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Pattern The Great December Dump

Webberweather53 said:
The curators of this data have basically locked it up except to a few select individuals. I know the individual who makes or provides said graph so I can ask for access if need be & provide an updated version of this.

Luckily, Ventrice has provided a similar graphic (although not the same because it only shows 250mb winds while the AAM graphic like the one above integrates through the entire troposphere). Very strong but equatorward displaced jet stream in the NH will be the name of the game going forward. Seeing -AAM/negative zonal wind (easterly) anomalies (in blue) near 60N is indicative of a pattern that's favorable for polar blocking (-AO/NAO), (obviously there's more that goes into polar blocking than that). Curious to see if we get some +AAM build-up in the tropics later though.

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Do you not have a chart more updated than 12/9?
 
Feel like I'm in 1st grade on this one ... 2 Questions: 1) what's better: a + or - AAM, and 2) any links to some basic primers on the AAM?
 
More food for thought about Jan's prospects after a mild Dec,:

There have been at KATL four MB Jans (all in coldest 1/8) that followed mild Decs: 1884, 1924, 1985, and 2014. So, anything is possible.

Jan of 1985, the 8th coldest Jan/7 colder than normal, followed the 3rd warmest Dec!
Jan of 1940, the coldest Jan on record, followed a near normal Dec.
 
pcbjr said:
Feel like I'm in 1st grade on this one ... 2 Questions: 1) what's better: a + or - AAM, and 2) any links to some basic primers on the AAM?
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I've always understood it as you want a + global aam with the negative values at the pole. If you have the negative values at our latitude that is a sign of strong subtropical ridging and warmth. The last few summers have had big -aam around 30 north and we have responded with big time late season heat ridges

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GaWx said:
More food for thought about Jan's prospects after a mild Dec,:

There have been at KATL four MB Jans (all in coldest 1/8) that followed mild Decs: 1884, 1924, 1985, and 2014. So, anything is possible.

Jan of 1985, the 8th coldest Jan/7 colder than normal, followed the 3rd warmest Dec!
Jan of 1940, the coldest Jan on record, followed a near normal Dec.
Click to expand...

January 2014 will never show how truly cold it was based on front timing. Clear and far away the coldest month of my lifetime.
 
pcbjr said:
Feel like I'm in 1st grade on this one ... 2 Questions: 1) what's better: a + or - AAM, and 2) any links to some basic primers on the AAM?
Click to expand...

I'm no expert, whatsoever, as anything I say here is just passing along info from Maxar. What the met there told me today is that a +AAM is better for the SE because it has some correlation to an El Nino type pattern of colder anomalies (and wet) in the S US and warmer anomalies in the N US. So, for the SE, +AAM is better per them. For many months the N US has been colder anomalywise. Look how cold it has been in the N Plains/upper Midwest for example while much warmer in the SE. That's a typical La Nina pattern. SE cold lovers obviously don't want that. We want the cold to concentrate down here, not up north.

But still, AAM is but one of many factors.
 
SD said:
I've always understood it as you want a + global aam with the negative values at the pole. If you have the negative values at our latitude that is a sign of strong subtropical ridging and warmth. The last few summers have had big -aam around 30 north and we have responded with big time late season heat ridges

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Click to expand...
1st day of 1st grade and I learned something ... Thanks!
 
GaWx said:
I'm no expert, whatsoever, as anything I say here is just passing along info from Maxar. What the met there told me today is that a +AAM is better for the SE because it has some correlation to an El Nino type pattern of colder anomalies in the S US along with wet and warmer anomalies in the N US. So, for the SE, +AAM is better per them. For many months the N US has been colder anomalywise. Look how cold it has been in the N Plains/upper Midwest for example while much warmer in the SE. That's a typical La Nina pattern. SE cold lovers obviously don't want that. We want the cold to concentrate down here, not up north.

But still, AAM is but one of many factors.
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Day 1.5 in 1st grade and I can print my name now ... Thanks Larry and Shane!

Now if I can only learn to read ... :eek:
 
GaWx said:
More food for thought about Jan's prospects after a mild Dec,:

There have been at KATL four MB Jans (all in coldest 1/8) that followed mild Decs: 1884, 1924, 1985, and 2014. So, anything is possible.

