csnavywx

Depends on how the trailing northern stream vort goes. A phase there makes it more likely. But, usually, in order to get the biggest totals, you need to smell the sleet.

Good thing about the 6Z GFS coming into line is that this lessens the risk from the southern stream/cutoff. It was consistently the slowest and most guidance has trended slower and stronger with it over time. Gives some confidence in it not getting stuck or coming out too piecemeal. We have other potential issues, like interaction with the trailing NS wave, but the big failure modes are getting crossed off first.

Still want one more day of runs before I start barking. Time enough to let the SW cutoff and northern stream settle down.

If we're doing verbatim, quite a bit of mixing on the southern half of the 12Z run whereas virtually none on the 18Z and surface temps in the teens and low 20s. Anywhere near 1" of liquid in those conditions is gold.

Remember to use "max temp in profile" maps where possible or take a look at 700mb even if the 850mb-SFC maps are all below freezing. Warm nose can get pretty elevated in these scenarios.

The one nitpick I have is that the lead TPV lobe is slowing over time, strengthening the eastern lobe of the Arctic high. If it were sliding nicely off the coast, I'd agree more with him. Probably aborts the cut and forces a transfer earlier than the 06Z AIFS. The 12Z runs came back down to earth a bit.

Normally we lose out in these CAD-type storms. This one looking different. Northern stream looks strong and suppressive and the subtropical jet is finally coming back from the dead.

Low key had a lot of 1995 analogs pop when I did my seasonal for the office this winter. It was strong enough that I've got a wager going for a 20+" seasonal here. Doesn't mean we're getting the nutty 50+ that season had, but not at all surprising that this stuff is starting to pop off now that WPac warm pool forcing is strengthening and Nina forcing is waning.

Agree. Hard to get a better large scale pattern than this for us.

Yeah ended with a little less than a quarter inch here. Quite a bit more on the ground about 10 miles north. We get another shot coming up this next weekend. Hoping the TPV and the NEPac cutoff low decide to play ball here. The floor and ceiling are pretty high on this if both cooperate.

Still going to be a day or two until the cutoff underneath the western ridge (that opens up and serves as the trigger) is well resolved. Good to great setup for it as long as the TPV doesn't overwhelm and the wave actually opens up in a timely fashion.

Correct

Well after this dud, we've got another shot this weekend. Finally a decent slider track. Boundary layer temps are super marginal and I expect we "waste" some liquid to cool the column via diabatic cooling. It's also during the middle of the day, but that's a little less of a showstopper in mid-Jan. The trough orientation isn't the best, so there's still a chance of a whiff, but there's at least some agreement between the RRFS, AIGFS and EC-AIFS on track now and it should be able to produce a decent band of accumulation on the northwest side.

CFSv2 has been doing that since 2020, give or take. A better system, UFS, is linked below: https://www.cpc.ncep.noaa.gov/products/people/jszhu/seaice_seasonal/index.html

Some mood flakes and a dusting to start the morning. But my current focus is on the upcoming pattern that looks to offer some real chances, including a strong west-based -NAO pattern. The first chance appears to be this weekend with a southern slider that, at first glance, appears to be a miss to the south. However, the track is very close to the benchmark for our area and it would not take much of a north trend to produce here. Temps are marginal, but evaporative cooling and melting along the system's northern edge could help produce enough diabatic cooling to support a changeover to snow.

Yeah, going to end up about 10-20 miles south. Got a few flakes so far this morning but the accumulating stuff is going to end up just south of here and probably just south of SBY as well. We've got at least 7 more days of this pattern though, so plenty of chances for more clippers.

Made a comment in the office on Friday that we may see a lot of last minute adjustments this winter as this is the kind of pattern where that happens. Shoulda taken my own advice. Monday was indeed *not* off the table completely and my original thought from last week is going to end up being at least partially correct. Still looks like a grazer, but it's going to be close for the southern end.

Great little storm. Nice dendrites for most of it. Monday's system is a miss to the south, but might give some crumbs to the NC and SE VA crowd. Hopefully we get a decent clipper track or the like next week.

Just preconditioning the next drop, barring steady AMOC weakening. I expect noise from the usual suspects to get louder right up until the point that they (once again) go silent. Difference this go-around is that the cave-out is likely to come from the Atlantic front this time around since most of the MYI losses that could happen on the Pacific front already have. The vicious feedback of shoaling AW layer --> sensible+latent heat flux to trop --> stronger Ural/Scand. ridging --> PV disruption --> strengthening meridional transport --> shoaling AW layer has a lot further to go if CMIP6 is onto something. And winter warming is necessary to precondition the next drop anyways.

First couple of targets to track are this Friday (marginal, but halfway decent track) and next Mon/Tues (trailing wave needs to dig a bit more to develop a full blown slider, but there's a shot there with enough cold air already in place.

Getting pretty excited about this season, tbh. Pretty bullish start upstream and even though today is just cold rain, it's good to see a more southern coastal track light up so early on. Leaning towards '13/'14 and '95/'96 for analogues atm. Current setup is weak -ENSO/strong (collapsing) -IOD, -AO/-NAO and -WPO favored, a rare early SSW and PV placement favored over the NH side of the hemisphere. Still digging around doing some research, but am leaning quite bullish. Seasonal models have been screaming a tight gradient with plenty of cold air available to produce snow *for months* now, and so far it's panning out. Just need to keep the pedal to the metal on the cold and the SE ridge on the weak side.

Thanks, been looking for failure modes. If this strong -IOD collapses in the next 1-2 mo and we end up with this kind of DJF pattern in the NPac, both of those are typically Nino harbingers:

Yeah, I believe it for the WPac. It's been in a counter-trend to the Atlantic. Probably reverses as aerosols get progressively cleaned up. ATL itself has some competing factors, namely lapse rate/stability issues and a tendency for the ITCZ to lurch northward with asymmetric hemispheric warming (a la Broecker et. al '17). That'll put more waves over the cooler/more stable Canary current for the MDR track. Then there's the potential issue of MJO and ENSO amplification (+ and -). To me it seems that more volatility is an easier call than a continuance of the upward ATL trend.

There was a very unusual WWB in the far EPac in March '23 that was very strong. That started Costero conditions pretty early and may have helped contribute to an earlier response (a la 1877-78). Aerosol loading dropouts after '20 didn't help either -- unmasked pretty quickly after the end of the triple-dip Nina. I still expect some retracement from here through March/April, but if we don't get meaningful drops, that in itself will be pretty telling.

Another paper that might become relevant this coming year: https://www.nature.com/articles/ngeo760