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Snow to ice to wind driven rain discussion/obs 2/23-2/25 SNE CNE NNE


Ginx snewx

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It's pretty much turning into an elevation deal now. CON is up to 34F. I'll probably creep up to 32.1F within an hour or 2. SW Merrimack County, up around 1400-1500', is still 29-30F so they have plenty of glazing to go.

 

 

Yeah the higher terrain is definitely having a half decent glaze event.

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Yeah the higher terrain is definitely having a half decent glaze event.

Still 25F and pouring at 3000-4000ft up here. A solid half inch of ice so far. It just accumulated so fast at those temps and there's cloud droplets/drizzle to go with the sheets of ZR.

30.5F at 1,500ft which is actually mostly sleet still from the 2,000ft+ thick subfreezing layer on the east slope.

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Solid quarter inch there. I'm guessing we have a lot of that going on at similar elevations.

 

We have a report from 1800 feet in Alexandria of 1/4 inch, but on the other side of that ridge in Randolph at 1500 feet, it's 37 and rain with no ice. Fun times.

 

Interesting - you don't take the maximum there? So it would be the average on both sides of the branch? 

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Solid quarter inch there. I'm guessing we have a lot of that going on at similar elevations.

We have a report from 1800 feet in Alexandria of 1/4 inch, but on the other side of that ridge in Randolph at 1500 feet, it's 37 and rain with no ice. Fun times.

Heard 26 was a mess ,more from Wolcott per Twitter

post-7-0-87020800-1456329536.jpg

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Interesting - you don't take the maximum there? So it would be the average on both sides of the branch? 

 

Correct, because the wind favors upwind side accretion you take the average of the up and downwind measurements. Flat surface accumulation is different because there is no wind component assumed to factor in there.

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No, it's 1/4 inch but still solid damage. Actual impact power companies appear to care more about 1/3 than 1/2 inch amounts. So closer to 1/4 starts the damage cycle.

 

I'm surprised the warning criteria isn't 1/4" of accretion. That's a lot of ice!

 

Please take all ice accretion reports I've posted here and sent to NWS over the last 20 years and divide by 2. 

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No, it's 1/4 inch but still solid damage. Actual impact power companies appear to care more about 1/3 than 1/2 inch amounts. So closer to 1/4 starts the damage cycle.

 

 

My anecdotel evidence from years of ice storms at elevation in ORH supports the 1/4 inch line...usually get a few sporatic power outages at 1/4 inch but tends to increase rapidly once we're at 3/8" and half an inch is like a chain reaction that goes off.

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I'm surprised the warning criteria isn't 1/4" of accretion. That's a lot of ice!

 

Please take all ice accretion reports I've posted here and sent to NWS over the last 20 years and divide by 2. 

 

I think a lot of people mess it up. We usually try and post the CoCoRaHS method to social media before we expect significant FZRA to remind our spotters. Of course like I said, it's only on lines or branches that you measure both sides and divide. If you measured your deck, car (hood not window), or other flat surface, it's just the total accretion because wind wasn't involved.

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My anecdotel evidence from years of ice storms at elevation in ORH supports the 1/4 inch line...usually get a few sporatic power outages at 1/4 inch but tends to increase rapidly once we're at 3/8" and half an inch is like a chain reaction that goes off.

 

Eversource power in NH basically confirmed that with Ekster. Got really worried about 1/3 inch, didn't much care whether we got to 1/2. So basically every time we go sub-warning, 1/4 to 1/2 it's their worst nightmare for impacts. Not much at 1/4, huge at 1/2.  

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Eversource power in NH basically confirmed that with Ekster. Got really worried about 1/3 inch, didn't much care whether we got to 1/2. So basically every time we go sub-warning, 1/4 to 1/2 it's their worst nightmare for impacts. Not much at 1/4, huge at 1/2.  

 

Yeah by the time you are at half an inch, it's already shotguns going off basically. That's what happened in 2008...we actually lost power (almost perfectly timed) right after I had gone on a weenie walk in the dark measuring the ice accretion on various branches and surfaces. I had around 3/8" at that point. Maybe slightly more.

 

By the time we got another 2-3 hours into the storm, the shotguns started going off every 5 seconds or less...so I'd assume by that point we were over half an inch.

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Yeah by the time you are at half an inch, it's already shotguns going off basically. That's what happened in 2008...we actually lost power (almost perfectly timed) right after I had gone on a weenie walk in the dark measuring the ice accretion on various branches and surfaces. I had around 3/8" at that point. Maybe slightly more.

 

By the time we got another 2-3 hours into the storm, the shotguns started going off every 5 seconds or less...so I'd assume by that point we were over half an inch.

 

What was the final accretion you had in ORH from that one?

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Yeah by the time you are at half an inch, it's already shotguns going off basically. That's what happened in 2008...we actually lost power (almost perfectly timed) right after I had gone on a weenie walk in the dark measuring the ice accretion on various branches and surfaces. I had around 3/8" at that point. Maybe slightly more.

 

By the time we got another 2-3 hours into the storm, the shotguns started going off every 5 seconds or less...so I'd assume by that point we were over half an inch.

 

Which makes it all the more ironic that we weren't able to verify the 2013 ice event up here because it wasn't widespread enough 1/2 inch reports, but we had basically all greater than 1/3 around here.

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I honestly feel like I experience more thunderstorms during the winter months as opposed to during the so called 'severe season'

 

Unless it's vastly different there than here, it's a perception/anomaly thing.  Days with thunder, 40 years of data from sites in northern, southern and western Maine:

 

DJFM:  14 days with thunder, 2.5% of total

 

MJJA:  467 days with thunder, 83% of total

 

Augusta reporting freezing rain and 29 at 1 PM.  Looks like no more than fzdz outside the office, 2 miles SE and 200' lower than the co-op site.  No sign of accretion on trees and shrubs, though there might be 1/20" that I can't detect from inside.

 

My anecdotel evidence from years of ice storms at elevation in ORH supports the 1/4 inch line...usually get a few sporatic power outages at 1/4 inch but tends to increase rapidly once we're at 3/8" and half an inch is like a chain reaction that goes off.

 

Anecdotal evidence from a NNE forester (not me, though I agree) with 40+ years of experience:  Serious damage begins as accretion (thickest side, not the average) reaches 20mm.  Would probably translate to 0.4-0.5" when measured in the prescribed manner.  In the 1998 event, I saw grass stems, frozen in vertical position, with diameters approaching 2.5" - soda-can size.  Not sure how that would translate.

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