Jan of 1985, the 8th coldest Jan/7 colder than normal, followed the 3rd warmest Dec!
Jan of 1940, the coldest Jan on record, followed a near normal Dec.
Click to expand...

The big difference those 2 Januarys have on this year was a major sudden stratospheric warming event occurred in both winters during December that obliterated the polar vortex and led to a very prolonged period of -AO/-NAO.

The few available radiosonde observations available during World War 2 strongly suggested a SSWE occurred in every winter from 1939-40 thru 1941-42 during the rare triple El Nino event of the early 1940s & those SSWEs and the resulting cold from them likely changed the entire course of world history because those were some of the coldest winters of the 20th century in eastern Europe, potentially hindering Hitler's invasion of Russia.

Jan 1940 20CRv3 temperature anomalies SSWE.png

Stratospheric Warming Event Surface Temperature Composite SSW Compendium.png

This is a SSWE surface temperature composite via figure 4b from Butler et al (2016), the stippled areas (including right over the SE US) represent "significant" temperature anomalies attributable to SSWEs.

https://www.earth-syst-sci-data.net/9/63/2017/essd-9-63-2017.pdf

if you're a history buff &/or would like to learn more about these stratospheric warming events & the "triple" El Nino that contributed to them and how these forms of climate variability potentially impacted the outcome of World War 2, this paper is a good read!

https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1256/wea.248.04


Screen Shot 2019-12-19 at 6.00.44 PM.png

Screen Shot 2019-12-19 at 6.00.54 PM.png
 
Webberweather53 said:
The big difference those 2 Januarys have on this year was a major sudden stratospheric warming event occurred in both winters during December that obliterated the polar vortex and led to a very prolonged period of -AO/-NAO.

The few available radiosonde observations available during World War 2 strongly suggested a SSWE occurred in every winter from 1939-40 thru 1941-42 during the rare triple El Nino event of the early 1940s & those SSWEs and the resulting cold from them likely changed the entire course of world history because those were some of the coldest winters of the 20th century in eastern Europe, potentially hindering Hitler's invasion of Russia.

View attachment 28591

View attachment 28592

This is a SSWE surface temperature composite via figure 4b from Butler et al (2016), the stippled areas (including right over the SE US) represent "significant" temperature anomalies attributable to SSWEs.

https://www.earth-syst-sci-data.net/9/63/2017/essd-9-63-2017.pdf

if you're a history buff &/or would like to learn more about these stratospheric warming events & the "triple" El Nino that contributed to them and how these forms of climate variability potentially impacted the outcome of World War 2, this paper is a good read!

https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1256/wea.248.04


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I pray and hope we can get a SSW event that materializes especially if the QBO can reverse easterly before winter is over.
 
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pcbjr said:
1st day of 1st grade and I learned something ... Thanks!
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Yeah it's one of those things where broadbrushing can give you a general answer but the specifics of it can make a difference since there is a latitudnal component to it. Now if you want to get really fun you can go down the rabbit hole of the gwo. Personally I love the gwo but I haven't been able to find any updated information on it

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SD said:
Yeah it's one of those things where broadbrushing can give you a general answer but the specifics of it can make a difference since there is a latitudnal component to it. Now if you want to get really fun you can go down the rabbit hole of the gwo. Personally I love the gwo but I haven't been able to find any updated information on it

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With you ... broad-brushing anything is silly ... but you gotta learn the lingo and basics before tearing the engine down to figure out what the ping is ... as for rabbits ... they're a hard, tiresome chase and even harder to catch ... but ... if you want rabbit stew, you'd better get to chasin' ...
 
Webberweather53 said:
Here's a few places to start w/ AAM, GWO, Mountain Torque, etc:

https://www.netweather.tv/forum/topic/90558-the-fundamentals-of-atmospheric-angular-momentum/

https://www.weather.gov/media/grr/GLOM2015/Presentations/Marino_GWOSevereStorms.pdf
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Here are some basic definitions you can pull from the first link, I've added some of my own discussion in this first half of this post.

