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Snow bomb obs March 21

Damage In Tolland

By Damage In Tolland,
in New England

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CT Rain

CT Rain

Posted
Posted
Just now, OceanStWx said:

Speaking for what we deal with, our ranges are locked in mainly because of southern offices. We would prefer more details in the mid to high ranges of snowfall, but southern offices need a lot of detail at the low end. And HQ wants consistency from office to office. So we start 6 inch bins at 12". And we jump from 36-50" to 50-100". 

Snowfall forecasting in general though is tough. At the most basic level it is a temp, QPF, snow ratio forecast. Those variables combine to produce a snowfall. Aside from the many ways a temp or snow ratio can bust, QPF is often far too broad (you miss the maxes and the mins). More often than not, the high QPF is too expansive as well. So the highest snowfall amounts are usually not as widespread. 

For sure. The predictability horizon for mesoscale features in these storms is still awfully short. 

This storm was interesting that even the Euro (which was on its own) was even too snowy around here. The issue really was dry air - I only had 0.11" of liquid here with a boundary layer that never moistened. It was painful. Even New Haven struggled. Not sure why the dry air was so robust... but have a feeling it was a different evolution/track of the mid/low level features. 

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OceanStWx

OceanStWx

Posted
Posted
1 minute ago, CT Rain said:

For sure. The predictability horizon for mesoscale features in these storms is still awfully short. 

This storm was interesting that even the Euro (which was on its own) was even too snowy around here. The issue really was dry air - I only had 0.11" of liquid here with a boundary layer that never moistened. It was painful. Even New Haven struggled. Not sure why the dry air was so robust... but have a feeling it was a different evolution/track of the mid/low level features. 

I mean even up here, PWM has at least 1.3" and GYX just a T. It's like 12 miles between the two.

I do think for New England we suffered poor moisture transport. NNE flow in the boundary layer isn't abnormal, but the lack of robust easterly flow in the lower/mid levels didn't saturate (especially farther W). 

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HoarfrostHubb

HoarfrostHubb

Posted
Posted
8 minutes ago, OceanStWx said:

Speaking for what we deal with, our ranges are locked in mainly because of southern offices. We would prefer more details in the mid to high ranges of snowfall, but southern offices need a lot of detail at the low end. And HQ wants consistency from office to office. So we start 6 inch bins at 12". And we jump from 36-50" to 50-100". 

Snowfall forecasting in general though is tough. At the most basic level it is a temp, QPF, snow ratio forecast. Those variables combine to produce a snowfall. Aside from the many ways a temp or snow ratio can bust, QPF is often far too broad (you miss the maxes and the mins). More often than not, the high QPF is too expansive as well. So the highest snowfall amounts are usually not as widespread. 

Lol  50-100"...

How often are those rolled out?

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ORH_wxman

ORH_wxman

Posted
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25 minutes ago, CT Rain said:

I feel like the big ranges are a way to convey uncertainty (at least that's what I do). This is pretty much the only probabilistic forecast we put on TV. 

We were also about 50% of what the NWS was forecasting and we were still way too high.

Yeah it is not reasonable to expect very small snowfall ranges except in situations where the QPF is clearly capped....like small storms and clippers and scrapers. Then you can spit out 1-3/2-4 type stuff.

 

Trying to give a range of like 8-10" is kind of stupid IMHO and it's conveying a level of certainty that is not actually present. Ranges like 6-12 have been around for decades...so the public is used to them. The mesoscale aspect of snow in larger systems is not really that much more predictable than it was 20 or 30 years ago, so we're still going to need larger ranges. Back when I forecasted all the time for DOT clients, I tried to use 4 inch ranges as often as I could in larger storms (i.e 8-12/10-14), but sometimes I just couldn't....there was too much uncertainty and I'd have to say "look, you could get 6" or a foot...so it's 6-12 inches"

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snowman21

snowman21

Posted
Posted
5 minutes ago, CT Rain said:

I feel like the big ranges are a way to convey uncertainty (at least that's what I do). This is pretty much the only probabilistic forecast we put on TV. 

We were also about 50% of what the NWS was forecasting and we were still way too high.

Yeah this one was a tough one for sure, but I can't for the life of me figure out why a forecaster wouldn't always hedge low as you did knowing that to maximize accumulation into some of these high end ranges needs everything to go just right. There's also the public perception which you know well. If you forecast a foot and it ends up being 18 inches I feel like there's less backlash than if it ends up being 6 even though the error is the same.

