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Pattern Jammin January 2023

SD said:
2014 evolution

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Getting a more poleward N Pac ridge is critical for this very reason (not just for cold in the short term). Without a poleward NP ridge, the ridge doesn’t retrograde as quickly (or much at all) into Siberia because the Pacific Jet can’t undercut it & allow the ridge to break over the top + get replaced by Aleutian trough underneath to pump the +PNA

The other big, really key difference between this year and 2014 was the appearance of West Pac MJO in mid Feb. That further allowed the Pacific jet to undercut the already poleward-displaced blocking ridge & more easily generate an Aleutian Low.

A Feb 2014-style scenario isn’t totally crazy to me. However….

It really feels like this year is going to be at least a week or so behind that kind of scenario (maybe more?), w/ a more prolonged period of warmth in the front half of the month. :/

The good news is this canonical SE ridge pattern probably won’t last forever in the cold season, because the wavelengths start to collapse later in Feb into Mar (extratropics respond differently to the same forcing at different times of the year). I think we see some sort of legit +EAMT &/or Pacific jet extension around Feb 20 give or take, which eventually eats away at the canonical Feb Nina SE ridge pattern


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Curious to see today’s Euro weeklies. Should give us a good first look at what late Feb might look like and how we get out of this upcoming warm pattern. I also am intrigued how this SSWE or weak vortex event (< 5ms-1 at 60N/10 hPa) will look, because that could impact things from late Feb onward. Just read a paper on this earlier this morning: the ECMWF S2S model also has a strong vortex bias of about 5ms-1 on average, because it can’t properly resolve gravity wave drag in the middle-upper stratosphere.
 
Webberweather53 said:
Getting a more poleward N Pac ridge is critical for this very reason (not just for cold in the short term). Without a poleward NP ridge, the ridge doesn’t retrograde as quickly (or much at all) into Siberia because the Pacific Jet can’t undercut it & allow the ridge to break over the top + get replaced by Aleutian trough underneath to pump the +PNA

The other big, really key difference between this year and 2014 was the appearance of West Pac MJO in mid Feb. That further allowed the Pacific jet to undercut the already poleward-displaced blocking ridge & more easily generate an Aleutian Low.

A Feb 2014-style scenario isn’t totally crazy to me. However….

It really feels like this year is going to be at least a week or so behind that kind of scenario (maybe more?), w/ a more prolonged period of warmth in the front half of the month. :/

The good news is this canonical SE ridge pattern probably won’t last forever in the cold season, because the wavelengths start to collapse later in Feb into Mar (extratropics respond differently to the same forcing at different times of the year). I think we see some sort of legit +EAMT &/or Pacific jet extension around Feb 20 give or take, which eventually eats away at the canonical Feb Nina SE ridge pattern


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Where did you get the 2014 mjo plot I looked for 30 minutes this morning and couldn't find it.
 
NickyBGuarantee said:
This is great for building snow pack up north for more CAD cold air potential
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The snow pack + deep cold air mass are definitely going for any would-be end of Jan CAD potential.

Just need the 50-50 low to look more like the 0z GEFS from last night to have a real chance & get one of these troughs to eject from the Rockies at the right time. Atlantic Canada vortex, east-based -NAO, -PNA, w/ an Aleutian ridge is a classic CAD setup.
North America NCEPR1 z500a NC Miller B Winter Storms (1948-2019).png

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SD said:
I'd personally just like to get out of this wave timing cycle we are in. If it's going to be 70 in January that's fine but give it to me on Friday Saturday Sunday not Tuesday Wednesday Thursday with the weekend being around 50 with NW winds of 100
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It's going to rain this weekend. Cold rain.
 
SD said:
I'd personally just like to get out of this wave timing cycle we are in. If it's going to be 70 in January that's fine but give it to me on Friday Saturday Sunday not Tuesday Wednesday Thursday with the weekend being around 50 with NW winds of 100
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We seem to have a quasi-regular 35 ish day (+/- 5 days) cycle to periods of cold/warm this year (likely MJO related to a large extent).
 
BIG FROSTY said:
12z GFS not even close on the 22 storm even in the mountains or Va. Way to warm. sigh
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I would argue it’s very close. Only difference is the northern piece of energy holds into some strength and takes primary .. GFS likes to do this sometimes but it is another scenario that’s possible. If the southern takes over though it’s close
 
NickyBGuarantee said:
I would argue it’s very close. Only difference is the northern piece of energy holds into some strength and takes primary .. GFS likes to do this sometimes but it is another scenario that’s possible. If the southern takes over though it’s close
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I would much rather have ICON then GFS in the boat. I know that’s wild to say but…
 
GDPS is way different than GFS. Its cold enough in NC, if we can some of this energy to eject. See what happens here in a few


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Much like I did around this time in December (linked below), here's my general sentiment on the rest of meteorological winter.

Again, looking at the big, general picture, don't worry about any details this far out. Only concerned about the planetary-continental scale wave pattern evolution & tropical-extratropical subseasonal coupling processes, not individual storms, not rain/snow p-type maps, etc.

