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Pattern The Great December Dump

Webberweather53 said:
While the RMM index shows the MJO entering the west Pacific in early January, it's not that simple:

What we're really about to see are multiple fast moving convectively coupled kelvin waves projecting onto & interfering with low frequency variability associated w/ the +IOD & ENSO. This also means the downstream pattern over North America will differ considerably from the expected response during West Pacific MJO events.

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January is the month for us
 
tennessee storm said:
Yea time start the jamming January thread up... this month is toast ...
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I think a January thread should be created as well. I'm not expecting any severe cold or winter storms for the remaining days of this month. I don't think the January thread should be titled "Jammin January" though because we already had a January thread that was titled that. Perhaps it could be titled Jackpot January?

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WxWatch said:
I think a January thread should be created as well. I'm not expecting any severe cold or winter storms for the remaining days of this month. I don't think the January thread should be titled "Jammin January" though because we already had a January thread that was titled that. Perhaps it could be titled Jackpot January?

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It's a little early. I'd say we wait until Christmas for making next month. It'll be nothing but speculation until we get into actual model range.
 
The 06z GFS suppressed our New Year storm. I think it's still possible that there could be a winter storm come the New Year. Watching that baroclinic zone on the tail end of the boundry from the late month cutting system. This is still a good ways out, so expect many changes. Models should have a better idea on this by mid to late week next week as the time period closes in on the 5-7 day window.
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HM suggesting a snowy January in his neck of the woods. Not sure what that’ll mean for us.


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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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And here I was thinking I was smart for graduating after taking advanced physics for aircraft accident analysis along with analytical geometry and trigonometry. My brain is now fried.

Dude, you’re smarter than me that’s for sure. Thanks for that info. I learned quite a bit.
 
Latest CFS 500mb pattern for January 2020 from Judah Cohen this morning. This is something we can work with if correct
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@Webberweather53, Mike Ventrice mentioned a possible SSW toward mid January. I guess its starting now based on what he said from the eps. Do you think we can achieve one? Be interesting to see how the qbo plays out.
 
If you want to see something infuriating take a look at the 06z GFS and how that big low at the pole weakens slightly then recirculates even beastlier than before. A +AO like that would be a booger to get rid of
 
Jimmy Hypocracy said:
If you want to see something infuriating take a look at the 06z GFS and how that big low at the pole weakens slightly then recirculates even beastlier than before. A +AO like that would be a booger to get rid of
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Nothing the FV3 shows past 120hrs can infuriate me.
 
ForsythSnow said:
I'll believe it if it gets to January 1st and looks reasonable. Not now of course. Everyone did the whole "But next month" routine last year and it was nothing but false promises and torch. I'm starting to think winter will bust again.
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The good news is that it is still fall, so we have all of winter ahead of us. Too early to give up.
 
Jimmy Hypocracy said:
It has some GEFS support ? but agreed on this LR stuff being a shamView attachment 28635
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I'd think we can work with that and what the EPS has. Not an Arctic invasion by any means. But I'm not a fan of that anyway. Vodka cold is more often than not a shutout pattern just like an SER dominated pattern.
 
Snowless & Grumpy said:
I'd think we can work with that and what the EPS has. Not an Arctic invasion by any means. But I'm not a fan of that anyway. Vodka cold is more often than not a shutout pattern just like an SER dominated pattern.
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Yeap just need upper 20s for some nice powder.


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Today's 12z GFS is back on the idea of a cold start to 2020. Totally different from yesterday's 12z run.
 
@Webberweather53, the IOD atmospheric coupling is hindering the mjo activity or progression. Do you know how long that may last? I would like to see the mjo start to move out of the COD. Just curious on your thoughts on that.
 
Mr. Golf said:
@Webberweather53, the IOD atmospheric coupling is hindering the mjo activity or progression. Do you know how long that may last? I would like to see the mjo start to move out of the COD. Just curious on your thoughts on that.
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When looking at averages for January for the SE US over 40 or so year period ending 2014, the COD had actually not been a bad place to be in January if one likes cold. Actually, inside or just outside the COD averaged colder in Jan at Atlanta and nearby areas during 1975-2014 vs outside for all phases. Of course, these are just averages and don't mean anywhere near all cases are that way. Also, with GW, I wonder if this relationship still holds as warmth has been so dominant. Also, the MJO is but one of many factors. Furthermore, I'm not sure about Arkansas though I suspect it would be somewhat similar.
 
GaWx said:
When looking at averages for January for the SE US over 40 or so year period ending 2014, the COD had actually not been a bad place to be in January if one likes cold. Actually, inside or just outside the COD averaged colder in Jan at Atlanta and nearby areas during 1975-2014 vs outside for all phases. Of course, these are just averages and don't mean anywhere near all cases are that way. Also, with GW, I wonder if this relationship still holds as warmth has been so dominant. Also, the MJO is but one of many factors. Furthermore, I'm not sure about Arkansas though I suspect it would be somewhat similar.
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Larry, what I've been saying still has merit. I don't want us to be chasing unicorns all winter this winter.
 
Webberweather53 said:
The GEFS is finally settling in w/ the EPO in the longer-term (no longer becoming anywhere near as positive). North Atlantic blocking is finally beginning to show up more frequently in recent GEFS runs which often happens when legit tropical forcing enters the West Pacific.

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looks like a bowling ball ULL pattern that slides under the Canada ridge
 
Verbatim, this wave over TX would probably be capable of producing wintry weather around New Years if this Euro run went out more than 10 days. Obviously, it's futile to speculate so far out but the point that's trying to be made here is that this is very far from being a blowtorch.

Certainly would wager that this week's cut-off ULL may be far from the last one we see this winter esp if the STJ continues to remain active & we have blocking over eastern Canada. Also notice, the main lobe of tropospheric polar vortex is still lurking around in our backyard just north of Greenland.

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