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NNE Winter Thread


powderfreak

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51 minutes ago, CoastalWx said:

Where in Moultonboro? I honestly would love to know what happened there. It almost seems like some sort

of downslope wind there off the Ossipees, but I don't know.

If you look at the timing. About 45 minutes before the winds in NH there were thunder snow reports NE of ORH. I wonder if there was a core collapse and microburst.

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5 hours ago, CoastalWx said:

Where in Moultonboro? I honestly would love to know what happened there. It almost seems like some sort

of downslope wind there off the Ossipees, but I don't know.

 

4 hours ago, Ginx snewx said:

If you look at the timing. About 45 minutes before the winds in NH there were thunder snow reports NE of ORH. I wonder if there was a core collapse and microburst.

The downsloping is my gut feeling. We had 63 knots at just about 900 mb (2250 ft agl).

The highest Ossipees are about 2700-2900 feet. Our sounding inversion was around 2000 feet, could have been higher in NH. But you had pretty ideal conditions for downslope winds. Cross barrier flow near ridge level, inversion, sharp direction/speed change above the ridge line. Froudes were less than 1 (normally supports windward acceleration/leeward deceleration), but given the conditions mentioned before that would actually support acceleration of wind up the east slopes and also down the west slopes. 

Because that direction/speed change was there, it traps the wave energy from propagating upwards and instead directs it down the lee side (keeping the acceleration). Think water spilling over a rock in some rapids. 

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14 hours ago, dendrite said:

Cocorahs totals were pretty high up here (1.50"-2.00"+). I didn't check Mass, but I sorta tossed the ASOS liquid numbers. CON reported 0.96" from the ASOS, but they went with a straight 10:1 of 1.56" from the observer's 15.6" report.

Thought I would tuck our weenie liquid equivalent discussion from the model thread in here.

So we went with the observer's liquid, but the odd part about it was that even though she ended up dead nuts 10:1, the 6 hourly reports were all different liquid and snow amounts. In the end it just added up to 1.56 and 15.6. 

Precip (Snowfall): 0.02 (0.2), 0.33 (3.0), 1.05 (11.5), and 0.16 (0.9). 

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4 hours ago, OceanStWx said:

 

The downsloping is my gut feeling. We had 63 knots at just about 900 mb (2250 ft agl).

The highest Ossipees are about 2700-2900 feet. Our sounding inversion was around 2000 feet, could have been higher in NH. But you had pretty ideal conditions for downslope winds. Cross barrier flow near ridge level, inversion, sharp direction/speed change above the ridge line. Froudes were less than 1 (normally supports windward acceleration/leeward deceleration), but given the conditions mentioned before that would actually support acceleration of wind up the east slopes and also down the west slopes. 

Because that direction/speed change was there, it traps the wave energy from propagating upwards and instead directs it down the lee side (keeping the acceleration). Think water spilling over a rock in some rapids. 

That's what it seems like. Some sort of downsloping I think. Pretty crazy..does not happen often there.

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5 hours ago, OceanStWx said:

Thought I would tuck our weenie liquid equivalent discussion from the model thread in here.

So we went with the observer's liquid, but the odd part about it was that even though she ended up dead nuts 10:1, the 6 hourly reports were all different liquid and snow amounts. In the end it just added up to 1.56 and 15.6. 

Precip (Snowfall): 0.02 (0.2), 0.33 (3.0), 1.05 (11.5), and 0.16 (0.9). 

Sometimes that's how it adds up.  The Dec. 29-30 storm at my place had 0.49"/5.5" for 29th, 1.61" and 15.5" for 30th, for a perfect 10.0.  (My 3 big storms this winter have all been qpf-massive:  21.0" on 2.10", 21.0" on 1.84", and 15.5" on 2.12".) 
Then there are the cocorahs-confusers.  I had one obs of 0.1" snow and 0.10" precip, and it drew an error response.  I got around it by assigning 0.01" to the following day, which I thought to be less inaccurate than dropping it altogether.

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2 hours ago, CoolMike said:

Yes, I too am waiting to see the updated chart.  I'm curious to see how low it dropped during the torch and how well it has recovered since.

