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Baroclinic Zone

December 5-6, 2020 Storm Observations and Nowcast

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20 minutes ago, OceanStWx said:

Trying to dive deep to figure out what the real failure point was here, because I don't really think it was forcing. The QPF was pretty good, right ballpark anyway, clearly there was strong f-gen in the right location relative to the storm. 

I keep coming back to our 00z sounding last night with DGZ up around 500 mb. That's not a great spot and indicative of a pretty torched air mass. Dropping less than dendrite ratios into a deep near freezing layer primed snow to melt at the surface. Even when rates were decent. There was a lot of 1/2 to 3/4SM snowfall that normally would accumulate if your flakes weren't already near slush by the time they reach the ground. Honestly the 04.12z NAM forecast soundings weren't bad in the vicinity of GYX, and it should've been a bigger red flag to me. 

We were running with ratios around 7:1, but they needed to be lower than that given the environment we were working with. Elevations did better because it shrunk the near freezing layer that flakes had to fall through and kept near surface temps slightly cooler. 

Yea when I flipped and started accumulating fast I thought for sure 12 was a distinct possibility. This quieted my appetite, but I’m already craving more! Thankfully it’s December and not late Feb. Any 12+ potential and I’m on the road these days, gotta enjoy my 30s no regrets!

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4 hours ago, MarkO said:

<400'

I'm dumb..

Location:Thornton, NH 1100'

 

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1 hour ago, OceanStWx said:

It takes some stones to forecast a significant period of 3:1 or worse ratio. 

I had a general 3-5" in my Portland/Augusta/Bangor forecast when I left on Friday, but given what the NWS and folks on the board were discussing, I was really worried I was going to bust low. I'm glad there was such a struggle in that regard. Lack of drier dewpoint advection and strong lift but in the wrong spot kinda makes sense to me. Given the lack of good antecedent airmass, there's more bust potential if things don't align. 

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13 minutes ago, STILL N OF PIKE said:

This storm was impossible to forecast in CP of Maine 

We’re about 1/2 mile from the ocean. Wouldn’t be surprised if there’s more west of Route 1.  Good discussion earlier about the torched layer and how it likely inhibited accumulation even with decent intensity. When we started to flip around noon I figured we were primed for a thumping.

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8 minutes ago, HoarfrostHubb said:

Lots of tree damage in my neighborhood. Mostly birch trees that snapped or pine branches.   I am very surprised we never lost power

Yeah got a few maple branches in my driveway.  Saw 2 transformers pop while outside last night, my folks lost power for a bit 

IMG_20201206_072955121_HDR_compress52.jpg

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2" here in Salem, CT.  It really came down under that heaving banding from 12-3pm but changed back to rain by 4:30pm and never got below 34 until after midnight.

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2 minutes ago, Whineminster said:

Yeah got a few maple branches in my driveway.  Saw 2 transformers pop while outside last night, my folks lost power for a bit 

IMG_20201206_072955121_HDR_compress52.jpg

What’s your elevation there? That looks up there . Is that Wachusett in background?

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42 minutes ago, Damage In Tolland said:

Posting on the toll road looks up as he read ends the park ranger 

Definitely not driving as they don’t plow this in winter lol. Buried above 1400- 1500’. Drier top half of accums as you go high. Passed a skier and thanked him for his tracks .

Just Stopped around 1750’ as drifting became an issue even with someone’s boot tracks to use to climb.

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1 hour ago, stormtracker said:

Ended up with 13" here in Eustis, ME.  Was a beautiful night

If you haven’t done it yet and if the air and roads are clear, take a drive up and to the end of Eustis Ridge Rd. For me, of the best views in all NE.

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10 hours ago, PhineasC said:

I should have bought a yardstick.

lol, That's a rookie mistake, You're no in Kansas anymore Dorothy.

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3 hours ago, moneypitmike said:

Anyone who scored the most and how much from this?  I'm guessing it was Jeff.

Nope, 5.5" garbage ratios.

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1 hour ago, OceanStWx said:

Trying to dive deep to figure out what the real failure point was here, because I don't really think it was forcing. The QPF was pretty good, right ballpark anyway, clearly there was strong f-gen in the right location relative to the storm. 

