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Wxeastern's Final Winter Outlook


WXeastern

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OP, what could cause the -NAO/AO to turn positive? (i'm generally curious, just getting into meteorology and trying to learn as much as possible smile.png )

Well.. its according to how far back in the atmospheric and oceanic oscillations you want to go.

Stratospheric cooling would could cause the polar vortex to become stronger and that in turn would cause less blocking in the high latitudes because lower pressures/heights would be dominating the higher latitudes where the NAO/AO are measured when hen the PV become stronger and more concentrated!

Now you could take this further back.. but its a long drawn out process that I dont have the time to go into right now. HM here at this forum is one of the best at root drivers of Oceanic and Atmospheric Oscillations. If you want to take it back past stratospoheric cooling I suggest you search out some of his threads.

Hope that helps you understand what would cause the NAO/AO to go from - to + smile.png

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Well.. its according to how far back in the atmospheric and oceanic oscillations you want to go.

Stratospheric cooling would could cause the polar vortex to become stronger and that in turn would cause less blocking in the high latitudes because lower pressures/heights would be dominating the higher latitudes where the NAO/AO are measured when hen the PV become stronger and more concentrated!

Now you could take this further back.. but its a long drawn out process that I dont have the time to go into right now. HM here at this forum is one of the best at root drivers of Oceanic and Atmospheric Oscillations. If you want to take it back past stratospoheric cooling I suggest you search out some of his threads.

Hope that helps you understand what would cause the NAO/AO to go from - to + smile.png

Kinda sorta! lol. I think I need to do some more reading so I can more fully understand NAO, I thought I had a general idea but bleh the internet (and this site) has a plethora of information! :)

But I sure hope it doesnt turn positive, I'm in the mood for snow!

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Kinda sorta! lol. I think I need to do some more reading so I can more fully understand NAO, I thought I had a general idea but bleh the internet (and this site) has a plethora of information! smile.png

Excuse the typos im sleepy

Maybe you were looking for a more simple and directly triggered answer so I will explain it in shorterm synoptic trends.

During winter there is an upper level jetstream that we call the "Polar" jet stream. Its called polar because its average latitude is in the polar regions of the globe. It generally controls what sections of North America sees colder and warmer temperatures. It rides overtop of upper level high pressure systems and underneath upper level low pressure systems! If the polar jet is to your north you will normally see warmer temps and if the PJ is over the same latitutde or south of you.. temps are normally colder than normal!

There are exceptions to this rule though (Cold air damning... elevation/microclimates... low/high pressure systems that get cutoff from the jet stream etc)

Now that you know this jet is located on average at the polar latitudes the only way to get it more southward are stronger ridges of upper level high pressure systems placed in partcular spots where they work in tandem to send the PJ southward by riding up and down the ridges in the higher latitudes of the polar regions. This is called high latitude blocking!

Here are the rough and general locations of high latitude oscillations where one or more of these general locations have to have an upper level high pressure system to setup in order to allow troughs of lower pressure and colder air to make it into our latitudes.

Courtesy of Larry Cosgrove

REGION_DESIGNATIONS_FOR_BLOCKING.jpg

The movement of higher pressure out of the AO/NAO positions allows lower pressure to move in and in turn sends the NAO/AO from negative phase to positive one

So if you have this -NAO phase

blocking.jpg

And if that HPS is steered out of the NAO position then lower pressure will begin to move in and the PJ will be allowed to retreat back northward allowing an upper level ridge of higher pressure to move in where there was once an upper level trough of lower pressure

positivenaomap.jpg

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Excuse the typos im sleepy

Maybe you were looking for a more simple and directly triggered answer so I will explain it in shorterm synoptic trends.

During winter there is am upper level jetstream that we call the "Polar" jet stream. Its called polar because its average latitude is in the poalr regions of the globe. It generally controls what sections of North America sees colder and warmer temperatures. It rides overtop of upper level high pressure systems and underneath upper level low pressure systems! If the polar jet is to your north you will normally see warmer temps and if the PJ is over the same latitutde or south of you temps are normally colder than normal!

There are exceptions to this rule though (Cold air damning... elevation/microclimates... low/high pressure systems that get cutoff from the jet stream etc)

Now that you know this jet is located on average at the polar latitudes the only way to get it more southward are stronger ridges of upper level high pressure systems placed in partcular spots where they work in tandem to send the PJ southward by riding up and down the ridges in the higher latitudes of the polar regions. This is called high latitude blocking!

Here are the rough and general locations pf high latitude Oscillations where one or more of these general locations have to have an upper level high pressure syste setup in order to allow troughs of lower pressure and colder air to make it into our latitudes.

Courtesy of Larry Cosgrove

REGION_DESIGNATIONS_FOR_BLOCKING.jpg

The movement of higher pressure out of the AO/NAO positions allows lower pressure to move in and in turn sends the NAO/AO from negative pase to poistive phase

So if you have this -NAO phase

blocking.jpg

And if that HPS is steered out of the NAO position ten lower pressure will begin to move in and the PJ will be allowed to retreat back northward allowing an upper level ridge of higher pressure to move in where there was once an upper level trough of lower pressure

positivenaomap.jpg

It made perfect sense in this post. You are very good at explaining complicated processes! I'm saving this post in my "notes" word document! Thank you for bearing with me and my lack of knowledge. LOL

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It made perfect sense in this post. You are very good at explaining complicated processes! I'm saving this post in my "notes" word document! Thank you for bearing with me and my lack of knowledge. LOL

Glad I could help...and thanks for the nice words. Just ignore the trolls!

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