The global wind oscillation (GWO) took me a while to wrap my head around but the GWO at its core just atmospheric angular momentum & the tendency of atmospheric angular momentum, or the rate of change over time thus:

Global Wind Oscillation (GWO) = Atmospheric Angular Momentum (AAM) + Change in Atmospheric Angular Momentum per unit time (t).

The GWO thus encompasses phenomena like Convectively Coupled Kelvin Waves, the MJO, mountain & frictional torques, & even the El Nino Southern Oscillation to some extent. Why? Because all of these significantly impact AAM on timescales of several days to several weeks which is what we're mainly concerned about from a subseasonal standpoint.

Mountain & frictional torques operate on timescales of roughly several days to 2-3 weeks or so and are closely tied to variability in the extratropical storm track. A Rossby Wave (or mid-latitude cyclone or anticyclone) passing over major topographic features like the Rockies or Himalayas is what actually causes mountain torques. The resulting patterns from these mountain torques create Atmospheric Angular Momentum (AAM) anomalies and frictional torques then act to damp or weaken these anomalies.

This post goes very in depth on Atmospheric Angular Momentum & does a better job explaining than I personally would be able to:
https://www.netweather.tv/forum/top...ular-momentum/?do=findComment&comment=3907466

Angular momentum at its most basic level is a combination of the mass or weight of an object, how fast that object is rotating & the distance from its rotational axis.

I.e. Angular momentum = Mass + Rotational Speed + Distance (from axis of rotation).

Once you also consider that the earth system is relatively closed and therefore the total momentum of the earth system is just the summation of the solid earth angular momentum plus atmospheric angular momentum and must always be conserved

Total momentum = AAM + Momentum of Solid Earth

Change in momentum (M) over time (t) w/ change in time represented by "dt"

i.e. (M/dt) >>> AAM/dt + Earth Momentum/dt = 0

Hence, variations in one of these dictate the other. If AAM rises, as is often the case during El Nino events or West Pacific & Western Hemisphere MJO events or as we are going to see over the coming weeks, the earth's solid rotation will slow down in response (actually causes very minute changes to our length of day!) and frictional torques will act to try and weaken these AAM anomalies!

Torque: " "A turning force" that increases the angular momentum of the atmosphere creating a positive torque, one that decreases the angular momentum of the earth is a negative torque."

Mountain torque: "Mountain Torque is a function of pressure and orography and is the ‘turning force’ exerted due to a difference in pressure across any raised surface on the earth, but most significantly, mountains or mountain massifs. Consider a mountain with a high pressure on the west side of a mountain and low pressure on the east. The pressure system will exert an eastward torque that causes the earth to increase it’s rate of rotation, imparting angular momentum from the atmosphere to the solid earth. The opposite case, where there is higher pressure on the east side of the mountain, will slow the earth’s rotation down, reducing the solid earth’s angular momentum, and imparting it to the atmosphere. "

Frictional torque: "The friction torque is the torque that is exerted on the earth’s surface due to the frictional force that occurs because of the wind directly above the Earth’s surface moving relative to the solid earth. If there is an net global westerly surface wind (i.e. a surface wind from the west) the atmosphere will speed the earth’s rotation up, transfer angular momentum to the earth, and thus the atmosphere loses angular momentum. Analogously, if there is a net easterly surface wind (i.e. a surface wind from the east), the atmosphere slows down the rotation of the earth and angular momentum is transferred from the earth to the atmosphere"


Hope this post helps everyone.
 
Webberweather53 said:
Here are some basic definitions you can pull from the first link, I've added some of my own discussion in this first half of this post.

The global wind oscillation (GWO) took me a while to wrap my head around but the GWO at its core just atmospheric angular momentum & the tendency of atmospheric angular momentum, or the rate of change over time thus:

Global Wind Oscillation (GWO) = Atmospheric Angular Momentum (AAM) + Change in Atmospheric Angular Momentum per unit time (t).

The GWO thus encompasses phenomena like Convectively Coupled Kelvin Waves, the MJO, mountain & frictional torques, & even the El Nino Southern Oscillation to some extent. Why? Because all of these significantly impact AAM on timescales of several days to several weeks which is what we're mainly concerned about from a subseasonal standpoint.

