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Pattern Dazzling December

76F with a 62F dew here as the sun sets. It’s the time of year that tricks people into thinking Miami is a great place to live ?
 
8de293b4f3102459a22af9b90a753100.gif

Meh


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This is not good. The ensembles are not on our side anymore.
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Myfrotho704_ said:
Not ideal View attachment 124701
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I've moved on from the first 2 weeks of December, it's clearly going to be seasonal to perhaps a bit warm through the 15th. Western trough wins for the foreseeable future. My focus is on what can we get to happen the week of the 19th leading up to the holiday. If we can get the EPS to set up I think we'll be in business. Huge if though.

1670111827010.png
 
Loganelliott99 said:
This is not good. The ensembles are not on our side anymore.
101db6f4223c555e3a78f09d1aa19f8f.jpg



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Click to expand...
What are you talking about? The euro was fine.

I understand you seemingly have been personally offended the last few weeks but damn, that is patently untrue.
 
CaryWx said:
Come on RC, that's Dec 8th!
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I know man. That's my point. It's December 3rd. The models are awful. There's way too much worrying for December 3rd. This is middle of January level worrying, and we're barely 2 toes down in December.
 
Hope yall don't mind, but I wanted to step away from the models for a moment and go thru some thoughts on where we are and where we are headed with tropical forcing.

First off, here is OLR averaged over the last 3 months. This is the ENSO signal (also referred to as the low frequency signal) whereby convection has been anomalously high (-OLR) in the Maritime Continent / Indonesia and anomalously low (+OLR) near and just to the west of the dateline. This is a classic La Nina profile. A mature El Nino would have the exact opposite profile of -OLR near the dateline and +OLR in Indonesia.

KRgECfV.gif



Now, superimposed on top of the low frequency ENSO signal is the MJO which travels west to east in the tropics (also referred to as the high frequency signal). One way to track the MJO is by viewing the anomalous Velocity Potential signal (also referred to as CHI200 on this chart below). Velocity Potential / CHI200 is simply an indication of anomalous divergence (-VP / -CHI) or convergence (+VP / +CHI) at the upper levels of the atmosphere (200mb). If there is anomalous divergence in the upper levels of the atmosphere, that is a convection enhancer (upper level divergence fosters rising motion and convection / thunderstorms in the tropics)....and anomalous convergence in the upper levels fosters sinking motion (anomalously low amounts of convection).

We can see on this chart below that the MJO signal for enhanced convection in the tropics for Dec1-2 extends from South America thru the Atlantic Ocean, and thru Africa.

9mTBHZm.png



Both the GEFS and EPS move this -VP signal east and maximize it in the Indian Ocean here on Dec 7th

YgdVTfw.png

cQ4gyRu.png



The MJO doesn't have full control of weather patterns of course, but on average, when the convective signal is maxed out in the Indian Ocean in early Dec (-VP in blue in Indian Ocean on image below), this favors a -PNA / +NAO pattern as seen here (of course, we have other processes ongoing that favor a -NAO developing).

zYc53p3.png



The question then becomes, how fast will the convective signal move east to where it is maximized in Indonesia, then the West Pacific, then finally in South America (during La Nina, the convective signal is weak across the central and eastern Pacific, and it will later ignite convection in S America as the signal moves east). As E Webb pointed out, there has been some level of delay shown on the modeling with the propagation of the MJO east out of the Indian Ocean, but based on the repeating MJO cycle we've seen this fall, we should expect to see the signal eventually move east. Once this occurs, the MJO will enhance the background La Nina convective signal (referred to as constructive interference). That constructive interference should have the capability to impart more of an impact to the atmospheric pattern over N America.

On the GEFS (EPS is similar), we can see the convective signal in the eastern Maritime Continent and W Pacific on Dec 16, with the signal shown also extended to S America on Dec 18

pteJhMk.png

Xgcd4xP.png



Here is the average pattern map for mid-Dec when the convective signal is in the Maritime Continent and W Pacific....-EPO / -NAO

zB56mxf.png



And here are the average pattern maps for late-Dec when the convective signal has move east to S America....-EPO / -NAO to -EPO / +PNA / -NAO

pcV2o0f.png

bbzKiU7.png



Anthony M highlighted his thoughts on this progression here:

mypC8Ki.png

jOiIuaM.png



Bottom line: if we can get the MJO convective signal to move out of the Indian Ocean and then constructively interfere with (combine with) the background La Nina convective signal, then move east out of the Maritime Continent, this would favor better prospects for ridging moving closer to the west coast, not to mention a continued signal for a -NAO. The fly in the ointment to watch would be if the -VP MJO signal stalls and somehow just collapses in the Indian Ocean....that would favor a problematic continuation of a heavy -PNA regime. So far this fall, we haven't seen this type of stall in the Indian Ocean....we've actually seen more of the opposite where the convective signal is largely bypassing that region due to a bit cooler waters there this year associated with the -IOD...but we'll have to see how this turns out this round.

Lastly, I wanted to post the most recent Mtn Torque chart which shows a sharp recovery in the previous very low numbers. You can see on the chart how the E Asia Mtn Torque numbers (red line) were lower in Sep, higher in Oct, and lower in Nov. I suspect / hope that the number will rebound higher in Dec. Higher E Asian Mtn Torque helps to extend the Pacific Jet which is needed during La Nina to get the ridging closer to the west coast.

bIVkwPw.png



If you've made it this far, you deserve some type of reward or compensation. May tonight's model runs be good ones!
 
