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Pattern Jammin January 2023

Hmmm, overall we have definitely become colder on the modeling post Jan 25, but I wish another model was in agreement with the CMC Ens. The GEFS and EPS show more of a cold shot then a fairly quick move to -PNA / SE Ridge. Hopefully, we can continue to trend better going forward and sneak something in the colder window here

Here are comparison loops of GEFS / EPS / CMCE, first on Jan 29, then on Feb 2

5OqoB5Q.gif


Weq7L9w.gif
 
griteater said:
Hmmm, overall we have definitely become colder on the modeling post Jan 25, but I wish another model was in agreement with the CMC Ens. The GEFS and EPS show more of a cold shot then a fairly quick move to -PNA / SE Ridge. Hopefully, we can continue to trend better going forward and sneak something in the colder window here

Here are comparison loops of GEFS / EPS / CMCE, first on Jan 29, then on Feb 2

5OqoB5Q.gif


Weq7L9w.gif
Click to expand...

Has there ever been a time when the CMC ensembles have led the way on a pattern change? Honestly, because I tend to ignore them.

Is there any forcing or background reasons to believe the strong Atlantic troughing on the CMC?
 
I’d personally give the GEPS -NAO scenario about a 25% chance or so of verifying.

Still seems somewhat unlikely to me, but there are a few things in its corner right now.

-The overall trend on NWP lately (remember we didn’t have much of an -NAO in the forecast a couple days ago & the GEPS was one of the first to jump on it for next week, while the GEFS has seemed late to the party.)

-The AAMa dip we saw this past week makes it easier for the ridge to retrograde over the top from the Urals, because planetary vorticity advection is more able to overcome background westerly advection by the jet stream itself.

-Being in a La Niña helps us in a big way to maintain this -NAO here, because through wave interference and more disjointed Pacific + Atlantic jet streams, La Niña actually mutes the canonical Indian Ocean >> +NAO teleconnection that models like the GEFS are showing (perhaps erroneously at that in this particular case)

See: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL084683


In fact, I think each model’s depiction of the MJO and how they believe it teleconnects downstream have a lot to do with their disagreement with the -NAO in the extended. The GEFS suite may just have a harder time than other models handling the fact that this teleconnection is actually muted in La Ninas (?). It’s the kind of question I wish I had the computational resources for to investigate using the S2S reforecast database (linked below).

https://iridl.ldeo.columbia.edu/SOURCES/.ECMWF/.S2S/index.html?Set-Language=en

Notice in these MJO forecasts how much stronger the GEFS’s is. Although the EPS and CMET (GEPS) are similar, suggesting that this model teleconnection bias isn’t everything, it might be something

Will be closely watching how this all unfolds the next several days, because imho confidence has overall decreased somewhat for a warm early-mid Feb in the eastern US (although it remains probable-likely still).

BCB3BDD7-FF1B-408C-9034-60E1DBA27536.png

45155736-A08F-4BF2-9A2B-9B7AC96945A8.png

68A297CD-BD73-45C8-B446-1DD3478EF2F9.png
 
SnowNiner said:
Has there ever been a time when the CMC ensembles have led the way on a pattern change? Honestly, because I tend to ignore them.

Is there any forcing or background reasons to believe the strong Atlantic troughing on the CMC?
Click to expand...
Well, the CPC most certainly incorporates it into their extended forecast. They throw the GFS into the mix out of patriotic pity at 25% of the blend.

The official 6-10 day 500-hPa height blend consists of 25% of Today's 0z GFS
Ensemble Mean centered on Day 8, 40% of Today's 0z European Ensemble Mean
centered on Day 8, and 35% of Today's 0z Canadian Ensemble Mean centered on Day 8

Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussions

The CPC issues the official U.S. 6 to 10 and 8 to 14 day outlooks. These outlooks illustrate the probabilities of having above, normal, and below normal temperature and precipitation for the 6 to 10 day period, respectively. The outlooks also include forecast 500 millibar heights for the 6 to...
www.cpc.ncep.noaa.gov
 
SnowNiner said:
Has there ever been a time when the CMC ensembles have led the way on a pattern change? Honestly, because I tend to ignore them.

Is there any forcing or background reasons to believe the strong Atlantic troughing on the CMC?
Click to expand...
I would say it lead the way with the overall December pattern… at the very least it was in step with EPS
 
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GFS represents what we're looking for really, with the wider, more bowl shaped trough, then look for the long-fetch of SW flow aloft into the 'cold' dome. A little less amplitude and a little less phasing of the trailing wave would get more folks involved, with a more west to east sliding system. Anyway, the bowl shaped trough look is a good starting point.
 
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