It was posted in the storm obs thread yesterday, just go back a few pages. Page 66 I believe.

gendateplot.pnggendateplot.php3.png

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Its too bad that the gradient pattern seems to have set up with the cold/snowy side up in Canada for the next few weeks.  I was hoping to see the models return to a better solution for NNE but it doesn't seem to be in the cards.  Two big cutters potentially coming through before the end of the month.

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The storm currently modeled as coming in warm and wet for next weekend would pose a serious risk for flooding. There is so much snow out there. With not much melting occuring between now and next weekend, a big rain event on this snow pack would result in some intense flooding. 

 

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18 minutes ago, adk said:

The storm currently modeled as coming in warm and wet for next weekend would pose a serious risk for flooding. There is so much snow out there. With not much melting occuring between now and next weekend, a big rain event on this snow pack would result in some intense flooding. 

 

Wouldn't this fluffy stuff soak up quite a bit though?

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16 minutes ago, mreaves said:

Wouldn't this fluffy stuff soak up quite a bit though?

I'm not sure about that. It's losing its low elevation "fluff" with strong march sun and I think there is quite a bit of water in the pack. 2"...add another 2" of rain to that and that's pretty bad. 

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22 hours ago, Ginx snewx said:

No Mansfield stake depth report today, only 9.1 new???

 

8 hours ago, Ginx snewx said:

Did PF suffocate in the snow?

Ha!  Been a little MIA from here... just been going non-stop with the storm.  Pretty much just came home to sleep the past two days and spent most of my time at the mountain.

What a wild few days.

Yesterday's MMNV1 report was definitely low based on my stakes but there was a ton of wind so the elevated precipitation gauge probably had some significant under-catch...where as the day before the wind was surprisingly almost dead calm and they picked up the 24-hour record.

Either way, the COOP had 45.1" of snowfall for the storm, which for that collection method is incredibly impressive to me.  I don't think I've ever seen a storm total near that from the COOP.  And on a seasonal average they collect roughly 30% less snow than my sheltered snow board collection method...and in this event there was only a 13% difference (45" vs. 52"), so I was fairly impressed with the numbers they had.  Toss in the fact myself or my co-worker were doing twice daily clears (early morning and then again late afternoon) while the COOP is a once a day reading, having only a 7" difference in a storm of this scale seemed pretty decent.

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I also found out some more information from the NWS about the 24-hour record that was set on Wednesday with 28" of snowfall...and I'm not sure how I feel about it but I think they should've been doing this all along.

The precipitation collection can that they measure rain and snow in is only 24" tall.  Therefore the old 24-hour snowfall records were all 24" (there were 3 or 4 of them, Valentines Day 2007 was one) because once the thing fills up and overflows with snow you can't tell how much snow there is.  So they report the maximum possible which is 24". 

On Wednesday, it was a similar case where the new snow just completely buried the precipitation station and obviously the collection can was overwhelmed with the snow.  So what they decided to do was take the change in snow depth (which was 28"...78" to 106") instead of just default to 24" like had been done in the past in these situations when the snow overwhelms the precip station.  So while technically Wednesday was a record, there's a reason why the other 3-4 max 24-hour totals are all 24.0"...those other storms delivered more snow, it just couldn't be measured by the method they use.

I need to hike up and get a good picture of the Mansfield collection method but here's a real small one I found on google of the precipitation can (left side of this microscopic photo).  There's a wind screen around the inner precip can, and the actual can in the middle is 8" in diameter and 24" deep. 

Now one can visualize how that might lead to undercatch with any sort of real wind.  Even with a wind screen on that thing, its not hard to imagine how my sheltered snow-board in a clearing surrounded by tall evergreens that block a good deal of wind and gets 30% more snow than the COOP method.  The snow falls sideways at one spot (on average, though in certain events it works out fine), while it falls straight down at the other spot (on average, while sometimes there is some wind).  

A comparison I can think of would be put this precipitation can set-up on a beach in Massachusetts during a nor'easter when the snow is falling sideways in 30-60mph winds and see how much snow ends up in it, vs. what people may actually experience for snowfall inland in slightly more sheltered areas.  The elevated precip can on the wind-swept beach may only collect 6" of snow while just inland where winds are much less severe and is measures 12" or 14" on the ground.