I keep coming back to our 00z sounding last night with DGZ up around 500 mb. That's not a great spot and indicative of a pretty torched air mass. Dropping less than dendrite ratios into a deep near freezing layer primed snow to melt at the surface. Even when rates were decent. There was a lot of 1/2 to 3/4SM snowfall that normally would accumulate if your flakes weren't already near slush by the time they reach the ground. Honestly the 04.12z NAM forecast soundings weren't bad in the vicinity of GYX, and it should've been a bigger red flag to me. 

We were running with ratios around 7:1, but they needed to be lower than that given the environment we were working with. Elevations did better because it shrunk the near freezing layer that flakes had to fall through and kept near surface temps slightly cooler. 

I have to go back and find that great paper about dendritic and ice crystal growth but I also remember from it that it talked about how the well-formed dendrites/ice crystals will latently cool more efficiently when they melt than marginal ice crystals. So kind of a double whammy there in a super marginal air mass. 

There was a ton of QPF that fell in the CCB...agreed on that. So it wasn’t like we got dried out over E MA. It just ended up basically being sleet ratios there. 

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2 minutes ago, ORH_wxman said:

I have to go back and find that great paper about dendritic and ice crystal growth but I also remember from it that it talked about how the well-formed dendrites/ice crystals will latently cool more efficiently when they melt than marginal ice crystals. So kind of a double whammy there in a super marginal air mass. 

There was a ton of QPF that fell in the CCB...agreed on that. So it wasn’t like we got dried out over E MA. It just ended up basically being sleet ratios there. 

I wasn't positive of that, but intuitively it makes sense. If you create a crystal at -5C it's going to take less heat to warm it up to 0C than if you create a crystal at -12C. Even if your crystal structure may be more delicate. 

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3 minutes ago, OceanStWx said:

I wasn't positive of that, but intuitively it makes sense. If you create a crystal at -5C it's going to take less heat to warm it up to 0C than if you create a crystal at -12C. Even if your crystal structure may be more delicate. 

Yeah if you’re throwing a bunch of marginal ice crystals at relatively warm temps (like around -5C as you said) into a layer at 32-33F, that sounds uglier than throwing a bunch of hooked dendrites at -10 to -14C into that same layer. 

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10 minutes ago, ORH_wxman said:

I have to go back and find that great paper about dendritic and ice crystal growth but I also remember from it that it talked about how the well-formed dendrites/ice crystals will latently cool more efficiently when they melt than marginal ice crystals. So kind of a double whammy there in a super marginal air mass. 

There was a ton of QPF that fell in the CCB...agreed on that. So it wasn’t like we got dried out over E MA. It just ended up basically being sleet ratios there. 

Is it a mass issue? Melting large aggregated dendrites would remove more heat from the environment than smaller flakes? 

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3 minutes ago, OSUmetstud said:

Is it a mass issue? Melting large aggregated dendrites would remove more heat from the environment than smaller flakes? 

I think spatial area coverage too. Big hooked dendies will be efficient in cooling.

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Without the drier dewpoints you also lose any heat of vaporization effects, which is about 8 times larger than the heat of fusion. So you're only left with heat of fusion and a smaller contribution of sensible heat from the flakes themselves. 

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2 minutes ago, OSUmetstud said:

Is it a mass issue? Melting large aggregated dendrites would remove more heat from the environment than smaller flakes? 

Yeah I’m not sure. The temperature of the ice matters too. I’ll have to search for the paper I mentioned...I think I have it saved on my pc downstairs. It’s like my go-to source for this kind of stuff. It talks about everything including how you can get ice crystals in areas close to the ocean as low as -4C to -5C due to the salt nuclei being far more efficient at warmer temps. 

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2 minutes ago, ORH_wxman said:

Yeah I’m not sure. The temperature of the ice matters too. I’ll have to search for the paper I mentioned...I think I have it saved on my pc downstairs. It’s like my go-to source for this kind of stuff. It talks about everything including how you can get ice crystals in areas close to the ocean as low as -4C to -5C due to the salt nuclei being far more efficient at warmer temps. 

Right, I usually use -6 out here and then -8 in Ontario, but it's just an estimate because of the stochastic nature of cloud droplets. 

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2 minutes ago, CoastalWx said:

I think spatial area coverage too. Big hooked dendies will be efficient in cooling.

Goes back to what you said originally though Scott how most places didn't see flakes flourish in the DGZ. I remember looking at soundings and x-sections yesterday and saw the same thing. Best lift was either above or below it (at least the stations I was looking at). 

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