March 2-4th ... first -NAO anchored storm perhaps in years

[Typhoon Tip]

Well, sufficed it is to say ... we have reasonable to above normal confidence for a strong, westerly based NAO blocking event throughout the latter middle and extended range, and ..related too, an event that is trackable. 

We could go into a lot of discussion about the NAO for its own identity and evolution, but, the focus of this thread is on the event scheduled to impact the MA/NE regions from roughly March 1 through the 3rd or 4th, which is obviously directly related.

Firstly, this is not likely to be a 'clean' snowy storm.  Expectations for rain...perhaps a lot of it, should be in play, particularly in the first half of this. In fact, as is, the models are hitting at cold rain that transitions to snow as the mid levels close off and dynamics work into the N-NW arc of the low circulation. Wind swept cat-paws over to 'parachutes' with occasional thunder.  

Therein enters a reasonably good chance that a large area will eventually transition to a lot of snow!  One thing that is interesting is that the 500 mb heights deepen some 6 to 10 DAM as the axis passes quintessentially underneath LI by about 2 or 3 Deg latitude, descending to 528!  That's nooooot usually a rain event at those depths - red flag.

This is early speculative on details that are certainly going to change, but ... the focus on this as a meaningful event is warranted at this time (in my mind) as it has some more hemispheric scaled events behind it's emergence. Those tend to have a bit more confidence for occurrence at extended leads. 

There are a lot of correct-able facets about the details ... we can iron those out as the week progresses.  For now, there is a decent agreement from all operational model sources, for an important event of wind and QPF, and one that is associated to the total behavior of the NAO.

[USCAPEWEATHERAF]

Great write-up Tip, great points as always highlighted.  Again this is the transitional storm from March 1-4th next week.  It looks to be a big rain maker turning to perhaps warning level snows according to the GFS

[Typhoon Tip]

'Course ... Part of me thinks it would be deliciously ironic if we get this -NAO so many have been pining for, for so long .. .only to have our storm component expression of the whole thing end up being 3.5" of cold rain and wind swept cat paws...

Wah wah wahhhh

[Typhoon Tip]

Well, ...interesting Euro run.. .nice to come back from a good disk golf outing, crack a beer and see 35" of snow for Fitchburg ... zomb!

I think the important take away is the potential more so than the particulars of the model run alone. 

Again...echoing the sentiments above, this particular arrangement looking 'marginal' in the atmosphere at this sort of time lead, tends to verify isothermal in the -2 to 0C range ... This per my own experience, so taken for what you will, but it's a quasi-spring snow type scenario. They will always look a tick or two warmer in the mid and extended range than they tend to verify.

Also, echoing the above...the general modeling appeal for a large SD easterly flow component is alarming. I would add QPF  to this system's potential. We have several factors that I wouldn't be certain are being modeled that deal with topography/local studies.  There is likely to be maxes that exceed the general layout ... one perhaps close to the coast where BL differences between the ocean environment and the land cause a zone of lift - not necessarily the same as CF, however, if the high up north exerts a colder profile in its own rite, that becomes a player for snow totals. Multifaceted threat from flood concerns where it's rain, to a potential crippling snow in the 8/10::1 weighty variety.  

I certainly don't wanna get ahead...  The problem is, the NAO block. It is imposing a tropospheric vent at the same time is helping to direct the easterly flow through a very unusually deep amount of mass moving west into perfect conversion mechanics.

I have to also think that tides are a growing concern as successive cycles tend to magnify those sorts of concerns.

[Ginx snewx]

Here ya go Tipper

[ackwaves]

Interesting input from Taunton this morning in AFD...

Strong -NAO, -4 to -5 SD, would expect a cool,
dry setup for NE CONUS, storm track lying further S per block. Mid-
Atlantic getting crushed. Interrogating Washington DC top 10 snows
versus the NAO time series after 1948, 5 out of 7 storms, 3 prior to
1948, were associated with a -NAO around -3. Recall February 2010?
Washington DC "snowmageddon" of 17.8"? Monthly NAO averaged near -2.
Cherry picking data? Perhaps. CIPS analogs? Interrogating where NAO
indices <= -1, noting trend of sliding low S of New England, further
so with a stronger -NAO.

[Typhoon Tip]

51 minutes ago, ackwaves said:

Interesting input from Taunton this morning in AFD...

Strong -NAO, -4 to -5 SD, would expect a cool,
dry setup for NE CONUS, storm track lying further S per block. Mid-
Atlantic getting crushed. Interrogating Washington DC top 10 snows
versus the NAO time series after 1948, 5 out of 7 storms, 3 prior to
1948, were associated with a -NAO around -3. Recall February 2010?
Washington DC "snowmageddon" of 17.8"? Monthly NAO averaged near -2.
Cherry picking data? Perhaps. CIPS analogs? Interrogating where NAO
indices <= -1, noting trend of sliding low S of New England, further
so with a stronger -NAO.

Mmm, the analogs are risky to use in my opinion.  About all that represents re whatever happened in lore, is the index numbers happened to be in whatever range; but that does not make for a causal link, and offers little or no connection there - and I think particularly in regard to NAOs that is a very important distinction to make.  Statistics, in any science .. often do belie what is actually taking place, but in this case, we know there is a huge difference.

