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Pats/Chiefs Miller B-elichick

40/70 Benchmark

By 40/70 Benchmark,
in New England

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bobbutts

bobbutts

Posted
Posted

NIce cool evening in North Dendriteville.    23.9/20F at  6:25pm.   The way cold air dams around here its going to take awhile to get to 32F

It's a good gradient North to South.. I drove from Boston area earlier this afternoon and it steadily dropped from 39 to 31, given your obs that continues up 93.

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CoastalWx

CoastalWx

Posted
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yeah, sorry... i'm stealing moments away from work, dropping by with occasional excitement (ya, i like this look personally). - not sure whose posted what to be frank :)

Oh I didn't mean it like that, I wa basically agreeing with that map. It's the area I would watch. I have a hard time, should the mid level look verify, of seeing rain for at least the high terrain of ORH countY. I also think low levels below 2k may be slightly underestimated. But should models not cool and dynamics not occur, forget it.

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powderfreak

powderfreak

Posted
Posted

I certainly think the colder solution could verify with several inches of heavy wet snow in the ORH hills and monads...but I'm leaning marginally away from that at the moment. I'm like 60/40 against right now. I think 925mb layer or thereabouts is going to be just a pinch too warm...and there's also the issue of absolutely needing that insane 50+ microbars of lift...no guarantee we get that.

 

But I'm not closed off to the idea that there will be a snowier surprise...I may change my thoughts tonight as more real time data comes in.

 

Will the lift be strong enough with sort of the low QPF values?  I guess it is a quick hitter so it will still come down heavily. 

 

But total QPF at 18z models seemed meh.

 

These are all through 36 hours:

 

18z RGEM

 

 

18z GFS

 

 

18z 4km NAM

 

 

The 18z 12km NAM is definitely the wettest...this would get the job done.

 

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powderfreak

powderfreak

Posted
Posted

I just checked and the 18z NAM and 18z RAP...looks like they are running about 2C too warm over SNE at 925mb...closer to 1C down on the south coast and they are pretty on target over LI.

 

SO yeah, they are still running too warm...but we'll see if that changes tonight.

 

If there is a time for something like this to bust cold/snowy, its in mid-January.  These are like those things that you see at the early/late season time frames, but marginal in mid-January might lean colder than it normally would at other times of the year.

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powderfreak

powderfreak

Posted
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Well you'll need to see how the mid levels work out PF. As we have seen, QPF is part of the story. That's actually more important to see where they go because it's under their magic where we may see a flip.

Yeah I'm not worried about QPF. I'm worried about mid level low track and CCB dynamics. The QPF will come if those occur. That said, runs like the 18z GFS and RGEM were a bit weak on that front.

Well yeah I guess I look at QPF as a function of the mid-level low track and CCB. Like the model prints out heavy QPF, its got a favorable CCB and strong lift. Like you said, if they happen the QPF will come. But can't you look at the QPF and sort of assume whether or not it would happen based on what the model prints out? If its got a strong band of QPF, chances are its got huge UVVs and good banding signals there, too. Like the GFS and RGEM were weak on that front, and likewise had weak QPF.

Convective feedback would be the main reason I could see a disconnect between QPF progs and the processes that cause the QPF such as mid-level lift and CCB development.

I also think I may assume the models are smarter than they actually are...

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ORH_wxman

ORH_wxman

Posted
Posted

PF, QPF is a good crude tool but I will look at mid levels and lift if it is available to confirm it. Euro has massive lift tomorrow morning so I would favor heavier QPF in that scenario. Ditto NAM.

RGEM and GFS are indeed a bit weaker. But sometimes the models don't always do well with QPF even with lift and good mid levels. We see it all the time in Nor Easters when the model doesn't put good QPF far enough to the northwest of the mid level center. It will have this gradient where SE areas get the most and taper it outward....when in reality I'm sitting there saying "that area which shows 0.55" of QPF is gonna get rocked."