Mountain & frictional torques operate on timescales of roughly several days to 2-3 weeks or so and are closely tied to variability in the extratropical storm track. A Rossby Wave (or mid-latitude cyclone or anticyclone) passing over major topographic features like the Rockies or Himalayas is what actually causes mountain torques. The resulting patterns from these mountain torques create Atmospheric Angular Momentum (AAM) anomalies and frictional torques then act to damp or weaken these anomalies.

This post goes very in depth on Atmospheric Angular Momentum & does a better job explaining than I personally would be able to:
https://www.netweather.tv/forum/top...ular-momentum/?do=findComment&comment=3907466

Angular momentum at its most basic level is a combination of the mass or weight of an object, how fast that object is rotating & the distance from its rotational axis.

I.e. Angular momentum = Mass + Rotational Speed + Distance (from axis of rotation).

Once you also consider that the earth system is relatively closed and therefore the total momentum of the earth system is just the summation of the solid earth angular momentum plus atmospheric angular momentum and must always be conserved

Total momentum = AAM + Momentum of Solid Earth

Change in momentum (M) over time (t) w/ change in time represented by "dt"

i.e. (M/dt) >>> AAM/dt + Earth Momentum/dt = 0

Hence, variations in one of these dictate the other. If AAM rises, as is often the case during El Nino events or West Pacific & Western Hemisphere MJO events or as we are going to see over the coming weeks, the earth's solid rotation will slow down in response (actually causes very minute changes to our length of day!) and frictional torques will act to try and weaken these AAM anomalies!

Torque: " "A turning force" that increases the angular momentum of the atmosphere creating a positive torque, one that decreases the angular momentum of the earth is a negative torque."

Mountain torque: "Mountain Torque is a function of pressure and orography and is the ‘turning force’ exerted due to a difference in pressure across any raised surface on the earth, but most significantly, mountains or mountain massifs. Consider a mountain with a high pressure on the west side of a mountain and low pressure on the east. The pressure system will exert an eastward torque that causes the earth to increase it’s rate of rotation, imparting angular momentum from the atmosphere to the solid earth. The opposite case, where there is higher pressure on the east side of the mountain, will slow the earth’s rotation down, reducing the solid earth’s angular momentum, and imparting it to the atmosphere. "

Frictional torque: "The friction torque is the torque that is exerted on the earth’s surface due to the frictional force that occurs because of the wind directly above the Earth’s surface moving relative to the solid earth. If there is an net global westerly surface wind (i.e. a surface wind from the west) the atmosphere will speed the earth’s rotation up, transfer angular momentum to the earth, and thus the atmosphere loses angular momentum. Analogously, if there is a net easterly surface wind (i.e. a surface wind from the east), the atmosphere slows down the rotation of the earth and angular momentum is transferred from the earth to the atmosphere"


Hope this post helps everyone.
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Is there a place to get a current phase diagram for the gwo

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SD said:
Is there a place to get a current phase diagram for the gwo

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Unfortunately, none that I am currently aware of. There used to be several places to attain real-time data but they've all either become proprietary or are no longer in service & the researcher at NOAA ESRL who used to provide this data & is among those who discovered the GWO retired several years ago. :(
 
I'm gonna figure out some way to get all of this consolidated and in to Wiki ... as a subtopic in models or winter

Any Mods - can you get all of Webb's AAM info, and the materials Larry and Shane have posted, into a new (maybe duplicate) thread called "AAM" - that would be the easiest way to load it all in to Wiki without taking it out of this one altogether? If so, please PM me when it's done, and then folks can add to the specific topic and Wiki will self-update.

Credits and kudos to Webb for providing so much info - do not want it lost in the middle of this thread!
 
It sure seems like SST’s are driving our current streak of AN Dec’s. Warm phase seems to be reigning compared to say the 80’s. GW? Cycle? I know I don’t know.

0AACF075-61EE-4F8B-9FE8-C3E1559378D4.png60DECDE9-8287-41E8-BF0F-FE5A7C8C6609.png
 
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