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January 2021 General Discussions & Observations Thread


Stormlover74
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4 minutes ago, bluewave said:

The retrograding block will also have a MJO 3-6 standing wave. We could very well go +EPO/+PNA/-AO/-NAO. So a high water content heavy wet snow for the storms that are cold enough. Maybe a continuation of the tree damage theme as branches could snap under the weight of the snow. 

AC956BCF-0537-41ED-B5B8-1BCC640A56C2.thumb.png.b20c5b2dc80cc5da0684fe80c8abb313.png

 

 

I wonder if the block retrogrades into the epo/pna domain by the start of February in response to the ssw ? 

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On 12/31/2020 at 5:22 AM, wdrag said:

Have noted a few posts noting the blocky and possibly more favorable pattern the 8th-15th. No topic yet. Kind of want to clear the table of 1/1 and 1/3-4. I do see the potential... definitely would like a freshening of a colder boundary layer.  If we can't deliver something decent in this pattern the next several weeks... At least there are some marginal wintry threats. 

the 12Z models will start running soon - what we need for next weekend is what happened for the mid -December snowstorm - MODEL RUN CONSISTENCY ! And most models on board for a majority of NYC metro. If we get 2 or 3 days in a row of this then start the thread IMO.

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58 minutes ago, Allsnow said:

I wonder if the block retrogrades into the epo/pna domain by the start of February in response to the ssw ? 

It’s possible if the SSW can shift the MJO. Phases 6-7 would be more -EPO in February. Plenty of moving parts so we’ll just have to wait and see how things go.

https://iopscience.iop.org/article/10.1088/1748-9326/ab98b5

4. Conclusions

The intraseasonal variability in tropical heating related to the MJO can exert an impact on the stratospheric polar vortex (e.g. Garfinkel et al 2012, 2014). However, there has been little written about the propagation features and intensity of the MJO after SSW event occur. In the present study, it is expected that SSWs can affect the MJO based on the above findings. The dominant occurrence of MJO phases 6 and 7; the simultaneously enhanced convective activity over the equatorial Central and Western Pacific during 1 ~ 24 d after onset of SSW events; and then the coherent eastward propagation of tropical intraseasonal convection in the following days all indicate that the influence of SSWs on tropical intraseasonal convection related to the MJO cannot be ignored. Although the dynamic and physical mechanism(s) are unclear, this SSW–MJO link is consistent with the thermal stratification change in the tropical upper troposphere.

Presumably, the SSW–MJO link is associated with multiple factors. The responses of static stability in the tropical upper troposphere and lower stratosphere (UTLS) to SSW event described above may not be the sole potential mechanism by which SSW affects the MJO. Other mechanisms, such as vertical wind shear (Ho et al 2009), absolute vorticity (Collimore et al 2003), and tropopause changes (Gray et al 1992), can also be adopted to explain the responses of tropical convection to the anomaly in the UTLS region. Thus, to identify the exact mechanism(s), further studies using both observations and numerical model simulations are necessary.

The impacts from SSWs could affect tropical intraseasonal convection related to MJO on time scales exceeding 20 d. More importantly, this work demonstrated the complex relationship between the MJO and SSW. Previous studies have shown a strong impact of the MJO on the NH wintertime stratospheric polar vortex. However, the results of this study allude to the reverse route, i.e. alteration of the tropical intraseasonal convection related to the MJO due to the abrupt change in the extratropical stratosphere. Although the results need to be further confirmed by numerical models that resolve stratospheric processes, this study suggests that SSW is indispensable for the subseasonal-to-seasonal prediction of the evolution of MJO. In this regard, it is also anticipated that the statistical prediction of MJO could be improved by taking variability in the extratropical stratosphere into consideration as a potential predictor especially in boreal winter.

 

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I think we're giving causal power to "the block" that doesn't actually exist. The global-scale atmospheric features are interconnected.  The upper and lower level features are integrally related.  A change in one feature doesn't really force the other... the changes happen in unison. And the jet streams spinning around the globe are like buckling strings. Movement anywhere along the string affects the whole chain.