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CoastalWx

CoastalWx

Posted
Posted

PF should knows this lol. Models sometimes will underestimate QPF in the H7-H5 layer of strong frontogenesis and sort of over emphasize QPF in the low level WAA regimes. Now the one thing about this that is different, is that it has a lot of convection or at least low level convergence and heavy rain possibly robbing moisture like we see in the summer. This usually isn't the case in the cold season...but given the warm nature of this...I sort of wonder. The RGEM and GFS were rather weak in the CCB/fronto dept, but the other meso models looked rather robust. BTV WRF too. It will come down to a nowcast deal I am sure. You need dynamics or else it's catpaws

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powderfreak

powderfreak

Posted
Posted

PF should knows this lol. Models sometimes will underestimate QPF in the H7-H5 layer of strong frontogenesis and sort of over emphasize QPF in the low level WAA regimes. Now the one thing about this that is different, is that it has a lot of convection or at least low level convergence and heavy rain possibly robbing moisture like we see in the summer. This usually isn't the case in the cold season...but given the warm nature of this...I sort of wonder. The RGEM and GFS were rather weak in the CCB/fronto dept, but the other meso models looked rather robust. BTV WRF too. It will come down to a nowcast deal I am sure. You need dynamics or else it's catpaws

 

Thanks for the responses Will and Coastal.  I guess I always thought of the banding more as a snow growth thing than necessarily a straight QPF thing.  For example, last Thanksgiving's storm when I was all bummed out about getting under a half inch of QPF while Dendrite got 1.5" of QPF.  You guys kept saying I'd get nailed because of banding above 700mb.  Then we got 11" of snow...however QPF was pretty spot on with around 0.4" of liquid.  It was just that due to strong banding we were ripping huge dendrites and made the most of our 0.4" of liquid. 

 

So we got 11" and 0.4" liquid, while Dendrite got his foot and like 1.5" of QPF along with power outages and stuff.

 

I guess I always thought of that banding as more ratio driven than QPF-driven.  You know you get under that 30-40dbz band and its ripping dendrites at inches per hour but still only 0.05"/hr in the bucket. 

 

So you still get "nailed" per se in total snowfall, but the QPF was fairly close to what was progged, if that makes sense.  That place progged to get 0.55" but with a good mid-level track ends up with 15" of 30:1 snow while the guy getting 1.0" QPF gets 11" of needles.

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CoastalWx

CoastalWx

Posted
Posted

Thanks for the responses Will and Coastal. I guess I always thought of the banding more as a snow growth thing than necessarily a straight QPF thing. For example, last Thanksgiving's storm when I was all bummed out about getting under a half inch of QPF while Dendrite got 1.5" of QPF. You guys kept saying I'd get nailed because of banding above 700mb. Then we got 11" of snow...however QPF was pretty spot on with around 0.4" of liquid. It was just that due to strong banding we were ripping huge dendrites and made the most of our 0.4" of liquid.

So we got 11" and 0.4" liquid, while Dendrite got his foot and like 1.5" of QPF along with power outages and stuff.

I guess I always thought of that banding as more ratio driven than QPF-driven. You know you get under that 30-40dbz band and its ripping dendrites at inches per hour but still only 0.05"/hr in the bucket.

So you still get "nailed" per se in total snowfall, but the QPF was fairly close to what was progged, if that makes sense. That place progged to get 0.55" but with a good mid-level track ends up with 15" of 30:1 snow while the guy getting 1.0" QPF gets 11" of needles.

You are absolutely right in that sense. I agree. I think that's why I also mentioned how this is a warmer storm that could have convection to possibly rob moisture from going into the conveyor belts too. But overall, I feel fairly confident in saying models do underestimate QPF in banding zones despite the ratios. But, the EC and NAM made sense from the QPF output and H7 lows. GFS was kind of meh there which made me wonder if the GFS does not have the theta-e injection the euro and nam have. Again though, if that is weak like RGEM and GFS, then forget it. I find this an interesting test here.

You are getting to really get the hang of forecasting. That was a good thought out response there because you are correct in that.