Last edited:
griteater said:
Hope yall don't mind, but I wanted to step away from the models for a moment and go thru some thoughts on where we are and where we are headed with tropical forcing.

First off, here is OLR averaged over the last 3 months. This is the ENSO signal (also referred to as the low frequency signal) whereby convection has been anomalously high (-OLR) in the Maritime Continent / Indonesia and anomalously low (+OLR) near and just to the west of the dateline. This is a classic La Nina profile. A mature El Nino would have the exact opposite profile of -OLR near the dateline and +OLR in Indonesia.

KRgECfV.gif



Now, superimposed on top of the low frequency ENSO signal is the MJO which travels west to east in the tropics (also referred to as the high frequency signal). One way to track the MJO is by viewing the anomalous Velocity Potential signal (also referred to as CHI200 on this chart below). Velocity Potential / CHI200 is simply an indication of anomalous divergence (-VP / -CHI) or convergence (+VP / +CHI) at the upper levels of the atmosphere (200mb). If there is anomalous divergence in the upper levels of the atmosphere, that is a convection enhancer (upper level divergence fosters rising motion and convection / thunderstorms in the tropics)....and anomalous convergence in the upper levels fosters sinking motion (anomalously low amounts of convection).

We can see on this chart below that the MJO signal for enhanced convection in the tropics for Dec1-2 extends from South America thru the Atlantic Ocean, and thru Africa.

9mTBHZm.png



Both the GEFS and EPS move this -VP signal east and maximize it in the Indian Ocean here on Dec 7th

YgdVTfw.png

cQ4gyRu.png



The MJO doesn't have full control of weather patterns of course, but on average, when the convective signal is maxed out in the Indian Ocean in early Dec (-VP in blue in Indian Ocean on image below), this favors a -PNA / +NAO pattern as seen here (of course, we have other processes ongoing that favor a -NAO developing).

zYc53p3.png



The question then becomes, how fast will the convective signal move east to where it is maximized in Indonesia, then the West Pacific, then finally in South America (during La Nina, the convective signal is weak across the central and eastern Pacific, and it will later ignite convection in S America as the signal moves east). As E Webb pointed out, there has been some level of delay shown on the modeling with the propagation of the MJO east out of the Indian Ocean, but based on the repeating MJO cycle we've seen this fall, we should expect to see the signal eventually move east. Once this occurs, the MJO will enhance the background La Nina convective signal (referred to as constructive interference). That constructive interference should have the capability to impart more of an impact to the atmospheric pattern over N America.

On the GEFS (EPS is similar), we can see the convective signal in the eastern Maritime Continent and W Pacific on Dec 16, with the signal shown also extended to S America on Dec 18

pteJhMk.png

Xgcd4xP.png



Here is the average pattern map for mid-Dec when the convective signal is in the Maritime Continent and W Pacific....-EPO / -NAO

zB56mxf.png



And here are the average pattern maps for late-Dec when the convective signal has move east to S America....-EPO / -NAO to -EPO / +PNA / -NAO

pcV2o0f.png

bbzKiU7.png



Anthony M highlighted his thoughts on this progression here:

mypC8Ki.png

jOiIuaM.png



Bottom line: if we can get the MJO convective signal to move out of the Indian Ocean and then constructively interfere with (combine with) the background La Nina convective signal, then move east out of the Maritime Continent, this would favor better prospects for ridging moving closer to the west coast, not to mention a continued signal for a -NAO. The fly in the ointment to watch would be if the -VP MJO signal stalls and somehow just collapses in the Indian Ocean....that would favor a problematic continuation of a heavy -PNA regime. So far this fall, we haven't seen this type of stall in the Indian Ocean....we've actually seen more of the opposite where the convective signal is largely bypassing that region due to a bit cooler waters there this year associated with the -IOD...but we'll have to see how this turns out this round.

Lastly, I wanted to post the most recent Mtn Torque chart which shows a sharp recovery in the previous very low numbers. You can see on the chart how the E Asia Mtn Torque numbers (red line) were lower in Sep, higher in Oct, and lower in Nov. I suspect / hope that the number will rebound higher in Dec. Higher E Asian Mtn Torque helps to extend the Pacific Jet which is needed during La Nina to get the ridging closer to the west coast.

bIVkwPw.png



If you've made it this far, you deserve some type of reward or compensation. May tonight's model runs be good ones!
Click to expand...
Excellent post. However, I'm sure all will be lost once again when the GFS shows orange colors over the eastern US in a few minutes. ?
 
Would be nice to see some consistencies in the model runs. I know we all can only take what’s given but the ebb and flow of the runs is getting old as usual.
 
Rain Cold said:
Excellent post. However, I'm sure all will be lost once again when the GFS shows orange colors over the eastern US in a few minutes. ?
Click to expand...
Like my night couldn’t get any better…..AD2D4235-CC2E-4F55-8883-5F630829B64D.png22129ED4-256F-4EEB-A947-3F72F4ECB02E.png
 
jeremyt said:
Would be nice to see some consistencies in the model runs. I know we all can only take what’s given but the ebb and flow of the runs is getting old as usual.
Click to expand...
That’s the thing this pattern is known to keep models inconsistent until forcing and things are well mapped out which usually doesn’t happen until and under your 180 .. but it’s okay things will work out and once the forcing grit was talking about becomes more well established and we get further into winter where wave lengths get larger the models should get somewhat more trustworthy than they are right now
 
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