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Mid to Long Term Discussion 2017

buckeyefan1

By buckeyefan1,
in Southeastern States

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FallsLake

FallsLake

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Posted

So dealing with the indices, what is the optimal look?

* I know a negative AO helps with cross polar flow.

* The NAO helps block the NE (~ Greenland) forcing cold air to buckle in eastern NA.

* The PNA blocks the pacific air, forcing air to come southward out of Canada.

But what are the best values? Do we want very negative NAO & AO values and a very positive PNA value? Would the extremes just cause dry and cold, etc.... 

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Cold Rain

Cold Rain

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7 minutes ago, FallsLake said:

So dealing with the indices, what is the optimal look?

* I know a negative AO helps with cross polar flow.

* The NAO helps block the NE (~ Greenland) forcing cold air to buckle in eastern NA.

* The PNA blocks the pacific air, forcing air to come southward out of Canada.

But what are the best values? Do we want very negative NAO & AO values and a very positive PNA value? Would the extremes just cause dry and cold, etc.... 

It's difficult to place a numerical value on it, as the configurations within the domains ultimately dictate how the pattern is influenced and what it produces.  My suspicion is that a strongly -AO/NAO coupled with a strongly +PNA would yield suppressing cold and dry.  However, the PNA ridge placement and it's orientation, for example, could make the difference between cold/dry and cold/wet.  If you have a tall enough PNA ridge, you have at least an opportunity for waves in the jet to travel southeast toward the Gulf, possibly spinning up a storm.  A flatter ridge would dampen out the wave and you may get little in the way of precip.  Having the -AO/NAO allows cold air to be close by.  But does the orientation of those features squash any wave or suppress it too far south?  Or does it allow the wave to travel too far north?  Looking at h500 is more important than the numerical value, IMO, as it will provide clues as to what is possible in any given pattern.

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FallsLake

FallsLake

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1 minute ago, Cold Rain said:

It's difficult to place a numerical value on it, as the configurations within the domains ultimately dictate how the pattern is influenced and what it produces.  My suspicion is that a strongly -AO/NAO coupled with a strongly +PNA would yield suppressing cold and dry.  However, the PNA ridge placement and it's orientation, for example, could make the difference between cold/dry and cold/wet.  If you have a tall enough PNA ridge, you have at least an opportunity for waves in the jet to travel southeast toward the Gulf, possibly spinning up a storm.  A flatter ridge would dampen out the wave and you may get little in the way of precip.  Having the -AO/NAO allows cold air to be close by.  But does the orientation of those features squash any wave or suppress it too far south?  Or does it allow the wave to travel too far north?  Looking at h500 is more important than the numerical value, IMO, as it will provide clues as to what is possible in any given pattern.

Thanks CR. You know the old saying (...from us), lets get the cold air and then worry about the precipitation. ORH just posted to the NE folks, saying the NAO was definitely more important for the MA and SE. So I would say get the value for that as negative as we can.   

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FLweather

FLweather

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26 minutes ago, Cold Rain said:

It's difficult to place a numerical value on it, as the configurations within the domains ultimately dictate how the pattern is influenced and what it produces.  My suspicion is that a strongly -AO/NAO coupled with a strongly +PNA would yield suppressing cold and dry.  However, the PNA ridge placement and it's orientation, for example, could make the difference between cold/dry and cold/wet.  If you have a tall enough PNA ridge, you have at least an opportunity for waves in the jet to travel southeast toward the Gulf, possibly spinning up a storm.  A flatter ridge would dampen out the wave and you may get little in the way of precip.  Having the -AO/NAO allows cold air to be close by.  But does the orientation of those features squash any wave or suppress it too far south?  Or does it allow the wave to travel too far north?  Looking at h500 is more important than the numerical value, IMO, as it will provide clues as to what is possible in any given pattern.

Good post.  More along the lines of Goldy locks and 3 bears.  Too strong of -AO/NAO -PNA the pattern becomes supper suppressed. With all 3 going negative values which we havent seen in some time.  But think 09/10 was unanimously cold for FL.  Haven't looked but what was the nao ao pna  then?

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Cold Rain

Cold Rain

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6 minutes ago, FLweather said:

Good post.  More along the lines of Goldy locks and 3 bears.  Too strong of -AO/NAO -PNA the pattern becomes supper suppressed. With all 3 going negative values which we havent seen in some time.  But think 09/10 was unanimously cold for FL.  Haven't looked but what was the nao ao pna  then?

Wasn't 09/10 the super blocky winter?  Or was it 10/11?  But yeah, one (maybe both) of those winters we had some really good, strong blocking.  And it's pretty much sucked ever since!

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mackerel_sky

mackerel_sky

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9 minutes ago, packbacker said:

Good start to met winter. Atleast Mack stays BN.

gfs_T2ma_us_22.png

Packs at it again! You know it's about to get cold, he's started posting the maps with the most red on them! We all know it's going to be well above normal, til atleast the 10th! ;)

Good try tho! That's probably about Thursday, when a lot of people in the Carolinas will see 70s!!

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griteater

griteater

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57 minutes ago, FallsLake said:

Thanks CR. You know the old saying (...from us), lets get the cold air and then worry about the precipitation. ORH just posted to the NE folks, saying the NAO was definitely more important for the MA and SE. So I would say get the value for that as negative as we can.   

Yeah, the AO and NAO can't be too negative for us in my view.  In the Pacific, I like the mean ridging to be in between the PNA and EPO....so, best to have it in Eastern Alaska and NW Canada

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