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Amplification and Spatial Variations of the 500 mb pattern over NA

tornadojay

By tornadojay,
in New York City Metro

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tornadojay

tornadojay

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With all this talk about good set-up patterns for snow for our area, it sparked an idea in my head to look back at a Macroclimatology paper I wrote back March of 1997 in my Synoptic class. The topic was "Amplificiation and Spatial Variations of the 500 mb Pattern over North America and Surrounding Ocean Environs for Dec 1995 - March 1996 and December 1996 - March 1997". I would love to hear any comments from other Mets/Mets students or anyone else, for that matter, who have done any similar studies or have any comments.

The focus was to investigate transitions of split flow and zonal patterns to highly amplified ones over NA. In addition to looking at the phases of NAO/PNA/WA, etc... one of the other things I looked at was relative positions and strengths of cyclones and anticyclones in the Pacfic and their tracks.

Since these 2 sesons (95-96 vs. 96-97) set up so differently for us, I decided this would be a good case study in studying the patterns.

To kind of summarize what I kept finding during that busy 95-96 season:

  • A strengthening of the Pacific jet at the latitudes of 30 - 40 degrees Norrth, underneathe a broad trough with very low surface pressures. Generally, the lowest pressure was near 50 N, 155 W. Then, in the northwest Alberta region, center of high pressure near 60 N and 120 W. In some extreme case, I found a pressure gradient between these points of up to 80 mb. Then, another 30 degrees longitude east of the Alberta High was the Polar Vortex. The PV was not even all that strong in some cases, however, the gradient of a strong high in Alberta still allowed for a large pressure gradient. As an example, I found that the Jan 96 blizzard featured a 970 mb low near 50 N, 140 W in the Pacific with a high of about 1040 mb located about 40 degrees east of this location.
  • So then, later in this month, which was basically one of the few periods where we had the longwave pattern reverse on us, I found that the orientation of lows/highs in the Pacific switched from an east/west orientation to more of a north/south orientation, which basically allowed for colder thicknesses to spread in a southwest direction, which ultimately lead to WAA and rising thicknesses along the east coast.
  • The overall favorable pattern set-up for us had 4 centers of interest: 1) 20 N, 160 W (near Hawaii), 45 N, 165 W (North Pacific), 55 N, 115W (Alberta), and 30 N, 85 W (Gulf Coast region)... and then there was a positive correlation with the WA (western Atlantic) pattern, which had high 500 mb heights near 55N, 55W, and is associated with a weak Iceland low.
  • During 96-97, there was a predominant split flow with minimal activity in the Pacific.
  • When the Pacific did become active in 96-97, it was often offset by strong confluence off the Atlantic coast, which did not allow for amplification.

So, that was basically the main points... sorry if I'm basically stating the obvious here. I think the key was in relative placements and strenghts of cyclones and anticyclones in certain areas of the Pacific which were indicators of tremendous amplifications of the overall pattern across NA and one which favors potential east coast snow events.

:snowman: :snowman: :snowman:

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tornadojay

tornadojay

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You got the whole paper link?

Man, that sounds like a great read!

Thanks! This is old school, sitting in a binder I have with all my Met papers, probably using some prehistoric version of Microsoft Word. I don't have it electronically. I suppose I could type the whole thing again at some point when I'm not too lazy.

I can't even remember half the stuff I learned or did anymore. :whistle:

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Chris L

Chris L

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Thanks! This is old school, sitting in a binder I have with all my Met papers, probably using some prehistoric version of Microsoft Word. I don't have it electronically. I suppose I could type the whole thing again at some point when I'm not too lazy.

I can't even remember half the stuff I learned or did anymore. :whistle:

Well, I don't want you to type the whole thing..... that would be crazy. How long is the paper?

But those are great points! Someome will do a comparasion between 2008-2009 and 2009-2010.... :snowman:

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dbc

dbc

Posted
Posted

With all this talk about good set-up patterns for snow for our area, it sparked an idea in my head to look back at a Macroclimatology paper I wrote back March of 1997 in my Synoptic class. The topic was "Amplificiation and Spatial Variations of the 500 mb Pattern over North America and Surrounding Ocean Environs for Dec 1995 - March 1996 and December 1996 - March 1997". I would love to hear any comments from other Mets/Mets students or anyone else, for that matter, who have done any similar studies or have any comments.

The focus was to investigate transitions of split flow and zonal patterns to highly amplified ones over NA. In addition to looking at the phases of NAO/PNA/WA, etc... one of the other things I looked at was relative positions and strengths of cyclones and anticyclones in the Pacfic and their tracks.