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weathafella

weathafella

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24 minutes ago, CT Rain said:

For sure. The predictability horizon for mesoscale features in these storms is still awfully short. 

This storm was interesting that even the Euro (which was on its own) was even too snowy around here. The issue really was dry air - I only had 0.11" of liquid here with a boundary layer that never moistened. It was painful. Even New Haven struggled. Not sure why the dry air was so robust... but have a feeling it was a different evolution/track of the mid/low level features. 

Did you arrange that kid a seat on the NY Philharmonic yet?

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OceanStWx

OceanStWx

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6 minutes ago, snowman21 said:

Yeah this one was a tough one for sure, but I can't for the life of me figure out why a forecaster wouldn't always hedge low as you did knowing that to maximize accumulation into some of these high end ranges needs everything to go just right. There's also the public perception which you know well. If you forecast a foot and it ends up being 18 inches I feel like there's less backlash than if it ends up being 6 even though the error is the same.

That's not really the case. This board rejoices with a positive bust, but the general public does not. And positive busts can be very costly to cities and states when they aren't prepared for it. 

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CT Rain

CT Rain

Posted
Posted
Just now, OceanStWx said:

That's not really the case. This board rejoices with a positive bust, but the general public does not. And positive busts can be very costly to cities and states when they aren't prepared for it. 

I think the general public is probably more forgiving if we forecast 12" of snow and 18" falls than 6". But I think from a NWS standpoint they hear from government partners that they'd rather be overpepared than underprepared.

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OceanStWx

OceanStWx

Posted
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2 minutes ago, CT Rain said:

I think the general public is probably more forgiving if we forecast 12" of snow and 18" falls than 6". But I think from a NWS standpoint they hear from government partners that they'd rather be overpepared than underprepared.

Definitely. There is a cost to negative busts of course (pre-treating roads that didn't need it for instance), but the costs of a poorly forecast positive bust far outweigh the other way around. For a big city, you're talking millions of dollars per storm.

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CT Rain

CT Rain

Posted
Posted
Just now, snowman21 said:

I can't wait for the day OKX has to put me in that 50-100 range. The craziest one I've seen is where they just gave up and put everyone in the 24-36.

I will say the forecasts have been better this year - or at least reasonable - than in the past. I wonder if the way the snow grids are getting edited at the WFO frequently skews things on the high side of things - more so than they would if the grids were just drawn from scratch. The numbers for this storm were really high even when compared to the WPC 50th percentile forecast. 

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henry1978

henry1978

Posted
Posted
11 minutes ago, CT Rain said:

I think the general public is probably more forgiving if we forecast 12" of snow and 18" falls than 6". But I think from a NWS standpoint they hear from government partners that they'd rather be overpepared than underprepared.

The New York local tv mets are having an easier day today than the PVD, Hartford and Boston tv mets.  Manhattan, the Bronx, part of north jersey and Westchester and rockland got screwed compared to Brooklyn, queens, staten island and Nassau and Suffolk, but nevertheless Manhattan, the Bronx and most of north jersey still had 6 plus. People who got zero in the boston and providence dma's are the ones who are really furious.  The dirty little secret is that most people love snow and they get pi$$ed when the snowstorm busts.  People can complain about daycare and cancelled concert recitals all they want, the truth is the adults want their snow as much as we do. A lot of people like snow more than porn.

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ORH_wxman

ORH_wxman

Posted
Posted

The hard part about this storm was how subtle the differences were from a huge hit to not...it's not dissimilar to the 2/10/10 event. We just squashed the northern side of the big ULL just enough to really disrupt the moisture transport and of course at the sfc that translated into a little more drier air from north and sinking air.

Both storms too it was the Euro that had the caution flags...John McClane style.

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CT Rain

CT Rain

Posted
Posted
Just now, ORH_wxman said:

The hard part about this storm was how subtle the differences were from a huge hit to not...it's not dissimilar to the 2/10/10 event. We just squashed the northern side of the big ULL just enough to really disrupt the moisture transport and of course at the sfc that translated into a little more drier air from north and sinking air.

Both storms too it was the Euro that had the caution flags...John McClane style.

Man did that storm suck too. 

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