Gnarly Nor'easter 1/24 to 1/25/17 our favorite week

[OceanStWx]

Day 4 GEFS variance. We probably don't want the EOF1 variance (lower pressure near SNE probably means warmer overall).

Which means we want the opposite sensitivity of whatever EOF1 shows. 

Unfortunately we don't get a strong sensitivity signal until about 72 hours (from 00z last night), so there's a lot of time left. But moral of the story, we would want the opposite of the blue (meaning higher heights across the western CONUS and into Canada).

[OceanStWx]

FWIW, the EPS is a similar sensitivity.

[HIPPYVALLEY]

10 minutes ago, 40/70 Benchmark said:

I just want a large precipitation event to be something other than rain here. Been about exactly two years.

Three years for me. 

[HoarfrostHubb]

25 minutes ago, 40/70 Benchmark said:

That never works out here.

I wonder if your hood has ever experienced a siggy ice event (1"+ accretion)   1920s event?

[HoarfrostHubb]

18 minutes ago, dryslot said:

What the hell is going on in here? Its like a funeral home.

I'm driving the hearse.   We all know the pattern has been crap, so for this to stay rain or sleet should not surprise many in SNE... just gets kind of tedious.  Looking forward to Feb

 

If I call this wrong I will be ecstatic

[Whineminster]

It's very hard to get a big icing event on the coastal plain, it's ether rain or snow or maybe some IP

[ORH_wxman]

30 minutes ago, OceanStWx said:

Day 4 GEFS variance. We probably don't want the EOF1 variance (lower pressure near SNE probably means warmer overall).

Which means we want the opposite sensitivity of whatever EOF1 shows. 

Unfortunately we don't get a strong sensitivity signal until about 72 hours (from 00z last night), so there's a lot of time left. But moral of the story, we would want the opposite of the blue (meaning higher heights across the western CONUS and into Canada).

Def matches a stronger block being better and the block further west...a further west block really raises heights over the Great Lakes and up into James bay. 

[RUNNAWAYICEBERG]

33 minutes ago, 40/70 Benchmark said:

I just want a large precipitation event to be something other than rain here. Been about exactly two years.

I would trade places in a heartbeat if two years ago I shoveled 30"+ and took swan dives off my roof as a deform band massaged my groin for hours.

[40/70 Benchmark]

4 minutes ago, Whineminster said:

It's very hard to get a big icing event on the coastal plain, it's ether rain or snow or maybe some IP

Get beyond me, and you're fine....honestly, no sarcasm intended. About 2-3 mi wnw of me and you're golden.

[USCAPEWEATHERAF]

6z NAM was down to 973mb at the Delmarva Peninsula.

[40/70 Benchmark]

1 minute ago, RUNNAWAYICEBERG said:

I would trade places in a heartbeat if two years ago I shoveled 30"+ and took swan dives off my roof as a deform band massaged my groin for hours.

There is always someone who has it worse, yet we always yearn for better.

[Typhoon Tip]

1 hour ago, OceanStWx said:

I mean the signal is there for decent probabilities of freezing rain on the analogs. 

I'm getting more interested in that "rarefied" coatal/Nor'easter type of ice storm. ...at least, listening to the sale's pitch.. 

What has me spooked is that the last 6 cycles of the NAM has gotten steadily, albeit subtly, more aggressive with the cold in the 850 mb level.  

850 mb is typically too deep for icing - hydrometeoroids tend to bind back up from that altitude, but ..more than anything for me, that "tendency" described above flags a colder surface thickness than guidance may be painting at this time in general.   So.. in sort of a corrective mode, if we think colder lowest level with any sort of strongish 800 mb warm tongue/intrusion ... a fairly wide band could get a few hours of intense accretion from east flow riding over top of llv cold.  I tell you what ... look at 2008 if one needs an example of how fresh low-ish dew points can help an icer over-perform. 

At 48 hours, the 06 Z NAM continued with that behavior.  It actually even bears some semblance a backdoor cold front ... and with that block up there and a large attending surface +PP tending to displace SE anyway, ... think of it this way... a 90 forecast in late April, 38 in drizzle results...  It's a silly comparison in mid winter, but it is said to point out that cold air ALWAYS wins in our particular lat/lon given to certain recognizable larger scaled features.  What part of block and 'fresh' polar air building into N Maine and our history lends anyone to believe in warmer surface results?  If so...immediately you need to fire off an email to an Admin requesting the violent termination of any history of your account on this, or any, weather -related social media. 