From a tropical forcing perspective & using weekly model forecasts + Nina climatology & analogs as a basic guide line (not actual forecast), this is what things generally look like to me. Tropical forcing will be very dominant over the next several weeks as the MJO &/or Kelvin Waves in the E Hem superposes onto La Nina (gets an assist from the SSWE in the form of an enhanced Brewer Dobson Circulation & we begin to approach the annual peak in MJO amplitude in Feb-Mar).

The big -EAMT event we saw this past week set this pattern evolution into motion and the Pacific jet retraction will get handed off & further reinforced by the MJO as we enter February, leading to a prolonged period of -PNA/SE ridge pattern in the first half-2/3rds of February.

Thus, I think we'll probably go from this central-western weighted trough & southern Canada vortex late month w/ occasional bouts of cold + an outside chance of a CAD event, to a more traditional -PNA in the first week of February that probably shuts down any real chance we have wintry weather, unless we see the 50-50 low go completely crazy like a few EPS & GEFS runs have hinted at.

Thereafter, as we get into the 2nd week of February, I suspect the SE US ridge will actually amplify + flex up the East Coast as the -PNA retreats further into western Canada, yielding a potentially very/unusually mild pattern for much of the E US (not just the SE US this time). I think this pattern will try to persist into at least the 3rd week of February (Feb 14-21), even as the MJO (or whatever comes of subseasonal tropical forcing) enters the West Pacific but by then, I believe we'll see the large-scale puzzle pieces begin to start shuffle around, eventually yielding a potential +EAMT &/or MJO-induced Pacific jet extension sometime around Feb 20th or so.

Eventually, I think that coupled with rapidly shortening jet wavelengths will cause a lot of reshuffling of the circulation pattern over the N Pacific + N America, allowing us to shake off this -PNA/SE ridge pattern sometime around the last week of February & transition to a favorable look for cold/snow right at the tail end of February &/or early March, a time of the winter where we tend to see the most big dog winter storms per capita.

Given that we're not only in a La Nina but would be closing in on a time of the year where the MJO tends to be the most amplified (& therefore slow), plus potential interaction with a SSWE &/or ENSO, there's a risk this overall timeline on the back end of February gets pushed back some closer to early March, but not favoring that scenario for now.

I think these RMM regression maps from Paul Roundy get the general idea generally right here.

Late January: (Very) marginal pattern for cold/snow w/ mean trough centered to our west w/ trough south of Greenland. Slight chance of a CAD event.
Early-mid February: Transition to a more canonical La Nina -PNA/SE ridge pattern w/ the SE ridge flexing up the East Coast, & getting warmer (anomaly wise) as time progresses during this period.
Late February: +EAMT &/or MJO-induced jet extension flips the Pacific pattern, pattern reshuffles over N America in response to that & seasonal changes to the jet stream. Favorable pattern for cold/snow tries to return during the last week of Feb or so.
Early March: A favorable pattern for cold/snow seems most likely to return during this time period. Fighting against increasingly unfavorable climo as early March turns into mid-March. Suspect after our "false spring" in early-mid February, actual spring may get put on hold for a bit this year once we flip the calendar to March.

https://www.atmos.albany.edu/facstaff/roundy/waves/rmmcyc/index200reg.html




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Here are the JMA MJO composite OLRa & VP200a for each MJO as a rough reference guide to compare w/ against the extended GEFS above.

https://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html

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Webberweather53 said:
Fwiw, this my general sentiment on January (as things currently stand)

-The first week or so is very likely going to be warm & fairly wet/stormy. Need to be on the lookout for severe weather across the lower MS Valley & Gulf coast especially.

Once we get to/past Jan 10th ish, we should see more of a canonical El Nino/+PNA pattern return. We'll probably progressively step down from this super mild pattern to a seasonable one, that eventually becomes rather cool again as we move into mid-late January.

Imho, after this potential chance ~Dec 26-27th or so, our next best window is probably somewhere in/around the 3rd week of January (~ Jan 14-25 ish). There may very well be a storm or two that shows up between now & then, but the air masses earlier on in January are more liable to be stale, more temperate continental polar ones, capable of delivering snow primarily to climo favored areas of the Appalachian mountains, etc.

I also tentatively suspect we may see the -EPO also make a return sometime late in January and eventually evolve into a more classic -EPO/-PNA/SE ridge La Nina pattern in February (typical evolution for a winter like this).


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CMCE has the bad looking pacific ridge but has enough blocking on top and it keeps a TPV tucked more towards us. Some pretty big run to run changes as well. But it’s weird seeing that type of NPAC ridge and us being cold, normally this flatter NPAC ridge look is associated with a warmer eastern US DDB24CB1-2D3F-4E66-8C2E-B854B0813EC6.pngDAE15556-226E-4F5B-B929-3DFD6E80428A.png321459D7-FB25-4388-A7F9-B8C8A64CCD4E.png
 
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