Since these 2 sesons (95-96 vs. 96-97) set up so differently for us, I decided this would be a good case study in studying the patterns.

To kind of summarize what I kept finding during that busy 95-96 season:

  • A strengthening of the Pacific jet at the latitudes of 30 - 40 degrees Norrth, underneathes a broad trough with very low surface pressures. Generally, the lowest pressure was near 50 N, 155 W. Then, in the northwest Alberta region, center of high pressure near 60 N and 120 W. In some extreme case, I found a pressure gradient between these points of up to 80 mb. Then, another 30 degrees longitude east of the Alberta High was the Polar Vortex. The PV was not even all that strong in some cases, however, the gradient of a strong high in Alberta still allowed for a large pressure gradient. As an example, I found that the Jan 96 blizzard featured a 970 mb low near 50 N, 140 W in the Pacific with a high of about 1040 mb located about 40 degrees east of this location.
  • So then, later in this month, which was basically one of the few periods where we had the longwave pattern reverse on us, I found that the orientation of lows/highs in the Pacific switched from an east/west orientation to more of a north/south orientation, which basically allowed for colder thicknesses to spread in a southwest direction, which ultimately lead to WAA and rising thicknesses along the east coast.
  • The overall favorable pattern set-up for us had 4 centers of interest: 1) 20 N, 160 W (near Hawaii), 45 N, 165 W (North Pacific), 55 N, 115W (Alberta), and 30 N, 85 W (Gulf Coast region)... and then there was a positive correlation with the WA (western Atlantic) pattern, which had high 500 mb heights near 55N, 55W, and is associated with a weak Iceland low.
  • During 96-97, there was a predominant split flow with minimal activity in the Pacific.
  • When the Pacific did become active in 96-97, it was often offset by strong confluence off the Atlantic coast, which did not allow for amplification.

So, that was basically the main points... sorry if I'm basically stating the obvious here. I think the key was in relative placements and strenghts of cyclones and anticyclones in certain areas of the Pacific which were indicators of tremendous amplifications of the overall pattern across NA and one which favors potential east coast snow events.

:snowman: :snowman: :snowman:

This is awesome. I love that you documented where cyclones were in different regions during the 1996 blizzard. I think someone did something like this just before the February 2006 snowicane on Eastern but with maps of prior storms as compared to the setup for the February 2006 storm. Very interesting analysis. It almost serves as a road map to what is needed to favor east coast snow.

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tornadojay

tornadojay

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This is awesome. I love that you documented where cyclones were in different regions during the 1996 blizzard. I think someone did something like this just before the February 2006 snowicane on Eastern but with maps of prior storms as compared to the setup for the February 2006 storm. Very interesting analysis. It almost serves as a road map to what is needed to favor east coast snow.

Thanks a lot! appreciate it... :thumbsup: It's funny.. I actually do have all of the maps as reference figures to go along with the paper. I think I should scan those and make them electronic.

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Chris L

Chris L

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This is awesome. I love that you documented where cyclones were in different regions during the 1996 blizzard. I think someone did something like this just before the February 2006 snowicane on Eastern but with maps of prior storms as compared to the setup for the February 2006 storm. Very interesting analysis. It almost serves as a road map to what is needed to favor east coast snow.

Yes. Here is is...

http://www.philip-lu...ISON%20PAGE.htm

http://www.philip-lutzak.com/weather/Snow%20Storm%2002-11-2006%20Project/Snow%20Storm%2002-11-2006.htm

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dbc

dbc

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These look familiar and are awesome but someone actually posted 850mb maps (like you'd see on the GFS model run with the low and high pressure areas along with the 0 line) in a thread that compared the February 2006 setup to several other memorable storms. I don't think it was an expanded look like what tornadojay is discussing here but it was at least a North American depiction.

Oh btw, well deserved pinnage tornadojay!

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wkd

wkd

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I think the second link is one of the best discussions of the genesis and development of a winter storm that i have read. Very concise and covers all the important factors. Perhaps it should be pinned in some way as a reference in this upcoming winter season.

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A-L-E-X

A-L-E-X

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Well, I don't want you to type the whole thing..... that would be crazy. How long is the paper?

But those are great points!  Someome will do a comparasion between 2008-2009 and 2009-2010.... :snowman:

He can scan the paper-- I have a scan to pdf thing on my multifunction unit, maybe Jay has that too :)

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