Typhoon Tip

I also wouldn't sleep on the 29/30th either... The index signature is still there, and there have been some starts and frets by some of these models to hit that... Man, this speed bias in the flow- I've just about grown sick and tired of it. It just won't stop.

18z GFS is partially collapsing toward the earlier consensus. The 18z Euro should be interesting...

Weakish low but huge isentropic signature served me my biggest snow/dumbest low scenario, Dec 23 1997. It was just like a thermonuclear S-bomb was smuggled out of Siberia. The forecast? 1-3 of slush in the Worcester Hills, ranging to just cat paws in Boston. 16.5" fell in 5 hours in Acton Ma, 7" of which fell in a single hour. I still vividly recall standing outside at the base of my driveway and not being able to see my house. Totals as high as 23" fell not to far gone as the crow chokes from falling snow up by Pepperil. Never before, nor since have I seen 7" fall in a 1 hr... made inimically worse because 2 or 3" fell in the hours immediately preceding and following - just sort of went from 4 low visibility fast inches to 7 in blindness. Where ever you were, you were basically hosed and froze in amber, with another 5" yet coming. I've heard of 12"/hr falling in Sierra events ... Italian Alps .. etc, where a direct marine moisture source is being jammed over terrain... but we're down here on a coastal plain. That clear sky the night before was fuck-up forecast exhibit A. It was supposed to have been cloudy... But it was dead calm, crystal clear, with a 37/25 type air mass in situ. By the time the cirrus veil's edge like slate arrived at dawn it was 13 to 19F everywhere. Exhibit B was the ETA was forecasting a sounding of like +2/+1/-3 at 980, 900, 800 mb respectively, at Logan. Umm.. it's going to be colder west of the city... hello. Meanwhile, damming signature in the PP nosing down from the direction of Fryeburg Maine - you know ... like the perfect not going to get warm you ding dongs orientation? QPF was what it was, .8 to 1.0", but with UVM (upward vertical velocity) close 20! I've often heard it said, "well the modeling standards of the day..." but I disagree. That sounding and those constraints I just described were going to be snow a million years ago. 1-3" of slush my ass. I remember emailing Harvey Leonard, who I was interning with at the time, and telling him, ah... people better think twice. I was completely wrong! I completely missed 16 to 24" out of that (ps, I'm pretty sure Ray got 15 - )

yeah there's an IVT sig on the op Euro... GGEM's actually spinning up a new cyclogen with that. both these models have more N/stream attempting to run up after the escaping low pressure, and it's helping to lower/expand back west as that's happening.

for some reason ... i feel better about this opinion coming from you than the representatives of the NYC law enforcement lol

whatever's the culprit aside, that's a major event in and off itself It's maximizing potential given structure. Perfect E inflow 850mb, over a 920 mb ENE frigid air mass, with 700-500 mb flow running up SW-->NE over a steep isentropic surface You could produce a foot of snow out of a 1010 mb low and one closed isobar with that. geez.

Yeah, I was just gonna type that. heh that said, there's a lot depending on the N/stream orientation in this - it's almost purely a geometry problem, really. If the vectors post the elbow of the N/stream are oriented W-E ...we're fucked. If it's even 15 deg headed N of due E we're probably getting fuzzy chalk dust snow up to HFD... go up from there.

Looks like this GGEM's gonna carry the 30th bomb ...or close to it judging by this 500 mb evolution. It's the index storm we're waiting on the dailies to get around to ... not that they have to of course.

That super storm in Russia is an astounding story... just arresting

Mixed ideas on that.. That has the look of a classic/climo southern ice/mix storm. As a matter of climate course those more often stay safely S of the ~ Mason Dixie latitude. It depends how much is conserved of the jet mechanics as that quasi S/stream wave squeezes E under the continental N/stream. If there's more there, than there's more feedback that subtly but crucially elevates heights over the west Atlantic via feed backs, while it also generates more coherent low pressure/mechanics. That appears to be the pathway to getting clipped this far N. Less, and this stays a southern classic. Either way ...they're likely getting their winter storm.

Heh ... the suppression hasn't been an end to end issue on the guidance. It's really only 2.5 ... 3 days of it, roughly 23-26. just sayn'

Has a typical south icing event climatology look to me... that is how they get their winter down there - arctic outbreak then overrunning gets going. It happens that way, but if the model's too aggressive with the cold loading et al the overrunning and wave transit latitude could be higher. Sure.

the differences are really easy to detect in the mid range. the AI versions have less cold exertion (less deep layer total mechanics therein), such that a vague S/stream wash runs up farther N as a wave/series/overrunning around the 25th. the standard versions preclude that from taking place because as they depict, an overbearing polar-arctic branch jams a confluence to an usually deep latitude across the conus ... utterly suppressive. Which is right? the AIs would get cold but seasonally so, then a durational ( which is hard to do in a fast footprint but given the flow orientation, about the only way to do it is this shallow azimuth rise coming E) multi regional winter event. the standard versions would plummet the NP/Lakes, with an somewhat attenuated eventual arrival here, but dry.

so, still haven't formulated an opinion of these AI tools ... but, if the assertion of superiority in that extended range is true this actually lands ideally in the best time

best spatial-temporal window is still 29/30/01 ... but the PNA moves positive from the 24th - roughly GHD