For example, in -4 SD lead up to "snowmageddon," there was a difference in the morphology of the circulation: the block was stationary.  In this case...it is not.  If we happened to have a -4 SD when this week's end system is taking place, it is because the NAO happened to time in passing through that particular scalar value.   Back whence, the DC event had an anchored system that stalled there under a block that was far less transient for one, and not actually displacing across the planetary coordinates, such as this one is modeled to do so.. With rather odd looking rapidity I'll add - that's another issue entirely. wow.. 

The latter complicates the hell out of the handling in the models for one .. but, really makes the two scenarios NOT a very good comparison.  The forecaster does admit to perhaps cherry picking the data, so they get a pass. And, I also appreciate the approach - but only to a degree.  I think the fact of the matter is, this is just a very tough scenario. Even if the models coalesce around a higher impact ordeal for us, we don't know if A  ... the QPF is correct ... B  ... the ptype could go either way ... D ... strength of over all system ...( the 06z came in more potent again)  C ... whatever I'm missing..

For me, this is about two enhanced probabilities:  one around the end of this week/next weekend; another perhaps D10 to 12. 

I do wanna say though ...that NAO handling is really throwing monkey wrenches in every cycle. It's like the rest of the atmosphere over our side of the hemisphere is stepping aside ...giving the NAO carte blanche in dictating the storm track ... and via feedbacks, probably effecting intensities too.. etc. Yet, the NAO is not being consistently handled.  It's really trying to speed up and also lower in magnitude in the guidance and has been now in inches and minutes every cycles going back 4 or so days when I first mentioned it in the modeling thread. I don't think its magnitude is that problematic, but definitely "where" it exists ... in particularly "how long it exists there" is the problem.  It's careen across the N arc of the Atlantic... fusing into the heights over the middle latitudes ...trying to do so before our storm at the end of the week can really completely cycle - it looks pretty directly culpable in why the storm is shooting out to sea instead of stalling like some previous runs. 

It could all happen that way.. Hell, this could end up being an egg-on-the-face non even for us as we get a whiff misted by long fetch while all the UVM slips a pube too far S... Lot of things are valid in the probability envelope here.

[wxeyeNH]

For what it is worth here is the 12Z 2/25 Euro "clown" map for potential snow totals for the late week storm.

[moneypitmike]

Just now, wxeyeNH said:

For what it is worth here is the 12Z 2/25 Euro "clown" map for potential snow totals for the late week storm.

Hmm.....BGR or bust.  

[ORH_wxman]

Not quite the 30 inches from yesterday here but we would take it. 

Gonna be some swings though like we saw between 12z and 00z last night. That strength of the energy ejecting plus timing and also the block retrograding. 

[SnowHole413]

That one looks better than this one

[moneypitmike]

1 minute ago, dryslot said:

That run was good down to you as well.

We get the QPF instead of yesterday's screw-job.

[ORH_wxman]

It all depends on the algorithm used. The ones that really punish sfc temps above 32 will give much less overall. 

[moneypitmike]

1 minute ago, ORH_wxman said:

It all depends on the algorithm used. The ones that really punish sfc temps above 32 will give much less overall. 

Those are the ones we toss. 

[monadnocks]

5 minutes ago, Powderboy413 said:

That one looks better than this one

As someone who is going to have to go from AFN to ORH on Thursday, Friday and Saturday, I'm really OK with lower snow totals. Sorry folks who want another snowmaggedon but the higher storm totals would make life harder and/or more expensive for a bunch of people.

[dryslot]

3 minutes ago, ORH_wxman said:

Not quite the 30 inches from yesterday here but we would take it. 

Gonna be some swings though like we saw between 12z and 00z last night. That strength of the energy ejecting plus timing and also the block retrograding. 

The timing is key, Sooner is better for my reasoning..........

[Damage In Tolland]

3 minutes ago, ORH_wxman said:

It all depends on the algorithm used. The ones that really punish sfc temps above 32 will give much less overall. 

Starts Thursday night rain or snow? And ends Saturday?

[ORH_wxman]

3 minutes ago, moneypitmike said:

Those are the ones we toss. 

Theyre typically the least accurate so I often do toss them. Esp in isothermal profile looks. I remember a lot of the clown maps in 2/23/10 event giving almost nothing to my area and I was forecasting 9-13". 

The algorithms that look at as many slices of the midlevels as possible are typically going to be better in a marginal isothermal situation. 

[TauntonBlizzard2013]

That is better for a good chunk of folks.... and probably the closest solution to a winter storm we have down this way. Still not rally close for Boston and points se though. Closer but not enough 

[CoastalWx]

That would be a lot of fun. No need to jack, just rain to tree snapping paste. I'd hit it. Despite the QPF, that is sort of a good inflow look into SNE on Friday night. Those always seem underestimated as modeled.

[weathafella]

8 minutes ago, TauntonBlizzard2013 said:

That is better for a good chunk of folks.... and probably the closest solution to a winter storm we have down this way. Still not rally close for Boston and points se though. Closer but not enough 

Boston gets buried in that euro run Friday morning onwards.  If you’re using surface temperature know it’s wrong if everything obtainable by ECMWF is cold 2000 feet on up.

