a weak Nino climo +PNA (W ridge/E trough), in a heartbeat. The problem is that the JMA can't forecast well just 7 days out, much less 2 months out. So, this map could easily be totally wrong/too cold for the SE.
 
GaWx said:
I would take that, showing a weak Nino climo +PNA (W ridge/E trough), in a heartbeat. The problem is that the JMA can't forecast well just 7 days out, much less 2 months out. So, this map could easily be totally wrong/too cold for the SE.
Click to expand...
"easily" is quite understated ... ;)
 
95365b0bfa2744ca7367fe7d6a197d45.jpg


Brrr


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Not sure if this would fall under this thread, but I was hoping some people on here could maybe provide info on shed some light on some reason why it does this.
Something I noticed about trends here at least in the Southeast is it seems like winter storms come in 2's around here. Now I know that's not always the case, but its something I have noticed. I also know that a lot of areas get more than 1 significant winter storm a year here in the South. Here are a few example years that are recent mainly here in the Carolina's. In multiple cases, winter storms fell EXACTLY two weeks apart from each other, so i'll just name those occasions.


2007 - We had a winter storm on Jan 18th or so then exactly 2 weeks later on Feb 1st

2010-2011 - We had a winterstorm the day after Christmas on the 26th then exactly 2 weeks later, we had another one into the next year on Jan 9th I believe. The one that had the South froze up for about a week.

2014 - Jan 29th, we had the winter storm that shut down Atlanta. Then exactly 2 weeks later, we had another one. The crippling ice storm for parts of GA and SC

2018 - Then as recent as less than 2 years ago, we had the coastal storm on Jan 3th, then exactly two weeks later on the 17th, we had another winter storm.

I was just wondering if anyone else noticed this or have thought about it. Seems as if in some cases, depending on location, the second storm was always bigger too. I don't there is any correlation, but just interesting. I know here in the Midlands of SC, when we have a significant winter event, they come in 2s it seems, especially in my lifetime of following weather.
 
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