Models don't "see" a block and then adjust. Models forecast a pattern that we describe as a block simultaneously with depicting synoptic features that are placed in concert with that block. If models forecast a stronger block they will also forecast synoptic features that appear to be responding to that block. But that is not the models responding to something tangible that has the power to force weather changes.  That is our ability to see into the future evolving in time. The apparent causal connection is just an illusion. Just like the notion that a surface high can force the movement of a surface low. Highs and lows are merely dance patterns linked in a complex choreography with all the features of the atmosphere.

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3 hours ago, snowman19 said:

That is a very ugly PAC. EPO floodgates wide open

I mean, the heart of the negative anomalies is centered over the Aleutians rather than, say, Fairbanks.  So it could be worse.  We definitely won't get Vodka-cold air in that pattern but, in mid and late January, it can be a glorious one in terms of snowfall.

Overall, I'll take it!

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3 minutes ago, Eduardo said:

I mean, the heart of the negative anomalies is centered over the Aleutians rather than, say, Fairbanks.  So it could be worse.  We definitely won't get Vodka-cold air in that pattern but, in mid and late January, it can be a glorious one in terms of snowfall.

Overall, I'll take it!

Agree.  I just would like to see some colder air close by though.   We don't want a bunch of BM rainers. 

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7 minutes ago, MJO812 said:

The Para GFS is way different than the GFS. GFS has a huge ridge in the east at 384 while the Para has a big storm gearing up down south.

 

I mean come on

From what I have been reading it seems like the Para is a scoring higher than GFS.

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The current version of the GFS is on track to get retired in February. The  new v16 parallel has been doing much better with storm tracks. It looks like they fixed the cold and suppressed bias.  Let’s hope the NAM replacement can see the WAA aloft as well as the current NAM did back on December 16-17th with the sleet.

 


 

https://vlab.ncep.noaa.gov/web/environmental-modeling-center/fv3-convective-allowing-forecast-system

UNIFIED FORECAST SYSTEM : CONVECTIVE-ALLOWING FORECAST AND DATA ASSIMILATION SYSTEM

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3 hours ago, NEG NAO said:

the 12Z models will start running soon - what we need for next weekend is what happened for the mid -December snowstorm - MODEL RUN CONSISTENCY ! And most models on board for a majority of NYC metro. If we get 2 or 3 days in a row of this then start the thread IMO.

I agree regarding a specific 1/8-9 thread.  Just not convinced yet on the quick check of 12z ops.  Also thinking of a thread:

"Is this boring?: I84 and possible I95 ice/snow threats 1/8-9 and/or 1/11 with marginal thermal profiles prevailing."

Just waiting on this til i get a chance to be more ensemble cognizant of potential, which is not likely to be til Saturday morning. 

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Just now, wdrag said:

I agree regarding a specific 1/8-9 thread.  Just not convinced yet on the quick check of 12z ops.  Also thinking of a thread:

"Is this boring?: I84 and possible I95 ice/snow threats 1/8-9 and/or 1/11 with marginal thermal profiles prevailing."

Just waiting on this til i get a chance to be more ensemble cognizant of potential, which is not likely to be til Saturday morning. 

Walt - IMO and from past experience on this forum its way too early to start a thread for 1/8-9 especially after reviewing the 12Z models so far - No Consistency - and the EURO misses completely at 12Z - on to the ensembles to see what they say...........

prateptype_cat_ecmwf.conus.png

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11 minutes ago, NEG NAO said:

Walt - IMO and from past experience on this forum its way too early to start a thread for 1/8-9 especially after reviewing the 12Z models so far - No Consistency - and the EURO misses completely at 12Z - on to the ensembles to see what they say...........

prateptype_cat_ecmwf.conus.png

Good place for the storm to be at hour 186

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