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dendrite

dendrite

Posted
Posted

Thanks for the responses Will and Coastal.  I guess I always thought of the banding more as a snow growth thing than necessarily a straight QPF thing.  For example, last Thanksgiving's storm when I was all bummed out about getting under a half inch of QPF while Dendrite got 1.5" of QPF.  You guys kept saying I'd get nailed because of banding above 700mb.  Then we got 11" of snow...however QPF was pretty spot on with around 0.4" of liquid.  It was just that due to strong banding we were ripping huge dendrites and made the most of our 0.4" of liquid. 

 

So we got 11" and 0.4" liquid, while Dendrite got his foot and like 1.5" of QPF along with power outages and stuff.

 

I guess I always thought of that banding as more ratio driven than QPF-driven.  You know you get under that 30-40dbz band and its ripping dendrites at inches per hour but still only 0.05"/hr in the bucket. 

 

So you still get "nailed" per se in total snowfall, but the QPF was fairly close to what was progged, if that makes sense.  That place progged to get 0.55" but with a good mid-level track ends up with 15" of 30:1 snow while the guy getting 1.0" QPF gets 11" of needles.

I had a decent amont more of liquid in my 2011 deformation bands than QPF...but you and Scoot are right about the ratios. I feel like you and I discussed this topic before one day. Maybe it's just deja vu.
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CoastalWx

CoastalWx

Posted
Posted

And by the way, think of theta-e as a nice combo of heat and moisture. The higher the value, the more warmth and moisture you have in a system. Note this comprises of warmth and moisture. You can achieve a certain value by warm temps and lower moisture, or higher moisture with slightly lower temps. So, it's a combination of two variables in a sense. I'm not getting into logistics of it because it's a bit complicated.

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CoastalWx

CoastalWx

Posted
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You just get a feeling something is up. Temps and dews are low even along the water . Models 1-2 degrees too warm. Coastal stronger than modeled . Maybe it's nothing

Nah I wouldn't get too weenie and think 8" en route, but it may be interesting if NAM and Euro happen. Not an easy scenario.

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powderfreak

powderfreak

Posted
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You are absolutely right in that sense. I agree. I think that's why I also mentioned how this is a warmer storm that could have convection to possibly rob moisture from going into the conveyor belts too. But overall, I feel fairly confident in saying models do underestimate QPF in banding zones despite the ratios. But, the EC and NAM made sense from the QPF output and H7 lows. GFS was kind of meh there which made me wonder if the GFS does not have the theta-e injection the euro and nam have. Again though, if that is weak like RGEM and GFS, then forget it. I find this an interesting test here.

You are getting to really get the hang of forecasting. That was a good thought out response there because you are correct in that.

Thanks dude, and I do think you are right that where those bands set up there is enhanced QPF that the models under-estimate. I just went back to look at the storm referenced above and we were progged around a third of an inch, yet realized 0.4-0.5". So the banding definitely helped but the biggest difference is the ratios under those bands, as without the ratios it's an increase of 3" to 5"....as opposed to 3" to 11" lol.

And I fully know and love being a weenie and a QPF queen...and not just because I like looking at the pretty colors of a QPF map, but because I assume the models are consistent throughout the layers. If it's got big QPF it's got big lift, and likewise if you see big UVVs values, the model prints out big QPF.

I'll definitely heed the information of under-doing QPF in banding, but also that in a lot of our snowstorms it's the banding that drives ratios. Even the October 2011 event, Blizz got a foot (right?) of absolute mashed potatoes, while SkiMRG got over 30" of relative fluff in that deform band. Their actual QPF was probably very similar, just that mid-level band caused the snow growth to go to town.

However, QPF queen or not, when looking back on old snowstorms and maps of past events, the event is remembered by the inches of snow that fell not the liquid equivalent. Same with the end of a snow season, it's the total snowfall not QPF that gets measured. So you look at an old storm and see a stripe of jackpot in the interior, what isn't necessarily shown is that the "lesser snow amounts" further SE were likely the larger impact due to water content.

I could talk snow for hours...getting off topic anyway. Haha, thanks for the conversation.

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