Larger scaled "tuck" and f pattern or not...Then, as the low deepens along he mid Atlantic coast .. the tendency for cross-isobaric flow only increases; particularly if said low gets closer to an interval of rapid intensification - less likely given the nebular baroclinicity to work with in that area of the M/A, I know... But sufficed it is to say, any deepening S, with +PP N, is a cold solution here and the models will almost never assess the surface correctly, anyway regardless of ageostrophy. 

So, combining all things .. that sale's pitch doesn't sound so much like a slick one really.. (well, pun intended, it could end up that way).  

Part of the additional concern there is that (as the NAM shows..) there is a fresh polar air source.  It is not as rotted as the present air mass.  The 850 mb temperature is less than -6 C over Lowell Massachusetts and about 0 C just S of Kevin's shiny dome.  That's cold in that level (most probably almost isothermal to the surface) wedging/tucking/whatever verb ...backdooring/ bullying its way in.   New air kinda changes the landscape a little.  Loop this and you can really get a solid impression of the 'newness' of the cold air pulsing in from the NNE... 

http://ggweather.com/loops/nam_06z_850.shtml     ... plus, that's shedding off a pervasive snow pack and (eyes roll..) that's not hurting regardless...

(I by now you may be wondering why I'm diatribing these things that you already know...? I'm not: this is morning coffee, arm chair quarterbacking for the general reader)

So, beyond what I see is certainly a possible icer nor'easter should those NAM solutions work (and that model hasn't been performing exactly horrendous this season - I wonder if the petaflop up grades in computing capacity is helping?  ), I would also be concerned that the cold is just deep enough anyway and this ends up being ginormous bust in the under with snow/PL stuff, too. 

If the NAM were not doing that at all, I wouldn't have probably written 90% of this... But considering all models and their respective behavior, this has been the most consistent over the last 24 hours. 

[HoarfrostHubb]

Anyone care to explain to me the physics/importance of "fresh" polar air vs rotted?  Is it just colder?

[Damage In Tolland]

4 minutes ago, Typhoon Tip said:

 If so...immediately you need to fire off an email to an Admin requesting the violent termination of any history of your account on this, or any, weather -related social media. 

 

Talk dirty to us ice storm fetishers

[klw]

NAM looking a little weaker, further west at 12Z that the 6Z did.

850 cold is a little later moving in

 

[Hoth]

Great read, Tip. Maybe see the cold bleed south through the CT Valley?

[Typhoon Tip]

6 minutes ago, HoarfrostHubb said:

Anyone care to explain to me the physics/importance of "fresh" polar air vs rotted?  Is it just colder?

yes... no mysteries there.. 

by fresh, it's got less tainted mixing with other air and/or modulation from things like the ocean or the sun and so forth.  

loop that nested link i provided, you'll see/sense what i mean there.   also, by 'fresh' it is also implied that there is a bit of an unknown there as to just 'how' cold it is, but given that loop and common experience with highs building in that fashion from the N, said correction is LESS likely pointed warmer -

 

[dendrite]

4 minutes ago, HoarfrostHubb said:

Anyone care to explain to me the physics/importance of "fresh" polar air vs rotted?  Is it just colder?

The phase change of liquid to ice (ZR) releases latent heat into the atmosphere. Think of it this way...in order to go to a lower energy state (liquid to ice) there has to be a conservation. So the water "loses" the energy (heat) and the environment has to "gain" it. So what you need is a continuous supply of fresh (low dews) air into the low levels to offset the latent heating from the ZR. Without it, the low levels warm up to ~32F and rot there without anymore glazing taking place. When we lose that low level dry/cold advection we usually call the events in-situ damming. Basically we're just working with the cold, dry air that's already in place. We ZR with it until the cold rots. Ice storms like 98 and 08 keep the fresh, cold air supply coming.

[Typhoon Tip]

1 minute ago, dendrite said:

The phase change of liquid to ice (ZR) releases latent heat into the atmosphere. Think of it this way...in order to go to a lower energy state (liquid to ice) there has to be a conservation. So the water "loses" the energy (heat) and the environment has to "gain" it. So what you need is a continuous supply of fresh (low dews) air into the low levels to offset the latent heating from the ZR. Without it, the low levels warm up to ~32F and rot there without anymore glazing taking place. When we lose that low level dry/cold advection we usually call the events in-situ damming. Basically we're just working with the cold, dry air that's already in place. We ZR with it until the cold rots. Ice storms like 98 and 08 keep the fresh, cold air supply coming.

haha, I was scared to get deep - nice! ...but yeah, this is a 'taint' factor - one of few. 

[dendrite]

I probably should've fully read Tippy's post before replying to Dave. I guess that's not what John was implying with "fresh".

My post still stands though.

