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January Medium/Long Range Discussion


WinterWxLuvr
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1 hour ago, brooklynwx99 said:

The GEFS and EPS have a gorgeous pattern evolution towards the end of their runs... this is thanks to the extension of the Pacific jet in the medium-long range:

ecmwf-ensemble-avg-nhemi-uv200_stream-1640347200-1640995200-1641643200-10-1.thumb.gif.c274a883ea137a1baad427691d3b4306.gif

This jet extension is thanks in part to the +EAMT that is forecasted to develop in the short range:ecmwf-ensemble-avg-asia-mslp_anom-1640347200-1640606400-1641124800-10.thumb.gif.1d1038cd908d5a75a3e1f8aa487b409b.gif

So, overall, it looks like there is some forcing that may be able to shake up this pattern. The jet extension will allow for the anomalous Aleutian ridge to build poleward and kick the mean trough out of the Pac NW and into the N Plains. This, in turn will allow for cold air to bleed into the E US.

ecmwf-ensemble-avg-nhemi-z500_anom-1640347200-1640995200-1641643200-10-1.thumb.gif.1489f5fd731047f685fab07dd1bde832.gifgfs-ensemble-all-avg-nhemi-z500_anom-1640347200-1640995200-1641729600-10-1.thumb.gif.15287047bc42a60f14feceadf138f46d.gif

It's nice to see the changes to the Pacific jet, as those kinds of shifts on modeling are usually representative of a large shift in the pattern and not a temporary blip. It's great to see the blocking signal still holding strong as well, as the 50/50 ULL and -NAO remain prominent features throughout the runs. As long as the mean position of the trough changes to anywhere east of where it is now, that would be a massive improvement. The patterns on the end of the runs would be quite cold and stormy with the Pacific becoming much more favorable with the cold dumping into the midsection of the country.

Now, of course, this could be a head fake, but I really don't believe so. The MJO is taking its time propagating through the Pacific, and Phase 7 forcing is more favorable in January anyway, so I don't see it as an issue. The +EAMT is also forecast to begin very soon, and the changes to the jet over the Pacific aren't very far out either. The forcing mechanisms that might help shake things up are in a tangible range.

Overall, I would like to see these changes continue into the weekend. The Jan 2 period is intriguing, as there could be some TPV influence in Canada and some SS wave trying to cut underneath. That's really all you can say at this range. However, it's nice that we're getting some chances.

During the next 15 days, the Pacific should relax enough to pull out support for the SER. Mid and late January is promising.

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CPC is skeptical that any pattern change will be more than transient.   After seasonal temperatures in week 2 (January 1-8), their 3-4 week outlook for January 8-21 (see link and below) suggests that the southeast ridge will be a bit muted in week 3 before strengthening once again in week 4.  

No reason for too much concern as they only give us a 55% chance of above normal (1990-2020) temperatures, which may be closer to a coin flip with respect to a mean centered on this year.  

 

https://www.cpc.ncep.noaa.gov/products/predictions/WK34/

"A manual blend of dynamical and statistical model guidance favors a continuation of the negative PNA and negative NAO patterns, showing up as a pair of ridges south of the Aleutians and over Greenland, and troughs over the West and the North Atlantic. A persistent ridge also remains over the Southeast, which is consistent with La Nina conditions. While the statistical guidance depicts more troughing and cold air intrusion into the eastern US, these tools are based on a more progressive and canonical MJO evolution than what is currently observed." 
 

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1 hour ago, dallen7908 said:

CPC is skeptical that any pattern change will be more than transient.   After seasonal temperatures in week 2 (January 1-8), their 3-4 week outlook for January 8-21 (see link and below) suggests that the southeast ridge will be a bit muted in week 3 before strengthening once again in week 4.  

No reason for too much concern as they only give us a 55% chance of above normal (1990-2020) temperatures, which may be closer to a coin flip with respect to a mean centered on this year.  

 

https://www.cpc.ncep.noaa.gov/products/predictions/WK34/

"A manual blend of dynamical and statistical model guidance favors a continuation of the negative PNA and negative NAO patterns, showing up as a pair of ridges south of the Aleutians and over Greenland, and troughs over the West and the North Atlantic. A persistent ridge also remains over the Southeast, which is consistent with La Nina conditions. While the statistical guidance depicts more troughing and cold air intrusion into the eastern US, these tools are based on a more progressive and canonical MJO evolution than what is currently observed." 
 

When did they do that outlook ? Before todays guidance and subsequent huge changes ? Could be, they're cautious even if written afterward until the writing begins to show on the wall. So many headfakes it's hard to blame them really, and I'm not a fan of CPC.

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2 hours ago, BristowWx said:

That is solid CAD as depicted.  I didn’t expect that until I looked at 2m temps.  Nice 

3 of the 31 GEFS members give us measurable snow during that period with one of the members giving us 2 1/2".  Let's watch this improve with time (I hope)

25% of the EPS members show a near-zero or slightly positive PNA by late on the 8th! 

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1 minute ago, dallen7908 said:

3 of the 31 GEFS members give us measurable snow during that period with one of the members giving us 2 1/2".  Let's watch this improve with time (I hope)

25% of the EPS members show a near-zero or slightly positive PNA by late on the 8th! 

I was about to say, while I don’t have individual members, the TT 6z GEFS maps don’t seem supportive of the OP.  Most certainly a LP emerging from the SE but the mean HP is over the plains.

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37 minutes ago, dallen7908 said:

3 of the 31 GEFS members give us measurable snow during that period with one of the members giving us 2 1/2".  Let's watch this improve with time (I hope)

25% of the EPS members show a near-zero or slightly positive PNA by late on the 8th! 

Good patterns seem to take way longer than we think to develop and way end quicker than we hope.  But hey it’s Christmas. 

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20 minutes ago, CAPE said:

Outside of being stuck in a really crappy pattern like we have now, you gotta like the odds of seeing some snow during that period, climatologically speaking.

Good to see a few bowling balls in the 500 anoms, even if a bit north of what we'd like to see.  I don't see any petunia killers though.  If anything this warm weather today has given them more strength and boldness.  In a few weeks from now the sun angle will be so high they'll probably bolt and go to seed...

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29 minutes ago, CAPE said:

Outside of being stuck in a really crappy pattern like we have now, you gotta like the odds of seeing some snow during that period, climatologically speaking.

Gefs shows normal to below normal 850s and 2m temps with some waves running the boundary starting around the 3rd or 4th.

Just talking in general at this range but there definitely seems to be a window of opportunity the first half of January. 

Hopefully we get several chances as it usually takes many tries for us to score 1.

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Main thing DC always has to stay away from is never ending 1-2 week push backs.  Once that starts it rarely stopped.  Couple weeks ago looked like 12/27ish might start a change so let’s hope first several days of Jan do because once we start the 1/8, no 1/18 then we are most usually SOL. Feb 2007 an exception but far from the rule 

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