SnowenOutThere

Something I've been trying to watch with this storm is the initial energy phasing between the NS and the low off Mexico and how that impacts the ability for downstream cyclogenesis. Though being honest that analysis starts to stretch the limit of my understanding. Generally I've assumed we want the low off Mexico to be further North and East (and more energetic) in order to feed energy and get fully captured by the NS shortwave though I'd like to know your read on it as I could also see a possibility where that Mexican low destructively interferes by not getting cleanly absorbed eastward.

It was perfectly executed cause as much harm as possible by having the Saturday 12z GFS finally cave to a snowstorm so for exactly one run we had all models showing a major storm. Masterful ragebait I gotta hand it to the atmosphere on that one.

Do not invoke such a storm in this happy go lucky 12/5 thread

I like this bit from the NWS disco FWIW, snow and ice has trended up slightly over the past couple of runs. While amounts are forecast to generally be light (an inch or two, perhaps three should a higher end solution verify), the northward shift is notable. Looking at clusters featuring the greatest variance (EOF) regarding amplitude does suggest additional northward expansion is possible. Just something to keep in mind.

And the NAM is weird cause the wave itself is a bit more stretched but the vorticity behind it is a bit more N/S oriented so probably be somewhat close (maybe a bit worse if gun to my head) to 6z

I did NOT make 4+ analysis posts for the show hole to be squarely over Charlottesville imma need that to change to some rando place like 50 miles east. That said, seems like positive trends so I’ll take a look at them later

Minus the Nams the 0z cycle has pretty much been exclusively positive for Friday. Lets hope the Euro does its job and holds

I think this would be a pretty good ending considering what we've got to work with

Lmao it's more fun when its all mixed together anyways

Remember when this thread was made to separate out the two threats. Pepperidge farm remembers

I mean its an obvious show to what happened if you look towards new England between the 0z and old 12z run. On our 0z run we just have a wall of confluence over New England which obviously is not gonna help our case in getting to move the storm north 12z for comparison has that same confluence just a causal couple hundred miles to the North (and even that suppresses the storm a bit too far south for some in our area). The other things that may help us is the confluence moving out of the area fast enough to not matter as 0z seems to have sped it up.

Step in the right direction

Looks like the main PBP is going on in the 12/5 thread, which ironically enough was made to separate the discussions lmao

If we’re talking Mondays threat it’s over here. Though I agree so far that it looks like mix between 12 and 18z

Looking closely it appears the reason its better is a slightly (and I mean slightly) better configuration of the NS up around the Great Lakes as being a little more North/South orientated and slightly less connected to the fastest flow. steps are in the right direction but they are baby steps.

ICON completely whiffs even getting close Monday as it has the energy off Mexico retrograde further southwest.

RDPS is significantly improved too (though not enough to help NOVA but Short Pump makes out like a bandit). It generally follows the positive aspect I've been highlighting which is the secondary bands of NS energy being modestly further west

So far it looks like it should at least hold from its 18z improvement I think. Still sorta does the Nam more connection with the low off western Mexico but seems like it should be fine for it.

I'm actually not quite sure what goes wrong as I agree that on paper that what happens out west and to the north looks better with less push/suppression of the NS. My best guess is something happens either internally with the shortwave or the interaction between it and the low of Mexico causes its energy to become more stretched and further eastward based. Looking at it more the only real difference seems to be that the shortwave remains a bit more connected to the low of Mexico and there are slightly stronger H5 winds which as @CAPE pointed out hurts us by stretching out the vort. 0z wind map 18z wind map

Thank you so much for this post, and sorry for the confusing initial wording. This also helps clarify to me a how the arctic front theory of storm formation (while generally "wrong") can make some sense as I assume it comes from seeing the stretch between air masses as a line of vorticity that eventually spins up into a concentrated area to force surface low formation. Of course, it doesn't actually get into why that happens but it makes more sense regardless. If I read your post right in sensible terms we are in the best place for surface low development when we have a strong baroclinic boundary to our south (aids in convergence though my course didn't go too much in depth with it so I'll just accept a stronger temp gradient is better), a jet streak that is either positioned to the northwest (right entrance which I guess may be associated with a negatively tilted trough usually?) or a jet to our southeast (maybe more for broad bowl patterns?), and a condensed ball of vorticity (shortwave) to act as the initial perturbation in the system. I also know that 500mb low wise a sharper amplitude with shorter wavelength wave tends to increase vorticity though I don't actually know why (to be honest my ability to connect vorticity to low pressure is sketchy at best and I'd appreciate resources to find that connection). Additionally, If you have any websites to look at the upper air patterns for past storms I'd love to dive into that to see examples of this.

That makes sense, but as Cape alluded to with the flow stretching the vorticity apart is it best for a developing low to be displaced from the strongest winds? I know that oftentimes the jet isn't able to "round the base" of a trough and once it does it indicates a matured/max developed storm and is that the logic behind it or am I mistaken?

I edited my previous post to give you a shoutout for those posts as they are what got me largely to where I'm at! Thank you for them. BTW the best part about being a student is that while doing these breakdowns is procrastinating it feels infinitely better than doom scrolling as I can rationalize it as learning for future classes.

To be honest the upper winds is where my knowledge gets confused as we went over how the jet forms (I can tell you why the jet increases on the northward heading side of an upper low and decreases when heading south) but didn't go over the practical effect on the surface. I'm currently trying to research it on my own but generally it confuses me as my intuition says that areas of lift should form where winds are accelerating in the upper atmosphere (as it induces lower level lift as air is pulled into the upper flow) yet I know from the 4 quadrant model that understand I have is flawed. Additionally, I would've expected that stronger upper winds generally encourages cyclogenesis and didn't consider that it could actually hurt consolidation (which admittedly does make sense). Basically, what upper wind profile would actually be conductive to forming a strong surface low pressure?

Thank you! We finally got to the actual H5 Jet stream ageostrophic wind etc part of my course last month! Of course, it wasn't anything crazy but its given me just enough tools to begin identifying how the upper air connects to the surface and making predictions. That said, I'm very confident that this is very much a Dunning-Kruger effect where I know just enough to make broad forecasts and identify what I we need models to trend and make predictions from an earlier hour to but I am unable to "correct" model behavior as I just don't have the confidence (wait till Spring 2027 and Synoptic met for that) to do so. So with that said please feel free to correct any mistakes I make as it literally might save my grade! I also should of course mention that a lot of this knowledge was built through posts by you @psuhoffman @brooklynwx99 @high risk @WxUSAF@Terpeast @Bob Chill alongside the many other more occasional in depth breakdowns by our "on-event" posters. It's just this class has finally given me just enough to start synthesizing my own analyses so genuinely thank you.

Doesn't look the 18z Euro should cave too much if at all so far.