[SnowlieSnowstormson]

Interesting though that the 12Z 4KM NAM at Hour 60 seems to hint at that cold air bleeding southward at 850 and surface. Also seems to have an entirely different take on storm location. 

[OceanStWx]

One thing my SOO and I were talking about is the wet bulb temps through the event (seeing as our local media is already playing up big ice). To get significant mixed precip you want a surface wet bulb below zero, and a wet bulb aloft above zero. In this example I have the surface wet bulb image (black line is 32F), and the white lines are max wet bulb in the 0-6km layer. 

06z Tue:

12 Tue:

The GFS actually shows a fair bit of sub 32F surface air below wet bulbs aloft > 0C. That is a good signal for mixed precip.

[OceanStWx]

Conversely, the Euro.

06z Tue:

12z Tue:

See how closely the 0C surface wet bulb matches the 0C max wet bulb aloft? That is more of rain or snow signal versus mixed precip. Your isothermal snow.

[Typhoon Tip]

9 minutes ago, klw said:

NAM looking a little weaker, further west at 12Z that the 6Z did.

850 cold is a little later moving in

 

sure did ... The changes seem to be keyed into the handling of the primary low on this run - 

Firstly, this is the first in like 6 cycles where front-side cold from eastern Canada was less aggressive - so, for fwiw, it doesn't have continuity on its side in general.  But, the primary is deeper also at 850 mb level back toward Ohio, and so that may also impact the total evolution of this thing in general. 

The other thing, the cold is actually more intense in western Maine despite holding back the 6 or so hours on this run... 

One thing about this: it's probably a 24 hour evolution to get through this thing's influence/impacts... so, what we think of leading into this thing, may be entirely irrelevant by hour 12, too.  

[HoarfrostHubb]

I appreciate the lesson Brian and John

[HoarfrostHubb]

12 minutes ago, Typhoon Tip said:

haha, I was scared to get deep - nice! ...but yeah, this is a 'taint' factor - one of few. 

I seem to recall you explaining the 2008 storm to me in a similar way as Brian did (this was a while ago).  It really helped me understand how precarious that event was and how the actual mechanics worked

[qg_omega]

Just now, White Rain said:

Without some major positive trending in the near term..this looks like most of SNE is going to see primarily rain from this. Looks good for MPM area up into NNE.  I'm all set with ice here and sleet is pretty boring but that's prob our best case around here without some changes fast.  I'm not sure why people root for ice, a small amount looks nice but ice storms suck. Maybe we grab a couple of inches of snow on the front end. 

NAM brings incredible winds to NJ / NYC / Long Island

[Typhoon Tip]

1 hour ago, OceanStWx said:

Day 4 GEFS variance. We probably don't want the EOF1 variance (lower pressure near SNE probably means warmer overall).

Which means we want the opposite sensitivity of whatever EOF1 shows. 

Unfortunately we don't get a strong sensitivity signal until about 72 hours (from 00z last night), so there's a lot of time left. But moral of the story, we would want the opposite of the blue (meaning higher heights across the western CONUS and into Canada).

that's not exactly good for winter weather enthusiasts when objectively being deterministic/analytical, ...no.

one would want the spread smeared less than right over land hahaha.   That means the ensembles are telling us, "they feel" whatever correction is coming, don't get your hopes up..  

In 1997, end of March... I recall seeing a product very similar to this where the 'spread' was smeared back well west of a strong west Atlantic spring bomb .. some 6 days prior to lore.

That said, the operational guidance has been trended SE across the board ..inching...erratically..but ending at present modeled form, so that spread could also be lag with lesser resolved members - I guess what I mean is, is this one of those times where the spread is telling lies or tipping off the Feds -

[Typhoon Tip]

Yeah, 12z NAM has the appeal of just starting out as a miserable 33 F rain after several hours of snow grains.... wah wah waahh

It's a fantastic look though, ptype aside though.  It's got some facets to consider now, such as a deeper system maybe have greater impacts of coastal/marine districts... I think tides are not appreciably high right now (check that...) just as typing.  But, the high up N is actually a little stronger this run, and together with a somewhat  stronger system is creating a pretty impressive gradient along the M/A and NE coasts. 

 

[OceanStWx]

15 minutes ago, HoarfrostHubb said:

I seem to recall you explaining the 2008 storm to me in a similar way as Brian did (this was a while ago).  It really helped me understand how precarious that event was and how the actual mechanics worked

Ice storms require a great deal of balance. In addition to being destructively beautiful, they are also very delicate systems. You need the WAA and latent heating of freezing to be offset by CAD and latent cooling of evaporation. Or in the case of 2008, just enough wind to carry away all that latent heat.