[ORH_wxman]

Just now, CoastalWx said:

That would be a lot of fun. No need to jack, just rain to tree snapping paste. I'd hit it. Despite the QPF, that is sort of a good inflow look into SNE on Friday night. Those always seem underestimated as modeled.

YEah the last 12-18 hours of the event that run reminded me of that classic firehose look where models decay the precip a little too much. The first 18 hours though is ridiculous. Even if the first 6-8 hours is heavy rain here. 

[CoastalWx]

Hopefully the EPS agrees.

[Damage In Tolland]

Can anyone give idea on precip start time estimates 

[Baroclinic Zone]

8 minutes ago, CoastalWx said:

That would be a lot of fun. No need to jack, just rain to tree snapping paste. I'd hit it. Despite the QPF, that is sort of a good inflow look into SNE on Friday night. Those always seem underestimated as modeled.

Yeah, that would be wild to see unfold.

[ORH_wxman]

3 minutes ago, Damage In Tolland said:

Can anyone give idea on precip start time estimates 

Why are you obsessed wth the timing this far out? 

This run is like mid to late Thursday afternoon but that is rain to start. Flips to snow Friday morning (maybe Thursday night for ORH county to berks in SNE) 

[moneypitmike]

9 minutes ago, weathafella said:

Boston gets buried in that euro run Friday morning onwards.  If you’re using surface temperature know it’s wrong if everything obtainable by ECMWF is cold 2000 feet on up.

I can work with landing in BOS.........

[Typhoon Tip]

33 minutes ago, Damage In Tolland said:

Starts Thursday night rain or snow? And ends Saturday?

It has as shot at being a 30 -hour sort of system...

I could see that really pounding the region for 12 hours, than going consistently moderate for 20 hours straight thereafter... Where most areas get their snow... but, during the 12 hours, that could be a flash dynamic bomb as a wild card.

Things is... (for the purer winter enthusiasts), this is about where you want the thermal plumbing to laid out at this sort of time lead for systems that are destined to be the isothermal affairs we've memed the schit out of lately.  That said, this could still in the off chance even end up sort of like 0 C, -3C, -5C at max dynamic depth.... But that's imagination rooted in science, not yet depicted - so taken for what it's worth.

Anyway, that look reminds me of 1992 a bit... Not so much for the mid level evolution, but the way you have a nebular commitment to -2 C at 850, then the storm bombs suddenly there is a focused coherent transition axis - that's dynamics forcing that hand there. 

I was up at UML in 1992 ..Freshmen (crap, I'm dating myself) and it was one helluvan inauguration into the Met major.  I still to this day I have never witnessed a more explosive, instantaneous dynamically forced change in an environmental setting that compares to what took place that faithful evening of the 10th of December.  I've told this story before ... but, paraphrasing, seeing heavy rain flash to heavy snow is something extraordinary. Seeing that happen in under a minute... that's just eerie.  I mean, I am not talking about it flipping over pretty quick ... no! I'm literally and not figuratively saying that in 30 seconds, we went from wind swept sheeting rain to 1/4 visibility snow... period. 

I was just keying my door to my dorm room on the 7th floor of Fox Tower, when through the window on the far side of the darkness, flashed a couple of brilliant pulses of light. Knowing immediately that it was lightning, I naturally had to stumbled through the darkness to the window right as the cacophony of thunder made the pane of glass buzz at the edges... And, as I stared out over the parking lot below toward the lamp lights, waiting for the next flash, my peripheral vision was rather drawn straight ahead; a dull glow emerged from over the distant hills on the other side of Merrimack River...It's about three or four miles from that vantage point. 

I did not know what it was at first; one does not normally see such apparitions suspended between Earth and sky.  But as distant lights were disappearing one by one ... blinking out as this abyssal glowing vertical wall was clearly advancing forward, just about the time I internally monologued that it must be snow, the street lamps below confirmed as they were immediately illuminating swirling particles like sun beams through dust... moving sideways. And at that, there were no distant lights visible at all.  That whole transition took about 30 seconds to a minute to unfold, and we ended up with 15" by dawn... 18 total for the event, from a starting point of nothing.

Well...obviously... one does not 'predict' such events, but, this thing in the Euro and others.. it sort of reminds me of that, when looking at the DeJaView charts for the week of that event, Dec 1992, over at the NCEP library site.

[jbenedet]

21 minutes ago, TauntonBlizzard2013 said:

That is better for a good chunk of folks.... and probably the closest solution to a winter storm we have down this way. Still not rally close for Boston and points se though. Closer but not enough 

Honestly though, the winds, coastal flooding and beach erosion will be the story down there either way. NNE and CNE win on the winter impacts but you guys get hammered with the other storm impacts.

[Baroclinic Zone]

2 minutes ago, ORH_wxman said:

Why are you obsessed wth the timing this far out? 

This run is like mid to late Thursday afternoon but that is rain to start. Flips to snow Friday morning (maybe Thursday night for ORH county to berks in SNE) 

Gotta time his TH stop.