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Learning Atmospheric Pattern Discussion / Explanations

GaWx

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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.
 

Webberweather53

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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.
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

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Webberweather53

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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/topic/90558-the-fundamentals-of-atmospheric-angular-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.
 

Ollie Williams

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QBO chart explanation
This graphic is called a Radiosonde sounding
Think of it like a Skew-T but a measure of the winds in the Tropical stratosphere
Note: The stratosphere runs from 100-10mb, which are the numbers on the Y-axis.

The tropical stratosphere is the stratosphere located near the equator in comparison to the polar stratosphere we typically refer to in the winter.

The Radiosondes are very similar to weather balloons, they are launched in the Canton Islands, Maldive Islands, and Singapore as where this graphic came from

Typically the QBO is measured between 10-40mb
The X-axis is the wind direction
The East phase is on the left side, the West phase is on the Right side.

Interpretation: The East QBO is slowly propagating southward. It is strongly east between 10-20mb, but over the next few months that should cover 30mb and 40mb over the next few months.
qbo_phase_plot.png
 

Six Mile Wx

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A group of researchers from the Potsdam Institute for Climate Impact Research, Beijing Normal University and Justus-Liebig-Universität Giessen has found a way to predict El Niño events up to a year before they occur. In their paper published in the Proceedings of the National Academy of Sciences, the group describes their complexity-based approach to better predicting the seemingly random weather events.
https://m.phys.org/news/2019-12-el-nio-event-year.html
 

Jon

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This might be a ridiculous question, but knowing how models can flip from one run to the next, how often do these MJO models flip? I'm hoping like most the MJO continues to move into more favorable phases for the Southeast.
The MJO phase diagram is based on modeling so technically they can flip and change around by going in a different direction, but at high amplitude are more predictable and less likely to flip because the MJO is a measure of tropical rainfall and circulation, and as it moved eastward, enters different “phases”. Because we are confident we have a strong MJO, it’s less likely to all of a sudden turn around and go back to Phase 4 or 5, because since it’s moving East, it has to go counter clockwise on the phase diagram.


By just following precipitation accumulation on this composite, you can see how it moves from left to right (west to east) and the corresponding phases.


There’s other ways to look at the MJO, through 200VP maps and OLR maps, but they’re all measuring the same propagation of the wave...so I find it’s easier for people to look at precipitation diagrams or OLR (outgoing long wave radiation) which measures thunderstorm activity as a way of “tracking” the MJO. The blue colors in the following diagrams is lower OLR (strong thunderstorms have high cooler/cold cloud tops, which registers as low on this chart) as you can see the blue lines up with the precip maps above.


It’s much easier for the MJO diagram to loop around and change direction when there’s not a prominent wave and some other waves are impacting the phase diagrams, such as the tropical storms north of Australia we saw, spiking us into Phase 4.

I know very little about the MJO and still trying to learn but I hope this helps.


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metwannabe

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The MJO phase diagram is based on modeling so technically they can flip and change around by going in a different direction, but at high amplitude are more predictable and less likely to flip because the MJO is a measure of tropical rainfall and circulation, and as it moved eastward, enters different “phases”. Because we are confident we have a strong MJO, it’s less likely to all of a sudden turn around and go back to Phase 4 or 5, because since it’s moving East, it has to go counter clockwise on the phase diagram.


By just following precipitation accumulation on this composite, you can see how it moves from left to right (west to east) and the corresponding phases.


There’s other ways to look at the MJO, through 200VP maps and OLR maps, but they’re all measuring the same propagation of the wave...so I find it’s easier for people to look at precipitation diagrams or OLR (outgoing long wave radiation) which measures thunderstorm activity as a way of “tracking” the MJO. The blue colors in the following diagrams is lower OLR (strong thunderstorms have high cooler/cold cloud tops, which registers as low on this chart) as you can see the blue lines up with the precip maps above.


It’s much easier for the MJO diagram to loop around and change direction when there’s not a prominent wave and some other waves are impacting the phase diagrams, such as the tropical storms north of Australia we saw, spiking us into Phase 4.

I know very little about the MJO and still trying to learn but I hope this helps.


Sent from my iPhone using Tapatalk
Posted in here for future reference...
 

Ollie Williams

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I came across a thread on 33andRain to about every research paper out there.
 
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