111a68fa4a02714ef8a3b255e79e2d91.jpg

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14 hours ago, eyewall said:

Awesome and love seeing that 41 on your list. I assume that is an all time #1 for you. Anyway here are some shots not far down the road from Smuggs I took today:

 

Yeah, this storm is definitely #1 at the house with respect to snowfall since we’ve lived there – it blew away the 2007 Valentine’s Day Storm by more than 10 inches.  Unfortunately I wasn’t measuring liquid for CoCoRaHS back in 2007, so I don’t know quite how much liquid was in the 2007 Valentine’s Day Storm.  If I had to guess based on how substantial that snowpack felt, it was probably between 2 and 3 inches of liquid, whereas Winter Storm Stella contained just over 2 inches of liquid.

 

Your shots from Winter Storm Stella have been excellent, great work documenting the snow around here!

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5 hours ago, powderfreak said:

I also found out some more information from the NWS about the 24-hour record that was set on Wednesday with 28" of snowfall...and I'm not sure how I feel about it but I think they should've been doing this all along.

The precipitation collection can that they measure rain and snow in is only 24" tall.  Therefore the old 24-hour snowfall records were all 24" (there were 3 or 4 of them, Valentines Day 2007 was one) because once the thing fills up and overflows with snow you can't tell how much snow there is.  So they report the maximum possible which is 24". 

On Wednesday, it was a similar case where the new snow just completely buried the precipitation station and obviously the collection can was overwhelmed with the snow.  So what they decided to do was take the change in snow depth (which was 28"...78" to 106") instead of just default to 24" like had been done in the past in these situations when the snow overwhelms the precip station.  So while technically Wednesday was a record, there's a reason why the other 3-4 max 24-hour totals are all 24.0"...those other storms delivered more snow, it just couldn't be measured by the method they use.

I need to hike up and get a good picture of the Mansfield collection method but here's a real small one I found on google of the precipitation can (left side of this microscopic photo).  There's a wind screen around the inner precip can, and the actual can in the middle is 8" in diameter and 24" deep. 

Now one can visualize how that might lead to undercatch with any sort of real wind.  Even with a wind screen on that thing, its not hard to imagine how my sheltered snow-board in a clearing surrounded by tall evergreens that block a good deal of wind and gets 30% more snow than the COOP method.  The snow falls sideways at one spot (on average, though in certain events it works out fine), while it falls straight down at the other spot (on average, while sometimes there is some wind).  

A comparison I can think of would be put this precipitation can set-up on a beach in Massachusetts during a nor'easter when the snow is falling sideways in 30-60mph winds and see how much snow ends up in it, vs. what people may actually experience for snowfall inland in slightly more sheltered areas.  The elevated precip can on the wind-swept beach may only collect 6" of snow while just inland where winds are much less severe and is measures 12" or 14" on the ground.

111a68fa4a02714ef8a3b255e79e2d91.jpg

Same can set up as MWN. Hell if I know how they measure any snow up there. I'm sure Mansfield is the same when the wind is ripping. 

But they are staffed 24/7, so maybe they swap cans real quick when it gets close? I've never gotten a good run down of how they report.

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5 hours ago, powderfreak said:

Figured mreaves and dryslot would appreciate this...

Stowe (Performing Arts Center) parking lot this afternoon... a snowmobile from like the 1980s stuffed into the back of a Subaru.  Ha.

17240362_10211131938628760_5585391371669

Lol. That's a winter warrior right there!  Taking his sled to the ski area. I guess if the lift lines were too long he would have had his own way up!

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Yeah, this storm is definitely #1 at the house with respect to snowfall since we’ve lived there – it blew away the 2007 Valentine’s Day Storm by more than 10 inches.  Unfortunately I wasn’t measuring liquid for CoCoRaHS back in 2007, so I don’t know quite how much liquid was in the 2007 Valentine’s Day StormIf I had to guess based on how substantial that snowpack felt, it was probably between 2 and 3 inches of liquid, whereas Winter Storm Stella contained just over 2 inches of liquid.

 

Your shots from Winter Storm Stella have been excellent, great work documenting the snow around here!



Thank you! I had to document history for sure. For me it smoked the blizzard of 96 and PD2 on LI and the Carolina Crusher in 2000.

Sent from my VS987 using Tapatalk

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