Typhoon Tip

Wondering if there'll be a couple of swaths of blinding snow squalls associated with that arctic front Thursday afternoon.

It's true - ish. And the reason is because the basal velocities around the mid latitudes have risen in recent decade(s). It's just straight up statistically not favored to maintain a 'delicate' total confluent structure to the flow, when the fervency et al is tending to move everything along. I.e, less able to resonate in position. The same thing is happening with teleconnectors, too. The correlations are still there, but mass field biases, negative or positive, break down faster than the statistically favored or related events have time to materialize. This is likely why we keep seeing so many fast field/progressive patterns by behavior. Then we get these torpedo lows slipping along via shortwaves escaping out over the N Atl barely 84 hours from arriving off the Pacific.

Or missing?

One would think the models are physically handling this ... but there's an almost nondescript cold front and associated 'bubble' high over lower Ontario and Upstate NY ... DPs in that region are < 20F ... with temperatures about 10-15 F colder. It's moving this way. It may prove important as an antecedent prep for this thing

Little detail about this NAM run ... it's gotta pretty defined CCB band lagging back into central zones passing through 42 hours out. That was less clearly defined in previous runs. If that's true, areas that disappointingly had gone over to big droplet cold rains with one or two windshield cat paws would likely flash freeze while a couple of exit inches.

...and I didn't even know any of this was in the works until about 10 minutes ago so .. heh

I also want to point out an aspect ( that I'm sure no one will acknowledge haha). I'm noticing this is trying to be weaker as it gets closer in the guidance. This is an aspect that I have been advertising ... because it is a coherent bias in all guidance, really. Regardless of Euro this and Ukmet that, and JMA to NAVGEM and back... as I've mentioned all but ad nauseam in the past, there's something like a variable % in reduction of systemic prominence at go times. It's unclear why exactly, but ignore at own peril. I'm honing in a testable assumption. Anyway, it's variable, but more times than not there's some loss coming down the stretch with these things. Perhaps this will be one of the lower % gyppings (ha!), and if the NAM is correct with its oversensitivity to cyclogenesis/strength then so be it. But, this run is losing/lost something and with it ... there's probably dynamical reduction and the sfc/900 layer is thus marginally warmer.

just analyzing the last several cycles of this guy ... the reason it is so robust isn't really rocket science. It's straight up meeting the bombogenesis check list. 1004 mb --> 987 type spread in 12 hours is sufficient. But what comes along with that is the total potency in the deep layer... There's clearly going to be a whopper frontogenic band with something UVM exotic in the 700 mb ...probably smack in the growth region of the sounding - just based off the (synoptic + experience)/2 one doesn't really even have to look at the software to see that's the case. The question is ... is it all right ? proooobably not. I gotta say, back in the headier days of 2005, the then ETA ( I think it was still the ETA? but either way) was pimping a bomb big time, and the reason was pretty clear why then. I'm not sure I'm seeing that set up here, because the antecedent frontal/thermal compression from NJ to Cape Cod is not nearly as extreme in this case. I think the NAM is over processing in that lower levels as systemic bias in that model - it's probably why it has a NW bias in its outer ranges, one that it then sans when it gets closer and exposes said bias... But, that actually helps it do better than other guidance when the situation is like Dec 2005 set up. The problem is ...it's always on, even when the situations are softer.

Yeah between ~ Nov 10 and Feb 10, that range gets the lowest solar insolation. We can get away with at least holding ice between 10 and 2pm in icing situations at 32/no new... vs losing at that same temperature and marginal condition outside that date range.

Is it going to inherit the NAM's legacy physics, or be a uniquely new tool -

Yup has rain/snow line flash collapse SE look to it. … probably in the process of correcting it’s native NW bias

This system would have to snow at 4"/hr rates to load those numbers. I dunno. just sayn'

Ah not really.

I still am a little leery of this thing suffering some %age to model magnification correction in the short term. Flow’s compressed some. The embedded S/W’s, open and progressive. Those two predominating characteristics tend to foretell lesser production so we’ll see. We seem to have two concurrent hemispheric mode types, which is interesting. Blocking is competing with a velocity anomaly at lower latitudes May have a similar quandary the 6/7th then again out there toward the 10th.

In principle we may be seeing this

It’ll likely pass thru 2 or 3 cycles selling a NW bias between 24 and 60 hours

there appears to be assimilation bias in the gfs

Perhaps too early to drill into details but a flatter wave correction toward middling low depth will tend to parallel the flow with the isobaric layout … basically an ENE vs a NNE/NE with cf genesis … that’s going mean snow tot headaches for eastern zones.

The pattern recognition/suggestion/modulating favorably into the first week of Dec has been in the scaffolding of the outlook since at least two weeks ago. It’s not suddenly emerging thus challenging … that’s good. Perhaps even reassuring but I could see this robbing 20 someodd percent squeeze limiting things. Interesting testing modeling perf this time vs that leitmotif

This isn’t relaying off the eastern Pacific via a S route/split stream (along the 564) until ~ Sat morning … traversing the continent in 72 hrs in fast compression/progressive flow type. Those circumstances don’t lend to confidence even at this range. Still, at least the wave space actually existing in the field is higher confidence. Something’s there. But smaller giga corrections are like .5 deg on golf ball swing ending up on the left or right side of the fairway at a 200+ yd drive - it’s why fast flow bangs around model perf I’m also leery of model-biased amplitude —> correcting down post arrivals out of assimilation regions. Once this relays into the denser sounding array, as we’ve observed more frequently than not … there’s been this recurring theme of correction toward less by 20some % … suggesting an over evaluation was taking place and running that out into mid range results in fantasy.

This worked out reasonably well

Suppression, kind of is negative interference… But yeah, either way we look at it

In fact it would harm matters

The majority don’t appear to have this right, anyway. There is no SSW.... there never was yet. There may be one about Dec 7 or so... but antecedent to the -WPO/ -D(EPO) that was not the case. This is a ridging that is emerging from mid to upper troposphere and the tropopausal heights are elevated around the N arc of the ridge at upper levels; that does have an effect on the morphology of the PV. As I explained the other day, it may be splitting hairs? Either way, a -WPO/-EPO arc can arrive into that scenario however it does, when it gets into that mode, we load ... cold air in the winter. The cold you noted in Canada ( 2-meter temp anomalies... and 850...etc), that is a direct result of the activated loading pattern. This is just -WPO/-EPO, nothing else. Not sure why social media can't help itself but go from 0 to sci fi drama with such little excuse to do so - sometimes I suspect it's society dopamine plague since we've become tech zombies. How's that for sci fi. jesus As far as the colder pattern, this is all greater confidence than people are letting on - a lot of which I suspect is not having patience. Part of the problem of visualizing these changes at long leads ... ( over 15 days in some case...), about 5 days in waiting all the doubts start happening ... People expect to see things now. Meanwhile, models will come in and out of the signal ( operational versions). By the way, here's the 360hr 10 hPa GFS prog... this is a warm intrusion - we'll see if it's real.

Fell for the bait ... after 20 something years of this pastime, too